Progress Check 2: Genes & Alleles

What does it mean for an organism to be homozygous for a particular gene?

• It has two different alleles for that gene.

• It has two identical alleles for that gene.

• It has only one allele for that gene.

• It has no alleles for that gene.

Answer explanation

For an organism to be homozygous for a particular gene means it has two identical alleles for that gene. This is in contrast to being heterozygous, where there are two different alleles.

Which of the following is an example of a heterozygous genotype?

• AA

• aa

• Aa

• A

Answer explanation

A heterozygous genotype consists of two different alleles for a trait. 'Aa' represents one dominant allele (A) and one recessive allele (a), making it heterozygous. In contrast, 'AA' and 'aa' are homozygous genotypes.

Which of the following statements is true about homozygous chromosomes?

• They always carry different alleles.

• They always carry the same alleles.

• They carry no alleles.

• They carry only one allele.

Answer explanation

Homozygous chromosomes have identical alleles for a specific gene. This means they always carry the same alleles, making the statement 'They always carry the same alleles' the correct choice.

Which of the following best describes a heterozygous chromosome pair?

• Both chromosomes carry the same allele.

• Each chromosome carries a different allele.

• One chromosome carries an allele, and the other does not.

• Neither chromosome carries an allele.

Answer explanation

A heterozygous chromosome pair consists of two different alleles, one on each chromosome. This means each chromosome carries a different allele, making 'Each chromosome carries a different allele' the correct choice.

An organism with two identical alleles for a trait is called:

• Heterozygous

• Homozygous

• Hemizygous

• Hyperzygous

Answer explanation

An organism with two identical alleles for a trait is termed homozygous. This contrasts with heterozygous, which refers to having two different alleles. Hemizygous and hyperzygous are not standard terms for this context.

If an individual has two different alleles for a given gene, they are considered:

• Homozygous

• Heterozygous

• Hemizygous

Answer explanation

An individual with two different alleles for a gene is termed heterozygous. In contrast, homozygous refers to having two identical alleles, while hemizygous indicates having only one allele for a gene.

The genetic makeup of an organism

• heterozygous

• punnet square

• genotype

Answer explanation

The genetic makeup of an organism is referred to as its genotype. This term describes the specific alleles an organism carries, distinguishing it from terms like heterozygous, which describes a specific genotype, and punnet square, which is a tool for predicting genotypes.

Hair colour is an example of

• genotype

• phenotype

Answer explanation

Hair colour is a visible trait resulting from the expression of genes, making it a phenotype. Genotype refers to the genetic makeup, while phenotype is the observable characteristic.

Tags

NGSS.HS-LS3-1

The physical appearance of an organism based on traits

• Genotype

• Phenotype

• Meiosis

• Genetics

Answer explanation

The phenotype of an organism refers to its physical appearance and observable traits, which are influenced by its genotype and environmental factors. Therefore, the correct answer is phenotype.

Tags

NGSS.HS-LS4-4

TT an example of a....

• Genotype

• Phenotype

Answer explanation

TT represents a specific genetic makeup, which is referred to as a genotype. In contrast, phenotype describes the observable traits resulting from the genotype.

Tags

NGSS.HS-LS3-2