Inheritance: Practice Questions

Which term describes the specific location of a gene on a particular chromosome?

In snapdragon flowers, the allele for red petals (\(R^R\)) is codominant with the allele for white petals (\(R^W\)). Heterozygous plants (\(R^R R^W\)) produce pink petals. If a red-flowered snapdragon is crossed with a pink-flowered snapdragon, what percentage of the offspring are expected to have white petals?

In a species of fruit fly, genes for body colour (B/b) and wing length (L/l) are located on the same autosome. A pure-breeding wild-type fly with grey body and long wings was crossed with a pure-breeding mutant fly with black body and vestigial wings. The \(F_1\) offspring all had grey bodies and long wings. When \(F_1\) males were test crossed with homozygous recessive females (black body, vestigial wings), the following offspring were produced:
Grey body, long wings: 480
Black body, vestigial wings: 490
Grey body, vestigial wings: 20
Black body, long wings: 10

What is the recombination frequency between the genes for body colour and wing length?

A person has the genotype I^AI^B for the ABO blood group system. Both the I^A and I^B alleles are expressed in the phenotype, resulting in blood group AB.
What type of inheritance is shown by these two alleles?

Which of the following terms describes an organism that has two identical alleles for a particular gene?

Explain the difference between a genotype and a phenotype.

In a test cross, an organism with a dominant phenotype but unknown genotype is crossed with a specific partner. Identify the genotype of this partner and explain how the offspring phenotypes reveal the unknown genotype.

Compare and contrast inducible enzymes and repressible enzymes within the context of bacterial gene regulation, providing one condition that triggers each system.

In a species of pea plant, the height of the plant is determined by a single gene. The allele for tall stems (T) is dominant over the allele for short stems (t).

(a) A homozygous tall plant is crossed with a homozygous short plant to produce the \(F_1\) generation. State the genotype and phenotype of the \(F_1\) plants.

(b) Two plants from the \(F_1\) generation are then crossed to produce the \(F_2\) generation. Using a Punnett square, predict the ratio of phenotypes in the \(F_2\) generation.

In pea plants, the allele for yellow seeds (Y) is dominant over green seeds (y), and the allele for round seeds (R) is dominant over wrinkled seeds (r). A plant heterozygous for both traits is self-pollinated.
a) State the genotypes of the gametes produced by this parent plant.
b) Using a Punnett square, determine the phenotypic ratio of the offspring.
c) Calculate the probability of obtaining an offspring that is homozygous recessive for both traits (\(yyrr\)).