BIO99 1/3 Questions and Answers

BIO99 1/3 Questions and Answers

Question 1.
are nucleotide bases hydrophobic or hydrophilic? where do they face?
Correct Answer: hydrophobic, so they face inside.

Question 2.
what histones sit ontop of which histones in the octomer?
Correct Answer: H2A sits on H2B, and H3 sits on H4, vice versa.

Question 3.
what is alternative splicing?
Correct Answer: using different combinations of exons to make different
proteins.

Question 4.
what site does he DNA go if a mistake is made?
Correct Answer: exonuclease site

Question 5.
where do ribosomes come from"?
Correct Answer: ribosomes come from the nucleolus by rRNA

Question 6.
evidence of DNA packaging:
Correct Answer: chromatin and small amounts of nuclease are mixed.the results
are base pairs of fragment length in multiples of 200, meaning a histone has
200bp fragments wrapped around it.

Question 7.
what is Tm?
Correct Answer: the melting temperature when 50% of the DNA is double
stranded and the other 50% is single stranded.

Question 8.
what's good about knowing genomic sequences?
Correct Answer: you can identify homologous genes from different species. you
can mutate specific genes to see what happens to function. helps identify
genetic diseases. lets us compare closeness between different organisms.

Question 9.
what does the beta clamp do?
Correct Answer: beta clamp keeps pol III on a leash, preventing it from falling
off after only adding a couple nucleotides

Question 10.
what is a promoter:
Correct Answer: the sequence where the RNA polymerase binds. it is the start of
the gene.

, Question 11.
what is base stacking and why is it favored?
Correct Answer: when the bases are directly on top of each other. It's stable
because the electron cloud is shared and this is very stable.

Question 12.
where does translation occur?
Correct Answer: translation occurs in the cytosol.

Question 13.
what does a nucleoside consist of?
Correct Answer: sugar - nitrogenous base

Question 14.
are the backbones of DNA and RNA hydrophobic or hydrophilic? what is their relationship
with water?
Correct Answer: the backbones of DNA and RNA are hydrophilic and so H-bond
with water.

Question 15.
after helicase unwinds, there are 2 DNA strands, both unstable due to no complementary
H bonding, have supercoiling, and are succeptible to nuclease breakdown. what enzyme
solves this problem?
Correct Answer: SSB. DNA wraps around SSB, getting rid of supercoiling, and
providing a stable protein/DNA complex that cannot be cleaved by nuclease

Question 16.
DNA in a cell is found as:
Correct Answer: DNA in a cell is found as chromatin, a DNA protein complex, not
naked DNA.

Question 17.
can chromosomes be made of RNA?
Correct Answer: yes. viruses have an RNA genome.

Question 18.
what is the shape of DNA pol1 like?
Correct Answer: a hand.

Question 19.
pyrophosphorolysis:
Correct Answer: the formation of dNMP's, the reverse rxn of DNA
polymerization. so dNMP is removed from the DNA chain

Question 20.
what fills in the nick? and hows it do this
Correct Answer: Ligase fills in the nick. ligase is used everyday in experiments
like putting genes into plasmids and cloning. Ligase fills the nick by using ATP
to add the phosphodiester bond.