Question

Problem 2. In humans, Rh-factor gene and gene responsible for erythrocyte shape are located in the same pair of chromosomes. The distance between them is 3 cM. Rh-positivity and elliptocytosis are dominant traits. Rh-negativity and normal (round) shape of erythrocytes are recessive traits. Prob knee link 10c A man is heterozygous for both characters. He inherited Rh- positivity from his father and elliptocytosis from his mother. His wife is Rh-negative and has normal erythrocytes. Find the ratio of possible genotypes of children in this family. Solving: anc blc ho рг ar Trait allele Elliptocytosis Normal shape of RBCS BR Rh-positivity Rh-negativity A 5 07 r 157 157. A 19 15 485 Rh' Yh incomp

Answer 1

let the alleles be E- elliptocytosis, e- normal, R-Rh-positive, r- Rh-negative.

the man has inherited the Rh-positive allele from father and allele for the elliptocytosis from mother, so her inherited R and e alleles from father and r and E alleles from mother, so his genotype is Re/rE.and the woman has normal RBC and Rh-negative so her genotype is re/re

the parental type gametes he produces are Re, rE, and recombinant type gametes are RE and re.

the distance between genes in cM is the recombination frequency between the genes in percentage.

recombination frequency = ( number of recombinant progenies/total number of progenies)*100

Re/rE * re/re

	RE	Re	rE	re
re	RE/re( recombinant)	Re/re ( parental)	rE/re ( parental type)	re/re ( recombinant)

the progenies formed from the recombinant gametes are recombinant progenies so the percentage of recombinant progenies=3%

each recombinant type progenies are expected in equal proportions, which is 3/2=1.5% each.

the percentage of parental type progenies=100-3=77%

percentage of each parental type progenies=77/2= 38.5%

so the expected genotypic ratio of progenies is

RE/re: Re/re: rE/re: re/re=1.5:38.5:38.5:1.5