examples of sex-linked diseases

Question 1

examples

Answer 1

• cleft pallet
• diabetes
• haemophilia
• muscular dystrophy
• occur more often in male

Question 2

red-green colour blindness

Answer 2

• genes responsible for sensitiveness to wavelengths of light are carries on x chromosome
• colourblind male, transported to all daughters becoming heterozygous carries
• sons of affected male won’t inherit it because of y chromosome only being inherited from him
• female will be colourblind if recessive allele on both x chromosomes

Question 3

haemophilia

Answer 3

• frequent, excessive bleeding
• dominant allele H allows blood clot
• recessive h allele does not allow blood to clot
• carried on x chromosome
• genotype XHY (normal phenotype) M
• genotype XhY (haemophiliac) M
• genotype XHXH (normal phenotype) F
• genotype XHxh (normal but carrier) F
• genotype XhXh (triggers natural abortion) F

Question 4

polygenic inheritance

Answer 4

• more than one pair of inherited alleles
• determined by the interaction of many different alleles
• range of phenotypes

Question 5

continuous variation

Answer 5

• greater number of characteristic controlling alleles, greater variety
• each phenotype differs slightly from the next
• examples, skin colour, height, metabolic rate, longevity
• some variation due to enviromental factors