The Only Prep You Need

Chapter 15: Genetics

Chapter 15: Genetics

Postby admin » Fri Aug 27, 2010 1:11 am

Be the first to discuss this chapter!
admin
 
Posts: 1065
Joined: Tue Jun 29, 2010 7:47 pm

Re: Chapter 15: Genetics

Postby ElleRT » Tue Sep 01, 2015 1:59 am

For Q.11

I understand how the mum is RrTt and dad rrtt
And so the child must have half the dad (rt) but from the mum couldn't the kid get RT or Rt? Or would both have to be dominant?
ElleRT
 
Posts: 55
Joined: Thu Jul 09, 2015 4:50 am

Re: Chapter 15: Genetics

Postby goldstanda3269 » Wed Sep 02, 2015 7:24 am

"And so the child must have half the dad (rt) but from the mum couldn't the kid get RT or Rt? "
- Randomly, yes, but the question gave this clue: " Suppose the Rh gene is linked to a hypothetical monofactorial, dominant gene for trait T". So the question is telling us that R is linked to T so in this situation, we have no choice.
goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm

Re: Chapter 15: Genetics

Postby goldstanda3269 » Sat Sep 12, 2015 9:58 pm

ilbe wrote:Queries with regards to Rh factors

I reorganised my queries.

1.
a.Rh+ has Rh antibody or not? My reasoning is yes as RBC has Rh antigen thus plasma will make antibody. But if so, this people will die as antibody will attack RBCs.
As far as I understand the immune system, if antigen exist, plasma will make antibody and attack it. Then why is this case different?


Rh+ does not have the Rh antibody.

If a FOREIGN antigen exists, then the body creates an antibody to destroy it. As long as the body is not diseased, it should not create antibodies against itself.


ilbe wrote:b. Rh- does not have Rh antibody as RBC does not antigen on it. Am I right?


Correct.

As explained in BIO 15.2 and the Genetics videos, Rh becomes a problem when Rh- pregnant women are exposed to Rh+ pregnancies.


ilbe wrote:c. if Rh- blood transfused to Rh+ person, then Rh- plasma will make antibody against Rh+ ! and will attack Rh+ RBC. Therefore it can't be a donor.
Am I wright??


Incorrect. As suggested above and in the book, Rh- has no antibodies unless first exposed to Rh+ blood.

ilbe wrote:d. What is blood transfusion? maybe it means 'only' RBC transfusion rather than 'whole blood' including plasama producing antibody?


As described in the Genetics videos, blood transfusion only involves RBCs and not plasma. This knowledge is interesting, but not required for GAMSAT (i.e. it would be provided in the passage if required).
goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm

Re: Chapter 15: Genetics

Postby goldstanda3269 » Fri Sep 18, 2015 8:12 pm

ilbe wrote:1. With this, Can I make a decision that Rh- blood does't have Rh antibody? and it is different from ABO blood type as they have already A, B, non antibody?


Correct, Rh is "different from ABO blood type" but actually Rh is normal for the immune system, meaning that exposure is required in order to develop antibodies. This is discussed in the Genetics videos.
goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm

Re: Chapter 15: Genetics

Postby goldstanda3269 » Tue Oct 06, 2015 8:17 am

goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm

Re: Chapter 15: Genetics -Q4

Postby zimengy17106 » Tue Feb 16, 2021 10:15 pm

I have a question with Q4.

If the disease is predominant in women than in men. Is it still possible that the disease can be X-linked dominant inheritance?

The answer is it can't be x-linked because if so, there would be more male patients than female patients, but this is based on the assumption that this is X-linked recessive?
zimengy17106
 
Posts: 11
Joined: Thu Feb 04, 2021 7:45 pm

Re: Chapter 15: Genetics -Q4

Postby goldstanda3269 » Wed Feb 17, 2021 6:29 am

zimengy17106 wrote:I have a question with Q4.

If the disease is predominant in women than in men. Is it still possible that the disease can be X-linked dominant inheritance?

The answer is it can't be x-linked because if so, there would be more male patients than female patients, but this is based on the assumption that this is X-linked recessive?


Good point, but not really. There are 3 possibilities for ***** genetic disease (apologies, but our forum automatically censors suggestive words!!):

1) Y-linked: very rare because there are fewer genes on the Y-chromosome. Obviously, only males get the condition.

2) X-linked recessive: Virtually all men get the disease because they do not have a second X, and potentially, normal chromosome. Women get the disease more rarely because they require 2 abnormal ***** chromosomes in order to express the condition.

3) X-linked dominant: Which means that 50% of males and 50% of females would acquire the condition. However, we were told that women are "overwhelmingly" more likely to contract thyroid disease. Such a statement is not consistent with any form of ***** genetic disease.
goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm

Re: Chapter 15: Genetics

Postby zimengy17106 » Wed Feb 17, 2021 7:23 am

Thanks,

But for X linked dominant disease the XBXB XBXb are affected, only XbXb not affected. So the prevalence in women should be higher than 50%?
zimengy17106
 
Posts: 11
Joined: Thu Feb 04, 2021 7:45 pm

Re: Chapter 15: Genetics

Postby goldstanda3269 » Wed Feb 17, 2021 1:15 pm

Now we are almost talking about unicorns.

First, X-linked recessive is far more likely. Second, you are suggesting that among extremely rare genetic disorders, we must take into account a male expressing the disease XB Y mating with a female expressing the disease XB XB or XB Xb producing an "overwhelming" greater number of females in a population of 10 million souls expressing the condition. On many grounds, this is thoroughly impossible.

Among this very rare genetic condition, it is more likely for a woman to receive an XB chromosome, it is more likely that her mate does not have XB, and it is more likely that 50% of the sons or daughters express the condition.

"In X-linked dominant inheritance, a son or daughter born to an affected mother and an unaffected father both have a 50% chance of being affected "
https://en.wikipedia.org/wiki/*****
goldstanda3269
 
Posts: 1719
Joined: Wed Aug 25, 2010 10:59 pm


Return to Masters Series GAMSAT Section 3 Biology

Who is online

Users browsing this forum: No registered users and 1 guest

cron