Biology SOL Unit 6.2 - Genotype and Phenotype

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

• Genotype refers to observable traits, while phenotype refers to genetic makeup.

• Genotype is influenced by the environment, while phenotype is only inherited from parents.

• Genotype is the genetic makeup inherited from parents, while phenotype is the observable traits resulting from genotype and environment.

• Genotype and phenotype are both directly observable traits.

Answer explanation

The correct choice states that genotype is the genetic makeup inherited from parents, while phenotype refers to observable traits influenced by both genotype and the environment, accurately capturing their relationship.

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A scientist wants to determine the genotype of an individual for a specific gene. Which method would be most appropriate for this task?

• Observing the individual's height and eye color

• DNA sequencing or PCR analysis

• Measuring the individual's body shape

• Recording the individual's behavioral traits

Answer explanation

DNA sequencing or PCR analysis directly analyzes the genetic material, allowing for accurate determination of an individual's genotype, unlike the other methods which assess phenotypic traits.

Which of the following is an example of a phenotype?

• BB, Bb, or bb for eye color

• The DNA sequence of a gene

• Brown eyes or blue eyes

• The combination of alleles inherited from parents

Answer explanation

A phenotype refers to the observable traits of an organism, such as physical characteristics. 'Brown eyes or blue eyes' are examples of phenotypes, while BB, Bb, or bb represent genotypes, which are the genetic makeup.

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A researcher observes that a population of plants has a 3:1 ratio of tall to short plants. What does this ratio represent in genetics?

• The genotype ratio

• The phenotypic ratio

• The DNA sequence ratio

• The inheritance ratio

Answer explanation

The 3:1 ratio of tall to short plants represents the phenotypic ratio, indicating the observable traits in the population. This ratio typically arises from a monohybrid cross involving one dominant and one recessive trait.

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How does genotyping help in determining an individual's genetic makeup?

• By observing physical characteristics

• By analyzing the DNA to identify specific alleles at a gene location

• By recording environmental factors

• By measuring behavioral traits

Answer explanation

Genotyping analyzes DNA to identify specific alleles at gene locations, providing precise information about an individual's genetic makeup, unlike physical traits, environmental factors, or behaviors.

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Which of the following best explains how Mendel's Laws of Inheritance relate to the relationship between genotype and phenotype?

• They explain how genotype influences phenotype.

• They describe how phenotypes change genotypes.

• They show that all genotypes produce the same phenotype.

• They state that environment is the only factor affecting phenotype.

Answer explanation

Mendel's Laws of Inheritance explain how genotype, the genetic makeup, influences phenotype, the observable traits. This relationship is fundamental in understanding how traits are passed from parents to offspring.

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Why can one genotype lead to multiple phenotypes?

• Because of incomplete dominance or codominance

• Because all genes are dominant

• Because phenotypes do not depend on genotypes

• Because genotypes never change

Answer explanation

One genotype can lead to multiple phenotypes due to mechanisms like incomplete dominance or codominance, where alleles interact in ways that produce varying traits, rather than a simple dominant-recessive relationship.

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A person with the genotype 'Bb' for eye color has brown eyes. What does this example illustrate about dominant and recessive traits?

• Brown is the dominant trait, so it is expressed even if only one B allele is present.

• Blue is the dominant trait, so it is always expressed.

• Both brown and blue are expressed equally.

• Genotype does not affect eye color.

Answer explanation

This example illustrates that brown is the dominant trait for eye color. The presence of just one 'B' allele is sufficient for the brown eye color to be expressed, demonstrating the concept of dominance in genetics.

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If two people have the same genotype for eye color but live in different environments (one with limited sunlight and one with more sunlight), what might happen to their phenotypes?

• Their eye color might differ slightly due to environmental influence.

• Their genotypes will change to match the environment.

• They will always have identical eye color regardless of environment.

• Their eye color will become unrelated to their genotype.

Answer explanation

The correct choice is that their eye color might differ slightly due to environmental influence. While their genotype remains the same, factors like sunlight can affect the expression of traits, leading to variations in phenotype.

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Match the following descriptions with the genetic terms they describe.

• Monohybrid Cross

• Different forms of the same gene

• Alleles

• The passing of traits from parents to offspring

• Heredity

• A cross involving two sets of traits

• Dihybrid Cross

• A cross involving one set of traits

Answer explanation

Refer to your notes on Genetics.

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