Exam 3

Question 1

In what direction do DNA polymerases synthesize DNA?

Answer 1

5’ to 3’ only

Question 2

Of the forces acting on bouble-stranded DNA, which one is a type of van DER waals force?
a. base pairing
b. the hydrophobic effect
c. stacking forces

Answer 2

c. stacking forces

Question 3

Of the forces acting on bouble-stranded DNA, which one is sequence-specific?

Answer 3

base pairing

Question 4

The double helix is DNA’s what type of structure?

Answer 4

secondary structure

Question 5

What is the structure difference between deoxyribose and ribose?

Answer 5

deoxyribose: 2 OH group connected to the ring
ribose: 3 OH groups connected to the ring

Question 6

In a nucleotide triphosphate molecule where is the 5 prime located?
1 prime?
2 prime?
3 prime?
4 prime?

Answer 6

5 prime:
- CH2 Carbon attached to the triphosphate group and the ring

4 prime:
- C in the ring attached to the CH2

3 prime:
- C in the ring attached to an OH group (deoxyribose: only OH group)

2 prime:
- only CH2 in the ring (ribose: 1st OH group closer to the base)

1 prime:
- C in ring attached to the base

Question 7

Which evolutionary force is not random?
a. mutation
b. natural selection
c. genetic drift
d. non-random mating
e. migration

Answer 7

b. natural selection

Question 8

If a very large population only self-fertilizes, what happens to the homozygosity and allele frequency?

Answer 8

• homozygosity increases
• allele frequency remains the same

Question 9

Human DNA replication involves a number of different DNA polymerases. Despite the ability of more than one polymerase to copy the DNA, most of it is copied by the “main” polymerases. What is the primary advantage of the main polymerases that allows the to dominate DNA replication?

Answer 9

higher processivity

Question 10

In what direction is protein translated?

Answer 10

D-terminus to C-terminus

Question 11

Mature eukaryotic mRNAs are stabilized, in part, by a special structure at the beginning (first part to be transcribed). What is it?

Answer 11

the cap

Question 12

The spliceosomes remove something from most mRNA. What is it?

Answer 12

introns

Question 13

tRNA are well-known for incorporating non-standard nucleotides (nucleotide other than A,U,G,C). Where so they come from?

Answer 13

when enzymes modify standard nucleotides already present

Question 14

What specifically do promoters promote?

Answer 14

transcription

Question 15

Which level of protein organization includes the (alpha) helix and (beta) pleated sheet?

Answer 15

secondary

Question 16

Which level of protein organization is just the sequence of amino acids?

Answer 16

primary

Question 17

All of the factors listed below play a role in the level of gene expression, meaning how much protein is actually make from each gene. Circle the one that IS NOT one of the two most important factors:
a. initiation of transcription
b. termination of transcrition
c. mRNA stability

Answer 17

b. termination of transcrition

Question 18

Which level of protein organization describes the interaction of more than one polypeptide chain?

Answer 18

quaternary

Question 19

Which side group of free amino acids ALWAYS carries a negetative charge?
a. H
b. R
c. amino
d. carboxyl
e. central carbon

Answer 19

d. carboxyl

Question 20

RNA polymerases carry out transcription at a much slower rate than DNA polymerases carry out? Why is speed more important in replication than transcription

Answer 20

• replication needs to accurately duplicate the entire genome, which is a much larger amount of genetic information, so speed is crucial to ensure timely completion
• transcription only needs to produce a single RNA molecule for a specific gene
  
  • allows a slower pace

Question 21

Eukaryotic promoters generally contain three regions: the core promoter, the regulatory promoter, and distant sequences. Both the regulatory promoter and distant sequences usually contain DNA sequences called enhancers. The function of the enhancers is to bind activator proteins. Once they are bound, what is the function?

Answer 21

• increase the rate of transcription of the associated gene by facilitating the interaction between the distant enhancer and the core promoter
• they turn up the expression level of the gene by making it more likely for transcription to occur

Question 22

Some distant enhancer sequences can be thousands of base pairs away from the core promoter. How are the activator proteins they bind able to influence the core promoter at such a distance?

Answer 22

• physically looping the DNA
  
  • bringing the enhancer and promoter into close proximity
  • allows the activator proteins to interact with the transcription machinery at the promoter region
    
    • activate gene expression

Question 23

rRNA sequences are among the most highly conserved in nature. What does the word conserved mean in this context?

Answer 23

• the nucleotide sequence of ribosomal RNA remains very similar across different species
• minimal changes over evolutionary time

Question 24

Why are rRNA sequences so strongly conserved?

Answer 24

• they play a critical role in the fundamental process of protein synthesis
  
  • small mutations are likely to be detrimental, resulting in high sequence conservation throughout evolution

Question 25

The different stages of translationus several factors that are not part of the ribosome. What are these factors, what are they made of?

Answer 25

• initiation factors, elongation factors, and termination factors
• composed of proteins

Question 26

The part of all amino acids that they share includes both a positively charged side group and a negatively charged group. Despite this, most amino acids in actual proteins lack any charge. How is this possible?

Answer 26

• they have a neutral overall charge due to the balancing of the positive charge on the amino group and the negative charge on the carboxyl group, canceling each other out

Question 27

What is the one gene, one polypeptide hypothesis? What does it say? It is an early 20th century theory that now seems a bit basic.

Answer 27

a single gene sequence is the code of one polypeptide