Multiple Alleles Human, A/B/O Blood group: Alleles for the ABO blood group are l
ID: 68082 • Letter: M
Question
Multiple Alleles
Human, A/B/O Blood group: Alleles for the ABO blood group are located at the locus for the ABO blood group gene. Humans with the allele for blood type A express the “A” cell surface marker on the surface of their red blood cells. Similarly, humans with the allele for blood type B express the “B” cell surface marker. These alleles are codominant, so if an individual has both A and B alleles, both cell surface markers are expressed and that individual has the AB blood type. If an individual has the non-functional gene, O, no cell surface marker protein is produced.
a. Determine the results of a mating between a homozygous A and homozygous B individual.
b. Determine the results of a mating between a homozygous B and an AB individual.
Two Loci
Human Blood Types ABO & Rh+/ Rh-: The Rh locus is a separate locus from that for the ABO blood groups. This gene codes for another histocompatability protein on the cell surface. The gene Rh+ produces the protein and the gene Rh- does not produce a gene.
a. Determine the results of a mating between an individual who is Rh- and is heterozygous for type A with an individual who is Rh- and heterozygous for type B.
b. Determine the results of a mating between an individual who is heterozygous for blood type A and for the Rh factor with an individual who is blood type AB and is Rh negative.
c. Determine the results of a mating between an individual who is heterozygous for blood type A and for the Rh factor with an individual who is blood type AB and heterozygous for the Rh factor.
Sex-Linked Genes
Human, Red-green colorblindness: Red-green colorblindness is an X-linked trait and the normal allele is dominant to the colorblind allele.
a. Earl has normal color vision, while his wife Erma is colorblind. Determine the probability of their children being - Females who are red-green colorblind? Females who are carriers of red-green colorblind? Females who are NOT carriers of red-green colorblind? Males who are red-green colorblind? Males who are NOT red-green colorblind?
b. Mary’s father is red-green colorblind, as is her maternal grandfather (her mother’s father). Mary herself has normal color vision. Mary and her husband, Steve, who is also colorblind, have just had their first child, a son they have named Bill. What is the probability that Bill will be colorblind? Explain your answer.
c. In b above, three sources of the colorblindness allele are mentioned in this family. If Bill is colorblind, from which of these three men (Mary’s grandfather, Mary’s father, or Steve) did he inherit the allele? Explain your answer.
d. In b, above, if Steve were not colorblind, how would this affect the prediction about Bill? Explain your answer. Does the fact that Steve is or is not colorblind, change the chances of their next child, Susan being colorblind?
Explanation / Answer
a. Determine the results of a mating between a homozygous A and homozygous B individual.
b. Determine the results of a mating between a homozygous B and an AB individual.
Ans. Homozygous A mated with homozygous B
AA X BB
Resultant offspring will be AB because it is codominance.
So all the offspring will have AB blood group.
B. cross between AA X AB
the outcome offspring will have AA,AB genotype.
so half of the offspring will be having A blood group and half will have AB blood group.
Two Loci
Human Blood Types ABO & Rh+/ Rh-: The Rh locus is a separate locus from that for the ABO blood groups. This gene codes for another histocompatability protein on the cell surface. The gene Rh+ produces the protein and the gene Rh- does not produce a gene.
Ans. Heterozygous father for A blood group having Rh –ve and mother heterozygous for B
Then for blood group there is possibility of AO x BO
There is 25% possibility of blood group A, B , AB or O after cross.
And for Rh since both the parents are Rh –ve then, must have genotype dd
Dd X dd
This will produce all the offspring as Rh-ve.
So the offspring having blood group A, B, Ab and O will be Rh –ve.
Ans. In this case the blood group of parents is
AO X AB
Resultant offspring will be
AA,AO, AB or BO.
Therefore 50% A, 25% B and AB.
For Rh the Rh positive can have genotype DD or Dd and the Rh –ve will have dd genotype.
So cross between
DD X dd will produce 100% Dd children which are Rh +ve
And the cross between Dd and dd
Will produce 50% Dd and 50% dd.
Therefore 50% offspring will be Rh –ve.
Ans. AO X AB
Will produce 50% A blood group as in previous question.
25% each AB and B.
Dd X Dd
In this case the genotype obtained will be DD,Dd,Dd and dd.
So 75% will be Rh +ve and 25% will be Rh-ve.
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