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Microbiology > Chapter 7 > Flashcards

Chapter 7 Flashcards

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1
Q

Gregor Mendel

A

Determined traits are inherited as physical units called genes

George Beadle and Edward Tatum: reported that genes direct production of enzymes

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2
Q

Nucleotides

A

Three nucleotides in code a specific amino acid

Composed of nucleobases:

Adenosine (A):

Thymine (T):

Cytosine (C):

Guanine (G):

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3
Q

Amino acids

A

Amino acids make up proteins

Sequence of amino acids determine the structure and function of protein

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4
Q

Genome

A

Complete set of genetic information

Chromosome + plasmids

All cell have DNA genome
Viruses may have RNA genome

Genomics- study of nucleotide sequence of DNA

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5
Q

Cells must _____ to multiply

A

DNA Replication

Gene expression

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6
Q

Gene expression

A

Transcription: information in DNA is copied into RNA

Translation: RNA used to synthesize encoded protein

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7
Q

DNA

A

Double stranded helix

Carbon atoms of the pentose sugar are numbered

Nucleotides joined between Phosphate (PO) and hydroxyl (OH) by hydrogen bonds

Sugar phosphate backbone

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8
Q

Base pairing

A

(AT) Adenosine to Thymine: 2 hydrogen bonds

(CG) Cytosine to guanine: 3 hydrogen bonds

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9
Q

RNA

A

Ribose instead of deoxyribose

Uracil instead of Thymine

Shorter single strand

Transcript: synthesized from DNA template strand

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10
Q

3 types of RNA

A

Messenger RNA (mRNA)

Ribosomal RNA (rRNA)

Transfer RNA (tRNA)

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11
Q

Origin of replication

A

Bidirectional DNA replication

2 replication forks

Terminating site

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12
Q

Semiconservative

A

Replication conserves one original DNA strand and synthesized one new

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13
Q

Initiation of DNA replication

A

DNA gyrase and helicases bind to origin of replication

Break and unwind DNA helix

Primases: synthesized short regions of RNA called primers

enzymes form replisomes

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14
Q

DNA Polymerases

A

DNA polymerase can only add nucleotides, not initiate, requires primers

Synthesize in 5’ to 3’ direction

Can only add to 3’ end

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15
Q

Helicases

A

Unzip DNA strands, reveals template sequences

Leading strand: synthesized continuously

Lagging strand: synthesized discontinuously
Okazaki fragments : nucleic acid fragment after synthesis of lagging strand

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16
Q

DNA Ligase

A

Enzyme that joins to DNA fragments together by forming a covalent bond between the sugar and phosphate residues of adjacent nucleotides

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17
Q

Primer

A

Fragment of nucleic acid to which DNA polymerase can add nucleotides

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18
Q

Replisome

A

The complex of enzymes and other proteins that synthesize DNA

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19
Q

Transcription

A

RNA polymerase synthesizes single stranded RNA from DNA template, stops at terminator

RNA Polymerase: synthesizes in 5’ to 3’ direction, must bid to promoter

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20
Q

RNA sequence

A

Complementary, antiparallel to DNA template strand

DNA template is (-) strand
Complement is (+) strand

Uracil instead of Thymine

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21
Q

Prokaryotic mRNA transcripts

A

Monocistronic (one gene)

Polycistronic (multiple genes)

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22
Q

Initiation of RNA synthesis

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A

Sigma factor on RNA polymerase recognizes promoter

Various sigma factors for various promoters

23
Q

Promoter

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A

Orients direction of transcription

Upstream of genes

Once RNA polymerase has moved beyond promoter, another RNA polymerase can bind

24
Q

Terminator

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A

Nucleotide sequence at which RNA synthesis stop; the RNA polymerase falls off the DNA template and releases the newly synthesized RNA

25
Translation
Process of decoding information in nucleotides of mRNA into amino acids of proteins Major components: mRNA, ribosomes, tRNAs, and accessory proteins mRNA: Temporary copy of genetic information
26
Genetic code:
3 nucleotides= codon =one amino acid More than one codon can specify a specific amino acid; code is degenerate Universal
27
Reading Frames
There are three reading frames, or ways in which triplets of nucleotides can be grouped Wrong reading frames lead to non-functional proteins
28
Ribosomes
Serve as translation “machines” Forms peptide bond between amino acids Maintain correct reading frame
29
Transfer RNAs (tRNAs)
Deliver correct amino acid Specific anticodon sequence tRNA can be recycled
30
Initiation of translation
Ribosome binding site: part of ribosome binds to mRNA sequence Initiating tRNA brings altered form of Methionine (occupies P site)
31
Elongation of polypeptide chain
tRNA recognize next codon and occupies empty a site, next is P site Amino acid from tRNA in the P site added to amino acid carried by tRNA A site tRNA exits E site, new tRNA occupies A site Repeats
32
Termination
Elongation continues until ribosome reaches stop codon Enzyme break covalent bond joining two polypeptide to tRNA Ribosomes fall off (30S and 50S) Reusable
33
Anticodon
Sequence of three nucleotides in a tRNA molecule that is complementary to a particular codon in mRNA
34
Post translational modification
Polypeptides often modified after synthesis Folded into structures by proteins chaperones Polypeptides destined for transport are tagged
35
Eukaryotic mRNA
Synthesized in precursor form pre-mRNA Process during or after transcription Capping: add methylated guanine to 5’ end Polyadenylation: modifies 3’ end
36
Splicing
Remove segments of eukaryotic transcription Introns are removed Exons are the expressed regions
37
Quorum sensing
Allows some organisms to “sense” density of their own population
38
Two component regulatory system
Membrane spanning sensor: modifies internal region in response to specific environmental variations, phosphorylates amino acid Response regulator: phosphate group transferred from sensor, turns genes on or off
39
Natural selection
Can play role in gene expression
40
Antigenetic variation
Alteration of characteristics of surface proteins Helps pathogens
41
Phase variation
Involves switching genes on and off
42
Operon
A set of regulated genes transcribed as single mRNA along with its control sequences Regulon: separate operons controlled by single regulatory mechanism
43
Global control
Simultaneous regulation of numerous genes Types: Constitutive: enzymes synthesized constantly Inducible: enzymes synthesized only when needed Repressible: enzymes produced routinely, but are turned off
44
Most common regulatory mechanisms
Alternative sigma: Recognize different sets of promoters to control expression of specific groups of genes DNA binding proteins: can act as repressors, blocks transcription Activator facilitates transcription (positive regulation)
45
Mechanisms of repressors
Induction: repressor binds to the operator, blocks transcription Repression: repressor cannot bind to operator
46
Lac operon
Encodes proteins involved with transport in degradation of lactose Turned on: glucose not available Turned off: glucose is available
47
Carbon catabolism repression (CCR)
When both glucose and lactose are present Prevents expression of genes that metabolize lactose in the presence of glucose
48
Catabolite activator protein (CAP)
Required for transcription of lack operon Inducer called cAMP cAMP: only when glucose is low, synthesized by idle fork of glucose transporter
49
Inducer exclusion
Lactose transporter block during glucose transport by active glucose transporter
50
Eukaryotic gene regulation mechanisms
Modification of chromosome structure Regulation of initiation of transcription Altering pre-mRNA processing and modification RNA interference (RNAi)
51
RNA interference (RNAi)
Short RNA strand joins multi-protein unit RNA strand serves as probs for binding to mRNA Tags mRNA for destruction microRNA (miRNA) and short interfering RNA (siRNA)
52
Bioinformatics
Computer technology needed to store, retrieve, and analyze sequence data Data interpretation complex: Promoter orientation Which DNA strand is template Reading frame
53
Open reading frames (ORFs)
Stretches of nucleotides generally longer than 300 bp Begin with start codon, end with stop codon
54
Metagenomics
Analysis of total microbial genomes in environment Keeps track and changes of composition in microbiota overtime (healthy, diseased) Study microbial like in oceans, soils

Microbiology (10 decks)

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