Question 1

Which of the following best describes the difference between a gene and an allele?

Accepted Answer

A gene is a specific sequence of DNA that codes for a protein, while an allele is a variant form of that gene.

Question 2

A pea plant with genotype $Tt$ (where $T$ is tall and $t$ is short) is crossed with another $Tt$ plant. What is the expected phenotypic ratio of the offspring?

Accepted Answer

$3$ tall : $1$ short

Question 3

Which of the following scenarios best illustrates incomplete dominance?

Accepted Answer

A red-flowered plant crossed with a white-flowered plant produces all pink-flowered offspring.

Question 4

In a dihybrid cross between two individuals heterozygous for both traits ($RrYy 	imes RrYy$), what is the expected phenotypic ratio of the offspring, assuming independent assortment?

Accepted Answer

$9:3:3:1$

Question 5

Which of the following best defines pleiotropy?

Accepted Answer

A single gene affects multiple, seemingly unrelated phenotypic traits.

Question 6

A woman who is a carrier for hemophilia (an X-linked recessive disorder) has children with a man who does not have hemophilia. What is the probability that their son will have hemophilia?

Accepted Answer

$50\%$

Question 7

Which of the following is an example of a complex trait?

Accepted Answer

Height in humans, which is influenced by multiple genes and environmental factors.

Question 8

If two true-breeding plants, one with yellow seeds ($YY$) and one with green seeds ($yy$), are crossed, what will be the genotype of the F1 generation?

Accepted Answer

All $Yy$

Question 9

Which of the following statements about linkage is correct?

Accepted Answer

Linked genes are located close together on the same chromosome and tend to be inherited together.

Question 10

A person with genotype $IAIB$ for the ABO blood group system will have which blood type?

Accepted Answer

AB

Question 11

Which of the following best describes a dominant allele?

Accepted Answer

An allele that is expressed in the phenotype even when only one copy is present.

Question 12

A geneticist is mapping a gene using linkage analysis. If two genes are found to have a recombination frequency of $10\%$, what does this suggest about their physical distance on the chromosome?

Accepted Answer

They are relatively close together, about $10$ map units apart.

Question 13

Which of the following is an example of co-dominance?

Accepted Answer

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

Question 14

If a man with genotype $X^AY$ (normal vision) and a woman with genotype $X^AX^a$ (carrier for colorblindness) have a daughter, what is the probability that she will be colorblind?

Accepted Answer

$0\%$

Question 15

Which of the following best defines a true-breeding organism?

Accepted Answer

An organism that, when self-fertilized, produces offspring identical to itself for a given trait.

Question 16

A plant with genotype $Rr$ (round seeds) is crossed with a plant with genotype $rr$ (wrinkled seeds). What is the expected genotypic ratio of the offspring?

Accepted Answer

$1$ Rr : $1$ rr

Question 17

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype is the genetic makeup of an organism, while phenotype is the observable physical or physiological traits.

Question 18

A genetic disorder is caused by a single gene that affects both the nervous system and skin pigmentation. This is an example of:

Accepted Answer

Pleiotropy

Question 19

If two genes are located on the same chromosome and are inherited together more often than not, which principle is being violated?

Accepted Answer

The law of independent assortment

Question 20

A woman with blood type $O$ has a child with blood type $A$. Which of the following could be the genotype of the father?

Accepted Answer

$IAi$

Patterns of Inheritance: Classical Genetics Study Guide

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