Molecular Genetics Test (Ch.4,5,6)

Question 1

DNA is most often described as a double helix, which looks like a spiral ladder.

Answer 1

True

Question 2

The anticodon for the mRNA codon AGC is UCG.

Answer 2

True

Question 3

Some restriction endonucleases make zigzag cuts in double-stranded DNA leaving sticky ends.

Answer 3

True

Question 4

Ribosomes move along mRNA in a 5’–> 3’ direction

Answer 4

True

Question 5

The mRNA transcription of a gene is made up of the same bases, in the same proportion, as the strand of DNA complementary to the template strand, except the thymine, will be replaced by the uracil.

Answer 5

True

Question 6

Organisms without nuclease activity would replicate faster than other organisms since time would not be spent checking newly synthesized DNA and removing mismatched bases. The mutation rate would also be higher.

Answer 6

True

Question 7

The fact that the genetic code is very similar in almost all organisms indicates that it evolved early in the history of life on earth.

Answer 7

True

Question 8

The genetic code is very similar in

Answer 8

deer, maple trees, and bacteria

Question 9

A nucleotide consists of

Answer 9

deoxyribose, a phosphate, and an amino acid.

Question 10

A section of mRNA 6 codons long would most likely result in the addition of how many amino acids to a growing polypeptide (assume the stop codon is absent from the section of mRNA)?

Answer 10

6

Question 11

An enzyme, which excises (=removes) a mismatched base in a newly synthesized strand of DNA, is called

Answer 11

an exonuclease or nuclease

Question 12

The function of the polyadenine (=poly A) tail that is added to mRNA in eukaryotic cells is to

Answer 12

prvent degradation of the mRNA.

Question 13

An adenine molecule bonds to its complementary base with

Answer 13

two hydrogen bonds

Question 14

which of the following best describes mutations?

Answer 14

They are permanent changes in the DNA sequence of an organism.

Question 15

Base pairing due to hydrogen bonding is fundamental to

Answer 15

both processes

Question 16

DNA acts as a template (=guide) for transcription. Which of the following statements regarding the DNA of a gene being expressed is true?

Answer 16

After unwinding, only one of the DNA strands acts as a template.

Question 17

The main support to the DNA molecule is provided by two backbones which run along the two sides of the double helix. These backbones link together

Answer 17

sugars and phosphates

Question 18

An amino acid is

Answer 18

a building block of protein

Question 19

The number of molecules of cytosine in a sample of DNA will always be the same as the number of molecules of

Answer 19

guanine

Question 20

The splicing of the first-formed mRNA transcript by splicesomes is necessary because

Answer 20

introns need to be removed

Question 21

The flow of genetic information is usually in which of the following directions?

Answer 21

DNA–> mRNA–> protein

Question 22

(5’) GGCATA (A)
(B) CCGTAT (C)
If the above is a representation of a piece of double-stranded DNA, what symbols should occupy the positions (A), (B) and (C)?

Answer 22

3’,3’,5’

Question 23

Compare the two mRNA sequences below:
sequence 1- AUAUUCGGCAAUCCG
sequence 2-AUAUUCGGCAAUCG
This change could be a result of

Answer 23

deletion mutation

Question 24

Which of the following is a correct representation of a segment of DNA?

1. 5’ATTC3’, 3’ATTC5’
2. 5’AUUC3’, 3’UAAG5’
3. 5’CCGG3’, 5’GGCC3’
4. ‘5ATAG3’, 3’TATC5’
5. 5’ACGA3’,3’TGCT5’

Answer 24

4 and 5

Question 25

If the percentage composition of thymine in a DNA molecule is 26%, what is the percentage composition of cytosine?

Answer 25

24%

Question 26

The discovery of restriction endonucleases was crucial to the development of recombinant DNA technology because of these enzymes

Answer 26

cut DNA at specific and predictable sequences of bases.

Question 27

The model of DNA structure proposed by Watson and Crick suggests a way in which the DNA molecule can replicate itself, because

Answer 27

each base is capable of specifying the base opposite to it in the double helix.

Question 28

Consider the ends of the DNA fragments below. They have been produced by digestion of a single sequence of DNA using a number of restriction endonucleases. 
1. 5' A          3'
   3' TTCGA 5'
2. 5' G           3'
    3' CAGCT 5'
3. 5'AATTC 3'
    3'         G 5'
4. 5'TCGAC 3'
    3'          G 5'
5. 5'GGG 3'
    3' CCC 5' 
Which of these ends are capable of base pairing and being joined by DNA ligase?

Answer 28

2. 5’ G 3’
   3’ CAGCT 5’
3. 5’TCGAC 3’
   3’ G 5’

Question 29

Complementary base pairing is the result of

Answer 29

hydrogen bonding

Question 30

During DNA replication, one of the new strands of DNA is synthesized continuously, while the other is synthesized discontinuously as a number of separate fragments of DNA that are linked later by DNA ligase. This is because

Answer 30

DNA polymerase only synthesizes DNA in the 5’-3’ direction.