Biology: SA2 Review 11 IPA 1

1. No two people are genetically identical, except for identical twins. The chief cause of genetic variation among human individuals is ……………. .

• new mutations that occurred in the preceding generation.

• the reshuffling of alleles in sexual reproduction.

• genetic drift due to the small size of the population.

• geographic variation within the population.

• environmental effects

2. In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?

• directional selection

• disruptive selection

• stabilising selection

• sexual selection

• No selection would operate because the population is in Hardy-Weinberg equilibrium.

3. Carriers of the colour-blindness trait include ………………… .

• Men who are heterozygous for the trait

• Men who are homozygous for the trait.

• Women who are heterozygous for the trait.

• Women who are homozygous for the trait.

• Both men and women who have a parents that are homozygous recessive for the trait.

4. Which statement concerning a pair of alleles for a gene controlling a single characteristic in humans are true?

• Both genes come from the father.

• Both genes come from the mother.

• The genes come randomly in pairs from either the mother or father.

• One gene comes from the mother and one gene comes from the father.

• none of the above

5. Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?

• that the parents were true-breeding for contrasting traits 1

• that the trait shows incomplete dominance

• that a blending of traits has occurred

• that the parents were both heterozygous for a single trait

• that each offspring has the same alleles for each of two traits

6. When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

• 0%

• 25%

• 50%

• 75%

• 100%

7. When we say that an individual organism has a greater fitness than another individual, we specifically mean that the organism …………….. .

• lives longer than others of its species

• competes for resources more successfully than others of its species

• mates more frequently than others of its species

• utilizes resources more efficiently than other species occupying similar niches

• leaves more viable offspring than others of its species.

8. Crossing-over takes place during …………. .

• Anaphase II

• Late prophase I

• Interphase I

• Metaphase I

• late prophase II

9. The difference between anaphase of mitosis and anaphase I of meiosis is that ……. .

• the chromosomes line up at the equator in anaphase I.

• centromeres do not exist in anaphase I.

• chromatids do not separate at the centromere in anaphase I.

• crossing-over occurs only in anaphase of mitosis.

• the nuclear envelope breaks down

10. A pedigree chart shows ………….. .

• the genotypic ratios of the offspring.

• the types of gametes produced by the parents

• the pattern of inheritance of a specific gene.

• which genes are codominant

• the genotypes of any parents.