Genetics Practice

Consider a garden pea plant that Noah, Maya, and Aria are observing. The plant has purple flowers, which is visible to them. What term describes this visible characteristic of the pea plant, as a result of its genetic makeup?

• Genotype

• Phenotype

• Allele

• Homozygous

Answer explanation

The term for the physical appearance of an organism as a result of its genotype is called Phenotype.

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DOK Level 1: Recall

In a monohybrid cross between two heterozygous pea plants (Tt), what is the probability of producing a pea plant with tall stems (T-)? Scarlett and Kai are experimenting in their biology class to understand how traits are passed in pea plants. (T is dominant for tall stems, t is recessive for short stems.)

• 25%

• 50%

• 75%

• 100%

Answer explanation

The probability of producing a pea plant with tall stems (T-) in a monohybrid cross between two heterozygous pea plants is 75% because there is a 3/4 chance of getting the dominant allele for tall stems (T) in the offspring.

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DOK Level 2: Skill/Concept

Harper and Maya are studying genetics and decide to perform an experiment involving pea plants. They choose to track the inheritance of two traits: seed color and seed shape. Which of the following best describes this type of experiment?

• A cross involving one trait

• A cross involving two traits

• A cross between two different species

• A cross between two purebred parents

Answer explanation

A dihybrid cross involves two traits being studied simultaneously, making it the best description among the options provided.

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DOK Level 1: Recall

In a study on genetic mutations affecting fruit flies, Jackson discovered that a particular mutation involved the addition of one or more nucleotide base pairs into a DNA sequence. What type of mutation did Jackson discover?

• Deletion

• Insertion

• Substitution

• Inversion

Answer explanation

Insertion involves the addition of one or more nucleotide base pairs into a DNA sequence, making it the correct type of genetic mutation in this case.

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DOK Level 1: Recall

In a pea plant experiment, if a plant has two identical alleles for green pod color, what term describes its genetic makeup?

• Heterozygous

• Homozygous

• Hemizygous

• Hybrid

Answer explanation

Homozygous describes an organism with two identical alleles for a trait in Mendelian genetics.

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DOK Level 1: Recall

In a biology class, Daniel, Abigail, and Ava are studying flower pigmentation. They notice that a certain flower species does not follow the typical Mendelian inheritance patterns for its color. Which of the following inheritance patterns could explain their observation?

• Complete dominance

• Incomplete dominance

• Codominance

• Both B and C

Answer explanation

The correct choice is 'Both B and C' because incomplete dominance and codominance are examples of non-Mendelian inheritance patterns, unlike complete dominance.

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DOK Level 2: Skill/Concept

If a type of tomato plant shows a fruit color ratio of 1 red:2 pink:1 white after cross-pollinating two plants, what can be inferred about the parents' genotypes for the fruit color trait?

• Both parents are homozygous for fruit color.

• Both parents are heterozygous for fruit color.

• One parent is homozygous dominant for red fruit, and the other is homozygous recessive for white fruit.

• One parent is heterozygous for fruit color, and the other is homozygous recessive for white fruit.

Answer explanation

The genotype ratio of 1:2:1 indicates that both parents are heterozygous for the trait. This ratio is characteristic of a monohybrid cross between two heterozygous individuals.

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DOK Level 2: Skill/Concept

Imagine Ava and Noah are gardening enthusiasts who decide to cross two pea plants with heterozygous traits for flower color (Purple-white) and plant height (Tall-short), represented as AaBb x AaBb. Assuming complete dominance for both traits, what is the expected phenotypic ratio of the offspring?

• 9:3:3:1

• 3:1

• 1:2:1

• 1:1:1:1

Answer explanation

In a dihybrid cross between two heterozygous parents with complete dominance, the expected phenotypic ratio is 9:3:3:1, representing the combinations of dominant and recessive alleles for both traits.

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DOK Level 2: Skill/Concept

In a biology class, Lily is learning about genetic mutations and their effects on proteins. Which of the following mutations does not change the amino acid sequence of the protein produced?

• Missense mutation

• Nonsense mutation

• Silent mutation

• Frameshift mutation

Answer explanation

A silent mutation does not change the amino acid sequence of the protein produced, making it the correct choice in this scenario.

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DOK Level 1: Recall

In a garden, a red-flowered rose (R) is dominant over a white-flowered rose (r). If a heterozygous red-flowered rose is crossed with a white-flowered rose, what is the probability of obtaining a rose with white flowers?

• 0%

• 25%

• 50%

• 75%

Answer explanation

When crossing a heterozygous red-flowered plant (Rr) with a white-flowered plant (rr), there is a 50% probability of obtaining a plant with white flowers (rr) due to the 1:1 ratio of genotypes in the offspring.

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DOK Level 2: Skill/Concept