Question

An organism is heterozygous at three genetic loci (Aa, Bb and Cc) located on different chromosomes. Explain how these alleles are transmitted by the process of A) mitosis to daughter cells, and B) meiosis to gametes Show the final genetic composition of the daughter cells or gametes with respect to these loci? C. How many different allelic combinations are possible with 8 heterozygous loci on 8 different chromosomes?

Answer 1

A, B and C are three different loci present three different chromosomes

A) mitosis is equational division because daughter and parent cells have the same number of chromosomes.

For each chromosome, there is a homologous chromosome two different alleles of the gene are present in 2 different homologous chromosomes after mitosis daughter cells have the same number of chromosomes as the parent cell to daughter cell will have all alleles A, a at locus A and B, b at B locus and C, c at C locus.

B) in meiosis I recombination happens between homologous chromosomes since these genes are present in three different chromosomes recombination will not affect allelic distribution in the gametes after meiosis I homologous chromosomes will be separated so 2 daughter cell which is formed can get homologous chromosomes with any allele and after meiosis II sister chromatids are separated to for four gametes so gametes have only one allele of each locus, there 3 heterozygous loci so 2^3=8 gametes are possible

4) there are 8 heterozygous loci so 2^8 different allelic combinations are the possible 2^8=256 number of different allelic combinations= 2^ number of heterozygous loci.