problem 1) What are the two main causes of heritable variation?
problem 2) Classify the following variations as either
(i) caused entirely by genetic effects or
(ii) caused by a combination of genetic and environmental effects.
obesity, eye colour, tallness, ability to sing, maleness, masculinity, blood group, natural hair colour; sickle-cell anaemia, agility
problem 3) Alleles are genes which occupy corresponding positions on….. A ….. chromosomes. They control the same ….. B ….. but not necessarily in the same way.
problem 4)(a) What new combinations of characteristics might arise in the offspring when a tall plant with white flowers is crossed with a dwarf plant (of the same species) with red flowers?
(b) What selective advantage might either of the new varieties have?
problem 5) The genotypes of two guinea pigs, for two characteristics are represented as AABB and aabb. These guinea pigs are mated, and their offspring eventually mate with each other.
(a) What genotypes could emerge in the second generation?
(b) Which of these would be phenotypically different (i.e. be different in appearance) from the original pair?
problem 6) Suppose that there are six pairs of alleles which control height and that each dominant allele adds 5cm to the stature. Suppose also that the average height of an adult (with equal numbers of recessive and dominant alleles) is 160cm
(a) What is
(i) the tallest,
(ii) the shortest person you would expect from this pattern?
(b) On this basis, what would be the minimum difference in height between any two people?
(c) Why is this minimum difference unlikely to be observed in reality?
problem 7) Give two exs in each case of (a) continuous, (b) discontinuous variation in human populations.
problem 8) Which one of the following statements is the least accurate?
(a) Discontinuous variation results entirely from genetic differences.
(b) Continuous variation can result from genetic differences.
(c) Discontinuous variation cannot be altered by environmental effects.
(d) Continuous variation results from environmental effects.
problem 9) describe why identical twins will have the same genotype.
problem 10) When ….. A ….. and ….. B ….. put forward the theory of Natural Selection in 1858 they observed that there are ….. C ….. between the individuals of a species. They also observed that organisms produce more offspring than can possibly …. D …..to maturity. If the ….. E ….. are inherited and give the individuals an advantage over the other members of the species, they will live ….. F ….. and so leave more offspring with the same beneficial ….. G …..