in humans red hair and freckles are both autosomal recessive traitswhich are con
ID: 2930 • Letter: I
Question
in humans red hair and freckles are both autosomal recessive traitswhich are controlled by 2 different genes which are linked on thesame chromosome 15 map units from each other.Richard and Bettydon't have red and freckles but Richard's father had freckles andred hair, betty mother had red and no freckles and her father havefreckles and brown hair.none of richard and betty's slibling havered or freckles.richard and berry are interested in knowing the likelihood thattheir first child will have red hair and freackles .what will youtell them?explain
Explanation / Answer
Since the traits are recessive, the reason that Betty andRichard don't have the trait themselves is because they got thedominant gene from the other parent, and the recessive gene fromthe red hair/freckle parent.
For simplicity, let's say f is the gene for freckles, F is thethe no freckles gene, r is the gene for red hair, R is for no redhair.
Betty's mom = rr, FF , Betty's dad = RR, ff so Betty MUST beRr,Ff (she carries both recessive genes, but does not show thetrait since she exhibits the dominance of NO red hair and NOFreckles)
Richard's dad = ff, rr. We don't have info on his mom, but shemust be FF,RR is neither him nor any of his siblings have redhair/freckles. This means that Richard, like Betty, is alsoRr,Ff
Since the genes are linked, 15 map units away from each other(and 1 map unit = 1% recombination frequency), at least 15% of thegametes produced will be recombinant.
Recombinant Gametes are going to be RrFf x RrFf:
RRff, rrFF, RRFF, rrff
So the likelihood of them having a kid with red hair andfreckles is 25% of 15% which .25x.15 which is 0.0375, or about4%
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