6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: DNA and the GenomeA species of moth lives on the bark of trees. Most moths are pale, but a few are dark. When air pollution darkens the tree bark with soot, scientists find that the dark moths become much more common in the population over several generations.
Explain, using the theory of evolution by natural selection, why the dark moths become more common when the bark is darkened. (6 marks)
Cystic fibrosis is an inherited disorder caused by a recessive allele, f. The dominant (healthy) allele is F. Two parents who are both carriers (genotype Ff) have a child.
(a) Complete a genetic cross (Punnett square) for Ff × Ff and use it to give the ratio of genotypes in the offspring. (2 marks)
(b) Calculate the probability, as a percentage, that a child of these parents will have cystic fibrosis (genotype ff). (1 mark)
(c) State the genotype of a person who is a carrier of cystic fibrosis but does not have the disorder. (1 mark)
A gardener has a rare orchid plant with attractive flowers. They want to produce many genetically identical copies of it quickly, using a small number of cells from the parent plant. This method of cloning is called tissue culture.
(a) Describe how tissue culture is used to produce many cloned plants from the parent orchid. (2 marks)
(b) Explain why all the new plants produced by tissue culture are genetically identical to the parent plant. (1 mark)
Dairy farmers have used selective breeding over many years to produce cows that give large volumes of milk.
(a) Describe how a farmer could use selective breeding to increase the milk yield of a herd of cows over several generations. (2 marks)
(b) Give one problem that can result from selective breeding. (1 mark)
The genetic material in the nucleus of a cell is composed of a chemical called DNA, which is contained in structures called chromosomes.
(a) Name the type of large molecule that DNA codes for the production of. (1 mark)
(b) State what is meant by the term genome. (1 mark)
Sexual reproduction involves the fusion of male and female gametes. Gametes are produced by a type of cell division that halves the chromosome number.
Name the type of cell division that produces gametes. (1 mark)