Question 1

Which of the following best describes a lethal allele and its impact on Mendelian ratios in a cross between two heterozygotes?

Accepted Answer

It alters the expected 3:1 ratio to 2:1 because homozygous individuals for the lethal allele do not survive.

Question 2

A gene exhibits pleiotropy. Which scenario best illustrates pleiotropy?

Accepted Answer

A single gene affects both eye color and susceptibility to a metabolic disorder.

Question 3

How many different genotypes are possible for a gene with four alleles in a diploid organism?

Accepted Answer

10

Question 4

Which equation correctly calculates the number of possible genotypes for a gene with $$n$$ alleles in a diploid organism?

Accepted Answer

$$\frac{n(n+1)}{2}$$

Question 5

A cross between two sex-linked gene carriers (X-linked recessive) produces offspring. What is the expected ratio of affected males to unaffected males?

Accepted Answer

1:1

Question 6

In a pedigree analysis, a trait appears only in males and is passed from mother to son. What type of inheritance is most likely?

Accepted Answer

X-linked recessive

Question 7

Which of the following is an example of codominance?

Accepted Answer

A person with AB blood type expresses both A and B antigens equally.

Question 8

A patient with familial hypercholesterolemia (FH) has one normal allele and one mutant allele. What is the expected phenotype?

Accepted Answer

Intermediate cholesterol levels

Question 9

Which of the following best explains the maternal inheritance of mitochondrial DNA?

Accepted Answer

Mitochondrial DNA is inherited exclusively from the mother because the egg provides the cytoplasm.

Question 10

Which test is used to determine if the results of a cross fit Mendelian expectations?

Accepted Answer

Chi-squared ($$\$$chi^2$$) test

Question 11

A cross between two heterozygous sickle cell carriers produces offspring. What is the expected genotypic ratio?

Accepted Answer

1 normal : 2 carriers : 1 affected

Question 12

Which of the following chromosomal aberrations results in an extra set of chromosomes?

Accepted Answer

Polyploidy

Question 13

A patient is diagnosed with Down syndrome. Which chromosomal change is responsible?

Accepted Answer

Trisomy 21

Question 14

Which of the following best describes the difference between maternal effect and maternal inheritance?

Accepted Answer

Maternal effect refers to traits determined by the mother's genotype, while maternal inheritance refers to traits determined by organelles inherited from the mother.

Question 15

Which equation is used to calculate the expected value in a chi-squared ($$\$$chi^2$$) test?

Accepted Answer

$$\$$chi^2$$ = \sum \frac{(O - E)^2$}{E}$$

Question 16

Which scenario best illustrates incomplete dominance?

Accepted Answer

A cross between red and white flowers produces pink flowers.

Question 17

Which of the following disorders is caused by a single gene with multiple alleles?

Accepted Answer

ABO blood group

Question 18

A cross between a snail with right-handed shell coiling and a snail with left-handed shell coiling produces offspring. The direction of shell coiling is determined by which genetic phenomenon?

Accepted Answer

Maternal effect

Question 19

Which of the following best describes the effect of gene dosage in chromosomal aberrations?

Accepted Answer

Gene dosage can alter phenotype by increasing or decreasing the number of gene copies.

Question 20

Which inheritance pattern is most likely if a trait appears in every generation and affects both males and females equally?

Accepted Answer

Autosomal dominant

Genetics Study Guide: Mendelian Inheritance, Alleles, and Chromosomal Aberrations

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