Exam 3 Flashcards
In what direction do DNA polymerases synthesize DNA?
5’ to 3’ only
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
c. stacking forces
Of the forces acting on bouble-stranded DNA, which one is sequence-specific?
base pairing
The double helix is DNA’s what type of structure?
secondary structure
What is the structure difference between deoxyribose and ribose?
deoxyribose: 2 OH group connected to the ring
ribose: 3 OH groups connected to the ring
In a nucleotide triphosphate molecule where is the 5 prime located?
1 prime?
2 prime?
3 prime?
4 prime?
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
Which evolutionary force is not random?
a. mutation
b. natural selection
c. genetic drift
d. non-random mating
e. migration
b. natural selection
If a very large population only self-fertilizes, what happens to the homozygosity and allele frequency?
- homozygosity increases
- allele frequency remains the same
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?
higher processivity
In what direction is protein translated?
D-terminus to C-terminus
Mature eukaryotic mRNAs are stabilized, in part, by a special structure at the beginning (first part to be transcribed). What is it?
the cap
The spliceosomes remove something from most mRNA. What is it?
introns
tRNA are well-known for incorporating non-standard nucleotides (nucleotide other than A,U,G,C). Where so they come from?
when enzymes modify standard nucleotides already present
What specifically do promoters promote?
transcription
Which level of protein organization includes the (alpha) helix and (beta) pleated sheet?
secondary
Which level of protein organization is just the sequence of amino acids?
primary
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
b. termination of transcrition
Which level of protein organization describes the interaction of more than one polypeptide chain?
quaternary
Which side group of free amino acids ALWAYS carries a negetative charge?
a. H
b. R
c. amino
d. carboxyl
e. central carbon
d. carboxyl
RNA polymerases carry out transcription at a much slower rate than DNA polymerases carry out? Why is speed more important in replication than transcription
- 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
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?
- 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
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?
- 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
rRNA sequences are among the most highly conserved in nature. What does the word conserved mean in this context?
- the nucleotide sequence of ribosomal RNA remains very similar across different species
- minimal changes over evolutionary time
Why are rRNA sequences so strongly conserved?
- 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
The different stages of translationus several factors that are not part of the ribosome. What are these factors, what are they made of?
- initiation factors, elongation factors, and termination factors
- composed of proteins
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?
- 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
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.
a single gene sequence is the code of one polypeptide
