### Description

From the Rhesus phenotype of the father and mother, it is possible to guess the likely genotype and phenotype for their child.

Background

Rh combinations for c/C & d/D & e/E in a gene = (2 * 2 * 2 ) = 8

gene combinations for 2 genes = (8 * 8) = 64 possible

• with duplicates eliminated = 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 36 genotype combinations

for each of the Rhesus antigens:

(1) 10 genotypes are negative for the antigen

(2) 16 genotypes are heterozygous for the antigen

(3) 10 genotypes are homozygous for the antigen

There are 18 phenotypes for these genotypes:

(1) for c, C, e and E: 6 phenotypes are homozygous, 6 are heterozygous and 6 are negative for the antigen

(2) for D: 9 phenotypes are positive and 9 are negative

Most probable genotype (MPG) for given phenotype:

(1) 1 option: 8

(2) 2 options: 5

(3) 3 options: 4

(4) 4 options: 0

(5) 5 options: 0

(6) 6 options: 1

For each Rhesus antigen:

(1) percent heterozygous = percent complement antigen heterozygous

(2) percent negative = percent complement antigen homozygous

(3) percent homozygous = percent complement antigen negative = 100% - (percent homozygous for complementary antigen) - (percent heterozgyous for complementary antigen)

If points are assigned for positive reactions with antisera:

• D: 32 points

• c: 16 points

• C: 8 points

• e: 4 points

• E: 2 points

and summated, values from 10 - 62 can be generated which can be mapped to a phenotype.

Frequency of Rh Genes and Phenotypes in Different Populations

 Gene Asian Black Native American White cde 3% 26% 11% 37% cdE 0% 0% 1% 1% cDe 3% 44% 2% 4% cDE 21% 11% 34% 14% Cde 2% 2% 2% 2% CdE 0% 0% 0% 0% CDe 70% 17% 44% 42% CDE 1% 0% 6% 0% total 100% 100% 100% 100%

Phenotype

Gene 1

Gene 2

Asian

Black

Native American

White

cCDE

cDE

CDE

4.1%

0.07%

cDE

CdE

0.0%

cdE

CDE

0.006%

cCDe

cDe

CDe

4.2%

15.0%

1.8%

2.1%

cDe

Cde

1.8%

0.2%

cde

CDe

4.2%

8.8%

9.7%

31.1%

cCdE

cdE

CdE

0.0%

cCde

cde

Cde

0.12%

0.14%

0.4%

0.7%

cCDeE

cDE

CDe

29.4%

3.7%

29.9%

11.8%

cDE

Cde

0.8%

0.4%

1.4%