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geri0108 geri0108
wrote...
Posts: 47
Rep: 3 0
9 years ago
 ( I don't know how to copy the table but this is the questions, if somebody can make a picture with the answers I would appreciated )Part C Experimental prediction: Comparing autosomal and sex-linked inheritance
You now know that inheritance of eye color in fruit flies is sex-linked: The gene encoding eye color is located on the X chromosome, and there is no corresponding gene on the Y chromosome.

How would the inheritance pattern differ if the gene for eye color were instead located on an autosome (a non-sex chromosome)? Recall that for autosomes, both chromosomes of a homologous pair carry the same genes in the same locations.
Suppose that a geneticist crossed a large number of white-eyed females with red-eyed males. 
Consider two separate cases:
•Case 1: Eye color exhibits sex-linked inheritance.
•Case 2: Eye color exhibits autosomal (non-sex-linked) inheritance. (Note: In this case, assume that the red-eyed males are homozygous.)
For each case, predict how many of the male and female offspring would have red eyes and white eyes.

Drag the correct numbers on the left to complete the sentences on the right. Numbers can be used once, more than once, or not at all.
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Answer rejected by topic starter
wrote...
Staff Member
Educator
9 years ago
1 Eye color exhibits sex linked inheritance
-100 Fm osp,100 red eyes + 0 white
- 0 male osp 0 red eyes+ 100 white
-100 female Osp 100 red eyes+ 0white
-100Male osp 100 red eyes+0 white
rmckay13,  kimnguyen,  RaulRDos2,  chedautrang,  taylorprough
Mastering in Nutritional Biology
Tralalalala Slight Smile
wrote...
9 years ago
Case 1
1)100,0
2)0,100

Case 2
White is recessive
A a
A AA Aa
a Aa aa
3)0,100 (since female white eyed only recessive homozygous present)
4)75,25 (Normal case)
My answers are based on this explanation
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 were white-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.
mgspec,  leahdevito
Answer accepted by topic starter
doubleudoubleu
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Posts: 439
9 years ago
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wrote...
9 years ago
Sex-linked inheritance:

Morgan performed experiments with Drosophila melanogaster (fruit flies). Fruit flies have the same sex chromosome pattern as humans. On crossing white eyed male with red eyed female, leads to red eyes that are dominant over the white eyes. The crossing over leads to F2 generation, where 3 red-eyed: 1-white eyed ratio. He thought that all white eyed flies were males because male and female flies are differentiated just because of their sex chromosomes. Usually females have red eyes and they don%u2019t have Y chromosomes. The X-linked alleles have autosomes because Y chromosome is lacking, for these alleles, and it cannot offset the inheritance of an X-linked recessive allele.

Hence, male always receive X-linked recessive allele from female parent and sex linked recessive traits appear much more frequently in males than in females. The allele key, for X-linked gene shows an allele attached to the X. XR is red eyes and Xr is white eyes.

The possible genotypes in male and females are shown in below table.

XR XR -- Red eyed female

XR Xr -- Red eyed female

Xr Xr -- White eyed female

XR Y -- Red eyed male

Xr Y -- White eyed male

Therefore, the possible genotypes are three females and only two males. Females can be heterozygous XR Xr, they are carriers. They are having ability to pass on a recessive allele, for an abnormal condition. Males cannot be carriers, for X-linked traits because the dominant allele is on the single X chromosome. They show the dominant phenotype and vice versa, for recessive phenotype. Hence, males are considered as hemizygous, for X-linked traits.

Likewise, when a cross between brown-haired female represented as XB and black haired male is Xb. In the F1 hybrid, all male offspring have brown hair and all female offspring have black hair. Thus, the genotypes of all the individuals involved mother Xb Xb.; father XBY; female off springs are XB Xb., and males are Xb.Y.

Autosomal

Autosomal chromosomes recombine with meiosis, whereas Y chromosomes do not recombine and remains intact as it is passed from the father to the son. So, it is called lineage marker. It preserves simpler record of the history.

A couple carries four copies of each autosome, three X chromosomes, and only one Y chromosome. The effective population size of the Y chromosome is 1/4 that of autosome, 1/3 of the X chromosome and similar to mitochondrial DNA. There is lower sequence diversity in Y chromosome. It is more susceptible to genetic drift.
dfgd
geri0108 Author
wrote...
9 years ago
Thanks a lot !
Answer rejected by topic starter
wrote...
Staff Member
Educator
9 years ago
Can you mark the correct response as solved?
noobfish
Mastering in Nutritional Biology
Tralalalala Slight Smile
wrote...
9 years ago
Thank you so much for this post because I needed help on this too
wrote...
9 years ago
Thank you so much. It was a great help!
wrote...
9 years ago
thanks so much!
wrote...
9 years ago
Thank You!!!!!
wrote...
9 years ago
Does this help? Face with Open Mouth Face with Open Mouth

Thank you!
wrote...
9 years ago
Thank you
wrote...
9 years ago
thank you
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