Cuestionario: Basics of Genetics and Chromosomes — 12 preguntas

1. What best describes DNA in a cell?

A. A specific DNA segment that determines a trait

B. A rod-like structure made of tightly packed DNA

C. A pair of structures that decides biological sex

D. A chemical molecule that carries hereditary information

Answer: (D)

Explicación

DNA is the molecule that carries hereditary information inside cells. Chromosomes are made from condensed DNA, so they are not the same thing as DNA itself.

2. What are genes?

A. Pairs of chromosomes inherited from each parent

B. Rod-like structures in the nucleus made of packed DNA

C. Segments of DNA that contain instructions for inherited traits

D. Chemical molecules that determine the species name

Answer: (C)

Explicación

Genes are specific DNA segments that carry instructions for inherited traits. Chromosomes contain genes, but genes are the units that help determine characteristics.

3. How many chromosomes are found in a typical human cell?

A. 46 pairs of chromosomes

B. 23 chromosomes

C. 23 pairs of chromosomes

D. 39 pairs of chromosomes

Answer: (C)

Explicación

Human cells have 23 pairs of chromosomes, which makes 46 chromosomes in total. The option with 23 chromosomes is incomplete.

4. What chromosome count is given for dogs in the source material?

A. 46 pairs of chromosomes

B. 39 pairs of chromosomes

C. 23 pairs of chromosomes

D. 21 pairs of chromosomes

Answer: (B)

Explicación

Dogs are given as having 39 chromosome pairs. This shows that chromosome number differs between species.

5. Which sex-chromosome combination is associated with a female in the source material?

A. XY

B. XXY

C. XX

D. XO

Answer: (C)

Explicación

The source associates XX with a female and XY with a male. XX is the correct sex-chromosome pair for a woman in this material.

6. What does trisomy 21 mean?

A. Pair 21 contains no genes

B. Pair 21 is missing from the genome

C. Pair 21 has only one chromosome

D. Pair 21 has three chromosomes instead of two

Answer: (D)

Explicación

Trisomy 21 means there are three chromosomes in pair 21 instead of the usual two. It is a genetic condition linked to chromosome information.

7. What is inheritance?

A. The transmission of genetic characteristics from parents to children

B. The process by which chromosomes condense in the nucleus

C. The pairing of chromosomes inside each species

D. A change in DNA that creates a new trait

Answer: (A)

Explicación

Inheritance is the passing of genetic characteristics from parents to children. A mutation is different because it changes DNA rather than describing transmission.

8. According to the inheritance rule given, how do children receive chromosomes from their parents?

A. Half from the mother and half from the father

B. All chromosomes from the father

C. All chromosomes from the mother

D. An equal number from siblings and parents

Answer: (A)

Explicación

The source states that a child receives half of their chromosomes from the mother and half from the father. This explains why children resemble their parents but are not identical.

9. What are alleles?

A. A pair of sex chromosomes

B. A mutation that changes one trait

C. Different versions of the same gene

D. Different chromosomes found in one species

Answer: (C)

Explicación

Alleles are different versions of the same gene. They are the reason one trait can have multiple forms, such as different eye-color or blood-group versions.

10. Which set of blood-group alleles is listed in the source material?

A. XX, XY, and XO

B. A, B, and O

C. M, B, and X

D. 21, 23, and 46

Answer: (B)

Explicación

The source gives A, B, and O as blood-group alleles. These are examples of different versions of one gene.

11. When does a dominant allele express its effect?

A. With only one copy present in the genotype

B. Only when no other allele is present

C. Only after a mutation changes the gene

D. Only when two identical copies are present

Answer: (A)

Explicación

A dominant allele is expressed with just one copy. In contrast, a recessive allele needs two copies to show its effect.

12. Which statement matches the dominance rule for eye-color alleles in the source material?

A. M is dominant over B, so M+B gives M

B. M and B are both recessive, so M+B gives neither

C. B is dominant over M, so M+B gives B

D. M only appears when paired with B

Answer: (A)

Explicación

The source states that the brown allele M is dominant over the blue allele B, so M+B gives M. Blue appears only when two blue alleles are present.