Genetics and Plant Breeding

Incomplete dominance is a type of inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a combined phenotype (expressed physical trait). For example, if you cross pollinate red and white snapdragon plants, the dominant allele that produces the red color is not completely dominant over the recessive allele that produces the white color. The resulting offspring are pink.

Epistasis is an interaction between genotypes at two different gene loci, which sometimes resembles a dominance interaction at a single locus. Epistasis modifies the characteristic 9:3:3:1 ratio expected for two non-epistatic genes.

In case of autosomal dominant trait both the sexes are equally affected. Some autosomal dominant genes are preferentially expressed in one sex such as gout and pre-senile baldness affecting male.

This leads to variations in the population. Through the maternal gametes (ova) and paternal gametes (sperms), hereditary traits (characters) are passed on to child from parents. Genes are linearly arranged in chromosomes which are the carriers of hereditary traits. With the crossing over of two parental chromosome segments, a child inherits some of the traits from the mother and some from the father. This is why; two children from the same parents resemble each other in some characters and differ in others.

Heredity can be defined as the transmission of physical and mental characteristics from parents to offsprings. These characteristics can be called traits. These traits thus are transmitted from one generation to the next.

Linkage group is equal to haploid set of chromosome, but since in male there is Y chromosome, so total linkage group will be 23 + 1 = 24.

2n = 6x = 42 Therefore 42 / 6 = 7. Thus 7 linkage group.

The most prevalent type of consanguineous marriage, show that the excess risk for their offspring of having a significant birth defect ranges from 1.7-2.8%.

A homozygous genotype refers to the inheritance of the same allele for a trait from both parents.

According to Mendel's law of independent assortment, this cross shows the progeny in the phenotypic ratio of 9 : 3 : 3 : 1. This is the law related to dihybrid cross.

The 1 : 2 : 1 ratio is the result of a monohybrid cross between two heterozygous parents.

The ratio obtained by selfing is 9 : 3 : 3 : 1. The genotype RrTt would be present as 1.

Correct Answer: It worked on garden pea

The traits which are focussed for crossbreeding programmes are dwarf broiler parent and reduction in size of egg laying bird.

Hereditary traits are determined by specific genes.