Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medical Micro > Chapter 7 > Flashcards

Chapter 7 Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards
1
Q

Entire genetic complement which includes genes and nucleotide sequences that connect genes to one another

A

Genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Specific sequences of nucleotides that code for RNA or polypeptide molecules

A

Genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Basic building block of DNA

A

Nucleotides
- made up of phosphate attached to nucleoside (pentose sugar + a nitrogenous base)

Nitrogenous bases - G,C,T,A,U

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Bases of nucleotides are held together by…

A

Hydrogen bond in a specific way called complementary base pair

For DNA: A-T by 2H bonds

For RNA: A-U by 2H bonds

C-G by 3H bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Arrangement of DNA

A

5’ carbon
3’ hydroxyl group

Antiparallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Carries instructions for the synthesis of polypeptides and RNA molecules in much the way a sequence of letters carries info used to form words and sentences

A

Linear sequence of nucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Allows cell to make exact copies to pass to its progeny

A

Complementary structure of the two strands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

DNA of prokaryotic genomes are found in…

A

Chromosomes and plasmids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Consists of circular molecule of DNA localized in a region of the cytoplasm

A

Nucleotides

- is typically in prokaryotic chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Is a globular protein that has archaea DNA wrapped around them

A

Histones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Further folds and supercoils the entire prokaryotic chromosome like a skein of yarn into a compact mass

A

Gyrase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Small molecules of DNA that replicate independently of the chromosome

A

Plasmids

  • usually circular
  • found in prokaryotic cells
  • carries info required for its own replication
  • carries gene that give advantages to the cell that is carrying them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Have two copies of each chromosome

A

Eukaryotic cells

  • are diploids
  • are linear
  • located in a nucleus
  • has globular histones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Charge of DNA

A

Negative charged

- has positively charged histones wrapped around it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Histones + DNA

A

Nucleosomes
- found in eukaryotic cells

Nucleosomes + proteins = chromatin fibers (important during mitosis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When are chromatin fibers loosely packed?

A

In regions with chromosomes where genes are active

When chromatin are in this way they form euchromatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When inactive DNA is more tightly packed it is called…

A

Heterochromatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Type of DNA in mitochondria

A

Circular DNA

  • similar to prokaryotic DNA
  • contains 5% of DNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Has a haploid genome

A

Prokaryotic cells

  • also has chromosomal DNA in the form of single circular chromosome
  • also has plasmids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Has a diploid genome

A

Eukaryotic cells

  • nuclear chromosomal DNA in linear chromosomes
  • also has extra nuclear DNA in mitochondria, chloroplasts, and any plasmids present
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Has a haploid copy of one or rarely two chromosomes

A

Bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Plasmids are present in some cells

A

Bacteria
- usually more than one per cell

Archaea
- in some cells

Eukaryotic

  • fungi
  • algae
  • Protozoa
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Has circular or linear dsDNA

A

Bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Has circular dsDNA

A

Archaea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Has linear dsDNA in nucleus

Circular dsDNA in mitochondria, chloroplasts, and plasmids

A

Eukaryotic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

DNA is located in cytoplasm and plasmids

A

Bacteria and archaea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Does not have histones

A

Bacteria

- chromosome are associated with a small amount of no histones protein instead

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Process of DNA replication is described as…

A

semiconservative process

- each daughter DNA molecule is composed of one original strand and one new strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

DNA replication starts at….

A

origin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

enzyme that unzips the DNA to do replication

A

helicase

  • breaks the hydrogen bond between nitrogenous bases
  • exposes the bases in a replication fork
  • proteins will attach to the separated single strands so they do not rejoin when replication is occurring
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

of bacterial DNA polymerase

A

5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

catalyze synthesis of DNA by the addition of new nucleotides

A

polymerase

- adds nucleotide only to hydroxyl group at 3’ end so adds in 5’ to 3’ direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

usual enzyme used in DNA replication for bacteria

A

DNA polymerase III

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Leading strand is made continuously in what direction?

A

5’ to 3’ end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Lagging strands are made in what direction

A

5’ to 3’ end in sections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Synthesis of Leading strand

A

1 An enzyme called primase synthesizes a short RNA molecule that is complementary to the template DNA strand.
This RNA primer provides the 3’ hydroxyl group required by DNA polymerase III.
2 Triphosphate deoxyribonucleotides form hydrogen bonds with their complements in the parental strand. Adenine
nucleotides bind to thymine nucleotides, and guanine nucleotides bind to cytosine nucleotides.
3 Using the energy in the high-energy bonds of the triphosphate deoxyribonucleotides, DNA polymerase III covalently joins them one at a time to the leading strand. DNA polymerase III can add about 500 to 1000 nucleotides per
second to a new strand.
4 DNA polymerase III also performs a proofreading function
(not shown). About one out of every 100,000 nucleotides is mismatched with its template; for instance, a guanine might become incorrectly paired with a thymine. DNA
polymerase III recognizes most of these errors and removes the incorrect nucleotides before proceeding with synthesis.
This role, known as the proofreading exonuclease function, acts like the backspace key on a keyboard, removing the most recent error. Because of this proofreading exonuclease
function and other repair strategies beyond the scope of this discussion, only about one error remains for every
10 billion (1010) bp replicated.
5 Another DNA polymerase—DNA polymerase I—replaces the RNA primer with DNA (not shown). Note that researchers
named DNA polymerase enzymes in the order of their discovery, not the order of their actions.

37
Q

formed away from replication fork

A

lagging strands

- begins with its own RNA primer

38
Q

direction of DNA replication

A

bidirectional

DNA synthesis proceeds
in both directions from the origin. In bacteria, the process of
replication proceeds from a single origin, so it involves two sets
of enzymes, two replication forks, two leading strands, and two
lagging strands

39
Q

Removes supercoil after DNA is unwind

A

The enzymes gyrase and topoisomerase
remove such supercoils by cutting the DNA, rotating
the cut ends in the direction opposite the supercoiling, and then
rejoining the cut ends

40
Q

joining the cut ends.
Bacterial DNA replication is further complicated by
methylation of the daughter strands, in which a cell adds a
methyl group (¬CH3) to one or two bases that are part of specific
nucleotide sequences. Bacteria typically methylate adenine
bases and only rarely a cytosine base

A

Methylation plays a role in a variety of cellular processes,
including the following:
■ Control of genetic expression. In some cases, genes that
are methylated are “turned off” and are not transcribed,
whereas in other cases methylated genes are “turned on”
and are transcribed.
■ Initiation of DNA replication. In many bacteria, methylated
nucleotide sequences play a role in initiating DNA
replication.
■ Protection against viral infection. Methylation at specific sites
in a nucleotide sequence enables cells to distinguish their
DNA from viral DNA, which lacks methylation. The cells
can then selectively degrade viral DNA.
■ Repair of DNA. The role of methylation in some DNA repair
mechanisms is discussed later in the chapter (pp. 223–224).

41
Q

How is eukaryotic DNA replication different?

A

■ Eukaryotic cells use four different DNA polymerases to
replicate DNA. DNA polymerase α initiates replication,
including synthesis of a primer—the function performed
by primase in bacteria. DNA polymerase δ elongates
the leading strand, and DNA polymerase ε appears to
be responsible for replicating the lagging strand. DNA
polymerase γ replicates mitochondrial DNA.3
■ The large size of eukaryotic chromosomes necessitates
thousands of origins per molecule, each generating two
replication forks; otherwise, the replication of eukaryotic
genomes would take days instead of hours.
■ Eukaryotic Okazaki fragments are shorter than those
of bacteria—100 to 400 nucleotides long.
■ Plant and animal cells methylate cytosine bases
exclusively

42
Q

m is the actual set of

genes in its genome

A

genotype
-e. A genotype differs from a genome in that
a genome also includes nucleotides that are not part of genes,
such as the nucleotide sequences that link genes together. At
the molecular level, the genotype consists of all the series of
DNA nucleotides that carry instructions for an organism’s
life

43
Q

) refers to the physical features and
functional traits of an organism, including characteristics such
as structures, morphology, and metabolism

A

phenotype

44
Q

How does genotype lead to phenotype?

A

phenotypic traits result from
the actions of RNA and protein molecules that are themselves
coded by DNA

45
Q

Are genes always active?

A

no

46
Q

Making a RNA copy of the DNA

A

Transcription

47
Q

RNA is then used to make protein

A

Translation

48
Q

Central dogma is…

A

DNA transcribed to RNA which is then translated to form polypeptides

49
Q

Carry genetic info from chromosomes to ribosomes

A

.mRNA

50
Q

Combines with ribosomal polypeptides to form ribosomes

A

.rRNA

51
Q

Deliver the correct amino acids to ribosomes based on the sequence of nucleotides in mRNA

A

.tRNA

52
Q

Steps in initiation of transcription

A

Attaches to DNA and goes down its sequence until it reaches the promoter
- sigma factor is needed to recognize promoter in bacteria

After recognition, RNA polymerase will unzip the DNA at the promoter and form a bubble

53
Q

Steps in elongation of transcription

A

Triphosphate ribonucleotides align with their DNA complements
- triphosphate ribonucleotides also give the energy needed for RNA synthesis

RNA polymerase links them together and make RNA

No primer needed

54
Q

Steps in termination of transcription

A

For self-termination, transcription of GC rich terminator region produces a hairpin loop to create tension and loosen the grip of the polymerase on the DNA

For rho-dependent termination, tho pushes between polymerase and DNA to cause release of polymerase, RNA transcript, and Rho

55
Q

Can multiple copies of RNA be transcribed simultaneously?

A

Yes for bacteria

56
Q

Differences in transcription for eukaryotes

A

Transcription occurs in nucleus, mitochondria, and chloroplast

Has 3 types of nuclear RNA polymerase

  • transcribe mRNA
  • transcribe major rRNA
  • transcribe tRNA and small rRNA

Has many transcription factors to help RNA polymerase bind to promoter while bacteria only has sigma factor

Has elongation factors

Process mRNA before doing translation

  • capping by adding guanine to 5’ end of mRNA
  • polyadenylation by adding adenine nucleotide to 3’ end does not need DNA template to occur
  • splicing by removing introns to only have exons in the functional mRNA
57
Q

Define genetic code

A

Triplets of mRNA nucleotides called codon which code for specific amino acids

58
Q

Start codon AUG is for

A

Methionine

For bacteria
-fMet

59
Q

With most redundant codons, the… determine the amino acid

A

First 2 nucleotides

60
Q

Eukaryotic mRNA is different from prokaryotic mRNA due to….

A

Processing of pre-mRNA

Eukaryotic mRNA contains instructions for only one polypeptide

Eukaryotic mRNA is not translated until it is fully transcribed and processed and has left the nucleus
- so transcription and translation of mRNA does not occur simultaneously

61
Q

Has the anticodon

A

.tRNA

- has 3 hairpin loops held by hydrogen bonds

62
Q

Ribosomes of bacteria are

A

70S

- 50S and 30S

63
Q

Ribosomes for eukaryotes are

A

80S

-60S and 40S

64
Q

The tRNA binding site of ribosomes

A

A site
- accepts the tRNA varying the next amino acid to be added to the growing polypeptide

P site
- holds the tRNA carrying the polypeptide

E site
- is where the empty tRNA molecules exit

65
Q

Initiation of translation

A

The smaller ribosomal subunit attaches to mRNA at a ribosome-binding site (known as shine-dalgarno sequence) so as to position a start codon (AUG) at ribosomal subunit P site

.tRNA whose anticodon is UAC to complement the start codon, attaches at the ribosome’s P site

The larger ribosomal subunit then attaches to form a complete initiation complex

66
Q

Elongation of the translation

A

The transfer RNA whose anticodon is complementary to the next codon-delivers its amino acid- to the A site

Proteins called elongation factor escort the tRNA along with a molecule of GTP
- energy from GTP is used to stabilize each tRNA as it binds at the A site

An enzymatic RNA molecule called ribozymes- is the larger ribosomal subunit - forms a peptide bond between the terminal amino acid of the growing polypeptide chain and the newly introduced amino acid so that the polypeptide is now attached to the tRNA occupying the A site

6 Using energy supplied by more GTP, the ribosome moves
one codon down the mRNA. This transfers each tRNA
to the adjacent binding site; that is, the first tRNA moves
from the P site to the E site, and the second tRNA (with
the attached polypeptide) moves to the vacated P site.
7 The ribosome releases the “empty” tRNA from the E site.
In the cytosol, the appropriate enzyme recharges the empty
tRNA with another molecule of the type of amino acid
carried by that tRNA.
8 The cycle repeats, each time adding another amino acid,
at a rate of about 15 amino acids per second

67
Q

Termination of translation

A

uses release factors to stop elongation

ribosome seperates

68
Q

Differences in eukaryotic translation

A

■ Initiation of translation in eukaryotes occurs when the
small ribosomal subunit binds to the 5’ guanine cap rather
than a specific nucleotide sequence.
■ The first amino acid in eukaryotic polypeptides is methionine
rather than formylmethionine.
■ Ribosomes attached to membranes of endoplasmic reticulum
(ER), forming rough ER (RER), can synthesize polypeptides
into the cavity of the RER.

69
Q

Prokaryotic operon consists of…

A

promoter
series of genes that code for enzymes and structures
adjacent regulatory element called an operator which controls movt of RNA polymerase

70
Q

Inducible operons

A

not usually transcribed

must be activated by inducers

71
Q

Repressible operons

A

are transcribed continually until deactivated by repressors which bind to the operator and inhibit transcription

72
Q

lactose operon is example of…

A

inducible operon

lac operon controlled by regulatory gene located outside operon
- produces a repressor protein that attaches to DNA at lac operator
= repressor prevents RNA polymerase from binding to the promoter to stop mRNA synthesis
- allolactose is an inducer that inactivates the repressor by changing the repressor’s quaternary structure so that it can no longer attach to DNA so that transcription of the three structural genes can proceed–> operon is induced and can become active
- ribosomes then translate the newly synthesized mRNA to produce enzymes that catabolize lactose

  • once lactose supply has been depleted, there is no more inducer and the repressor becomes active again to suppress the transcription of the lac operon
73
Q

condition that needs to be met before transcribing lac operon

A

glucose is absent
- see increase in cAMP and binds to CAP–> together binds to the lac promoter and begin transcription of lac

if glucose present, cell does not synthesize cAMP so low lvl cAMP

74
Q

tryptophan operon is…

A

repressible operon
- repressor of repressible operon is usually inactive

if no tryptophan present, tryptophan operon is active—> leads to tryptophan synthesis

if tryptophan is available, repressor is activated and binds to operator and leads to stopping tryptophan synthesis

75
Q

point mutation is…

A

when a single nucleotide base pair is affected

- includes substitution and frameshift mutations (insertions and deletions)

76
Q

mutation causes a different amino acid to form

A

missense mutation

77
Q

mutation causes a stop codon to form

A

nonsense mutation

78
Q

radiation can lead to…

A

pyrimidine dimers

  • prevents hydrogen bonds
  • distorts sugar backbone
  • prevent proper replication and transcription
79
Q

Types of chemical mutagens

A

nucleotide analogs
- used in antiviral and anticancer drugs

Nucleotide-altering chemicals
- change structure of nucleotides

frameshift mutagen
- insert or delete a nucleotide base pair

80
Q

exchange nucleotide sequences between two DNA molecules and often involves segments that are composed of identical or nearly identical nucleotide sequences called homologous sequences

A

genetic recombination

81
Q

define genetic recombination

A

Simplified depiction of
one type of recombination between two DNA molecules. After an enzyme
nicks one strand (here, strand A), a recombination enzyme rearranges the
strands, and ligase seals the gaps to for m recombinant molecules.

82
Q

example of ancestors passing on their gene to their descendants

A

vertical gene transfer

83
Q

many prokaryotes acquire genes

from other microbes of the same generation

A

horizontal (lateral) gene transfer

  • a donor cell contributes part of its genome to a recipient cell,
    which may be of a different species from the donor. Typically,
    the recipient cell inserts part of the donor’s DNA into its own
    chromosome, becoming a recombinant cell. Cellular enzymes
    then usually degrade remaining unincorporated DNA. Horizontal
    gene transfer is a rare event, typically occurring in less
    than 1% of a population of prokaryotes.
84
Q

types of horizontal gene transfer

A

transformation, transduction, and bacterial conjugation.

85
Q

cell takes up DNA from the environment

A

transformation
- Cells that have the ability to take up DNA from their environment
are said to be competent.

86
Q

cells get DNA from a virus that took the DNA from another cell

A

transduction

- a virus that infects bacteria is called a bacteriophage or a phage

87
Q

uses a pilus to transfer DNA

A

conjugation

  • the gene coding for the pili is located in the F plasmid
  • cells that have F plasmid are F+ cells
88
Q

HFr cells are…

A

cells that have the F plasmid integrated at a specific DNA sequence in their chromosome

Medical Micro (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions