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Flashcards · Biology

Inheritance

111 cards from 7 lessons

  1. What is an allele?

    A different version of the same gene.

  2. How many alleles of a gene does a body cell have?

    Two, one from each parent.

  3. What is a dominant allele?

    One that shows its effect even if only one copy is present.

  4. What is a recessive allele?

    One that only shows its effect if two copies are present.

  5. How are dominant and recessive alleles written?

    Dominant with a capital letter, recessive with the lower-case letter.

  6. What does homozygous mean?

    Two identical alleles.

  7. What does heterozygous mean?

    Two different alleles.

  8. What is a genotype?

    The alleles an organism has, such as Tt.

  9. What is a phenotype?

    The characteristic that the organism shows.

  10. What is the phenotype of Tt if T is dominant for tall?

    Tall.

  11. What genotype must a plant have to be dwarf, if dwarf is recessive?

    tt.

  12. Does a gamete have one or two alleles of a gene?

    One.

  13. What is a carrier?

    A person with one recessive allele who does not show the disorder but can pass it on.

  14. What genotype does a person with cystic fibrosis have?

    ff (two recessive alleles).

  15. Does dominant mean most common?

    No. A dominant allele can be rare.

  16. Why can two plants have the same phenotype but different genotypes?

    TT and Tt both show the dominant phenotype.

  17. What is a monohybrid cross?

    A cross that looks at the inheritance of one gene.

  18. What is a Punnett square?

    A grid that shows all possible combinations of gametes.

  19. What gametes does a Tt parent make?

    T and t, in equal numbers.

  20. What is the genotype ratio from Tt x Tt?

    1 TT : 2 Tt : 1 tt.

  21. What is the phenotype ratio from Tt x Tt?

    3 dominant : 1 recessive.

  22. What is the probability of a recessive offspring from Tt x Tt?

    1 in 4, or 25%.

  23. What offspring result from TT x tt?

    All Tt.

  24. What ratio comes from Tt x tt?

    1 : 1.

  25. What is a test cross used for?

    To find out whether an organism with the dominant phenotype is homozygous or heterozygous.

  26. Two carriers of a recessive disorder have a child. What is the chance it has the disorder?

    1 in 4 (25%).

  27. What are the chances that this child is a carrier?

    2 in 4 (50%).

  28. What is the chance a child of two carriers is not a carrier and unaffected?

    1 in 4 (25%).

  29. Why might the actual results differ from the predicted ratio?

    Fertilisation is random, and small numbers give unreliable results.

  30. If two carriers have an affected child, what is the chance that the next is affected?

    Still 1 in 4.

  31. 80 offspring come from Tt x Tt. How many do you expect to be tall?

    60.

  32. What is the usual mistake in a Punnett square?

    Writing a heterozygous box as tT in one place and Tt in another. Choose one and write the capital first.

  33. What does a square represent in a pedigree?

    A male.

  34. What does a circle represent?

    A female.

  35. What does a filled symbol mean?

    The person has the characteristic or disorder.

  36. What do the rows in a pedigree show?

    Generations.

  37. What does a horizontal line between two symbols show?

    The two people are partners.

  38. Two unaffected parents have an affected child. Is the allele dominant or recessive?

    Recessive.

  39. What are the genotypes of the parents in that case?

    Both are heterozygous carriers (Ff).

  40. What genotype does a person with cystic fibrosis have?

    ff.

  41. What is the chance that the child of two carriers has cystic fibrosis?

    1 in 4 (25%).

  42. What is the chance a child of an affected Huntington's parent (Hh) and an unaffected parent (hh) is affected?

    1 in 2 (50%).

  43. Is Huntington's disease caused by a dominant or a recessive allele?

    A dominant allele.

  44. Is polydactyly caused by a dominant or a recessive allele?

    A dominant allele.

  45. If a dominant condition affects a child, must at least one parent have it?

    Yes, unless a new mutation has occurred.

  46. What is genetic counselling?

    Advice about the chances of passing an inherited disorder to a child.

  47. Can you tell the genotype of an unaffected child of two carriers?

    No. It could be FF or Ff, so the pedigree shows it as unknown.

  48. Common mistake with pedigrees?

    Saying the allele is dominant because both parents are unaffected. Unaffected parents with an affected child mean recessive.

  49. Which sex chromosomes does a woman have?

    XX.

  50. Which sex chromosomes does a man have?

    XY.

  51. Which sex chromosome do all eggs carry?

    X.

  52. Which sex chromosomes do sperm carry?

    Half carry X and half carry Y.

  53. What decides the sex of a baby?

    Whether the sperm that fertilises the egg carries an X or a Y.

  54. What is the genotype of a baby girl?

    XX.

  55. What is the chance that a baby is a boy?

    1 in 2, or 50%.

  56. What is the sex ratio from a cross of XX x XY?

    1 girl : 1 boy.

  57. If a couple have four girls, what is the chance that the fifth child is a boy?

    Still 50%.

  58. Which parent decides the sex of the baby?

    The father, because his sperm carries X or Y.

  59. What is the chance of 3 girls in a row?

    1 in 8 (12.5%).

  60. Which gene on the Y chromosome starts male development?

    SRY.

  61. Is the Y chromosome bigger or smaller than the X?

    Smaller.

  62. Which of the 23 pairs of chromosomes are the sex chromosomes?

    The 23rd pair.

  63. What is the common mistake when writing the sex cross?

    Writing the mother as XY. A mother is XX.

  64. Who discovered the basic rules of inheritance?

    Gregor Mendel.

  65. What organism did Mendel use?

    Pea plants.

  66. Give two reasons why peas were a good choice.

    They grow quickly and cheaply, have clear differences, and can be cross-pollinated by hand.

  67. What is a pure-breeding plant?

    One that always produces offspring like itself when self-pollinated.

  68. What was the F1 generation in the tall and dwarf cross?

    All tall.

  69. What was the F2 ratio of tall to dwarf plants?

    About 3 : 1.

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

    Hereditary factors.

  71. How many factors did Mendel suggest each plant has for a characteristic?

    Two, one from each parent.

  72. Did the features blend in Mendel's results?

    No. The recessive feature came back unchanged.

  73. What was blending inheritance?

    The idea that the features of the parents mix in their offspring.

  74. Why was Mendel's work ignored?

    It went against the idea of blending, no mechanism was known, and he was not well known.

  75. When was Mendel's work rediscovered?

    In 1900.

  76. Who linked Mendel's factors to chromosomes in 1902?

    Sutton and Boveri.

  77. What did Watson and Crick show in 1953?

    The structure of DNA.

  78. Mendel counted 787 tall and 277 dwarf plants in the F2. About what ratio is this?

    About 3 : 1.

  79. Common mistake about Mendel?

    Saying he knew about genes and DNA. He did not know about either.

  80. What are the four ABO blood groups?

    A, B, AB and O.

  81. How many alleles are there for the ABO gene?

    Three: \(I^A\), \(I^B\) and \(i\).

  82. How many ABO alleles does one person have?

    Two.

  83. What is codominance?

    When both alleles show their effect in a heterozygous person.

  84. What are multiple alleles?

    When a gene has more than two alleles in a population.

  85. What is the genotype of blood group AB?

    \(I^A I^B\).

  86. What is the genotype of blood group O?

    \(ii\).

  87. What genotypes give blood group A?

    \(I^A I^A\) or \(I^A i\).

  88. What genotypes give blood group B?

    \(I^B I^B\) or \(I^B i\).

  89. Which alleles are codominant?

    \(I^A\) and \(I^B\).

  90. Which allele is recessive?

    \(i\).

  91. What is the chance of group O from \(I^A i\) x \(I^B i\)?

    1 in 4 (25%).

  92. Can a group AB parent and a group O parent have a group O child?

    No. The AB parent has no \(i\) allele.

  93. Which blood group is the universal donor?

    Group O.

  94. Give an example of codominance other than blood groups.

    Roan cattle, with red and white hairs.

  95. What is the common mistake about ABO inheritance?

    Thinking that there are only two alleles. There are three in the population.

  96. What is a sex-linked gene?

    A gene on a sex chromosome, usually the X chromosome.

  97. Why are males more likely to have a sex-linked recessive disorder?

    They have only one X chromosome, so a single recessive allele shows.

  98. Can a male be a carrier of a sex-linked recessive allele?

    No. If he has the allele, he has the disorder.

  99. What is the genotype of a carrier female for haemophilia?

    \(X^H X^h\).

  100. What is the genotype of a male with haemophilia?

    \(X^h Y\).

  101. What is the genotype of an affected female?

    \(X^h X^h\).

  102. Name two sex-linked recessive disorders.

    Haemophilia and red-green colour blindness (also Duchenne muscular dystrophy).

  103. What happens in haemophilia?

    The blood does not clot properly.

  104. A carrier mother and a normal father: what is the chance of an affected son?

    1 in 2 (50%) for each son.

  105. A carrier mother and a normal father: what is the chance of an affected child?

    1 in 4 (25%).

  106. Can a father with haemophilia pass it to his son?

    No. He passes his Y chromosome to his sons.

  107. What will the daughters of an affected father and a normal mother be?

    All carriers.

  108. Who was a famous carrier of haemophilia?

    Queen Victoria.

  109. Is colour blindness more common in men or women?

    Men.

  110. Why does a female need two recessive alleles to be affected?

    A dominant allele on her other X chromosome hides the recessive one.

  111. What is the common mistake about sex-linked inheritance?

    Writing the alleles on the Y chromosome. The Y has no matching allele for the gene.