BIOL 115 EXAM 3

watson and crick

who “discovered” the structure of DNA

2nm

how wide is DNA?

nucleotides

what are the building blocks of DNA?

rosalind franklin

who ACTUALLY discovered the structure of DNA?

hershey and chase

who found out that DNA was not made of proteins?

bacteriophages

what did hershey and chase experiment with?

semi-conservative, conservative and dispersive

what are the 3 early models for DNA replication?

two parent strands separate and each strand is a template strand

what is the semi-conservative model?

parent strand remains intact and a new copy is made

what is the conservative model?

each strand contains a mix of old and newly synthesized parts

what is the dispersive model?

meselson and stahl

who supported the semi-conservative model?

variable forms of an element that differ in # of neutrons

what is an isotope?

antiparallel

which way do DNA strands run in relationship to each other?

5’ to 3’

which way do DNA replicate?

dehydration reaction

what reactions take place when new nucleotides are added?

reaction that releases water

what is a dehydration reaction?

towards the replication fork

which way does the leading strand go?

topoisomerase

relieves twisting forces

primase

lays down primer, tells enzyme where to go

helicase

opens the double helix

SSBPs

stabilizes strands so they don’t bind together again

sliding clamp

stabilizes DNA polymerase and keeps it in place

ligase

closes the gap between okazaki fragments

DNA Pol I

removes the RNA primer and replaces it with DNA

DNA Pol III

works 5’ to 3’ and adds new nucleotides to form new DNA

no

can replication take place if helicase no longer functions?

okazaki fragments would not be joined on the lagging strand

what happens if ligase can no longer perform?

lagging strand

which strand always ends up shorter than the other at the end of replication?

telomere

a short series of nucleotides found at the end of chromosomes that repeat over and over

no

do telomeres code for genes?

act as a buffer against genetic information loss

what is the function of telomeres?

telomerase extends unreplicated ends using it’s own RNA template

how are telomeres added?

they shorten

what happens to telomeres with age?

telomerase extends from its own RNA template

how do we solve the “end-replication” problem on the lagging strand?

naturally during replication and unnaturally from external forces

what are the two ways that DNA can be damaged?

DNA Pol III “proof reads“

how is DNA damage fixed DURING replication?

nucleotide excision repair

how is DNA damage fixed AFTER replication?

A and G

what bases are purines?

T and C

what bases are pyrimidines?

transition

If DNA Pol III accidentally swaps a C for a T, this is a:

transversion

If DNA Pol III accidentally swaps an A for a C, this is a:

bonding angles

incorrect base pairing results in abnormal ____ between nucleotides

thymine dimers

what occurs in DNA from UV light?

central dogma

what explains how genetic info is interpreted?

DNA to RNA

what is transcription?

RNA to protein

what is translation?

cytoplasm

where does protein synthesis take place?

the strand that codes for a protein

what is the coding strand?

the strand that is read as a template to create RNA

what is the template strand?

a sequence of 3 bases that equates to one amino acid

what is a codon?

N to C terminus

during translation which way do proteins grow?

wobble position

what is the third base of a codon called?

an existing base is swapped for another base

what is a point mutation?

mutation that doesn’t affect the final protein sequence, no effect on protein function

what is a silent mutation?

a mutation that causes a single amino acid to change

what is a missense mutation?

a mutation that causes a premature stop codon

what is a nonsense mutation?

a mutation that occurs when nucleotides are inserted or deleted

what is a frameshift mutation?

cytoplasm

where does transcription occur in prokaryotes?

nucleus

where does transcription occur in eukaryotes?

mRNA

messenger RNA, provides the message for protein production

beginning = promoter

middle = transcribed region (gene)

end = termination sequence

what is the beginning, middle and end of a gene?

5’ to 3’

which way is mRNA synthesized?

create phosphodiester bonds that link RNA nucleotides together

what do dehydration sequences do?

hydrogen bonds

what bonds temporarily form between DNA and RNA?

RNA Polymerase

what’s in charge of synthesizing RNA during transcription?

sigma

what enzyme helps attach RNA Pol to the promoter?

expressed

a gene being transcribed is the same thing as a gene being ________

\-35 and -10 box sequences

where does sigma bind in prokaryotic transcription?

TATA box

where does transcription initiate in eukaryotes?

1. initiation
2. elongation
3. termination

What are the steps of mRNA synthesis in prokaryotes?

DNA is pulled into RNA Pol active site while free NTPs enter and bind to template DNA using base pairing rules

what happens during initiation in mRNA synthesis in prokaryotes?

NTPs are incorporated into growing RNA

what happens during elongation in mRNA synthesis in prokaryotes?

RNA Pol hits the termination sequence, mRNA self-binds and forms a hairpin, then RNA detaches from RNA Pol

what happens during termination in mRNA synthesis in prokaryotes?

transcription factors

what enzymes are used during mRNA synthesis in eukaryotes?

true

t or f: prokaryotic mRNA is translated into proteins immediately

introns and exons

what is used to modify eukaryotic mRNA before translation?

coding

coding or noncoding: exons

noncoding

coding or noncoding: introns

splicing

how are introns removed?

snRNPs

what is used for splicing?

they are ligated together

how do exons come together?

5’ cap that prevents the end to degrade

what’s added to the 5’ end of eukaryotes?

poly-A-tail that prevents degradation on the 3’ end

what’s added to the 3’ end?

tRNA, rRNA and ribosomes

what “machinery” is used for translation in both types of cells?

tRNA

single-stranded RNA molecule that possesses an anticodon and amino acid attachment at the 3’ end

2

how many letters have to pair correctly for tRNA to stick?

rRNA

RNA that makes up a portion of ribosomes

1. assembly of tRNA
2. initiation
3. elongation
4. termination

what are the steps of translation?

aminoacly-tRNA synthetase

what enzyme adds an amino acid to a tRNA molecule?

1. small subunit of ribosome binds mRNA
2. f-Met tRNA binds
3. large subunit binds

what are the steps on initiation in translation?

1. incoming aminoacyl tRNA
2. 2. peptide bond formation
3. translocation

what are the steps of elongation in translation?

1. release factor binds to stop codon
2. polypeptide and remaining tRNAs are released
3. ribosome disassembles

what are the steps of termination in translation?

transcription level

what level do prokaryotes control gene expression at?

operon

several genes in a row that are transcribed and regulated together

regulatory proteins

what are operons controlled by?

activators

what positively regulates genes?

inhibitors

what negatively regulates genes?

inhibitor protein

what kind of protein regulates lac operon expression?

expression

when lactose is present…

repression

when lactose is absent….