OpenRevise

Flashcards · Biology

Inheritance

112 cards from 7 lessons

  1. What is a gene?

    A section of DNA that codes for a protein.

  2. What is an allele?

    A different version of the same gene, also called a variant.

  3. What does homozygous mean?

    Two identical alleles of a gene.

  4. What does heterozygous mean?

    Two different alleles of a gene.

  5. What is a dominant allele?

    One that shows in the phenotype even if only one copy is present.

  6. What is a recessive allele?

    One that only shows when there are two copies.

  7. What is a genotype?

    The combination of alleles of a gene, such as Tt.

  8. What is a phenotype?

    The feature that the organism shows.

  9. What is the genome?

    The entire genetic material of an organism.

  10. How many pairs of chromosomes are in a human body cell?

    23.

  11. About how many genes are in the human genome?

    About 20 000.

  12. What two things influence the phenotype?

    The genome and its interaction with the environment.

  13. Are most features controlled by one gene?

    No, most are controlled by many genes.

  14. Give an example of a single gene feature.

    Cystic fibrosis, or the flower colour of a pea plant.

  15. Can Tt and TT have the same phenotype?

    Yes, both are tall, but they have different genotypes.

  16. Common mistake about dominance?

    Saying that a dominant allele is the more common one. It only means that it shows when one copy is present.

  17. What is variation?

    The differences between individuals of the same species.

  18. What is discontinuous variation?

    Variation in which individuals fall into distinct categories.

  19. Give an example of discontinuous variation.

    Eye colour, or blood group.

  20. What is continuous variation?

    Variation in which a feature can have any value in a range.

  21. Give two examples of continuous variation.

    Height and weight.

  22. Which type of graph shows continuous data?

    A histogram, with touching bars.

  23. Which type of graph shows discontinuous data?

    A bar chart, with gaps.

  24. What are the causes of variation?

    The genome, the environment, or both.

  25. Give an environmental cause of variation.

    Scars, a suntan, or an accent.

  26. Where do all variants come from?

    Mutations.

  27. What effect do most mutations have?

    No effect on the phenotype.

  28. What does a mutagen do?

    Increases the rate of mutation.

  29. Name two mutagens.

    Ionising radiation and some chemicals, or ultraviolet light.

  30. Why does sexual reproduction not make new variants?

    It only mixes the existing ones into new combinations.

  31. Why use a large sample in an investigation of variation?

    The results are more reliable, and less biased.

  32. Common mistake about mutations?

    Saying that all of them are harmful. Most have no effect.

  33. What is coding DNA?

    DNA that codes for proteins, in genes.

  34. What is non-coding DNA?

    DNA that does not code for a protein.

  35. How can a variant in coding DNA affect a protein?

    It can change the amino acid sequence, so the shape and the activity change.

  36. How can a variant affect an enzyme?

    It can change the shape of the active site, so the substrate no longer fits.

  37. How can a variant in non-coding DNA affect the phenotype?

    It can change how the gene is expressed.

  38. What can a non-coding variant stop?

    Transcription of the mRNA.

  39. What is gene expression?

    How a gene is used to make its protein.

  40. What effect would stopping transcription have?

    Less, or none, of the protein is made.

  41. Do most variants affect the phenotype?

    No, most have no effect.

  42. What does a frameshift do?

    Changes all of the triplets after the change.

  43. Why can the same amino acid be made after a base change?

    More than one triplet codes for the same amino acid.

  44. Are the terms promoter and transcription factor required?

    No.

  45. What is sickle cell disease an example of?

    A variant in coding DNA that changes a protein.

  46. What is lactase persistence an example of?

    A variant in non-coding DNA that changes the amount of a protein.

  47. Why does a changed active site stop an enzyme working?

    The substrate does not fit, so no complex forms.

  48. Common mistake about non-coding DNA?

    Saying that it has no function. It can control how genes are expressed.

  49. How many parents are needed for asexual reproduction?

    One.

  50. Are the offspring of asexual reproduction identical?

    Yes, they are clones of the parent.

  51. Which cell division is used for asexual reproduction?

    Mitosis.

  52. How many parents are needed for sexual reproduction?

    Two.

  53. Are the offspring of sexual reproduction identical?

    No, they are all different.

  54. Give an advantage of asexual reproduction.

    It is fast, and needs no mate.

  55. Give a disadvantage of asexual reproduction.

    There is no variation.

  56. Give an advantage of sexual reproduction.

    It produces variation, so some survive a change.

  57. Give a disadvantage of sexual reproduction.

    It is slower, and fewer offspring are made, and it needs more energy.

  58. How fast can a bacterium reproduce?

    About every 20 minutes.

  59. How many babies do humans usually have per birth?

    One.

  60. Why does lack of variation make a species vulnerable to disease?

    Every individual may be equally affected.

  61. Give an organism that uses both methods.

    A strawberry plant, a fungus, or an aphid.

  62. What was the cause of the Irish potato famine?

    Potato blight, which affected genetically identical potatoes.

  63. Why can sexual reproduction help evolution?

    It gives variation, for natural selection to act on.

  64. Common mistake about asexual reproduction?

    Saying that it never produces variation. Mutations can make rare differences.

  65. What does diploid mean?

    Having two sets of chromosomes.

  66. What does haploid mean?

    Having one set of chromosomes.

  67. How many chromosomes are in a human body cell?

    46.

  68. How many chromosomes are in a human gamete?

    23.

  69. What does meiosis do to the chromosome number?

    It halves it.

  70. How many cells does meiosis make from one cell?

    Four.

  71. Are the cells made in meiosis identical?

    No, they are all genetically different.

  72. Where does meiosis happen in a human?

    In the ovaries and the testes.

  73. What is formed when two gametes fuse?

    A zygote.

  74. Is a zygote haploid or diploid?

    Diploid.

  75. Why must gametes be haploid?

    To maintain the diploid number when gametes combine.

  76. How does meiosis cause variation?

    The chromosomes are shared out randomly between the gametes.

  77. Which type of division is used for growth and repair?

    Mitosis.

  78. A cell has 24 chromosomes. How many are in a gamete?

    12.

  79. How many different gametes can one person make?

    Over 8 million.

  80. Common mistake about meiosis?

    Saying that it makes two cells, or identical cells. It makes four different cells.

  81. What does a Punnett square show?

    The possible combinations of gametes in a cross.

  82. What are the gametes of a Tt parent?

    T and t.

  83. What are the offspring of Tt x Tt?

    1 TT : 2 Tt : 1 tt.

  84. What is the phenotype ratio of Tt x Tt?

    3 dominant : 1 recessive.

  85. What is the probability of tt in Tt x Tt?

    1 in 4, or 25%.

  86. What are the offspring of TT x tt?

    All Tt.

  87. What are the offspring of Tt x tt?

    1 Tt : 1 tt.

  88. What is a carrier?

    A person with a recessive allele who does not show the disorder.

  89. What are the sex chromosomes of a female?

    XX.

  90. What are the sex chromosomes of a male?

    XY.

  91. What does every egg carry?

    An X chromosome.

  92. What do sperm carry?

    Half an X, and half a Y.

  93. What is the probability of a boy?

    50%, or 1 in 2.

  94. Why might the results of a cross not match the ratio?

    Fertilisation is random, so small numbers can vary.

  95. Are most features controlled by a single gene?

    No, by many genes.

  96. Common mistake about genetic diagrams?

    Not showing the gametes. Always write them before filling in the grid.

  97. Who was Mendel?

    An Austrian monk who studied inheritance using pea plants.

  98. Why did Mendel use pea plants?

    They grow fast, show clear differences and can be cross-pollinated by hand.

  99. What was blending inheritance?

    The idea that the features of parents mix together.

  100. What was the F1 generation of tall and dwarf peas?

    All tall.

  101. What was the F2 generation ratio?

    About 3 tall to 1 dwarf.

  102. What did the F1 result show?

    Features do not blend.

  103. What did Mendel call what we now call genes?

    Inherited factors.

  104. How many factors did he say a plant has for a feature?

    Two, one from each parent.

  105. Which factor is hidden in the F1 plants?

    The recessive factor.

  106. Why was Mendel's work ignored?

    It did not fit blending inheritance, and no mechanism was known.

  107. When was Mendel's work rediscovered?

    In 1900.

  108. Who suggested that factors were on chromosomes?

    Sutton and Boveri, in 1902.

  109. What did Watson and Crick describe in 1953?

    The structure of DNA.

  110. Why was his use of mathematics unusual?

    Few biologists used statistics at that time.

  111. Why did Darwin not know of Mendel's work?

    He never read it.

  112. Common mistake about Mendel?

    Saying that he knew about genes and DNA. He did not.