Question

1)

When Gregor Mendel conducted his genetic experiments with pea plants, he observed that a trait’s inheritance pattern was the same regardless of whether the trait was inherited from the maternal or paternal parent. Mendel made these observations by carrying out reciprocal crosses: For example, he first crossed a female plant homozygous for yellow seeds with a male plant homozygous for green seeds and then crossed a female plant homozygous for green seeds with a male plant homozygous for yellow seeds.
Unlike Mendel, however, Morgan obtained very different results when he carried out reciprocal crosses involving eye color in his fruit flies. The diagram below shows Morgan’s reciprocal cross: He first crossed a homozygous red-eyed female with a white-eyed male and then crossed a homozygous white-eyed female with a red-eyed male.

Drag the labels to their appropriate locations to complete the Punnett squares for Morgan’s reciprocal cross.

• Drag blue labels onto the blue targets to indicate the genotypes of the parents and offspring.

• Drag pink labels onto the pink targets to indicate the genetic makeup of the gametes (sperm and egg).

Labels can be used once, more than once, or not at all.

Blue label- w+ w+, w+ w,ww, w+Y, wY

Pink label- w, w+, Y

2)

In one of Morgan’s experiments, he crossed his newly discovered white-eyed male with a red-eyed female. (Note that all of the females at that time were homozygous for red eyes because the allele for white eyes had not yet propagated through Morgan’s flies.) All of the F₁ flies produced by this cross (both males and females) had red eyes.

Next, Morgan crossed the red-eyed F₁ males with the red-eyed F₁ females to produce an F₂ generation. Punnett square below shows Morgan’s cross of the F₁ males with the F₁ females.

Drag the labels to their appropriate locations to complete the Punnett square for Morgan’s F₁ x F₁ cross.

• Drag pink labels onto the pink targets to indicate the alleles carried by the gametes (sperm and egg).

• Drag blue labels onto the blue targets to indicate the possible genotypes of the offspring.

Labels can be used once, more than once, or not at all.

Answer 1

Part A

Answer 2

[REMOVED]

Answer 3

[REMOVED]

Answer 4

I am giving the percentage of the progeny produced in both cases analytically please fill in the boxes according to that as I could not understand to thatis to be done.

Morgan’sexperimentswithfruitfliestodemonstrateX-linkedinheritance
Wild type is red
First cross: red-eyed female with white-eyed male
F1:all red-eyed (½ female + ½ male)
In F2:¾ red-eyed(2/3rdfemale + 1/3rdmale) and ¼ white-eyed male

Also considering the other case
Second cross: Morgan performed the reciprocalcross i.e.
mating of white-eyed female with red-eyed male,
He found different results. Although, the F1 progeny were 50% female and 50% male as before but all the female flies were red-eyed and all the males werewhite-eyed. In F2 50% female and 50% male and 50% red eyed and 50% white eyed as well.
Here again the male received the X chromosome carrying the wild type allele from their mother.

Answer 5

1)

a. wY

b. Y

c. w+

d. w+Y

e. w+Y

f. Y

g. w

h. wY

 

Answer 6

Part A.

a. wY

b. Y

c. w+

d. w+Y

e. w+Y

f. Y

g. w

h.wY

Part B.

a. w+

b. w

c. w+w+

d. w+Y

e.w+w

f.wY

Part C.

Case 1

1. 100,0

2. 0,100

Case 2

3. 100,0

4 0, 100

Answer 7

A reciprocal cross is a pair of mating two opposite sexes with two different genotypes in opposite combinations. Reciprocal crosses are used to control paternal factors to influence the inheritance of characteristic. They detect sex-linkage, maternal inheritance, and cytoplasmic inheritance.

For example, a female of genotype A is crossed with a male of genotype B. In reciprocal cross, a female of genotype B is crossed with a male of genotype A.

If the crosses give the same results, for reciprocal cross, the observed phenotypes and proportions are same, for sons and daughters. This can arise when genes are carried on autosomes, not on the sex chromosomes. Hence, in sex-linkage, alterations arise in reciprocal crosses.

White-eye mutation in Drosophila melanogaster

When the white-eyed male is crossed with a red-eyed female, the offspring observed is red-eyed. In addition, when red-eyed male is crossed with a white-eyed female, the male offspring had white eyes, while the female offspring had red eyes. Thus, the reason was that the white eye allele is sex-linked (more specifically, on the X chromosome) and recessive.

Hence, the results has defined that the alleles specifying eye color are carried on the X chromosome.