Question 1

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

Accepted Answer

Genotype is the genetic makeup of an organism, and phenotype is the observable expression of those genes.

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 in the offspring?

Accepted Answer

3 tall : 1 short

Question 3

Which statement accurately describes Mendel’s law of segregation?

Accepted Answer

Each individual has two alleles for each gene, and these alleles separate during gamete formation.

Question 4

In a dihybrid cross between two heterozygous pea plants ($$YyRr 	imes YyRr$$), where $$Y = $$yellow, $$y = $$green, $$R = $$round, $$r = $$wrinkled, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

9 yellow round : 3 yellow wrinkled : 3 green round : 1 green wrinkled

Question 5

Which of the following best defines an allele?

Accepted Answer

A variant form of a gene at a particular locus.

Question 6

A testcross is performed between a pea plant with an unknown genotype for flower color (purple is dominant, white is recessive) and a white-flowered plant. If all offspring are purple, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant ($$PP)$$

Question 7

Which of the following scenarios illustrates incomplete dominance?

Accepted Answer

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

Question 8

If two genes are located on different chromosomes, which of Mendel’s laws explains their inheritance pattern?

Accepted Answer

Law of Independent Assortment

Question 9

A woman is a carrier for a recessive genetic disorder (genotype $$Nn$$), and her partner is also a carrier ($$Nn). $$What is the probability that their child will be affected by the disorder? Use the product rule.

Accepted Answer

$$\displaystyle \frac{1}{4}$$

Question 10

Which of the following is an example of codominance?

Accepted Answer

A person with AB blood type, expressing both A and B antigens.

Question 11

In a monohybrid cross, what is the probability of producing a homozygous recessive offspring if both parents are heterozygous? Use the sum rule if necessary.

Accepted Answer

$$\displaystyle \frac{1}{4}$$

Question 12

Which of the following best describes a polygenic trait?

Accepted Answer

A trait controlled by multiple genes, each contributing to the phenotype.

Question 13

A true-breeding plant with round seeds ($$RR) is $$crossed with a true-breeding plant with wrinkled seeds ($$rr). $$What will be the genotype and phenotype of the F1 generation?

Accepted Answer

All $$Rr ($$round)

Question 14

Which of the following best defines a locus?

Accepted Answer

The specific physical location of a gene on a chromosome.

Question 15

If two events are independent, what is the probability that both will occur? (Product Rule)

Accepted Answer

The product of their individual probabilities.

Question 16

Which of the following crosses would you use to determine if an individual with a dominant phenotype is homozygous or heterozygous?

Accepted Answer

Cross with a homozygous recessive individual (testcross)

Question 17

A geneticist observes that the presence of one gene can mask the expression of another gene at a different locus. This is an example of:

Accepted Answer

Epistasis

Question 18

Which of the following best describes a carrier in genetics?

Accepted Answer

An individual who is heterozygous for a recessive trait and does not express the trait.

Question 19

If the probability of event A is $$0.3$$ and event B is $$0.2$$, and the events are mutually exclusive, what is the probability that either event A or event B occurs? (Sum Rule)

Accepted Answer

$$0.5$$

Question 20

Which of the following is a common phenotypic ratio observed in the F2 generation of a monohybrid cross involving complete dominance?

Accepted Answer

3:1

Mendelian Genetics: Patterns of Inheritance and Probability

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