Two genes 'A'and 'BA' are linked. In a dihybrid cross...

Two genes 'A'and 'BA' are linked. In a dihybrid cross involving these two genes, the $\mathrm{F}_{1}$ heterozygote is crossed with homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation? (a) $1: 1: 1: 1$ (b) $9: 3: 3: 1$ (c) $3: 1$ (d) $1: 1$

Two genes 'A'and 'BA' are linked. In a dihybrid cross involving these two genes, the $\mathrm{F}_{1}$ heterozygote is crossed with homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation?
(a) $1: 1: 1: 1$
(b) $9: 3: 3: 1$
(c) $3: 1$
(d) $1: 1$

Key Concepts

Linked Genes

Linked genes are genes that are located close together on the same chromosome and tend to be inherited together because they do not segregate independently during meiosis. Their physical proximity reduces the likelihood of a crossover event separating them, which can result in offspring genotypes that reflect the parental combinations more frequently than recombinant types.

Testcross

A testcross involves crossing an individual with a dominant phenotype but unknown genotype with an individual that is homozygous recessive. This cross helps reveal the genotype of the dominant phenotype parent by analyzing the phenotypic ratios of the offspring, particularly useful in understanding inheritance when genes are linked.

Recombination

Recombination is the process by which genetic material is exchanged between homologous chromosomes during meiosis, resulting in new allele combinations. In linked genes, recombination can occasionally separate alleles that were originally inherited together, and the frequency of these events can be used to map gene distances on a chromosome.

Dihybrid Cross

A dihybrid cross examines the inheritance of two distinct traits simultaneously. When the genes governing these traits are linked, the typical 9:3:3:1 ratio seen in independent assortment is modified due to the reduced segregation of linked alleles, making it vital to consider linkage and recombination in predicting offspring ratios.

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