The genetic makeup of an individual is its ; the observable traits are its .

Answer: genotype; phenotype Genotype is what the genes are; phenotype is what's expressed.

What is the genotype of the unknown parent?

Answer: Tt (heterozygous) A 1:1 ratio in a test cross indicates the unknown parent must be heterozygous (Tt). A homozygous dominant parent would yield only tall offspring.

Which mode of inheritance best fits this pedigree?

Answer: Autosomal dominant Vertical transmission with no skipping, equal sex ratio, and at least one affected parent for every affected child are hallmarks of autosomal dominant inheritance.

AP Biology · Topic 5.3

Mendelian Genetics Practice

Part of Heredity.(IST-1.E)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$The genetic makeup of an individual is its _______; the observable traits are its _______.$
- A
  $homozygous; heterozygous$
- B
  $genotype; phenotype$
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- C
  $phenotype; genotype$
- D
  $allele; gene$
Why
$Genotype is what the genes are; phenotype is what's expressed.$
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Sample 2difficulty 1/5
$What is the genotype of the unknown parent?$
- A
  $tt (homozygous recessive)$
- B
  $Cannot be determined$
- C
  $Tt (heterozygous)$
  check_circle
- D
  $TT (homozygous dominant)$
Why
$A 1:1 ratio in a test cross indicates the unknown parent must be heterozygous (Tt). A homozygous dominant parent would yield only tall offspring.$
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Sample 3difficulty 1/5
$The trait appears in every generation and is passed by both sexes; affected individuals always have at least one affected parent.$
$Which mode of inheritance best fits this pedigree?$
- A
  $X-linked recessive$
- B
  $Autosomal recessive$
- C
  $Mitochondrial$
- D
  $Autosomal dominant$
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Why
$Vertical transmission with no skipping, equal sex ratio, and at least one affected parent for every affected child are hallmarks of autosomal dominant inheritance.$
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Sample 4difficulty 1/5
$A monohybrid cross of two heterozygous (Bb) parents is shown. B (black) is dominant to b (brown).$
$What is the expected phenotypic ratio of black to brown offspring?$
- A
  $All black$
- B
  $3 black : 1 brown$
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- C
  $1 black : 1 brown$
- D
  $1 black : 2 black-brown : 1 brown$
Why
$BB, Bb, Bb express the dominant black phenotype (3); bb expresses brown (1), giving 3:1.$
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Sample 5difficulty 1/5
$Mendel's law of segregation states that$
- A
  $Dominant alleles always mask recessive alleles in heterozygotes, determining the visible phenotype$
- B
  $Alleles of different genes assort independently of one another into gametes during meiosis$
- C
  $The two alleles for a gene separate during gamete formation, so each gamete carries only one allele$
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- D
  $Each gamete receives both alleles for a gene, preserving the parental diploid genotype intact$
Why
$Each parent passes one of its two alleles to each gamete (during meiosis I when homologs separate).$
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