Тест: Genetics Fundamentals and Cell Division — 12 въпроса

1. What best describes DNA in living cells?

A. A nucleic acid that stores hereditary information

B. A lipid that stores cellular energy

C. A carbohydrate that builds cell walls

D. A protein that transports amino acids

Answer: (A)

Обяснение

DNA is the nucleic acid that carries hereditary information in cells. The other choices describe different classes of biomolecules with other functions.

2. Why does the order of nucleotides in a gene matter?

A. It determines the information needed to produce a functional product

B. It prevents DNA from being copied

C. It directly forms the cell membrane

D. It changes the number of chromosomes in the cell

Answer: (A)

Обяснение

The sequence of nucleotides encodes genetic information, which directs the production of a functional product, often a protein. The other options are not roles of nucleotide order in genes.

3. What is a nucleotide in DNA made of?

A. Two sugars and one nitrogenous base

B. A phosphate group, a ribose sugar, and an amino acid

C. A protein, a sugar, and a lipid

D. A phosphate group, a deoxyribose sugar, and a nitrogenous base

Answer: (D)

Обяснение

A DNA nucleotide contains phosphate, deoxyribose, and a nitrogenous base. Ribose is found in RNA, not DNA.

4. What does antiparallelism mean in the DNA double helix?

A. The two strands are made of different sugars

B. The two strands have identical base sequences

C. The two strands run in opposite 5' to 3' directions

D. The two strands are not connected by bonds

Answer: (C)

Обяснение

Antiparallel strands are oriented in opposite directions, one running 5' to 3' and the other 3' to 5'. This is a defining property of DNA structure.

5. What is the key result of semiconservative DNA replication?

A. Each new DNA molecule contains two old strands

B. Each new DNA molecule contains one old strand and one new strand

C. Each new DNA molecule loses part of the original sequence

D. Each new DNA molecule contains two newly synthesized strands only

Answer: (B)

Обяснение

Semiconservative replication means each daughter DNA molecule keeps one parental strand and gains one newly synthesized strand. This is the accepted replication model.

6. Why is a caryotype useful in genetics?

A. It determines the sequence of every nucleotide in DNA

B. It helps identify chromosome number and structure abnormalities

C. It shows the amino acid sequence of a protein

D. It measures the amount of glucose in the cell

Answer: (B)

Обяснение

A caryotype is an ordered display of chromosomes used to detect numerical or structural abnormalities. It does not provide nucleotide-level or protein-level information.

7. What is the main outcome of mitosis?

A. Four genetically identical haploid cells

B. Two genetically identical diploid daughter cells

C. Two genetically different diploid daughter cells

D. Four genetically different haploid gametes

Answer: (B)

Обяснение

Mitosis produces two daughter cells that are genetically identical to the parent cell and keep the diploid chromosome number. The other options describe meiosis or incorrect outcomes.

8. How does meiosis contribute to genetic diversity?

A. By keeping daughter cells genetically identical

B. By preventing the formation of gametes

C. By recombination and independent assortment of chromosomes

D. By copying DNA without any change

Answer: (C)

Обяснение

Meiosis increases diversity through recombination and independent assortment, which create new combinations of alleles. It does not produce identical daughter cells.

9. What is a codon in the genetic code?

A. A sugar molecule that binds ribosomes

B. A triplet of nucleotides on mRNA that specifies an amino acid or stop signal

C. A chromosome region that stores all genes

D. A single nucleotide on DNA that specifies a protein

Answer: (B)

Обяснение

A codon is a three-nucleotide sequence on mRNA read during translation. It specifies an amino acid or a stop signal.

10. What determines the order of amino acids in a protein?

A. The type of ribose in DNA

B. The shape of the cell membrane

C. The sequence of codons along the mRNA

D. The number of chromosomes in the nucleus

Answer: (C)

Обяснение

During translation, ribosomes read mRNA codons in order, and that codon order determines the amino acid sequence of the protein. The other choices are unrelated to protein sequence.

11. What is a genetic mutation?

A. A change in the number of ribosomes

B. A temporary change in cell shape

C. A process that always improves fitness

D. A heritable change in the DNA sequence

Answer: (D)

Обяснение

A mutation is a heritable change in DNA sequence that can affect gene function or regulation. Mutations are not always beneficial.

12. What does Mendelian genetics focus on?

A. The way chromosomes are copied during replication

B. Inheritance patterns based on alleles and their transmission across generations

C. The chemical breakdown of proteins in cells

D. The structure of the DNA double helix

Answer: (B)

Обяснение

Mendelian genetics studies how alleles are transmitted and how dominance relationships help predict offspring genotypes and phenotypes. The other options concern different topics.