Test 1 Practice

Question 1

The HIV virus has a genome made of single-stranded RNA rather than double-stranded DNA. Which of the following will also be true of its genome?

a. The percentage of adenine bases will equal the percentage of thymine bases

b. The percentage of adenine bases will equal the percentage of uracil bases

c. It will form a right-handed helix with a uniform diameter

d. It has the potential to form complex stem-loop secondary structures

e. It will not contain phosphate groups

Answer 1

d. It has the potential to form complex stem-loop secondary structures

Question 2

Nucleic acids are the types of molecules used as coding instructions for all living organisms, except for bacteria. TRUE or FALSE.

a. TRUE

b. FALSE

Answer 2

b. FALSE

Question 3

A coworker in your lab is discussing a DNA sequence and refers to the 3´ end of the DNA strand. Which of the following would be most closely associated with the 3´ end?

a. phosphate group

b. sugar

c. negatively charged oxygens

d. hydrogen bonds

e. nitrogenous base

Answer 3

b. sugar

You would think that the phosphate group could be the other option because it connects to the 3’ end, but ultimately, the sugar is what the 3’ end is apart of, not the phosphate group.

Question 4

The primary structure of DNA is held together with ______ bonds, and the secondary structure is held together with ______ bonds.

Answer 4

phosphodiester bonds; hydrogen bonds

The phosphodiester bonds hold together the sugar backbone which is the primary structure, and the hydrogen bonds hold together the bases which are the secondary structure.

Question 5

Which of the following is NOT an example of DNA tertiary structure?

a. supercoiled double-stranded DNA

b. relaxed double-stranded DNA

c. nucleosome

d. 30-nm fiber

Answer 5

b. relaxed double-stranded DNA

The supercoiled DNA is considered a tertiary structure along with nucleosomes and 30-nm fiber.

Question 6

Which statement is true regarding negative supercoiled DNA?

a. Negative supercoiled DNA is under-rotated and allows for easier strand separation during replication and transcription

b. Negative supercoiled DNA is not usually seen in cells

c. Negative supercoiled DNA has 10 base pairs per turn of its helix

d. Negative supercoiled DNA carries more negative charges than does positive supercoiled DNA

Answer 6

a. Negative supercoiled DNA is under-rotated and allows for easier strand separation during replication and transcription

Question 7

Centromeres help control the cell cycle by… (complete the sentence with the correct option)

a. activating cell-cycle control genes

b. inhibiting the S phase until the cell is ready to double its DNA content

c. causing DNA without centromeres to be lost

d. inhibiting anaphase until spindle fibers are attached to chromosomes

e. coding for tumor suppressor proteins

Answer 7

c. causing DNA without centromeres to be lost