IB Biology Quiz: Understand Inheritance

Red-green colour blindness is an X-linked recessive trait. A woman with normal vision, whose father was colour-blind, marries a man with normal vision. What is the probability that their first son will be colour-blind?

A woman has blood type B, and her father had blood type O. She has a child with a man who has blood type A, but whose mother had blood type O. What is the probability that their first child will have blood type O?

A researcher performs a dihybrid cross assuming independent assortment and observes 480 offspring. To perform a chi-squared test on the results, the researcher needs to calculate the expected values. What is the expected number of offspring predicted to show both dominant phenotypes?

Coat colour in rabbits is controlled by a single gene with four alleles showing a dominance hierarchy: agouti (C) > chinchilla ($c^ch$) > Himalayan ($c^h$) > albino (c). What phenotypic ratio would be expected from a cross between a rabbit of genotype Cc^h and a rabbit of genotype c^chc?

A plant breeder crosses a homozygous red-flowered plant with a homozygous blue-flowered plant. The resulting F1 generation has flowers with distinct patches of red and blue. This is an example of which type of inheritance?

A farmer has a bull with a dominant trait for black coat colour (B). To determine if the bull is homozygous (BB) or heterozygous (Bb), the farmer should cross it with a cow of which genotype and look for which outcome?

Two linked genes, P and Q, have a recombination frequency of 18%. An individual is heterozygous for both genes, with a chromosome arrangement of PQ/pq. What percentage of gametes produced by this individual is expected to have the genotype Pq?

In cats, the gene for orange fur colour (O) is on the X chromosome. The allele O results in orange fur, while the allele o results in black fur. Heterozygous females ($X^O$ $X^o$) have patches of both orange and black fur, a pattern called tortoiseshell. A tortoiseshell female mates with a black male. What is the expected phenotypic ratio of their male offspring?

In Labrador retrievers, coat colour is determined by two genes. One gene determines pigment production (E/e), where E_ allows pigment and ee results in a yellow coat regardless of the other gene. The second gene determines the pigment colour (B/b), where B_ is black and bb is brown. A cross is made between two dogs with the genotypes BbEe x Bbee. What proportion of the puppies is expected to be yellow?

A single mutation in the human FBN1 gene can lead to Marfan syndrome, which affects the skeleton, eyes, and cardiovascular system. In fruit flies, the genes for body colour and wing length are located close together on the same chromosome and are often inherited together. What are the genetic principles that best explain these two observations, respectively?

A dihybrid cross is performed between two plants heterozygous for both flower colour (Pp) and seed shape (Rr). The resulting offspring show a large excess of parental phenotypes (purple flowers/round seeds and white flowers/wrinkled seeds) and a significant deficit of recombinant phenotypes. Which statement is the most likely conclusion?

Phenylketonuria (PKU) is an autosomal recessive disorder. A couple, John and Mary, are both phenotypically normal. John has a brother with PKU, and Mary's mother has PKU. What is the probability that their first child will be a carrier of the PKU allele?

Monozygotic twins share an identical genotype. A study of adult identical twins who were separated at birth and raised in different socioeconomic conditions finds significant, consistent differences in their IQ scores and susceptibility to certain diseases. What is the most valid scientific conclusion?

In fruit flies, grey body (G) is dominant to ebony body (g), and normal wings (W) are dominant to vestigial wings (w). A fly with a grey body and normal wings is test-crossed. The cross produces offspring in a phenotypic ratio of 1 grey-normal : 1 ebony-normal. What was the genotype of the grey-bodied, normal-winged parent?

Human skin colour shows continuous variation, resulting from the combined effects of several genes. Which term best describes the genetic basis for such traits?

Which aspect of Gregor Mendel's experimental design was most critical for his ability to deduce the principles of inheritance, which had eluded previous investigators?

A pedigree analysis reveals that an affected father has an unaffected daughter. This single observation definitively rules out which mode of inheritance?