1. a) What experiments led Mendel to the conclusion that genes are particulate units of inheritance?
b) If a strain of corn with shrunken yellow seed kernels is crossed to a strain with smooth purple pigmented seeds, all the resulting plants produce seed with shrunken purple seeds. What do you predict would be the result of self fertilising the F1 generation? Explain your answer.
c) In the human pedigree below the ABO blood group genes do not
appear to be inherited in a proper Mendelian manner. What possible
explanations are worth considering for this aberrant behaviour?
2. a) Explain the meanings of the following terms: uniparental disomy, variable expressivity, anticipation, lethal allele.
b) In the pedigree below the proband has the autosomal recessive genetic disease cystic fibrosis which maps close to the DNA polymorphism D7S8 on chromosome 7. Is there anything unusual about this family? Which of the terms above might explain the pattern of inheritance seen?
c) What test(s) might you ask to have performed? What is the
risk to subsequent children that they might suffer from cystic
fibrosis? Which member(s) of this family is (are) likely to be
a carrier(s) of the disease?
3. What are the most probable modes of inheritance of the conditions segregating in the following four pedigrees? There may be one or two 'problem individuals' in the pedigrees. Explain your answers.
4. a) What can normal and abnormal karyotypes tell us about human sex determination?
b) How are birds, alligators and Drosophila melanogaster different to us in this respect?
c) Why do all male tortoiseshell cats have the feline equivalent
of Kleinfelter's syndrome?
5. Discuss briefly the different types of mutations and their
6. a) What is the difference between a balanced and an unbalanced chromosomal rearrangement? Give an example of each.
b) What is a Robertsonian translocation? Why does a person with a Robertsonian translocation sometimes have an increased risk of having a child with Down's syndrome?
c) With the exception of trisomy for the smallest autosome, chromosome
21, we see far more individuals with abnormal numbers of sex chromosomes
than of any autosome. Why is this?
7. a) Briefly explain the benefits to medicine of human genetic
b) In the pedigree below, an autosomal recessive gene which maps
between the marker loci A and B is segregating. The alleles present
in some family members are shown. Will either or both of these
two loci provide any useful information if they are tested in
the unborn foetus in the current pregnancy?
8. a) Explain briefly the use of DNA polymorphisms in forensic science.
b) Why are databases of population frequencies of DNA 'fingerprint' alleles needed in these cases?