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Dear students, prepare for biology class 9th chapter 5 long questions. These important long questions are carefully added to get you best preparation for your 9th class biology ch. 5 exams.
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Question: 1
Define reproduction. Describe its importance in life.
Answer: 1
The most basic characteristic of life is reproduction. Definition It is a biological process in living things by which they produce their young ones which are similar to parents. Levels of Reproduction Reproduction occurs at different levels of organization. (i) Parts of the cell such as the chromosomes produce new chromosomes. (ii) Cells then produce new cells (iii) Individuals produce off springs like themselves. Reproduction for continuation of life Rudolf Virchow proposed an important biological principle that all cells come from pre¬existing cells. This principle tells us that the continuation of life, including all aspects of reproduction, is based on the reproduction of cells. We commonly refer cellular reproduction as cell division and it is a part of whole life of a cell i.e. cell cycle.
Question: 2
Define inter-phase. Explain the stages of inter-phase.
Answer: 2
Inter-phase is the time when a cell's metabolic activity is very high, as it performs its various functions. Stages of interphase It is divided into three phases. G1 (first gap) S (synthesis) G2 (second gap) G1 Phase After its production, a cell starts its cell cycle in G1 phase. During this phase, (i) The cell increases its supply of proteins, (ii) Cell increases the number of its organelles (such as mitochondria, ribosomes) (iii)Cell grows in size. (iv)This phase is also marked by the synthesis of various enzymes that are required in the next phase i.e. S phase, for the duplication of chromosomes. S Phase In this phase, DNA replication takes place, as a result the cell duplicates its chromosomes. As a result, each chromosome consists of two sister chromatids. G2 Phase In the G2 phase, the cell prepares proteins that are essential for mitosis, mainly for the production of spindle fibers. After the G2 phase of inter-phase, the cell enters in the division phase i.e. M phase. It is characterized by mitosis, in which the cell divides into the two daughter cells.
Question: 3
What is mitosis? Describe its Discovery and phases.
Answer: 3
Inter-phase is the time when a cell's metabolic activity is very high, as it performs its various functions. Stages of interphase It is divided into three phases. G1 (first gap) S (synthesis) G2 (second gap) G1 Phase After its production, a cell starts its cell cycle in G1 phase. During this phase, (i) The cell increases its supply of proteins, (ii) Cell increases the number of its organelles (such as mitochondria, ribosomes) (iii)Cell grows in size. (iv)This phase is also marked by the synthesis of various enzymes that are required in the next phase i.e. S phase, for the duplication of chromosomes. S Phase In this phase, DNA replication takes place, as a result the cell duplicates its chromosomes. As a result, each chromosome consists of two sister chromatids. G2 Phase In the G2 phase, the cell prepares proteins that are essential for mitosis, mainly for the production of spindle fibers. After the G2 phase of inter-phase, the cell enters in the division phase i.e. M phase. It is characterized by mitosis, in which the cell divides into the two daughter cells.
Question: 4
Define meiosis and explain its phases in detail.
Answer: 4
Question: 5
Describe significance of meiosis?
Answer: 5
. Introduction The significance of meiosis for reproduction and inheritance was described in 1980 by German biologist August Weizmann. (i) Maintenance of chromosome number August Weizmann noted that meiosis was necessary not only to maintain the number of chromosomes in the next generation but also to produce variations in next generation. (ii) Meiosis for sexual reproduction of Eukaryotas Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes including single celled organisms that reproduce sexually. Meiosis does not occur in prokaryotes, which reproduce asexually by binary fission. (iii) Meiosis in humans In human diploid gametes, mother cells or germ line cells undergo meiosis to produce haploid gametes. Male and female gametes unite to form diploid zygote which undergoes repeated mitosis and develops into the new diploid human. (iv) Gamete formation in fungi and protozoa Many haploid fungi and protozoa produce haploid gametes through mitosis. (v) Meiosis in plants Plants' life cycle shows alternation of generation. The cells of the diploid sporophyte generation undergo meiosis to produce haploid spores, which grow into haploid gametophyte generation. The haploid gametophyte generation produces haploid gametes through mitosis. The gametes combine to produce the diploid zygote. The zygote undergoes mitosis to become the diploid saprophyte. (vi) Meiosis as a source of genetic variations The chromosome pairs of each parent undergo crossing over during meiosis. So daughter cells i.e. gametes have genetic variations. When gametes fuse and form zygote; its genetic make-up is different from both parents. Thus meiosis allows a species to bring variations which help organisms to adapt to the changes in environment.
Question: 6
Write a note on necrosis.
Answer: 6
Question: 7
What is apoptosis? What happens in it? Describe its importance.
Answer: 7
"Between 50 billion to 70 billion cells die each day due to apoptosis in an adult human". Apoptosis is one of the main types of programmed cell death. Events of apoptosis Following is the series of events in apoptosis: (i) Cell shrinks and becomes rounded due to the breakdown of the cytoskeleton by enzymes. (ii) Chromatin undergoes condensation and the nuclear envelope breaks. (iii)In this way, nucleus spreads in the form of several discrete chromatin bodies. (iv)The cell membrane makes irregular buds known as blabs. (v) The blebs break off from the cell and are now called apoptotic bodies, which are then phagocytosed by other cells. Causes of apoptosis Apoptosis can occur when a cell is damaged, or undergoes stress conditions. Significance of apoptosis(i) Removal of damaged cell Apoptosis removes the damaged cell, preventing it from getting further nutrients or to prevent the spread of infection. (ii) Differentiation of fingers and toes in embryo Apoptosis generally gives advantages during development. For example, during the formation of fingers, the cells between them undergo apoptosis and the digits separate.
Question: 8
Q no: 5 (A) What is apoptosis? Describe Series of events in Apoptosis.
Answer: 8
Apoptosis is one of the main types of programmed cell death. During <gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859110795298974376923">apaptosis cell</gwmw> shrinks and become rounded due to the breakdown of <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859110795290624128698">cytoskeleton</gwmw> by enzymes. It <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859111277659833742299">chromation</gwmw> undergoes condensation and nuclear <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859111277651054326247">encelaps</gwmw> breaks<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859111277657991833704"> .</gwmw> In this way <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859111838878309894044">nuclesus</gwmw> spread in the <gwmw class="ginger-module-highlighter-mistake-type-2" id="gwmw-15859111838876424873203">from</gwmw> of several discrete <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859111838872572178192">chormatin</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859111838876631783303">bosies</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859111838876905562655"> .</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859112657070381620478">cell</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859112657074154978668">memberne</gwmw> makes irregular buds known as <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859112657079890764182">blebs</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859112657074485964924"> .</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859113099323823954501">Blebs</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859113099323685621988">breake</gwmw> from the cell and one <gwmw class="ginger-module-highlighter-mistake-type-2" id="gwmw-15859113099328797904361">know</gwmw> called <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859113099324322861619">apoplotic</gwmw> bodies<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859113099329759847453"> .</gwmw> Which are <gwmw class="ginger-module-highlighter-mistake-type-2" id="gwmw-15859113867255719235670">than</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859117195372027558993">phagocylosed</gwmw> by their cells.<div>Apoptosis con <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859117546546488885783">occur</gwmw> when a cell is <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859117546547820426812">demaged</gwmw> or <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859117546549321790105">endergoes</gwmw> stress condition apoptosis removes the <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859117546548184565560">demaged</gwmw> cell. <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859119313868262737202">preventing</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859117595176815071086">oit</gwmw> from getting further nutrients or to prevent this spread of infection <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859119313864520633971">Apaptosis</gwmw> also gives advantages during development. For Example</div><div><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859119776657385524030">during</gwmw> the formation of fingers. The cell between them <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859120161741854799011">under go</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859120060588889743527">apaptosis</gwmw>and the digit <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859120161744638095174">separate</gwmw></div>
Question: 9
Q no: (B) What is cell cycle and describe all the phases of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859120920584447283643">interphase</gwmw> in detail.
Answer: 9
Cell cycle:<div> <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859121626139389609881">Cell cycle</gwmw> is <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859121626137285710294">series</gwmw> of event from the time a cell is produced <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859121626131774232846">until</gwmw>. It completes mitosis and produce new cell. Cell cycle <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859122316540237019679">consist</gwmw> of two major phase <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859122136123874099247">interphase</gwmw>and mitotic phase.</div><div> Mitotic Phase:</div><div> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859122868251737663180">is</gwmw> a relatively short <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859122788014615448744">peviod</gwmw> of cell cycle<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859122868251065407511"> .</gwmw> It alternates with the much longer <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859123016631532856423">interphase</gwmw>where cell <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859123334445375328515">prepare</gwmw> itself for division.</div><div><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859123724119488157112">Interphase</gwmw>:</div><div><gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859131290506108645100">Interphase</gwmw> is the time when a <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859131290501687188462">cell</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859124796968721470306">metabalic</gwmw>activity is very high as its perform itsvarious <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859131290500300004202">function</gwmw> it is divided into three <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859131290505046234269">phase</gwmw>.</div><div>G1 phase:</div><div> After <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859133047493469417080">is</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859133047490372307547">reproduction</gwmw> a cell starts is cellcycle in <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859133047494095654734">G1 phase</gwmw> During this phase cell increase its supply of proteins increase the number of its <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859132648198475232565">organells</gwmw> or grow in size. This phase is also marked by the synthesis of various enzymes that are required in <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859133787140232488581">next phase</gwmw></div><div>S phase:</div><div>In this phase cell duplicates its <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859139118821102860180">choromosomes</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859139005740952774522"> .</gwmw> As a <gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859139780076462685464">result each</gwmw> chromosomes. As a <gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859140617456460862975">result each</gwmw> chromosome consist of two writer<gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859140706309147250777">chronatids</gwmw>.</div><div>G2 phase:</div><div> In The G2phase cell prepares proteins that are essential for mitosis mainly for the production of <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859145686030867900957">spindle fibres</gwmw>.</div><div>Go Phase:</div><div> In multicellular eukaryotic cell enter Go phase from G1 and stop dividing <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859147649019950118984">some one</gwmw>remain in Go for <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859147649016859010717">indefinite perioud</gwmw>of neurons.</div>
Question: 10
Q no<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859150051247305654841">:</gwmw>6 (A) Explain the changes which take place during prophase of mitosis.
Answer: 10
Prophase of mitosis:<div> Normally the genetic materials in nucleus <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859153868609138011764">is</gwmw> in a loose <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859152838758214042222">thread-like</gwmw> form called chromatin At the onset of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859153063483526641281">prophase</gwmw>chromatin condenses into highly ordered structures called <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859153868606232792362">chromosome</gwmw>. Sine the genetic materials has already been <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859154138285368100555">duplicatied</gwmw>either in S phase each <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859154610443899363982">chromatids</gwmw>. <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859155352605641249512">bound</gwmw> together at the same <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859154769432253419792">centromere</gwmw>Each <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859155352608085857482">chromosomes</gwmw> also has <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859155220568923664493">kinetochore</gwmw> at <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859155333772582416109">centomere</gwmw>. There are two <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859155460095555135365">centrioles</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859155530254468591129">.</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156388198226614258">Eachcentriols</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859155747766741250895">duplicae</gwmw> and thus two daughter <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156114812933838164">centrosomes</gwmw>are formed Both <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156213423763175493">centrosomes</gwmw>migrate to the opposite poles of <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859156388199489996103">cell</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859156388190581254240"> .</gwmw> The <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156491538250599760">microtubules</gwmw>thus formed are called spindle <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156702716575449782">fibres</gwmw>. <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859157157821170750501">complete</gwmw> set of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156928527738917479">rpindle</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859156973856034482705">fibres</gwmw>is known as <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859157157825971364385">mitotic spindle</gwmw>. <span style="">By this time <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859157366931545909993">nucleaslus</gwmw>and nuclear envelops have degraded and <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859157806986021261905">pindle</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859157838487733938884">fibres</gwmw>have invaded the central phase.</span></div>
Question: 11
Q no: (B) Write short note Necrosis.
Answer: 11
Necrosis is the accidental death of cell and living tissues<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859162156126347968273">.</gwmw>Necrosis <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859162156125111644508">is</gwmw> less sequential than apoptosis there are many <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859162156126580936637">cause</gwmw> of necrosis including injury inflection <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859162078303831521052">concer</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859162138107791762204">ect</gwmw>. Necrosis may occur when a cell is given hypoxia<gwmw class="ginger-module-highlighter-mistake-anim ginger-module-highlighter-mistake-type-1" id="gwmw-15859175016457588331094">enviroments</gwmw><div><br></div><div>During <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859164603917544740609">necrasis</gwmw>there is a release of special enzymes from lysosomes <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859165311631047651186">uysosomes</gwmw>enzymes break <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859165436809378248929">cellulan</gwmw>components and may also may be released outsides cell to break surrounding <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859165959074837254552">cell</gwmw>. Cells that necrosis may also release harmful chemicals that damage other cells.</div>
Question: 12
Q no: 7 (A) Describe the Significance of Meiosos Meiosis:<div></div>
Answer: 12
The significance of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859192867518820687601">meisos</gwmw> for reproduction and inheritance was described in 1890 by <gwmw class="ginger-module-highlighter-mistake-type-2" id="gwmw-15859194016320774073172">german</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859193887365688191676">biologsis</gwmw> August <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859194016321411369363">weismann</gwmw>.<div>Maintenance of the <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859194099644663457172">chromosomes</gwmw> number in next generation:</div><div>Meiosis <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859195503606658021914">is essential for sexual reprodution in humans diplaid</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859194570841656844951">gemete</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859194637272923437016">mather</gwmw>cells <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859194667596542569372">ot</gwmw>germ line cell undergo <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859194832713980171553">meisosis</gwmw> to produce haploid <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859195007417458842918">gemeter</gwmw> male and female <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859195342126435573030">gemetes</gwmw>unite to form <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859195621042686521941">diploid zygoat</gwmw>. Which <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859195698282217591071">undergoer</gwmw>repeated mitosis and develops into a new <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859195963468360819650">dipliods</gwmw>Humans.</div><div><br></div><div>Production of variation in next generation:</div><div>The <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859196428283606441340">chromomes</gwmw><gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859196590187841709928">paios</gwmw> of each parent undergo crossing over during meiosis. So daughter cell gametes have genetic <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859197226250247268589">vaiation</gwmw><gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859197269646333574509">.</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859197453352295465125">when</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859197330192603186384">gemeter</gwmw>fuse and form zygote</div><div>ERRORS In MEIOSIS:</div><div>During <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859198037094009813240">anaphase</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859198108382071487295">chromoseomes</gwmw>separated and go to opposite poles with during <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859198401650039947932">anaphase</gwmw><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859198877841101652406">anaphase</gwmw>2 sister chromosomes <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859199095309753072004">seprated</gwmw>. It is called</div><div>Disjunction:</div><div> Some time the <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859199453738795168922">seperation</gwmw> is not normal and it is called NoN Disjunction.</div><div>It <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859200921244498657283">result</gwmw> abnormal<gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859200921242353724786">chromosomes</gwmw> number in <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859200921243096987570">next generation</gwmw> for example 47 or 45 chromosomes in humans</div>
Question: 13
Describe <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859202853488600818329">prophase</gwmw>of Meiosis:
Answer: 13
<gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859203472956715752533">Prophase</gwmw> is the longest phase in meiosis during this stage chromatin condenses into chromosomes. The <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859204081077985201047">nomologue</gwmw>chromosomes line up with each other. <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859213883842298607485">form</gwmw> pairs by a process is called <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859204443897709151421">synapsis</gwmw>Each pair of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859204592200689249969">homologue</gwmw>chromosomes is called bivalent Each bivalent has far chromosomes so it may also be called <span style=""><gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859212982433593442512">terrad</gwmw></span> The two non sister <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859213185771403172507">chromotids</gwmw>of homologous chromosomes join each other at certain points along their length<gwmw class="ginger-module-highlighter-mistake-type-6" id="gwmw-15859213883840720676377"> .</gwmw> This point of attachment <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859214901300964389275">are called</gwmw> <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859214092069762080773">chiasmata</gwmw>In the next stage the non sister <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859214356267076725321">chromotids</gwmw>of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859214451677444565585">homologue</gwmw>chromosomes exchange their segments are the <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859214743037877934481">phenonmenon</gwmw>is known as Crossing over. <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859216338815593189395">Two kinetochores</gwmw>of <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859215232500761939104">chromoses</gwmw>while the spindle <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859215371390434138956">fibres</gwmw>attach <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859216338815681180355">with</gwmw> a pair of chromosomes in mitosis we have seen that two <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859216124945197667540">kinetochor</gwmw>spindle <gwmw class="ginger-module-highlighter-mistake-type-1" id="gwmw-15859216202004366912455">fibres</gwmw>attach with one <gwmw class="ginger-module-highlighter-mistake-type-3" id="gwmw-15859216338818930900113">chromosomes</gwmw>
Question: 14
Define cell cycle . Explain its phases
Answer: 14
Cell cycle : It is the series of events from the time a cell is produced until it completes mitosis and produces new cell<div><br>Phases of cell cycle :</div><div>It consists of two major parts</div><div>1: Interphase : The phase of cell cycle in which n a cell's metabolic activity is very high , as it performs its various functions but it is non-dividing phase of cell cycle</div><div>2: Mitotic phase : Mitotic phase is relatively short period of cell cycle . It alternates with much longer interphase where cell prepares itself for division</div><div>Interphase last for at least 90% of the total time required for the cell cycle</div><div>-Division of interphase : It is divided into three phases G1 (first gap) S(synthesis) and G2(Second gap)</div><div>-G1 phase : During this phase , a cell increases its supply of proteins and increase the number of its organelles (such as Ribosomes , Mitochondria ) and grows in size and synthesize various enzyme that are required in next phase i-e S phase for the duplication of chromosomes</div><div><br></div>
Question: 15
Define mitosis . Explain its phases
Answer: 15
Mitosis : The type of cell division in which a cell divides into two daughter cells . Each with a same number of chromosomes as were present in parent cell<div><br></div><div>Discovery of Mitosis: In 1880's German biologist , Walther Flemming discovered mitosis</div><div><br></div><div>Occurrence of mitosis : Mitosis occurs only in eukaryotic cell . In multicellular organisms the somatic cells undergo mitosis</div><div><br></div><div>Binary fission : In prokaryotic cell , it is a process in which one organism divide into two organisms</div><div><br></div><div>Phases of mitosis : Mitosis is complex it has two major phases</div><div>1: Karyokinesis : The division of nucleus is called Karyokinesis</div><div>2: Cytokinesis : The division of cytoplasm is called cytokinesis</div><div><br></div><div>KaryokinesisIt is further divided into four phases</div><div>1: Prophase</div><div>2: Metaphase</div><div>3: Anaphase</div><div>4: Telophase</div><div><br></div><div>1: Prophase :</div><div>Chromatin : Normally the genetic material in nucleus is in loose thread like form called chromatin</div><div>Chromosomes : (Chromo=color , Soma= body )</div><div>During cell division chromatin condenses into highly ordered structure called chromosomes</div><div>Kinetochore : It is a complex protein structure that is the point where spindle fibers attach</div><div>Centrosomes : The two centrioles are collectively called centrosomes</div><div>Spindle fiber : Mitochondria join together and form spindle fibers</div><div>Mitotic fibers : Complete set of spindle fibers is called mitotic fibers</div><div><br></div>
Question: 16
What is the singnificance of mitosis ?
Answer: 16
Importance of mitosis is maintenance of chromosomal set following are the occasions in lives organisms where mitosis happen<div><br></div><div>Development and growth :</div><div>The number of cell within an organism increase by mitosis . This is the basic of development of multicellular body from single cell i-e zygote and also the basis of the growth of multicellular body</div><div><br></div>
Question: 17
What happens if errors in mitosis occurs ?
Answer: 17
Errors in mitosis : Errors in the control of mitosis may cause cancer . All cells have genes that controls the timing and number of mitosis<div><br></div><div>Tumor: Sometimes mutation occur in such genes and cells contain to divide its result in growth of abnormal cells called tumors</div><div><br></div><div>Benign Tumors : A ling as the tumors remain in their original location they are called Benign Tumors</div><div>Malignant Tumors/ Cancerous Tumors</div><div>If the Benign Tumors invade other tissues they are called Malignant</div><div><br></div>
Question: 18
Define meiosis . Explain its phase
Answer: 18
Crossing over : After the formation of chiasmata the non-sister chromatids of homologous chromosomes exchange their segments and the phenomenon is known as crossing over<div><br></div><div>Process :</div><div>1: Chromosomes condense further the nuclei envelope disappear and nuclear envelope disintegrates</div><div>2: Centrioles which were duplicated during interphase migrate to the two poles and form spindle fibers</div><div>3: The kinetochore spindle fibers attach with kinetochore of chromosomes</div><div>4: Two kinetochore spindle fibers attach with a pair of chromosomes</div><div><br></div><div>Metaphase 1 : The pairs of homologous chromosomes align along equatorial plane forming the metaphase plate</div><div>3: Anaphase 1: kinetochore spindle fibers shorten . It results in pulling apart the chromosomes of each pair .Since one chromosomes is pulled towards one pole , two haploid sets are formed . Each chromosomes still contains a pair of sister chromatids</div><div>4: Telophase 1: Chromosomes arrive at the poles . Each pole now has the number of chromosomes each chromosomes still consists of two chromatids . Spindle network disappears , and nucleus envelope is formed around each haploid set . Chromosomes uncoil back into chromatin</div><div> a) Cytokinesis : The pinching of cell membrane in animal cells or the formation of cell wall in plant cells is called cytokinesis . It occurs and creation of two haploid daughter cells is completed</div><div><br></div>
Question: 19
What is the significance of meiosis ?
Answer: 19
The significance of meiosis for reproduction and inheritance was described 1890 by German biologists August Weismann . He pointed out that meiosis was necessary not only to maintain the number of chromosomes in the next generation but also to produce variations in next generation<div><br></div><div>1: Maintenance of chromosomes number in next generation :</div><div>Meiosis is essential for sexual reproduction</div><div><br></div><div>In humans : Meiosis is essential for sexual reproduction . In human diploid gamete-mother cells or germ line cells undergo repeated mitosis and develops into a new diploid human</div><div><br></div><div>In fungi and protozoans : Many haploid fungi and protozoans produce haploid gametes through mitosis</div><div><br></div>
Question: 20
What happens if errors in meiosis occur?
Answer: 20
During anaphase 1 , homologous chromosomes separate and go to the opposite poles while during anaphase 2 sister chromosomes separate it is called disjunction<div><br></div><div>Example:</div><div>In normal separation 46 chromosomes are present</div><div>Non disjunction :</div><div>Sometimes separation is not normal and it is called non disjunction</div><div>Increasing in number of chromosomes cause abnormality because meiosis results in the production of gametes which have either more or less than the normal number of chromosomes in the next generation</div><div><br></div>
Question: 21
Write note on<div>1: Apoptosis 2: Necrosis</div>
Answer: 21
Apoptosis and Necrosis are two phenomenon of cell death<div></div><div>1:Apoptosis:</div><div>Apoptosis is one of the main types of programmed cell death , and involves a series of biochemical events . This process is controlled by extracellular signals (e.g hormones ) or intracellular signals (e.g good deprivation , viral infection</div>