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AP Biology Unit 5B: Mendelian Genetics & Inheritance — practice questions

Explore 64 free Unit 5B: Mendelian Genetics & Inheritance questions in AP Biology Biology. Open each question or exercise to read its content, reference answers and available explanation.

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Unit 5B: Mendelian Genetics & Inheritance questions and exercises with answers

Showing questions 1–30 of 64.

In Mendel's monohybrid cross between tall (TT) and dwarf (tt) pea plants, what is the phenotypic ratio observed in the F2 generation?Read the answer and worked solution →A cross used to determine the genotype of an organism showing a dominant phenotype is called a:Read the answer and worked solution →In a typical Mendelian dihybrid cross of two heterozygous parents (RrYy x RrYy), what phenotypic ratio appears in the F2 generation?Read the answer and worked solution →Which type of sex determination is found in human beings?Read the answer and worked solution →Haemophilia in humans is inherited as:Read the answer and worked solution →How many distinct genotypes are possible for the human ABO blood group system, which is controlled by three alleles (I^A, I^B and i)?Read the answer and worked solution →Which insect group shows XO type of sex determination, where males have one X chromosome and females have two?Read the answer and worked solution →In which group is the female the heterogametic sex, producing two kinds of gametes with respect to sex chromosomes?Read the answer and worked solution →Klinefelter's syndrome in humans corresponds to which karyotype?Read the answer and worked solution →Turner's syndrome in human females is caused by:Read the answer and worked solution →A heterozygous yellow round seeded pea plant (YyRr) is test crossed with a green wrinkled seeded plant (yyrr). What phenotypic ratio is expected in the progeny?Read the answer and worked solution →In sickle-cell anaemia the mutation substitutes which amino acid in the beta chain of haemoglobin?Read the answer and worked solution →In Drosophila melanogaster, a normal female and a normal male respectively carry which sex chromosome compositions?Read the answer and worked solution →A substitution of a single base pair in the DNA that alters a single amino acid in the resulting protein is classified as:Read the answer and worked solution →Failure of segregation of chromatids during cell division, leading to gain or loss of a single chromosome, is termed:Read the answer and worked solution →Down's syndrome is caused by an extra copy of which chromosome?Read the answer and worked solution →Turner's syndrome is caused byRead the answer and worked solution →The karyotype in Klinefelter's syndrome isRead the answer and worked solution →Gain or loss of a chromosome caused by failure of chromatids to segregate is calledRead the answer and worked solution →Sickle cell anaemia is inherited asRead the answer and worked solution →Colour blindness is inherited asRead the answer and worked solution →In haemophilia, an unaffected carrier female mayRead the answer and worked solution →Phenylketonuria is best described asRead the answer and worked solution →The phenotypic ratio in the F2 generation of a dihybrid cross isRead the answer and worked solution →The phenotypic ratio in the F2 generation of a monohybrid cross isRead the answer and worked solution →Crossing an individual showing the dominant phenotype with a recessive parent is called aRead the answer and worked solution →When the F1 phenotype is intermediate between the two parents, the pattern is calledRead the answer and worked solution →In co-dominance, the F1 generationRead the answer and worked solution →A gene existing in more than two allelic forms in a population showsRead the answer and worked solution →The laws of inheritance were first worked out byRead the answer and worked solution →

Worked practice questions

In Mendel's monohybrid cross between tall (TT) and dwarf (tt) pea plants, what is the phenotypic ratio observed in the F2 generation?

  1. 3 tall : 1 dwarf
  2. 1 tall : 1 dwarf
  3. 9 tall : 1 dwarf
  4. All tall plants
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Correct answer: A. 3 tall : 1 dwarf

F2 segregation gives the classical 3:1 phenotypic ratio (1 TT : 2 Tt : 1 tt, with TT and Tt both expressing the dominant tall phenotype).

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A cross used to determine the genotype of an organism showing a dominant phenotype is called a:

  1. Reciprocal cross
  2. Back cross with heterozygote
  3. Test cross
  4. Outcross
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Correct answer: C. Test cross

A test cross pairs the unknown individual with the homozygous recessive parent. The offspring ratio directly reveals whether the unknown is homozygous or heterozygous dominant.

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In a typical Mendelian dihybrid cross of two heterozygous parents (RrYy x RrYy), what phenotypic ratio appears in the F2 generation?

  1. 3 : 1
  2. 1 : 2 : 1
  3. 9 : 3 : 3 : 1
  4. 1 : 1 : 1 : 1
Show answer and solution

Correct answer: C. 9 : 3 : 3 : 1

Independent assortment of two gene pairs produces the 9:3:3:1 ratio in F2, which is the product of two 3:1 monohybrid ratios.

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