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...."ruby" colored eyes instead of red.

Red Eyes (male)77 (female)151
"Ruby Eyes" (male)75 (female) 0

a) Are the ruby eyes recessive or dominant?

b) How do the results of the cross indicate that ruby eye color is sex linked?

c) Using x^R for the dominant allele and x^r for the recessive allele, write the genotyps of the two parents.

d) Do the female offspring all have the genotype? List all the likely genotypes of female offspring.

e) List the genotype of the red eyed males and ruby eyed males.

2007-03-13 20:48:37 · 3 answers · asked by Anonymous in Science & Mathematics Biology

3 answers

a) ignoring the sexes, ruby eyes ended up being about 1/4 of the offspring, so immediately you start thinking that it's recessive, and you might have something like a Rr x Rr cross (because it gives 3/4 dominant phenotype, 1/4 recessive). Answer: recessive
b) of the males, about 1/2 have red eyes, and 1/2 have ruby eyes, whereas, of the the females, all have red eyes. There has to be some sex-linkage here to get such vastly different proportions between the sexes.
c)X^RX^r (mother) x X^RY (father) [note: a common mistake is to forget that the father only has one X chromosome!]
d) No. If you do the cross, you will see that about 1/2 of the females will be X^RX^R and the other half will be X^RX^r.
e) Red eyed males: X^RY
Ruby eyed males: X^rY

2007-03-13 21:59:13 · answer #1 · answered by SteveK 5 · 0 0

First you have to look at the ratios present. Notice that the ruby males and red males are split about 50-50 and the females and males are split 50-50.
a) ruby eyes are recessive because none of the females have them.
b) The ruby eye color is sex linked because they are not present in females and are present in half the males.
c) the male must be x^R Y so all the females are dominant (sex is determined by the males because the female must have an x from the father) and the female must be x^R x^r so that the males have a 50-50 chance of getting either.
d) the female offspring are split half and half between the following genotypes because they have a 50-50 chance of inheriting either of the x's from the mother:
x^r x^r
x^R x^r
e) red eyed males are
x^R Y
ruby eyed males are
x^r Y
since they must have a y chromosome.

hope this helps :)

2007-03-13 21:53:13 · answer #2 · answered by birdie6089 3 · 0 0

In those particular alleles, the crimson eye function might have an allele of RR, or Rr (while you evaluate that's dominant) A capital R represents the crimson eyes gene at the same time as the little r represents a white eyed gene. using fact white eyes are recessive, a fly with white eyed features ought to have the allele rr. right this is the way you utilize a punnett sq.. this occasion shows 2 white eyed flies producing offspring. The sq. below shows the white eyed gene crossing over. determine Gene (allele rr) r r determine Gene (allele rr) r rr rr (forget approximately approximately this writing) r rr rr the unmarried letters above teach the genetic alleles of the determine alleles. The double letters teach all the obtainable outcomes (4 outcomes) that ought to happen. this provides a one hundred% probability of the allele rr, hence the only obtainable effect is a white eyed fly. this is confusing to be certain the punnett sq. above (formatting screws it up. seem up 'punnett sq.' there will be many pictures that provide examples).

2016-11-25 19:08:38 · answer #3 · answered by Anonymous · 0 0

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