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In 1953 James waston and Francis crick proposed the structure for DNA According to the waston crick model a DNA molecule consist of two polynucleotide stromds these strands are coiled around each other in the form of double helix there is a phosphate sugar back bone on the outside of double are on the inside .In double helix the nitrogen bonds bases of opposite. Nucleotides from through hydrogen bonds this pairing is very specific the nitrogenous base adenine of opposite/ apposing nucleotide. While cytosine forms pair of with guanine these are two hydrogen between adenine and thymine. While there are three hydrogen bonds between iytasine and guanine.
DNA is the genetic material it contain the instruction to direct all the function of cells it perform its sole by giving instruction for the synthesis of specific proteins some protein perform structural rates white the other act as enzymes to control all biochemical reaction of cells. In this way whatever a cell does is actually controlled by its DNA.In other words the characteristic or trait of cell or organism DNA control the this sequences of its amino acids by the sequences of its nucleatides.During protein synthesis the sequences of DNA nucleotides decide that what will be the sequence of amino acid the specific sequence of DNA nucleotides is capied in the form of messenger RNA nucleotides this process is called tromscription.The ribosome’s this sequence and joint specific amino acid according to it to form this step is known as tromslation.The part of DNA that contain the instruction for the synthesis of a particular protein is known as a gene.DNA each chromosome contain thousands of gene like gene also occur in pairs one on each homologous chromosomes the location of position of gene or chromosome are known as loci.
The main source of variation in sexually reproducing population is the genetic recombination produce through crossing over result in gametes with variations. Mutation is important source of variation. Mutations also happen during gametes formation through meiosis during fertilization one ofvthe million of sperms combine with a single egg.The chomce involved in this combination also act as the source at variation. Gene flow movement of gene from once population to another is also an important source of variation.
Model studied two contrasting trait at a time such cresses are called dihybird crosses he performed experiment on two seed traits shape and colourThe trait of raind seeds was dominonit over wrinkled seeds similarly yellow seeds colour was desminant over green model crossing a true bleeding plant that had raind yellow seeds with a true bleeding plant having wrinkled green seeds.All seed in Fi generation were ramd yellow when Fi seed grew into plants they were self-fertilized.This craes produced seed with four phenotypes there were 315 raimd yellow seed 108 raimd green seed 101 wrikled yellow seeds and 32 wrinkled green seed. The ratio of these phenotypes was model explain the two traite seed colour are not tide with each other. The segregation of R and alleles happen independently of the segregation of Y and alleles. Form his second experiment model included that different traits are inherited independently of one another .This principle is known as the law of independently assortment.
The term artificial selection was expressed by the pension scientist Abu Ryham Biruni in the 11th century Charles Darwin also used this term in his work or natural selection. He noted that many domestics’ cated animal and plants has special properties that were developed by intentional breeding among individuals and plants had special properties with desirable characteristic discouraging the breeding of individual with less desirable characteristics. Artificial selection means intentional breeding between individual selecting for certain traits of combination of traits. Selective breeding have revolutionized agriculture and livestock production throughout the world .Animals or plants having desirable characteristic are selected for breeding .In this way many new generation with desire able characteristic are produced .In artificial animals are known as breeds while bred plant are known as breeds, while bred plants are known varieties or cultivates numerous breed of sheep goat cow have been produced by artificial selection to increase the production of wood milk meat egg etc.
Similarly many plants varieties have been produced for better quantity and quality of careals, fruit and vegetables.
The specific combination of genes is an individual is known genotype it is of two types, homozygous and heterozygous. In order to understand the concept of genotype let us consider on example trait, albinism like other trait. It is also controlled by one pair of genes we can represent the two om alleles of the pair as .A and a three combination genotypes are possible for these two alleles AA and (aa).These genotypes can be grouped into two types. The genotypes in which the gene pair contains two identical alleles is homozygous genotypes. The genotype in which the gone pair contain two different alleles is called heterozygous genotype.
Genetic is the branch at biology in which we study inheritance.
Inheritance mean transmission of characteristics from parents to off spring.
Unit of heritance consist of the length of DNA that contains specific instruction for the synthesis of a protein molecule.
The process in which organisms with fevourable variations survie and produce more off spring then less well adapted organisms.
Orgamic evolution biological evolution is the change in the characteristic of a population species of organisms over the causes of generations.
When the gometes of male and female parents units the resulting off spring agains gets the genes in pair these conclusion were called the law of segregation.
The alternative form of a gone, dominant the trait that qppears in the off spring of a tross between two harmony gous individuals showing contracting forms of the trait.
Plural locis the location or position of genes on chromosomes.
The specific combination of genes in on individuals may be harmozygous and heterozygous.
A pair of chromosomes having the same size and shape and carrying alleles for the some traits.
The DNA double helix is unwound and two stomacts are separated much like the two sides of a zipper.
The DNA double helix I unwound and two stromds are separated much like the two sides of a zippers.
Selective breeding intentional breeding between individuals for certain traits or combinations of trecits.
A characteristic is an individuals that differs from the typical characteristics of other individuals of the some species.
It perform its role by giving instructions for the synthesis of specific protein some protein perform structural roles while the other act as enzymes to control all biochemical reactions of cells.
Model studied two contrasting traits at a time such crosses are called dihybird crosses he performed experiment on two seed traits shops and colour.
The solution of a agene pair express their trait independently instead of showing a dominanat recessive relationship.
The contievolution ideas all living things had been treated in their current form only a few thousand year ago it is known as the theory of special creation.
The genetype in which the gene pairs contains two indentical allele is called homozygous genetype.
The genotype in which the gene peciris contains two different alleles is called heterozygous genetype.
The specific requence of DNA nucleotides is capid in the form of messenger RNA nucleotides this process is called transpiration.
The ribesomes reads this sequence and joins specific amino acid according to it from protein this steps is form protein this steps is form as translation.
The specific combination of genes in an individuals may be homozygous or heterozygous
The expression of the genetype in the form of trait.
A genetic cross in which only one pair of contrasting traits is studied.
A genetic cross in which two pairs of contrasting traits are studied.
The situation where two allele of a gene pair express their traits independently instead of showing a dominant recessive realationship
A type of inheritance in which neither of the pair of contrasting allele is dominant over the other and the heterozygous individuals intermediate in phenotype.
Discontinuous variation show distinct phenotype the phenotypes of such variation cannot be measured.
In continuous variation the phenotypes show a complete range of measurement form one extreme to the other height, weight feet size.
The characteristics which are controlled and transmission to next generation through genes