# Genetic revision watch

1. Hi guys,

I know its the day before the exam, but, wanting to just fine tune my knowledge base.

I am a little shaky on genetic disorders and inheritance.

I chose D; 25%.

I thought, the father was H h and the mother h h.

But if she is h h; and the disorder is dominant, then wouldnt that mean there would need to be HH together? Using the genotype of father as H h and mother as h h, I get Hh Hh, hh, hh. Is that why the answer is 50%?
Attached Images

2. The father is Hh and the mother is hh
This means it is 50%
H x h = Hh
H x h = Hh
h x h = hh
h x h = hh

Posted from TSR Mobile
3. (Original post by SaffSmith)
The father is Hh and the mother is hh
This means it is 50%
H x h = Hh
H x h = Hh
h x h = hh
h x h = hh

Posted from TSR Mobile
I thought this was a dominant disorder, so the two dominant alleles would have to be present together; as in HH.

You got the same results as me it seems, but Im a little confused as to how to properly interpet them. I am leaning towards that it is the Hh Hh; given that is dominant and the hh is the genotype of a non-sufferer of the condition. Is my thinking correct?
4. (Original post by apronedsamurai)
I thought this was a dominant disorder, so the two dominant alleles would have to be present together; as in HH.

You got the same results as me it seems, but Im a little confused as to how to properly interpet them. I am leaning towards that it is the Hh Hh; given that is dominant and the hh is the genotype of a non-sufferer of the condition. Is my thinking correct?
If it's dominant only one H needs to be present.

So: Hh hH all result in huntingtons for that question

So Yh 50%
5. (Original post by Nucleotide)
If it's dominant only one H needs to be present.

So: Hh hH all result in huntingtons for that question

So Yh 50%
Ok, stuck with this question,

Sex linked condititon, carrier female; (must be heterozygous) so H h

Male is un affected (must be homozygous dominant) HH

HxH=HH
H x H=HH
Hxh =Hh
Hxh=Hh

Attached Images

6. (Original post by apronedsamurai)
I thought this was a dominant disorder, so the two dominant alleles would have to be present together; as in HH.

You got the same results as me it seems, but Im a little confused as to how to properly interpet them. I am leaning towards that it is the Hh Hh; given that is dominant and the hh is the genotype of a non-sufferer of the condition. Is my thinking correct?

It is a dominant condition so is cause by a dominant allele which is the D.
A dominant allele makes the phenotype whenever it is present i.e it doesn't not have to be DD, whenever a D is present in the phenotype that will control the phenotype.

I hope this is a bit clearer xx

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 13, 2015
Today on TSR

### A level Maths discussions

Find out how you've done here

### 1,445

students online now

Exam discussions

### Find your exam discussion here

Poll
Useful resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE