Keystone Test Biology: Genetics and Evolution 2

Question 1

A plant with genotype AaBb is self-fertilized. What fraction of offspring will be aabb?

Accepted Answer

1/16

Answer

Each heterozygous gene pair produces 1/4 homozygous recessive offspring, so 1/4 × 1/4 = 1/16.

Question 2

Which type of mutation involves the insertion of a nucleotide into a DNA sequence?

Accepted Answer

Frameshift

Answer

Inserting a nucleotide shifts the reading frame of all downstream codons, making it a frameshift mutation.

Question 3

During which phase of meiosis do homologous chromosomes separate?

Accepted Answer

Meiosis I anaphase

Answer

Homologous chromosomes are pulled to opposite poles during anaphase I, reducing chromosome number by half.

Question 4

A white-eyed female Drosophila (X^w X^w) is crossed with a red-eyed male (X^+ Y). What proportion of female offspring will have white eyes?

Accepted Answer

0%

Answer

All daughters receive X^+ from their father, making them X^+ X^w carriers with red eyes.

Question 5

What does a phylogenetic tree's branch length typically represent?

Accepted Answer

Amount of evolutionary change

Answer

Branch lengths on most phylogenetic trees represent the amount of evolutionary change (mutations) along that lineage.

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