Pedigrees and Sex Chromosomes

Question 1

Can recessive traits skip generations

Answer 1

Yes, people can be a carrier and not affected

Question 2

Define: consanguine

Answer 2

Consanguine: related family

Question 3

What are the 2 human sex chromosomes

Answer 3

X and Y

Question 4

Are human sex chromosomes homologous

Answer 4

Not true homologs of each other
Just enough homology allowing them to pair up during meiosis

Question 5

What do most chromosomes in the Y gene code for

Answer 5

Genes on Y chromosomes are involved in sex determination

Question 6

How are men commonly affected by X linked recessive traits

Answer 6

X-linked recessive alleles are expressed in males because males have only 1 x chromosome

A mutation is seen in the males phenotype because Y does not carry an allele of this gene

Question 7

Who is most affected by X-linked traits

Answer 7

1) Usually more males than females are affected

Question 8

Explain how X-linked traits skip generations

Answer 8

2) Affected sons are usually born to unaffected mothers: thus the trait skips generations

Question 9

If a mother is a carrier, how does that affect her sons

Answer 9

3) Approx half of a carrier (heterozygous) mothers sons are affected

Question 10

Can a dad pass down an x-linked trait to their sons? Why or why not

Answer 10

4) Never passed from father to son
– In sons there is a Y and X allele, the Y will always come from the dad

Question 11

What happens to daughters of affected fathers

Answer 11

5) All daughters of affected fathers are carriers
- Dad passes down ressessive X allele making daughter carrier