Biology Paper 2

    Cards (22)

    • Long=sightedness can be corrected by wearing spectacles.Describe how spectacle lenses can correct long-sightedness. (3 marks)
      • Convex/Converging lens
      • Light rays bent/refracted (inwards) more
      • Light rays focused on retina
    • Explain two biological reasons why most doctors think that a kidney transplant is a better method of treatment than dialysis
      Changes in concentrations/levels of substances/urea are minimised
      so less chance of causing damage to body cells
      Not repeatedly puncturing skin
      so less chance of infection
    • Plan an investigation to show the effect of light from one direction on the growth of plant seedlings.Include details of any controls needed.
      Several seedling in each batch
      Measure heights of shoots
      Leave some in dark with light from one side/direction in box with hole
      Control with all-round light
      Control variables e.g same temp, water, soil type
      After suitable time - several hours
      record appearance of seedlings
      re-measure heights of shoots
      e.g use thread or straighten them out
      calculate mean height increase for each group
      use ruler/protractor to estimate angle of bending
    • The farmer sprayed pesticide on his potato plants. The next day it rained heavily. Explain why the biodiversity in the river decreased.
      pesticide washed into river
      pesticide kills (some) organisms / plants / animals in river
    • Potatoes can also reproduce asexually. Potatoes from one plant can be planted in the ground to produce new potato plants. All the new plants from a parent plant that is resistant to blight will also be resistant to blight. Explain why.
      no fusion of gametes
      (so) offspring are genetically identical (to parent plant)
    • Most human body cells contain 6 × 10–12 grams of DNA. What mass of DNA will a human sperm cell contain?
      3 × 10–12 grams
    • Give the reason why a mutation in the gene coding for haemoglobin could be harmful.
      mutation means less oxygen for (aerobic) respiration
    • People with a family history of some genetic disorders are offered embryo screening. Suggest one way embryo screening can help people with a family history of a genetic disorder.
      any one from: • to help them prepare • to inform whether to consider having an abortion • to find out if they have passed on the disorder
    • DNA analysis can show people which alleles they have. Patients who have certain types of cancer can be offered DNA analysis. The family of the patient can also be offered DNA analysis. Suggest one advantage of having DNA analysis
      to determine if the cancer is genetic (or caused by lifestyle factors) • to inform / help treatment • to allow embryo screening to ensure allele is not passed on • to inform relatives if they have inherited (affected) gene / allele • to detect cancer early or before symptoms show • to understand cause of the cancer
    • Some parts of DNA do not code for proteins. Describe how non-coding parts of DNA can affect the expression of genes.
      non-coding parts) can switch genes on / off
    • Explain how the diagram above shows the allele for Dupuytren’s is not on the Y chromosome.
      female(s) / person(s) 3 / 11 / 12 have Dupuytren’s allow some females have Dupuytren’s
      females don’t have Y chromosome
    • A woman has three children, aged 4, 6 and 9 years. Why are the children not genetically identical?
      any two from: • different egg / sperm each time • genes from two parents • each gamete / egg / sperm has different alleles / genes / DNA /
    • The embryo may not implant in the lining of the uterus. The embryo will then be lost from the woman’s body several days later. Explain why the woman may not notice this has happened
      embryo is (very) small (so) embryo not seen / felt or lost in normal menstrual flow
    • Scientists have now studied the whole human genome. Give two benefits of understanding the human genome
      any two from: allow descriptions or named examples • diagnosis of inherited / genetic disorder allow research / understand genetic disorders • gene therapy or treatment of inherited disorders • understanding (human) evolution or understanding ethnic origins (of a person) or understanding ancestry • tracing human migration patterns
    • Figure 2 shows a tissue culture technique used for producing many plants from one plant.Several groups of cells are scraped off the leaf
      so many / several plants can be produced
    • tissue culture-Nutrients are added to the agar jelly
      for making protein / amino acids or for making chlorophyll or for providing energy or for respiration
    • tissue culture- Hormones are added to the agar jelly: _
      so differentiation occurs or so roots / shoots develop
    • tissue culture-The plant cells are kept in sterile conditions:
      (sterile conditions) to prevent growth / entry of microorganisms / named type or prevent decay / disease
    • tissue culture-The plant cells are kept at 20 °C:
      so optimum / good growth
    • Explain why sexual reproduction is an advantage for bluebells
      genetic variation (in offspring) (so) better adapted survive(and) colonise new areas by seed dispersal ,many offspring so higher probability some will survive
    • The parents shown in the diagram above have five children. Give two reasons why these children all look different from each other.
      any two from: • multiple genes determine appearance allow several / many genes determine appearance • different combinations of alleles allow description of combinations of alleles’ allow genes for alleles • different environmental effects allow example e.g. eat different diets • from different egg / sperm
    • Strand K shows a mutation in the DNA which has caused syndrome H. The enzyme IDUA helps to break down a carbohydrate in the human body. The enzyme IDUA produced from Strand K will not work. Explain how the mutation could cause the enzyme not to work. (
      mutation) changes from C to T DNA code or there is a change in the three bases / triplet from CAG to TAG (mutation) changes the amino acid (this could) change the protein (so it) forms a different shape / changed active site accept different tertiary structure (therefore) the enzyme no longer fits the substrate / carbohydrate
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