past paper questions

• What feature of a pathogen such as Mycobacterium tuberculosis could be altered by a mutation, making a vaccine ineffective

  • shape of proteins
• Most humans have a genetic mutation that prevents the shutdown of lactase production. State what structural detail of a polypeptide is altered by gene mutations

  • sequence of amino acids
• A gene mutation is a change in the sequence of nucleotides within a gene. Explain how it is possible for a mutation to have no effect on the protein produced from that gene.

  • some triplets code for the same amino acids (degenerate)
  • amino acid sequence is not altered
• Explain how a mutation could alter the protein so that it no longer performs its correct function in the cell.

  • tertiary structure will be different
  • an insertion/deletion will cause frame shift
• Adaptations can be divided into three types. State the type of adaptation represented by the tiger’s stripes.

  anatomical
• Mitosis is involved in growth and repair of tissues. State two other roles of mitosis in multicellular organisms

  • development of body plan
  • asexual reproduction
• Describe how gene expression can be regulated after transcription

  • primary mRNA is modified
  • splicing can produce different versions of mRNA
  • protein must be activated by cAMP
• describe how transcription can be controlled in eukaryotes

  • hormone enters cell and binds to a transcription factor
  • transcription factor binds to promoter region
  • RNA polymerase able to bind
• Suggest and explain why lactose is unable to cross membranes.

  • too big
  • needs a carrier protein
• In order for lactose to enter the cytoplasm of E. coli a protein is required. The E. coli living in the digestive system of young mammals are more likely to contain this protein than E. coli living in the digestive system of old mammals. Suggest an explanation for this observation

  • mammals diet high in milk, so high lactose concentration
  • lac operon is switched on
• Suggest two other reasons why fruit flies are chosen for research into genes controlling the development of body plan

  • rapid reproduction
  • simple body plan
• There are some public concerns about the ethics of using mice in these investigations. Suggest two reasons why mice are chosen as a suitable species for investigation

  • more similar to humans
  • rapid reproduction
• . Hox genes code for transcription factors and control the development of the body plan. Fig. 16.2 shows a congenital deformity caused by failure of the control mechanism. Explain how failure of the control mechanism during development could lead to such a deformity

  • Hox gene does not produce transcription factor
  • apoptosis to separate fingers does not occur
  • molecules signalling apoptosis not produced

  
• DNA codes for proteins within the cell. Some regions of DNA are described as non-coding. Explain why some regions of DNA can be described as ‘non-coding’

  • editing of primary mRNA
  • regulatory genes
  • not translated
• Suggest why non-coding regions of DNA show more variation.

  • not selected against
  • doesn't affect survival
• Immobilised enzymes can be produced by which of the following methods?

  enclosing enzymes within a partially permeable membrane
• Which option states the correct order for producing a clone of the giant Galapagos tortoise?

  1. somatic cell from tortoises is defrosted and nucleus is removed
  2. a donor egg is enucleated
  3. somatic cell nucleus is inserted into enucleated oocyte
  4. electrofusion of host cell and new nucleus
  5. transformed egg divides in vitro
  6. embryo develops into mature egg which is incubated
• The student found that the bacteria grew well when provided with glucose, sucrose and fructose, but did not grow well when provided with lactose. Which statement, A to D, provides the best explanation for these results?

  the bacteria did not possess the enzyme to digest lactose
• Mycoprotein is a food produced using the fungus Fusarium venenatum. Which statement about mycoprotein is correct?

  waste products can be used as a substrate
• Which of the following statements about asexually-produced coral offspring is not true?

  Meiosis occurred in order to produce the offspring.
• Strawberry plants produce clones using runners. This is an example of natural cloning. State one other method of natural cloning in plants.

  • bulbs
  • suckers
• Cells are removed from the meristem tissue in axial buds or shoot tips. The tissue sample that is removed is called the explant. Ethanol can be used to sterilise the plant tissue. Hormones are used to stimulate mitosis, which produces a mass of cells called a callus
• why is asepsis important?

  • reduces microorganisms and contamination
• . State how a clone of potatoes could be produced for this investigation and explain why it is important to carry out this procedure under aseptic conditions.

  tissue culture/ micropropagation
• Cloning plants is also known as vegetative propagation. Identify three advantages of vegetative propagation in agriculture

  • crop plants cant reproduce sexually
  • easier to harvest
  • quicker than growing from seed
• Describe how to clone a plant by taking a cutting

  • cut shoot from healthy plant
  • dip in auxin
  • place in soil and add water
  • cover with plastic bag
• Tissue culture greatly increases the number of cloned plants that can be produced from a single parent plant. Outline how it is possible to produce many clones from a single original parent plant.

  • plantlets can be subdivided
  • many explants taken from parent plant, calluses subdivided
• Mice are often used in laboratory studies to research treatments for heart conditions. These mice are often clones. Suggest one reason why clones are used in these studies.

  • ensures same responses to treatment
  • no genetic variation to affect results
• Laboratory techniques are used by workers in various professions, and by scientists. A patient has been coughing blood, and it is suspected that bacteria will be found in the blood. A medical technician cultures the blood on an agar plate. What measures should the technician take to keep the agar plate culture sterile?

  • flame inoculating loop
  • seal plates for incubation
• Some humans are lactose intolerant. Milk can be treated with lactase to reduce the concentration of lactose present. Fresh milk is passed over lactase molecules immobilised on a suitable matrix. Give two economic advantages of immobilising enzymes for large-scale production

  • enzymes re-used so less money/cost
  • higher temperatures allow more profit from faster yield
• Tannase is an enzyme produced by some microorganisms. Tannase is useful in many industrial applications including food production. The tannase used in food production can be free in solution or immobilised. State one method by which tannase could be immobilised.

  • adsorption
  • membrane separation
• State one disadvantage of using immobilised enzymes in industrial processes

  • fewer exposed active sites