Chapter 26 Quiz 1

A DNA molecule consists of two polynucleotide strands that twist around each other to form a (a)______________. The strands are held together by (b)______________ bonds between the nitrogenous bases.

• (a) single helix, (b) hydrogen

• (a) double helix, (b) hydrogen

• (a) double helix, (b) covalent

Genes are segments of DNA located on (c)______________. They control body characteristics by controlling the types of (d)_______________ made.

• (c) proteins, (d) chromosomes

• (c) chromosomes, (d) proteins

• (c) chromosomes, (d) carbohydrates

A gene may have two or more alternative forms called alleles. When an organism contains two different alleles of the same gene, it is described as a (e)______________. The allele that expresses itself in such a condition is said to be (f)______________.

• (e) homozygote, (f) dominant

• (e) homozygote, (f) recessive

• (e) heterozygote, (f) dominant

• (e) heterozygote, (f) recessive

In pea plants, the colour of flowers is controlled by a pair of alleles. The allele for purple flowers (F) is dominant to the allele for white flowers (f). A pure-breeding purple-flowered plant is crossed with a pure-breeding white-flowered plant.

What is the other term used for ‘pure-breeding’ in genetics?

• homozygous

• heterozygous

In pea plants, the colour of flowers is controlled by a pair of alleles. The allele for purple flowers (F) is dominant to the allele for white flowers (f). A pure-breeding purple-flowered plant is crossed with a pure-breeding white-flowered plant.

State the genotype of the pure-breeding purple-flowered plant and the pure-breeding white-flowered plant.

• Purple – FF; white – ff

• Purple – Ff; white – ff

• Purple – FF; white – Ff

In pea plants, the colour of flowers is controlled by a pair of alleles. The allele for purple flowers (F) is dominant to the allele for white flowers (f). A pure-breeding purple-flowered plant is crossed with a pure-breeding white-flowered plant.

State the phenotype(s) of the F₁ plants.

• FF

• Ff

• ff

• FF and ff

In pea plants, the colour of flowers is controlled by a pair of alleles. The allele for purple flowers (F) is dominant to the allele for white flowers (f). A pure-breeding purple-flowered plant is crossed with a pure-breeding white-flowered plant. An individual from the F₁ generation is crossed with a pure-breeding white-flowered plant.

State the expected phenotypic ratio in the F₂ generation.

• 1 : 3

• 3 : 1