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cell bio > Nucleic acid and protein synthesis and regulation > Flashcards

Nucleic acid and protein synthesis and regulation Flashcards

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1
Q

what are the four basic genetic process that help produce and maintain the proteins and nucleic acids of a cell?

A

protein synthesis
DNA replication
DNA repair
genetic recombination

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2
Q

what are some steps involved in the synthesis of protein?

A

DNA transcription
mRNA translation
ribosomal assembly

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3
Q

what is the first step in protein synthesis?

A

transcription

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4
Q

what does transcription do?

A

process takes the genetic information from DNA and transcribes it into form of a messenger RNA

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5
Q

how is immature mRNA modified?

A

RNA splicing to remove introns

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6
Q

describe the process of RNA splicing

A
  • done by enzyme RNA polymerase which recognize promoter sequence in DNA with help of transcription factors
  • RNA polymerase binds to this sequence and then initiates transcription of downstream genes
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7
Q

what happens when RNA polymerase reaches the termination sequence?

A

dissociates from template DNA strand and releases newly synthesized immature mRNA to be modified by splicing

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8
Q

what are some components that can affect whether or not certain genes are transcribed?

A

gene regulatory component
histone acetylation/deacetylation
methylation

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9
Q

what are the three main types of RNA involved in protein synthesis?

A

mRNA
rRNA
tRNA

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10
Q

what is rRNA?

A

ribosomal RNA
- makes up the structure of the ribosome

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11
Q

what do ribosomes catalyze the formation of?

A

peptide bonds (connections between each amino acid in a protein)

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12
Q

what is tRNA?

A

transfer RNA
- RNA that carries specific amino acids based on the genetic code to the ribosome that creates peptides

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13
Q

How does the tRNA know which amino acid it needs to take to the ribosome to make protein?

A

anticodons

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14
Q

what are codons?

A

three-nucleotide sequence that correspond to specific amino acids

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15
Q

what is a group of three nucleotides considered and what does that mean?

A

reading frame
- means that when protein synthesis occurs, DNA code is read by three nucleotides

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16
Q

what is used when a tRNA transfers an amino acid corresponding to the genetic code?

A

anticodon (complimentary to the codon present in DNA)
- tells tRNA which amino acid is next in the polypeptide sequence

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17
Q

in prokaryotes, the 70S ribosome is made of which subunits?

A

30S and 50S

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18
Q

in eukaryotes, 80S ribosomes are made up of which subunits?

A

40S and 60S

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19
Q

what is the A site of the ribsosome?

A

part of the ribosome where tRNA delivers amino acid

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20
Q

what is the P site of the ribosome?

A

where the formation of the peptide bond is catalyzed

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21
Q

what is the E site of the ribosome?

A

where the peptide chain exits the ribosome as it is being synthesized

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22
Q

list the stop codons

A

UAG
UAA
UGA

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23
Q

what is the start codon and which amino acid does it correspond with?

A

AUG
methionine

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24
Q

in prokaryotes, what is the start codon and what is special about it?

A

fMET because it has a formyl group attached to it

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25
how are disease causing mutations found in our cells usually eliminated from the population and only present at low rates?
natural selection
26
list types of mutations
silent frameshift missense nonsense
27
what is point mutation caused by and which types of mutations are included in this?
caused by a single base pair change - silent, missense, and nonsense
28
describe frameshift mutations and what does it produce?
- result in shift of reading frame - causes production of short (truncated) protein or change up protein structure entirely due to addition of wrong amino acid
29
what are the DNA repair mechanisms that are commonly used in cells?
base excision repair double stranded break repair mismatch repair
30
describe base excision repair
- only the damaged nucleotide is removed and then replaced - everything is glued back together using DNA ligase
31
describe mismatch repair
- mis-paired bases removed from DNA strand ~ done by proteins that first recognize mismatched area and then cut out that whole patch of DNA - DNA polymerase puts the new correct base - DNA ligase glues pieces back together
32
describe double stranded break repair
- occurs when DNA has been damaged and a double stranded break has been created - occurs when exposed to high-energy radiation - repaired via non-homologous end joining (NHEJ) and homologous recombination (HR)
33
describe NHEJ in double-stranded break repair
- cell glues DNA back together at breakage point - usually small mutation at the breakage site
34
why is NHEJ not the best way to repair?
the cell can lose some DNA at the breakage point or could be addition of new DNA at breakage point which results in small mutation at breakage site
35
describe HR in double-stranded break repair
information of damaged chromosome is found in homologous sister chromosome/chromatid, and information is used to repair DNA
36
what must happen in order to replicate DNA?
strand must be separated and each single strand is replicated by DNA polymerase
37
what is the purpose of primase?
RNA primer to start replication
38
what is the main idea behind DNA replication?
base pairing
39
what is base pairing?
explains which nitrogenous bases bond together
40
list which nitrogenous bases bond together
A (adenine) ------> T (thymine) G (guanine -------> C (cytosine)
41
how many hydrogen bonds are between A and T?
2
42
how many hydrogen bonds are between G and C?
3
43
If the DNA has a higher percentage of G and C base pairs, it will have a ______ melting point compared to DNA that has a ______ percentage of A and T base pairs.
higher
44
how does the DNA composition melt?
temperature at which it denatures or two strands separate
45
what DNA helicase work?
unzips DNA to make a replication fork
46
what is a replication fork?
point at which DNA transitions from being one double stranded molecule to two strands
47
the synthesis of the copy of DNA using the single strand as a ______ will begin
template
48
DNA polymerase only synthesizes DNA in which direction?
5’-3’ direction
49
describe the leading strand
- has normal DNA replication - DNA synthesis will occur continuously in the 5'-3' direction starting at the 3' end of the template strand
50
describe the lagging strand
- DNA replication occuring in a discontinuous manner - synthesis still occurs in 5'-3' direction - DNA polymerase will have to stop and then continue behind the previously synthesized fragment
51
what fills the space in between the okazaki fragments?
DNA ligase
52
what is the 3'-5' exonuclease activity?
removes mis-paired/unpaired bases during replication
53
When DNA is unzipped by DNA helicase, sometimes upstream the DNA gets wound up into a ________.
supercoil
54
what enzyme removes supercoils that appear downstream of the DNA helicase?
DNA topoisomerase
55
how does topoisomerase remove coils?
creates a "nick" in the DNA to relieve tension and prevent DNA from breaking - nick closed immediately because when DNA topoisomerase creates this break, its a reversible reaction
56
DNA topoisomerase I vs II
I- makes a single strand break II- makes a double strand break
57
how do viruses replicate their genetic material?
they infect other cells and hijack their replicative machinery in order to replicate themselves - genetic material can be either DNA or RNA, which can be linear, circular, double stranded, or single stranded
58
what is the result of genetic recombination?
increase in diversity of gene combinations in our chromosomes
59
what are the two types of genetic recombination?
- general recombination - site-specific recombination
60
describe general recombination
- process involves double strand breakage of a segment of DNA on a chromosome which is then switched with homologous region on the homologous chromosome - only occurs between two homologous regions on chromosomes - used in homologous recombination
61
what does site-specific recombination require?
recombination enzyme that recognizes specific sequences that are present on the recombining DNA molecules which are the ones that are involved in recombination - commonly occurs in bacteria
62
in prokaryotic and eukaryotic chromosomes, what are the mobile genetic elements that function in the same way as site specific recombination and how does it work?
transposable elements - move around in the host genome using recombination enzyme - elements can insert themselves in the middle of important genes, causing a disruption which may lead to disease

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