A plant of genotype A B a b is testcrossed with a b a b

step 1 A plant with genotype capital A small A, capital B, small B is test crossed with small A, small

A plant of genotype A B a b is...

A plant of genotype $$\begin{array}{cc} A & B \\\hline \hline a & b\end{array}$$ is testcrossed with $$\begin{array}{cc}a & b \\\hline \hline a & b\end{array}$$ If the two loci are 10 m.u. apart, what proportion of progeny will be $A B / a b ?$

Key Concepts

Testcross Analysis

A testcross involves crossing an individual of unknown genotype with a homozygous recessive partner for the traits of interest. This cross reveals the genotype of the individual being tested by analyzing the phenotypic ratios of the progeny. It's a fundamental tool in classical genetics for determining gene arrangement and allele segregation.

Linkage and Recombination

Linked genes are located close to each other on the same chromosome and tend to be inherited together. However, during meiosis, crossing over can occur between closely linked alleles, producing recombinant gametes. The frequency of these recombinations, measured as map units or centimorgans, reflects the physical distance between the genes.

Genetic Map Units (m.u.)

A genetic map unit, or centimorgan, represents a 1% chance of recombination between two loci. When loci are 10 m.u. apart, it implies that recombination occurs between them 10% of the time. This metric is central to predicting the proportions of parental and recombinant gametes in a cross involving linked genes.

Parental and Recombinant Gamete Production

For a heterozygote with two linked loci arranged in coupling (where one chromosome carries both dominant alleles and the other both recessive alleles), the non?recombinant (parental) gametes are produced with a frequency of (1 – recombination frequency)/2 each. In a testcross where the tester is homozygous recessive, the genotype of the progeny directly reflects the gametes produced by the heterozygote. The proportions of these gametes determine the observed progeny ratios.

Please give Ace some feedback