I dont understand the answer to this question Watch

Ann_Onymous
Badges: 6
Rep:
?
#1
Report Thread starter 2 years ago
#1
Name:  image.jpg
Views: 49
Size:  498.5 KBThe answer is in red but I dont understand the answer. Can someone explain this to me please?Attachment 587160587162
Attached files
0
reply
AortaStudyMore
Badges: 11
Rep:
?
#2
Report 2 years ago
#2
(Original post by Ann_Onymous)
Name:  image.jpg
Views: 49
Size:  498.5 KBThe answer is in red but I dont understand the answer. Can someone explain this to me please?Attachment 587160587162
Males have to inherit their X chromosome from their mother, they can't inherit it from their father because they inherit the Y chromosome from him. Because the mother is homozygous recessive, the son is 100% going to inherit the X chromosome with the recessive allele, so there is 0% chance that the son can inherit the antigen G allele. I hope that helps? if not let me know what you don't understand and I'll explain it better!
1
reply
macpatgh-Sheldon
Badges: 15
Rep:
?
#3
Report 2 years ago
#3
Basically, this is an example of a condition inherited in a sex-linked recessive manner. In such conditions, an abnormal allele on the X chromosome, is transmitted from the grandfather, via his daughter to his grandson, the daughter being a carrier because in her XX sex chromosome, one X is normal and one carries the abnormal allele.

In the grandfather and the grandson, the Y acts as what is referred to as a "sleeping partner" ie it has no effect on the phenotype; but because the mother and the grandmother in this example had the abnormal G antigen phenotype, they must have been homozygous for the abnormal allele.

One condition inherited in this way is haemophilia, in which there is a deficiency of Factor VIII in the blood clotting mechanism leading to a bleeding tendency. It ran in the ancestors of the British royal family. Because of the explanation above, haemophilia is 8 times more common in men than in women (because females need to have both X chromosomes with the abnormal allele (homozygous), which is of course less likely.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of Roehampton
    Department of Life Sciences; Department of Psychology Undergraduate
    Thu, 21 Feb '19
  • Edge Hill University
    Undergraduate and Postgraduate - Campus Tour Undergraduate
    Thu, 21 Feb '19
  • St George's, University of London
    Postgraduate Open Evening Postgraduate
    Thu, 21 Feb '19

Do unconditional offers make teenagers lazy?

Yes (229)
59.95%
No (153)
40.05%

Watched Threads

View All