Saved Bookmarks
| 1. |
Question : Very briefly explian the following : (i) Alleles (ii) Dominanet/recessive (iii) Homozygous (iv) Test cross(v) Back cross (vi) Pleiotropy (vii) Test cross (v) Backcrosss Pleiotropy (vii) Multiple alleles (viii) Incomplete (ix) Espistasisis/hypostaisis(x) Genotype (xi) Linkage (xii) Sex limited caracters (xiii) Sex-iunfluenced traits (xiv) Chromosome aberrations (xv) Gene mutation. |
|
Answer» Solution :(i) There are two alternative forms of a gene for each character, one controlling each of its two contrasting same loci in the homologous chromosomes are called alleles. (ii) An allele that influnces the appearance of the phenotype even in the presence of an alternative allele is called dominant. The alternative allele is called dominant. The alternative allele is called recessive. (iii) When the two allels of a gene are similar ans so two copies of thesame allele exists, they aresaid to be in homozygous combinatin. When the two alleles in apir are eidfferent they are in heterozygous state. (IV) Is is cross between a hybrid organism of an unknown genotype and a homozygous recesive organism. (v) A genetic cross btween a hybride organism and one of the original parental types is called a back cross (vi) the multiple effect of a gene is called pleiotropy. (viii) More than two alternativeforms (alleles) of a gene is aa popluataion occupying the same locus on a chromosome or its homologue are known as multpile alleles. (viii) The expression of the traits of two pure PARENTS as an intermediate CONDITION or fine mixturein `F_(1)` hybrids is known as incomplete dominance. (xi) A pair of genes at one locus may prevent the expression of a poir of genes at another locus. Such genes are called epistatic gnes. The prevention of the expression of one paor genes by another pair of genes is called epsitasis. The expresionow whichis prevented by epistatic genes are callled hypostatic genes and the phenomenon as hypostasis. (x) Genotype of an indivdual refers to the sum total of genes INHERITED from both the parents irrespective of whether they are expressed or not. (xi) The tendency of the gens present in the same chromosome to stay together in hereditary transmission is known as linkage. (xii) Certain genesproduce characters in one se only. but not in both even though they are present in both the sexes. Such characters ar called sex-limited charactes. (xiii) The autosomal traits in which the dominant expression depends on the sex hormones of the individuals are caleld sex-influenced traists. (xiv) Chrosomal alteration are often called chrosomalaberrations. These mutations affect large portions of the chromosomes and are observable under a mircoscope. They may involve a modificationin the morphology of the chromosomes or a change inthe number of chromosomes. (xv) Itis a sudden, stable, inheritable alternative in the base sequence of a gene capable of changing the phenotype of an organism |
|