Question 1

Which of the following best describes the structure of a DNA molecule as shown in the images?

Accepted Answer

A double-stranded helix with a sugar-phosphate backbone and nitrogenous base pairs held together by hydrogen bonds

Question 2

What is the correct pairing of nitrogenous bases in DNA, as illustrated in the diagrams?

Accepted Answer

Adenine pairs with thymine, and guanine pairs with cytosine

Question 3

Which chemical bond is responsible for linking nucleotides together in the backbone of a DNA strand?

Accepted Answer

Phosphodiester bond

Question 4

If a segment of DNA has the sequence 5'-ATCG-3', what is the complementary sequence on the opposite strand?

Accepted Answer

3'-TAGC-5'

Question 5

Which of the following statements about the sugar component in DNA and RNA is correct?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose

Question 6

What is the function of histone proteins in the organization of DNA within the nucleus?

Accepted Answer

They help package DNA into nucleosomes, allowing for compaction into chromatin and chromosomes

Question 7

Which of the following best explains why the number of purines equals the number of pyrimidines in double-stranded DNA?

Accepted Answer

Each purine always pairs with a specific pyrimidine through hydrogen bonding

Question 8

A mutation causes a change in the DNA sequence from 5'-GAA-3' to 5'-GUA-3'. Which type of nitrogenous base has been substituted?

Accepted Answer

A pyrimidine has been replaced by another pyrimidine

Question 9

Which of the following best describes the difference between a chromosome and chromatin?

Accepted Answer

Chromatin is the uncondensed form of DNA and proteins, while a chromosome is the highly condensed form visible during cell division

Question 10

During DNA replication, which enzyme is primarily responsible for forming the phosphodiester bonds between nucleotides?

Accepted Answer

DNA polymerase

Question 11

Which of the following equations correctly represents the number of hydrogen bonds between base pairs in DNA?

Accepted Answer

$$A-T: 2$$ hydrogen bonds; $$G-C: 3$$ hydrogen bonds

Question 12

Which of the following best describes the role of the phosphodiester bond in the DNA structure?

Accepted Answer

It links the phosphate group of one nucleotide to the sugar of the next nucleotide in the same strand

Question 13

If a DNA molecule contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

20%

Question 14

Which of the following is a correct description of a nucleosome?

Accepted Answer

A segment of DNA wound around a cluster of histone proteins

Question 15

Which of the following best explains why DNA is a more stable molecule than RNA in most cells?

Accepted Answer

DNA is double-stranded and contains deoxyribose, which is less reactive than ribose

Chromosomes, Mitosis, and Meiosis: Structure and Function of Genetic Material

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