CLEP Biology Mendelian Inheritance Patterns 3

Question 1

In a testcross, an organism showing the dominant phenotype is crossed with a homozygous recessive individual. If the offspring ratio is 1:1 (dominant:recessive), what is the genotype of the dominant-phenotype parent?

Accepted Answer

Heterozygous (Aa)

Answer

A 1:1 ratio in a testcross reveals that the unknown parent is heterozygous, contributing either A or a to offspring equally.

Question 2

Which statement correctly distinguishes Mendel's law of independent assortment from his law of segregation?

Accepted Answer

Independent assortment applies to genes on different chromosomes, while segregation applies to alleles of a single gene

Answer

Segregation addresses separation of alleles at one locus; independent assortment addresses how genes at different loci (on different chromosomes) distribute independently.

Question 3

A woman is a carrier for an X-linked recessive condition. Her partner is unaffected. What is the probability that their daughter will be affected?

Accepted Answer

0%

Answer

The father contributes a normal X to all daughters, so daughters will be either carriers or unaffected — none will be homozygous recessive.

Question 4

In ABO blood typing, both I^A and I^B alleles are expressed in the I^A I^B individual (blood type AB). This exemplifies:

Accepted Answer

Codominance

Answer

Codominance occurs when both alleles are fully and simultaneously expressed in heterozygotes, as seen in AB blood type.

Question 5

Two parents are each heterozygous for a condition caused by an autosomal dominant allele (Aa × Aa). What percentage of their offspring are expected to be unaffected?

Accepted Answer

25%

Answer

From Aa × Aa, offspring ratios are 1 AA : 2 Aa : 1 aa, so only aa (25%) are unaffected.

CLEP Practice Test

CLEP Practice Test

CLEP Biology Mendelian Inheritance Patterns 3