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Flashcards

6. Inheritance, variation and evolution

JR HN Biology GCSE English 81 cards

Cards in this deck (81)

  1. 1What are chromosomes?Chromosomes are long structures of DNA that normally come in pairs.
  2. 2What shape is a strand of DNA?It is a double helix.
  3. 3What is a gene?A gene is a small section of DNA found on a chromosome which codes for a particular sequence of amino acids that form a specific protein and also determines what proteins the cell produces.
  4. 4What is a genome?A genome is the entire set of genetic material in an organism.
  5. 5Why is understanding the human genome important?Genes can be identified that are linked to certain diseases so they can be better understood and can help trace the migration of certain populations of people around the world.
  6. 6What are nucleotides?Nucleotides are the repeating units DNA strands are made up of, consisting of one sugar molecule, one phosphate molecule and one of four bases.
  7. 7What are bases when referring to DNA?The four bases are A, T, C and G and the order of amino acids in the protein is coded for by a sequence of three.
  8. 8What is complimentary base pairing?Complimentary base pairing is where each base in a DNA strand links to a base on the opposite side, A with T and C with G.
  9. 9What do non-coding parts of DNA sometimes do?Some of these parts switch genes on and off, so they control whether or not a gene is expressed.
  10. 10How are proteins formed?A molecule called mRNA is made by copying the codes from the DNA in the nucleus, which carries it to the ribosomes and acts as a template. Then amino acids are brought to the ribosomes in the correct order by carrier molecules and it folds into a shape unique to its function.
  11. 11What are three examples of protein functions?- Enzymes
    - Hormones
    - Structural proteins e.g. collagen
  12. 12What is a mutation?A mutation is a random change in an organism's DNA that occurs continuously.
  13. 13What do mutations do?Mutations change the sequence of DNA bases in a gene, which produces a genetic variant. This usually has little to no effect, but sometimes it leads to a change in the protein it codes for which can affect its ability to function.
  14. 14What is an example of a mutation that affects a protein's function?If the shape of an enzyme's active site is changed, the substrate may no longer be able to bind to it.
  15. 15What are insertions?Insertions are where a new base is inserted into the DNA base sequence where it shouldn't be, which can change the amino acids that are coded for and also affects bases further on in the sequence.
  16. 16What are deletions?Deletions are where a random base is removed from the DNA base sequence where it shouldn't be, which can change the amino acids that are coded for and also affects bases further on in the sequence.
  17. 17What are substitutions?Substitutions are where a random base is changed to a different base.
  18. 18What are gametes and how are they produced?Gametes are sex cells and have half the number of chromosomes than in a regular cell. They are produced by meiosis.
  19. 19What is fertilisation?Fertilisation is the fusion of gametes to form a cell with the full number of chromosomes.
  20. 20Why are offspring from sexual reproduction genetically different from the parents?As there are two parents, the offspring contain a mixture of their parents' genes.
  21. 21Why are offspring from asexual reproduction genetically identical to the parent?The new cell formed by mitosis has exactly the same genetic information as the parent cell.
  22. 22In what way do flowering plants reproduce?Flowering plants reproduce sexually, they have egg cells that fuse with pollen.
  23. 23What is the main advantage of sexual reproduction?Offspring variation due to two parents increases the chance of a species surviving an environmental change through natural selection.
  24. 24What is selective breeding?Selective breeding is where animals with a desirable characteristic are bred to produce offspring with this characteristic.
  25. 25What are the advantages of asexual reproduction?The fact there needs to be only one parent means organisms don't have to find a mate, which also means it is faster. Also, many identical offspring can be produced in favourable conditions.
  26. 26What is an example of an organism that reproduces both sexually and asexually?Many species of fungus produce spores asexually unless there is an unfavourable change in the environment, where they are produced sexually to increase the chance that the fungus population will survive the change.
  27. 27What chromosomes cause the offspring to have a female or male gender?XY chromosomes cause male characteristics and XX cause female characteristics.
  28. 28What are alleles?Alleles are different forms of a gene that arise by mutation.
  29. 29How do you draw a Punnett square?The separate alleles from the parents should be written on two sides of the table, one side for each parent, and the squares in the table should show the possible combinations of alleles.
  30. 30How do you draw a 'tree' genetic diagram?There should be three layers, the first should have two circles showing each parent including their alleles, then below should be four circles with the parents' separate alleles. Below that should be the four possible combinations of alleles in the offspring.
  31. 31What does homozygous mean?An organism that is homozygous for a particular gene has two identical alleles for that gene.
  32. 32What does heterozygous mean?An organism that is heterozygous for a particular gene has two different alleles for that gene, one dominant and one recessive.
  33. 33What is the difference between a genotype and a phenotype?A genotype is the combination of alleles an organism has, a phenotype is the physical characteristics it has.
  34. 34What is a monohybrid cross?A monohybrid cross is a genetic mix between parents who both have homozygous genotypes, which means there is only one genotype possibility for the offspring.
  35. 35What is cystic fibrosis?Cystic fibrosis is an inherited disorder which results in the body producing a lot of sticky mucus in the air passages and pancreas.
  36. 36Can someone have an allele which causes cystic fibrosis but not have the disorder and why?Yes, the allele for cystic fibrosis is recessive, and those who have it but do not have the disorder are called carriers.
  37. 37What is polydactyly?Polydactyly is an inherited disorder where a baby is born with extra finger or toes.
  38. 38Can someone have an allele which causes polydactyly but not have the disorder and why?No, the allele for polydactyly is dominant.
  39. 39What is pre-implantation genetic diagnosis?PGD is where an embryo from IVF has its genes analysed to check the alleles are 'healthy'.
  40. 40What is chorionic villus sampling?CVS involves taking a sample of cells from a part of the placenta that developed from the same cell as the embryo for analysis. It is usually carried out between weeks 10 and 13.
  41. 41What are the four main pros of embryonic screening?- Helps stop suffering from inherited disorders.
    - Reduces healthcare costs.
    - During IVF most embryos are destroyed anyway.
    - Parents don't have to have a termination but it gives them the choice.
  42. 42What are the four main cons of embryonic screening?- Could develop to selecting more desirable offspring or induce prejudice.
    - Destroying embryos after PGD or terminating pregnancies seen as unethical by some.
    - CVS could cause a miscarriage.
    - Screening is expensive.
  43. 43What did Mendel conclude from his pea plant experiment?- CHaracteristics in plants are determined by 'hereditary units'.
    - These are passed unchanged from parent to offspring.
    - They can be dominant or recessive.
  44. 44What is the difference between genetic and environmental variation?Genetic variation is the differences in a population caused by the combinations of genes inherited from the two parents, whereas environmental variation is the differences in a population caused by any environmental factor.
  45. 45What is a mutation?A mutation is when a gene is altered, producing a genetic variant which is usually not significant enough to affect an organism's phenotype.
  46. 46What is the theory of evolution?The theory of evolution is that all of today's species have evolved from simple life forms that have developed over time.
  47. 47What is the process of evolution?1. Individuals within a species show variation, some of which are more suited to the environment.
    2. Those who are more suited are more likely to survive and breed successfully.
    3. The useful characteristic is passed on to the offspring and over time it will accumulate in a population.
  48. 48What proof exists to make Darwin's theory of evolution an accepted hypothesis?- The discovery of genetics.
    - The fossil record showing development over time.
    - Bacteria's ability to become resistant to antibiotics.
  49. 49What is speciation?Speciation is when a new reproductively isolated species is formed because the phenotype of organisms has changed drastically over time from natural selection.
  50. 50What does reproductively isolated mean?Populations of a species that are reproductively isolated cannot interbreed to produce fertile offspring.
  51. 51What are the reasons for species extinction?- Rapid environmental changes e.g. habitat loss.
    - A new predator or disease.
    - Competition for food with a new species.
    - Catastrophic event e.g. asteroid.
  52. 52Why was Darwin's theory of evolution controversial?- Religious beliefs.
    - No explanation of useful characteristic development.
    - Not enough evidence.
  53. 53What was Lamarck's theory of evolution?Lamark argued that changes an organism acquires during its lifetime will be passed on to its offspring, but this is a rejected hypothesis.
  54. 54What are four examples of uses of selective breeding?- Animals that produce more meat or milk.
    - Crops with disease resistance.
    - Dogs with good temperaments.
    - Decorative plants with big or unusual flowers.
  55. 55What is the main current problem with selective breeding?Reducing the gene pool increases the risk of harmful genetic defects and means that any new diseases might affect more of the population due to lack of variation.
  56. 56What is genetic engineering?Genetic engineering is transferring a gene responsible for a desirable characteristic from the genome of one organism to another organism's cells.
  57. 57What is a genome?A genome is the complete set of genes or genetic material in a cell or organism.
  58. 58What is the process of genetic engineering?1. A useful gene is isolated using enzymes and inserted into a vector, usually a virus or bacterial plasmid.
    2. The vector is introduced to the target organism and the gene is inserted into its cells.
  59. 59How can bacteria be genetically engineered to produce insulin?The insulin gene is isolated from human DNA and inserted into the bacterial DNA using enzymes, then the bacteria can be allowed to multiply and the insulin they produce can be purified and used by diabetics.
  60. 60What is gene therapy?Gene therapy is when working genes could be inserted into people with a disorder.
  61. 61What are the pros of GM crop production?- Yield can be increased.
    - Crops could be engineered to contain missing nutrients for those in developing nations.
  62. 62What are the cons of GM crop production?- Wildflower populations decreased affecting farmland biodiversity.
    - Health effects not fully understood.
    - Transplanted genes may access natural environment e.g. herbicide-resistant weeds.
  63. 63What is cloning?Cloning is the production of a genetically identical copy of an organism.
  64. 64How are tissue cultures used to clone plants and what are the advantages of this method?A few plant cells are put in a growth medium with hormones and they grow into new plants. They can be made very quickly, in very little space and all year round, and can be used to preserve rare plants.
  65. 65How are cuttings used to clone plants and what are the advantages of this method?Cuttings from good parent plants are planted and they grow into new ones. They can be made quickly and cheaply.
  66. 66How are embryo transplants used to clone animals?Artificial fertilisation occurs between gametes taken from the prize bull and cow, and the embryo that develops is split before specialisation begins. These are then implanted into lots of other cows.
  67. 67How is adult cell cloning used to clone animals?An adult body cell from the prize cow and an unfertilised egg cell have their nuclei removed, and the body cell nucleus is inserted into the empty egg cell. An electric shock then stimulates it to divide like a normal embryo, then it is implanted into a surrogate mother.
  68. 68What are the pros of cloning?- Produces many "ideal' offspring with known characteristics.
    - Could lead to a greater understanding of embryonic development and age-related disorders.
    - Could be used for preservation of endangered species.
  69. 69What are the cons of cloning?- Reduces gene pool.
    - Cloned animals might not be as healthy as normal ones.
    - Humans may be cloned in the future presenting issues such as risk of severe disabilities and debates on human rights.
  70. 70How do fossils form from gradual replacement by minerals?Long-lasting remains, e.g. bones and shells, are gradually replaced by minerals as they decay, forming a rock-like substance in their shape.
  71. 71How do fossils form from casts and impressions?If an organism is buried in a soft material e.g. clay, this later hardens and the organism decays, leaving a cast.
  72. 72How do fossils form from preservation what are two example of this?If conditions such as oxygen levels, moisture and temperature aren't right, the remains of an organism will not decay, such as in glaciers or peat bogs.
  73. 73Why is there lack of evidence concerning the origins of life on Earth?- Scientists believe many early organisms were soft-bodied, and so decayed completely.
    - Very old fossils may have been destroyed by geological activity.
  74. 74How can isolation result in speciation?Isolation within a population is usually due to a physical barrier such as river formation, which leaves the species to evolve in separate environments due to natural selection.
  75. 75What was Alfred Russel Wallace most famous for?He realised that warning colours on some species such as butterflies deterred predators from eating them, which is an example of how a characteristic evolved by natural selection.
  76. 76What is MRSA?MRSA is a common strain of resistant bacteria.
  77. 77What is increasing the rate at which antibiotic-resistant strains of bacteria are developing?Overprescription of antibiotics, such as for non-serious or non-bacterial conditions and illnesses, patients not taking the full course and antibiotics being used as a prevention method in farming all contribute.
  78. 78How does a patient not taking the full course of antibiotics increase the risk of antibiotic-resistant strains of bacteria developing?If the patient takes the antibiotics for a short period of time, the weaker strains are killed and the symptoms ease but the more resistant bacteria are left to multiply. If they resume treatment it will therefore have no effect.
  79. 79What is the Linnean system?The Linnean system is one that was used to classify organisms, the largest groups being kingdoms and the smallest being species.
  80. 80What is the three-domain system?The three-domain system is one that initially split organisms into the categories of either archaea (primitive bacteria), bacteria, and eukaryota (animals, plants etc.).
  81. 81What is the binomial system?The binomial system is one where each organism is given its own two-part Latin name referring to its genus and its species.

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GCSE Biology Flashcards on 6. Inheritance, variation and evolution, created by JR HN on 24/03/2019.
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JR HN
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  • Created by JR HN · Aug 29, 2018
  • Copied by JR HN · Mar 24, 2019
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