Biology
Enzymes and inheritance — Topics 5 and 17-18
- 1.
Explain why the rate of an enzyme-controlled reaction increases from 20 °C to 35 °C but decreases sharply above 45 °C.
[4 marks] · no calculator - 2.
In pea plants, tall T is dominant to short t. Cross a heterozygous tall plant with a short plant and state the expected phenotype ratio.
[4 marks] · no calculator - 3.
Define the term enzyme, and state what happens to the rate of an enzyme-controlled reaction if the substrate concentration is increased while enzyme concentration stays constant, at low substrate concentration.
[2 marks] · no calculator - 4.
Describe how the 'lock and key' model explains enzyme specificity, referring to the shape of the active site.
[3 marks] · no calculator - 5.
Distinguish between continuous variation and discontinuous variation, giving one human example of each.
[2 marks] · no calculator - 6.
In humans, blood group is controlled by three alleles: IA, IB and Iᴼ, where IA and IB are both dominant to Iᴼ. A person with genotype IAIᴼ is crossed with a person with genotype IBIᴼ. State the possible genotypes of their children.
[4 marks] · no calculator - 7.
Explain why immobilising an enzyme (e.g. on beads) is useful in industrial processes, compared to using a free enzyme in solution.
[3 marks] · no calculator - 8.
Outline how a mutation can lead to a new allele of a gene, and state whether all mutations are harmful.
[3 marks] · no calculator - 9.
Explain why enzymes are described as biological catalysts, referring to activation energy.
[3 marks] · no calculator - 10.
A pea plant with round seeds (genotype Rr) is self-pollinated. Round R is dominant to wrinkled r. Determine the expected phenotype ratio of the offspring.
[3 marks] · no calculator - 11.
Explain why enzyme activity is low at very low pH and very high pH, but high at the optimum pH.
[3 marks] · no calculator - 12.
Describe the structure of DNA, and state what is meant by the term gene.
[3 marks] · no calculator - 13.
State the relationship between chromosomes, genes and alleles.
[3 marks] · no calculator - 14.
Distinguish between mitosis and meiosis, in terms of the number and genetic content of the cells produced.
[4 marks] · no calculator - 15.
In humans, sex is determined by the X and Y chromosomes: females are XX and males are XY. Using a genetic diagram, explain why approximately half of all offspring are expected to be male and half female.
[4 marks] · no calculator - 16.
A pea plant with round seeds has an unknown genotype, either RR or Rr (round R is dominant to wrinkled r). Describe how a test cross could be used to determine its genotype.
[3 marks] · no calculator - 17.
In snapdragon plants, flower colour shows codominance: allele CR produces red pigment and allele CW produces white pigment, with heterozygous plants (CRCW) being pink. Explain what is meant by codominance using this example, and determine the phenotype ratio produced when two pink (CRCW) plants are crossed.
[4 marks] · no calculator - 18.
Explain, using the example of antibiotic resistance in bacteria, how natural selection can lead to a change in a population over time.
[4 marks] · no calculator - 19.
Distinguish between natural selection and selective breeding (artificial selection), giving an example of selective breeding.
[3 marks] · no calculator - 20.
Outline the basic process of genetic engineering used to produce human insulin using bacteria.
[4 marks] · no calculator - 21.
In an experiment, substrate concentration is kept very high while enzyme concentration is varied. State and explain the effect on the rate of reaction as enzyme concentration is increased.
[3 marks] · no calculator - 22.
Describe an experiment to investigate the effect of temperature on the rate of activity of the enzyme amylase, using iodine solution to test for starch.
[4 marks] · no calculator - 23.
Red-green colour blindness in humans is caused by a recessive allele carried on the X chromosome. A woman who is a carrier for colour blindness (genotype XᴺXⁿ) has children with a man with normal vision (genotype XᴺY). Determine the possible genotypes and phenotypes of their children, and state the probability that a son will be colour blind.
[5 marks] · no calculator - 24.
State two possible causes of variation between individuals of the same species, and explain how each contributes to variation.
[4 marks] · no calculator - 25.
Enzymes such as proteases and lipases are added to biological washing powders. Explain why these enzymes are effective at removing certain types of stains from clothing at relatively low washing temperatures.
[3 marks] · no calculator