Sex Determination

• Biology
• Upper Secondary (Key Stage 4)
• GCSE

How many chromosomes does this person have in a normal body cell?

What sex is this person and how do you know?

Red-green colourblindness is caused by a recessive allele on the X chromosome. Why are men more likely to get it?

Red-green colourblindness is caused by a recessive allele on the X chromosome. Why can't men pass it onto their sons?

Using the letters H or h for the alleles for polydactyly, which of the genotypes would have the disorder?

1. HH
2. Hh
3. hh

What combination of alleles did parents A and B have?

Give two possible combinations of alleles for cat D. Use the letters H or h.

CASADIL is an inherited disorder caused by a dominant allele. What is the evidence in the diagram that CASADIL is a dominant allele?

Is person 7 homozygous or heterozygous for the CASADIL allele? Explain.

What is polydactyly and is it caused by a dominant or recessive allele?

Using the letters C or c for the alleles for cystic fibrosis, which of the genotypes would have the disorder?

1. CC
2. Cc
3. cc

Cystic fibrosis is caused by a membrane allele. Both parents are carriers of cystic fibrosis. Suggest what this means.

What is the probability that the two carrier parents will have a child with cystic fibrosis?