AP BIOLOGY

Detailed explanation-1: -A two-point test cross is done to calculate the recombination frequency of two linked genes. It is useful for determining the frequency of gametes produced. If there is a deviation from the classical Mendelian ratio, then we know that the two genes are linked and present on the same chromosome.

Detailed explanation-2: -The # of recombinant offspring / total # of offspring x 100% = recombination frequency.

Detailed explanation-3: -The term used for crossing over is recombination. Recombination can occur between any two genes on a chromosome, the amount of crossing over is a function of how close the genes are to each other on the chromosome.

Detailed explanation-4: -The heterozygous parent with the dominant phenotype, if the genes showed independent assortment, should make four gametes AB, Ab, aB and ab in equal frequencies. Linkage will be detected if there are more testcross progeny who got the parental gametes from the dominant individual that you would expect by chance alone.

Detailed explanation-5: -The test cross is another fundamental tool devised by Gregor Mendel. In its simplest form, a test cross is an experimental cross of an individual organism of dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype (and phenotype).