Question 1

Which component distinguishes a DNA nucleotide from an RNA nucleotide, as shown in the diagrams above?

Accepted Answer

The sugar: DNA contains deoxyribose (with an H at the 2' carbon), while RNA contains ribose (with an OH at the 2' carbon)

Question 2

Which of the following best describes the structure of the DNA double helix?

Accepted Answer

Two antiparallel strands held together by hydrogen bonds between complementary bases

Question 3

According to Chargaff's rule, if a double-stranded DNA molecule contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

20%

Question 4

Which experiment provided the first direct evidence that DNA is the genetic material, as illustrated in the flowchart above?

Accepted Answer

Avery, MacLeod, and McCarty's fractionation and transformation experiment

Question 5

Which nitrogenous bases are classified as purines, based on their structure in the diagram?

Accepted Answer

Adenine and Guanine

Question 6

What is the significance of the X-shaped pattern in Photograph 51 (the X-ray diffraction image)?

Accepted Answer

It indicates the presence of a helical structure in DNA

Question 7

Which bond connects adjacent nucleotides in a DNA strand, as shown in the diagrams?

Accepted Answer

Phosphodiester bond

Question 8

If a DNA molecule has a GC content of 60%, what is the percentage of adenine?

Accepted Answer

$$A = \frac{100\% - 60\%}{2} = 20\%$$

Question 9

Which feature of the DNA double helix allows DNA-binding proteins to recognize specific sequences without unwinding the helix?

Accepted Answer

The presence of major and minor grooves

Question 10

Which of the following is NOT an essential element of a functional eukaryotic chromosome?

Accepted Answer

Exon

Question 11

A right-handed DNA helix curves in which direction relative to the fingers of the right hand when the thumb points upward?

Accepted Answer

In the direction of the fingers

Question 12

Which base pairing is stabilized by three hydrogen bonds, as shown in the diagrams?

Accepted Answer

G-C

Question 13

What is the function of telomeres in eukaryotic chromosomes?

Accepted Answer

They protect chromosome ends and enable complete replication

Question 14

Which of the following statements about genome organization is correct?

Accepted Answer

Genome size, gene number, and chromosome number can evolve independently

Question 15

During which phase of the cell cycle are chromosomes duplicated?

Accepted Answer

Interphase

Question 16

Which of the following best explains how genetic information is copied during DNA replication?

Accepted Answer

Each strand serves as a template for the other, allowing complementary base pairing

Question 17

Which of the following is a real-world application of chromosome painting?

Accepted Answer

Identifying chromosomal rearrangements in cancer cells

Question 18

If a segment of double-stranded DNA contains 10,000 base pairs, how many nanometers long is it, given that each base pair is spaced 0.34 nm apart?

Accepted Answer

$$10,000 	imes 0.34 = 3,400\ 	ext{nm}$$

Question 19

Which of the following best describes the relationship between exons and introns in a gene?

Accepted Answer

Exons are coding regions that specify amino acids, while introns are noncoding regions within the gene

Question 20

Which of the following is true about the nucleolus?

Accepted Answer

It forms around clusters of rRNA genes from multiple chromosomes

DNA Structure, Chromosomes, and Key Experiments: Study Notes for Anatomy & Physiology

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