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MICR 262 > (LE2) Microbial Genetics > Flashcards

(LE2) Microbial Genetics Flashcards

1
Q

Define genetics

A

the study of genes and inheritance patterns

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2
Q

Define chromosomes

A

the form DNA takes in cells

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3
Q

How many pairs of chromosomes do humans have?

A

23 pairs linear chromosome

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4
Q

How many chromosomes do bacteria have?

A

1 circular chromosome

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5
Q

Define genome

A

all the chromosomes of a single cell

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6
Q

Define genes

A

segments of a chromosome
1 gene = 1 protein

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7
Q

Define alleles

A

variations in a single gene

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8
Q

Define genotype

A

the complete set of genes in an organism

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9
Q

Define phenotype

A

the traits resulting from the genes

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10
Q

How are nucleotides bound together in DNA?

A

Covalent bonds
- sugar-phosphate backbone

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11
Q

How are the two strands of DNA bound together? What is the orientation they form in?

A

Nitrogenous bases bound by hydrogen bonds

Strands run antiparallel

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12
Q

How do you ID the 5’C end?

A

contains a phosphate group

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13
Q

Where do you add nucleotides

A

Always to the 3’ end
(5’ —-> 3’)

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14
Q

How do you ID the 3’C prime end?

A

contains hydroxyl group (-OH)

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15
Q

What type of reaction bonds nucleotides together? What is that bond called?

A

Dehydration synthesis to create the phosphodiester linkage

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16
Q

What is the first step in the flow of genetic information transfer?

A

DNA replication: occurs prior to cell division to make an exact copy of the genome to pass to next generation

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17
Q

Why is DNA replication a semiconservative process?

A

It uses two strands of the original DNA to serve as template for the synthesis of new strands

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18
Q

What enzymes are involved in DNA replication?

A
  1. DNA Helicase
  2. DNA Primase
  3. DNA Polymerase
  4. DNA Ligase
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19
Q

DNA Helicase function

A

separates two DNA strands to allow for replication
- creates replication fork
- binds ori (origin of replication)

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20
Q

DNA primase function

A

lays down temporary RNA primer
- leading strand is made continuously. Only needs one primer
- lagging strand made in fragments. Needs multiple primers

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21
Q

DNA polymerase function

A

builds new DNA chain by adding nucleotides to 3’ end
- contains proofreading ability to catch and correct mistakes

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22
Q

DNA ligase function

A

ligates lagging strand fragments (Okasaki fragments) together

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23
Q

Describe the steps of DNA replication

A
  1. Helicase binds at ori and unravels DNA
    • creates replication bubble and replication fork
  2. Primase lays down RNA primer at free 5’ end of new daughter strand
  3. DNA polymerase adds DNA nucleotides to 3’ hydroxyl end
    • leading strand keeps adding nucleotides
    • lagging strand requires multiple primers and be made in fragments (Okasaki fragments)
  4. DNA polymerase will replace RNA primers with DNA nucleotides
  5. DNA ligase joins Okasaki fragments together
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24
Q

What steps of DNA replication are occurring in this drawing?

A
  1. Helicase binds at ori and unravels DNA
    • creates replication bubble and replication fork
  2. Primase lays down RNA primer at free 5’ end of new daughter strand
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25
What steps of DNA replication are occurring in this drawing?
3. DNA polymerase adds DNA nucleotides to 3' hydroxyl end - leading strand keeps adding nucleotides - lagging strand requires multiple primers and be made in fragments (Okasaki fragments)
26
What steps of DNA replication are occurring in this drawing?
4. DNA polymerase will replace RNA primers with DNA nucleotides
27
What steps of DNA replication are occurring in this drawing?
5. DNA ligase joins Okasaki fragments together
28
What is different in bacterial DNA replication?
Contains DNA gyrase instead of DNA Helicase. All other steps are the same - target for magic bullet DNA Gyrase: separates DNA strands to create replication forks
29
Transcription vs. Translation
Transcription is used to make a copy of one gene Translation is to create protein from the copied gene
30
Where is gene expression done in eukaryotes?
TXN: nucleus TSN: cytoplasm (ribosome/RER)
31
Where is gene expression done in prokaryotes?
TXN and TSN done in cytoplasm (ribosomes)
32
What is gene expression?
how genetic information in DNA is expressed as a trait - how DNA is read to create a protein
33
What is transcription?
Synthesis of a complementary strand of RNA (mRNA) from a DNA template
34
What makes up one transcription unit?
35
RNA polymerase function
uses DNA as template to synthesize RNA - strand made in 5' -> 3' - binds promoter region, copies gene, detaches at terminator
36
What are the three steps of transcription?
1. initiation 2. elongation 3. termination
37
What happens during transcription initiation?
RNA polymerase binds promoter - dsDNA unwinds, exposing gene
38
What happens during transcription elongation?
RNA polymerase creates RNA strand by adding complementary nucleotides in 5' -> 3' direction
39
What happens during transcription termination?
RNA polymerase reaches terminator and detaches from DNA template - DNA rewinds
40
What happens during translation?
mRNA chain is used as template to synthesize amino acid strand - protein synthesis - Begins at start codon. ends at stop codon
41
Where does translation occur?
Ribosomes in cytoplasm
42
What components are involved in translation? What are their functions?
mRNA - the code Ribosome - organelle that synthesizes the protein tRNA - delivers amino acid to ribosome. matches the AA to correct codon using anticodon
43
What are your stop codons?
UAA, UAG, UGA
44
What is a codon?
3 base sequence that codes for specific amino acid - 64 combinations, 20 AAs
45
Why is their redundancy within codons?
protects from mutation
46
What happens in step 1 of protein synthesis?
Initiation step - the two subunits assemble around the mRNA with the start codon in the P-site
47
What happens in step 2 of protein synthesis?
48
What happens in step 3 of protein synthesis?
tRNA comes in at A-site
49
What happens in step 4 of protein synthesis?
Elongation step - ribosome forms bond
50
What happens in step 5 of protein synthesis?
51
What happens in step 6 of protein synthesis?
Termination: stop codon reaches A-site no tRNA to bind, Polypeptide chain is released
52
How is gene expression regulated in eukaryotes?
complicated process :p
53
How is gene expression regulated in prokaryotes?
many genes co- regulated in operon system -> one promoter for multiple genes
54
What are three types of genes?
1. constitutive 2. repressible 3. inducible
55
What are constitutive genes? Give an example
gene product is always needed so txn is always "on" (e.g. glycolytic proteins)
56
What are repressible genes?
txn is normally "on" but can be turned off
57
What are inducible genes?
txn is normally "off" but can be turned on
58
What is an example of an inducible gene in bacteria?
Lac Operon: lacZ, lacY, and lacA encode for different proteins in order to consume lactose - required genes are transcribed together as one transcript - all under the control of one promoter
59
What is the function of an operator in an operon?
Can block txn
60
What is lacI's function in this image?
encodes for a lac repressor, a constitutive gene, to bind to the operator to inhibit the transcription of lac operon
61
What is allolactose's function in this image?
It is an inducer that denatures the lac repressor to turn lac operon on
62
How do mutations in DNA sequence occur?
Can be spontaneous or induced
63
What is a point mutation?
single base change
64
What is frameshift mutation?
insertion or deletion of a base, shifting the reading frame down
65
What kind of mutation is shown?
Silent mutation: base doesn't result in AA sequence change
66
What kind of mutation is shown?
Missense mutation: base change results in a single AA change
67
What kind of mutation is shown? Give an example
Nonsense mutation: base change results in introduction of a premature stop codon e.g. sickle-cell anemia
68
What are three types of chemical mutagens?
1. base-pair mutagens 2. base analogs 3. frameshift mutations
69
What are the types of radiation mutagens?
1. ionizing radiation 2. non-ionizing radiation
70
What do base pair mutagens do? Give an example
alter base-pairing rules e.g. nitrous acid causes A to pair with C during DNA replication
71
What do base analogs do?
incorporated as one nucleotide but have altered base-pair rules e.g. 5-bromouracil replaces T but base-pairs with G
72
What do frameshift mutations do? Give an example
usually intercalate into DNA and cause DNA polymerase to make small insertions or deletions e.g. aflatoxin from peanut mold
73
What does ionizing radiation do?
Damages DNA and creates free radicals e.g. X-rays , gamma rays, Chernobyl
74
What does nonionizing radiation do?
Creates thymine-thymine dimers e.g. UV light - bacteria have created ways to get around it
75
How do we detect mutagens?
Using the Ames test: uses auxotrophic (specific dietary requirement) "His" strain (needs histidine) strain of Salmonella typhimurium that requires AA histidine in medium

MICR 262 (30 decks)

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