In: Biology
** Prior, which I forgot to include:
All Vulcans have pointed ears (P) and a right-sided
heart (R) which are dominant over Earthling alleles of
rounded ears (p) and a left-sided heart (r). Both
Vulcans and Earthlings are homozygous for each allele.
Mr. Spock has a Vulcan father and an Earthling mother.
Gametes produced by an individual that are the same as the gametes
contributed by each parent to produce that individual are called
parental types.
Gametes that have a combination of parental and maternal alleles
are called recombinant types.
Recombinant gametes are the result of independent assortment during
Metaphase I if genes are on different chromosomes or crossing over
during prophase I if genes are on the same chromosome.
In which I got the following: PR, PP, pR,Pr
_______
In Vulcans, the absence of adrenal glands (A) is
dominant over the Earthling allele for adrenal glands (a). All
Earthlings have adrenal glands.
A gene map of Mr. Spock shows that the genes for ear shape
(P/p) and heart sidedness (R/r) are 20 map units
apart on chromosome 7 while the gene for adrenal glands
(A/a) is on chromosome 3.
If Mr. Spock fathers a child with an Earthling female, what is the
chance that the child will have pointed ears and adrenal
glands?
Select one:
a. 10%
b. 20%
c. 25%
d. 50%
Can someone please show me how to get the proper answer? I keep getting myself confused on this self-check question, and I don't know where I keep messing up.
Thank you
1) genotype of Mr.Spock is PpRr
parental cross is
genotype of the Vulcan is PPRR and genotype of Earthling is pprr
PPRR * pprr
PR/pr
( P and R alleles comes the Vulcan parent and p and r alleles comes from the Earthling parent so PR and pr gametes produced by Mr.Spock are parental types and Pr and pR gametes are formed by the recombination between the chromosomes in the dihybrid)
gametes produced by Mr.Spock are PR, pr, Pr, pR.
2) considering A locus genotype of Mr.Spock is
PR/pr; A/a ( P and R are on one chromosome and A is on another chromosome)
wife of Mr.Spock is an Earthling so her genotype is pr/pr; a/a
we have to find out the chance that the child will have pointed ears and adrenal glands, so we have to consider only A and P genes, these genes are on different chromosomes ( P on chromosomes 7 and A on chromosome 3 so these genes are not linked)
so the cross is AaPp * aapp
AP | Ap | aP | ap | |
ap | AP/ap ( no adrenal glands, pointed ears) | Ap/ap ( no adrenal glands, rounded ears) | aP/ap ( adrenal glands, pointed ears) | ap/ap (adrenal glands, rounded ears) |
chance of getting child with pointed ears and adrenal glands= (number of children with pointed ears and adrenal glands/total number)*100=(1/4)*100=25%
so the answer is c) 25%