Unit 8.5 Quiz 4

A segment of DNA that codes for a particular trait:

• nucleus

• karyotype

• chromosome

• gene

Answer explanation

A gene is a specific segment of DNA that contains the instructions for coding a particular trait. Unlike a chromosome, which is a larger structure, a gene is the fundamental unit of heredity.

Tags

NGSS.HS-LS3-1

When an organism has DIFFERENT alleles for a gene (such as one dominant, one recessive), it is said to be:

• genotyped

• phenotyped

• homozygous

• heterozygous

Answer explanation

When an organism has different alleles for a gene, such as one dominant and one recessive, it is termed heterozygous. In contrast, homozygous refers to having identical alleles.

When an organism has SAME alleles for a gene, it is said to be:

• genotyped

• phenotyped

• homozygous

• heterozygous

Answer explanation

When an organism has the same alleles for a gene, it is referred to as homozygous. This means both alleles are identical, distinguishing it from heterozygous, where the alleles are different.

The specific genetic combination of alleles of an individual (such as BB, bb, or Bb):

• phenotype

• genotype

• variation

• karyotype

Answer explanation

The specific genetic combination of alleles, such as BB, bb, or Bb, refers to the genotype of an individual. The phenotype describes observable traits, while variation and karyotype are different concepts.

What does heterozygous mean?

• An organism has the same alleles for a trait (BB or bb)

• An organism has different alleles for a trait (Bb)

• When neither allele is dominant

• A different form of a trait

Answer explanation

Heterozygous refers to an organism having two different alleles for a trait, represented as 'Bb'. This contrasts with homozygous, where the alleles are the same (BB or bb). Thus, the correct choice is that an organism has different alleles for a trait.

An allele that expresses a trait even if there is only one copy.

• phenotype

• genotype

• codominant

• dominant

• recessive

Answer explanation

A dominant allele expresses its trait even with just one copy present, unlike a recessive allele, which requires two copies to be expressed. Therefore, the correct answer is 'dominant'.

A trait that is expressed only if both alleles are the same.

• phenotype

• genotype

• codominant

• dominant

• recessive

Answer explanation

A recessive trait is expressed only when both alleles are the same (homozygous). In contrast, dominant traits can be expressed with just one dominant allele. Therefore, the correct answer is 'recessive'.

A tool that traces a trait through several generations:

• Punnett square

• pedigree

• dichotomous key

• cladogram

Answer explanation

A pedigree is a diagram that traces the inheritance of traits through generations, showing relationships and traits in family trees. It is used to analyze genetic patterns, making it the correct choice for this question.