# Genetics Problem

1. Oct 29, 2005

### jena

My Question:
• What is the mechanism of inheritance for the trait?
• Which people in the pedigree are known to be heterozygous for the trait?
• What is the probability that III-2 is a carrier( heterozygous)?
• If III-3 and III-4 marry, what is the probability that their first child will have the trait?

Picture

View attachment Doc3.doc View attachment Doc3.doc

• I1, I2, II1, and II2
• ???
• ???
Of the answers I have so far are these correct?
Thank You

2. Oct 30, 2005

### Moonbear

Staff Emeritus
Are you using the usual convention that males are represented by squares and females by circles? If so, how would it be Y-linked if only females are affected? If you reconsider part 1, the rest will be easier to answer once you've gotten that part.

3. Oct 30, 2005

### jena

Opps
Wouldn't it be X-linked recessive since it couldn't be x-linked dominant otherwise one of the parents would of had it, right?

Also for these questions:

What is the probability that III-2 is a carrier( heterozygous)?

If III-3 and III-4 marry, what is the probability that their first child will have the trait?

Do I just need to figure them by making a punnett square based off the parents?

Thank You

Last edited: Oct 30, 2005
4. Oct 30, 2005

### Moonbear

Staff Emeritus
Correct.

With that information, you also have to go back to your answer for the second part.

Correct.

Yes and yes. I think you're getting the hang of this.

5. Nov 1, 2005

### Dr.Brain

• After meosis , when male and female gametes are fused , each gamete consists of a single gene. When two gamete fuse , they give genotypes which are combinations of alleles. Depending on the nature of the alleles , the phenotypes are formed. This phenotype when expressed shows the particular trait in the individual.

People heterozygous for trait are those whose genotype for that particular trait has two alleles each of different type.

Draw the punnett table and see for yourself.

BJ

6. Oct 17, 2007

### cmantzioros

I had a similar question, but what would the punnett square look like? Say A = dominant allele and a = recessive allele, then II1: Aa, II2: Aa (parents of III3) and II3: aa, II4: ? (parents of III4)

Would II4 be homozygous dominant (AA) since none of the children have it?

My question also asks to determine the probability using "the law of probability that relates to the simultaneous occurrence of independent events—the product law". I'm unsure of what this means...

7. Oct 17, 2007

### cmantzioros

Never mind about the punnett square