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DAT Molecular Genetics Flashcards

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Biology 101 flashcards
1
Q

DNA

A

A, T, C, G; the hereditary
information of the cell; contains a double
helix with major and minor grooves

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2
Q

DNA backbone

A

consists of 5’ to 3’

phosphodiester bonds to form a sugar-
phosphate backbone

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3
Q

RNA

A

A, U, C, G; has functional usage in
the cell; varies per type (mRNA is linear,
tRNA is in a clover shape, while rRNA is
globular)

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4
Q

DNA replication

A

begins at origins of
replication in the middle of a DNA
molecule

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5
Q

DNA strands separate to form

A

replication
bubbles that expand in both directions.

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6
Q

How many origin of replication do prokaryotes have

A

1

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7
Q

first step of DNA replicaiton

A

A second chromatid containing a copy
of DNA is assembled during interphase

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8
Q

Second step of DNA replication

A

Helicase is the enzyme that unwinds
DNA, forming a Y shaped replication
fork -

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9
Q

Single stranded binding proteins

A

attach to each strand of
uncoiled DNA to keep them separate

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10
Q

Topoisomerases

A

break and rejoin the DNA double
helix of the replication fork,
preventing knots

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11
Q

Third step of DNA relication

A

DNA polymerase moves from the 3’ →
5’ direction only, and synthesizes a new
strand that is antiparallel (5’ → 3’) -

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12
Q

Okazaki fragments

A

DNA ligase connects these, strand, the DNA
polymerase has to go back to the
replication fork and work away from
it. It produces fragments piece by
piece, and these fragments are called
Okazaki fragments

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13
Q

Fourth Step of DNA replication

A

Primase is an enzyme that creates a
small strip of RNA off of which DNA
polymerase can work since it can only
add to an existing strand

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14
Q

DNA replication requires

A

RNA primer

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15
Q

Every Okazaki fragment has

A

an RNA primer

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16
Q

what are RNA primers replaced with?

A

DNA by DNA polymerase i

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17
Q

DNA polymerase 3 main function

A

mainly for
replication

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18
Q

Polymerases I and III have..

A

3’ → 5’
exonuclease function, meaning
that they can break the
phosphodiester backbone on a
single strand of DNA and remove
a nucleotide. An exonuclease can
only remove from the end of the
chain.

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19
Q

Polymerase III also has some…

A

proofreading function

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20
Q

Polymerase I also has

A

5’ → 3’
exonuclease function to remove the
primer; polymerase I can also
proofread in the 3’ → 5’ direction
when laying down a new nucleotide
strand

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21
Q

helicase

A

unzips DNA to form
replication fork

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22
Q

Ligase -

A

‘glues’ two strands of DNA
together

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23
Q

Once the DNA has been replicated, we still need
to replicate..

A

the telomeres

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24
Q

what are telomeres termed as?

A

the aglets of a chromosome since they
protect the DNA from degradation by enzymes.

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25
Q

Telomerase carries an

A

RNA template and
binds to the flanking 3’ end of the telomere
that compliments part of its RNA,

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26
Q

mRNA

A
  • a single stranded template;
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27
Q

HOW many triplet codons are there

A

64

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28
Q

what is the least abundant RNA molecule

A

mRNA (high turnover rate)

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29
Q

what are the three stop codons

A

UAA,
UAG, and UGA

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30
Q

tRNA

A

a clover shaped transporter of
anticodons;

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31
Q

Wobbles

A

the exact base pair of the
third nucleotide in the codon is often
not required, allowing 45 different
tRNA’s to base-pair with 61 codons
that code for amino acids

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32
Q

what is tRNA’s clover shape held together by

A

hydrogen bonds

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33
Q

what Is the tiniest RNA molecule

A

tRNA

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34
Q

rRNA

A

come together to form
ribosomes.

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35
Q

nucleolus

A

an assemblage
of DNA actively being transcribed into
rRNA,

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36
Q

A ribosome has how many binding sites

A

4 total, 1 for mRNA and 3 for tRNA

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37
Q

Transcription

A

serves to create RNA molecules
from a DNA template in the nucleus.

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38
Q

First step of transcription

A

Initiation - RNA polymerase attaches to
the promoter region on DNA and unzips
the DNA into two strands.

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39
Q

TATA box.

A

A promoter
region for mRNA transcription often
contains a repeating sequence of A and T
nucleotides

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40
Q

consensus sequence

A

most common sequence of
nucleotides at the promoter region

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41
Q

what is the TATA box called in prokaryotes

A

‘Pribnow
box’

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42
Q

step 2 of transcription

A

Elongation - RNA polymerase continues
unzipping DNA and assembles RNA nucleotides using one strand of DNA as
a template.

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43
Q

Termination

A

occurs when RNA
polymerase reaches a special sequence,
often AAAAAA in eukaryotes

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44
Q

what direction does transcription occur

A

3’ to 5’

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45
Q

mRNA Processing modifications

A

5’ cap (5’ G-P-P-P-):, A poly-A tail (-A-A-A…A-A-3’):, RNA splicing, Alternative splicing

46
Q

5’ cap (5’ G-P-P-P-):

A

this sequence is
added to the 5’ end of the mRNA; a
guanine with 3 phosphate groups (GTP)
provides stability for mRNA and a point
of attachment for ribosomes

47
Q

A poly-A tail (-A-A-A…A-A-3’):

A

this
sequence is attached to the 3’ end of
the mRNA, The poly A tail consists of 200 A
nucleotides that serve to provide stability
and control the movement of mRNA
across the nuclear envelope

48
Q

RNA splicing

A

removes nucleotide
segments from mRNA before mRNA
moves into the cytoplasm via small
nuclear ribonucleoproteins (snRNP’s). The
spliceosome deletes the introns and
splices the exons. Prokaryotes have no
introns

49
Q

Alternative splicing

A

allows different mRNA to be generated from
the same RNA transcript by selectively
removing differences of an RNA
transcript into different combinations

50
Q

Translation

A

assembly of polypeptides based on reading
of new RNA in the cytoplasm with GTP used as
the energy source.

51
Q

First step of translation

A

Initiation - the small ribosome subunit
attaches to the 5’ end of mRNA; a tRNA
methionine attaches to the start
sequence of mRNA (AUG), and the
large ribosomal subunit attaches to
form a complete complex. Requires 1
GTP.

52
Q

second step of translation

A

Elongation - next tRNA binds to the A
site, peptide bond formation occurs,
and the tRNA without methionine is
released. The tRNA currently in the A
site moves to the P site (translocation)
and the next tRNA comes into the A site
to repeat the process. This requires 2
GTP per link.

53
Q

third step of translation

A

Termination - when the ribosome
encounters the stop codon (either UAG,
UAA, or UGA), the polypeptide and the
two ribosomal subunits all release due
to a release factor breaking down the
bond between tRNA and the final amino
acid of the polypeptide

54
Q

fourth step of translation

A

Post-translation - translation begins on
a free floating ribosome; a signal
peptide at the beginning of the
translated polypeptide may direct

55
Q

what is the amino acid for start codons in eukaryotes

A

methionine

56
Q

Silent mutations

A

when a mutation
occurs, but the new codon still codes for
the same amino acid, therefore the
effect is “silenced”

57
Q

Nonsense mutations

A

the
new codon codes for a stop codon

58
Q

Neutral mutations

A

there is
no change in protein function

59
Q

Missense mutations

A

a new codon
codes for a new amino acid → can have
minor or fatal results (as in sickle cell
anemia where glu → val)

60
Q

Proofreading

A

DNA polymerase checks
base pairs

61
Q

Mismatch repair

A

enzymes repair the
errors DNA polymerase missed —
mismatch repair deals with correcting
mismatches between normal bases

62
Q

Excision repair

A

enzymes remove
nucleotides damaged by mutagens

63
Q

Nucleotide excision repair

A

can be
used to repair issues like thymine
dimers

64
Q

Base excision repair

A

similar in
function to nucleotide excision repair,
but uses different enzymes. The main
difference is that nucleotide excision
repair will chunk out an entire
segment around the faulty base by
nicking the entire surrounding
phosphodiester backbone, not just
the faulty base.

65
Q

The key structure
responsible for DNA organization

A

nucleosome

66
Q

Nucleosome

A

structure formed when
DNA is coiled around bundles of 8-9
histone proteins, kind of like beads on a
string

67
Q

Euchromatin

A

chromatin is
loosely bound to nucleosomes;
present when DNA is actively
being transcribed

68
Q

Heterochromatin

A

areas of
tightly packed nucleosomes
where DNA is inactive and
appears darker.

69
Q

Transposons (jumping genes)

A

DNA segments that can move to a new
location on either the same or different
chromosome.

70
Q

Pseudogenes

A

former genes that
have accumulated mutations over a
long time and no longer produce a
functional protein

71
Q

Virus - consist of the following:

A

Nucleic acid, Capsid, Capsomeres, Viral envelope

72
Q

Nucleic acid

A

RNA or DNA that can
be double or single stranded

73
Q

Capsid

A

a protein coat that encloses
the nucleic acid

74
Q

Capsomeres

A

assemble to form the
capsid

75
Q

Viral envelope

A

surrounds capsid of
some viruses and incorporates
phospholipids and proteins obtained
from the cell membrane of the host

76
Q

Bacteriophage

A

a virus that only attacks
bacteria, is usually specific to a type of
cell via viral surface proteins binding to
specific receptors on the host cell of the
species.

77
Q

Host range

A

term used to
define the range of organisms or species a virus

can attack

78
Q

Viral replication

A

2 cycles: the lytic cycle, DNA viruses

79
Q

Lytic cycle

A

when the virus penetrates
the host cell membrane and uses host
machinery to produce nucleic acids
and viral proteins that are then
assembled to make new viruses

80
Q

DNA viruses

A

replicate by first
replicating DNA and forming new
viral DNA, which is then
transcribed to produce viral
proteins that combine with DNA
to form new viruses

81
Q

RNA virus

A

RNA serves as mRNA
which is translated into protein.
This protein and RNA assemble to
form a new RNA virus

82
Q

Retroviruses

A

single stranded
RNA viruses that use reverse
transcriptase to make a DNA
complement of their RNA by
hijacking the host cell’s replicating
machinery. This DNA is then used
to manufacture mRNA or enter
the lysogenic cycle (becoming
incorporated into the host DNA)

83
Q

Lysogenic cycle

A

when viral DNA is
incorporated into the DNA of the
host cell;

84
Q

2 phases of lysogenic cycle

A

a. Dormant stage - the virus is
referred to as a provirus
(prophage if a bacteriophage) and
remains inactive until an external
stimuli triggers the virus

b. When triggered, the virus enters
the lytic cycle, and follows the
same steps as mentioned in the
previous bullet

85
Q

Prions

A

are not viruses or cells, but are
infectious, mis-folded versions of proteins
in the brain that cause normal versions of
proteins to also become mis-folded.
Prions are fatal, and are implicated in
diseases such as Mad Cow disease, kuru,
scrapie in sheep, and Creutzfeldt-Jakob
disease

86
Q

Viroids

A

very small (even smaller than
viruses!) circular RNA molecules that
infect plants. These do not encode for
proteins, but replicate in host plant cells
via host enzymes, and cause errors in the
regulatory systems of plant growth

87
Q

Binary fission

A

bacteria reproduce via
this method in which the chromosome
replicates, the cell divides into two cells,
and each cell now holds the exact same
copy of the original chromosome

88
Q

Plasmids

A

short, circular DNA outside
of chromosomes that carry genes that
are beneficial, but not essential for
survival

89
Q

Episomes

A

plasmids that can
incorporate into bacterial
chromosomes

90
Q

Genetic exchanges

A

there are three
main ways bacteria can exchange
information with each other or their
surroundings : Conjugation, Transduction, Transformation

91
Q

Conjugation

A

donor bacteria
produces a bridge (pilus) and
connects to the recipient bacteria;
this allows the donor to send a
chromosome or plasmid to the
recipient, thus allowing
recombination to occur

92
Q

Transduction

A

DNA is introduced
into a genome via virus. When the
virus is assembled during the lytic
cycle, some bacterial DNA is
incorporated in the place of viral
DNA. When the virus infects another
host, the bacterial DNA part that it
delivers can recombine with the
resident DNA.

93
Q

Transformation

A

bacteria take in
DNA from surroundings and
incorporate it into the genome

94
Q

Operon

A

region of DNA that controls
gene transcription and consists of: Promoter, Operator, Structural genes, Regulatory genes

95
Q

Promoter

A

sequence of DNA where
RNA polymerase attaches to begin
transcription

96
Q

Operator

A

region that can block
action of RNA polymerase if occupied
by repressor proteins

97
Q

Structural genes

A

DNA sequences
that code for related proteins

98
Q

Regulatory genes

A

located outside
of operon region, and produce
repressor proteins. Others produce
activator proteins that assist the
attachment of RNA polymerase to the
promoter region

99
Q

Lac operon (E. coli)

A

controls the
breakdown of lactose; the regulatory
gene produces an active repressor that
binds to the operator and blocks RNA
polymerase

100
Q

Trp operon (E. coli)

A

produces enzymes
for tryptophan synthesis; regulatory
genes produce an inactive repressor,
which allows RNA polymerase to produce
enzymes.

101
Q

Repressible enzymes

A

are
when structural genes stop producing
enzymes only in the presence of an active
repressor.

102
Q

Regulatory proteins

A

repressors and
enhancers/activators that influence RNA
polymerase attachment to the promoter
region.

103
Q

Nucleosome packing

A

Methylation of histones, Acetylation of histones, Direct DNA methylation

104
Q

Methylation of histones

A

results in
tighter packing that prevents
transcription

105
Q

Acetylation of histones

A

uncoils
chromatin, encouraging transcription

106
Q

Direct DNA methylation

A

epigenetic control of DNA that can
be inherited and usually leads to
lower expression

107
Q

RNA interference

A

noncoding RNA
(ncRNA) plays a role in controlling gene
expression as well! Some are even
involved in chromatin modification.

108
Q

Micro RNA (miRNA)

A

single stranded
RNA molecules that bind to
complementary RNA sequences and
either degrade the target or block its
translation

109
Q

Short interfering RNA (siRNA)

A

function similarly to miRNA,

110
Q
A

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