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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
Q

What steps of DNA replication are occurring in this drawing?

A
  1. 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)
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26
Q

What steps of DNA replication are occurring in this drawing?

A
  1. DNA polymerase will replace RNA primers with DNA nucleotides
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27
Q

What steps of DNA replication are occurring in this drawing?

A
  1. DNA ligase joins Okasaki fragments together
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28
Q

What is different in bacterial DNA replication?

A

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

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29
Q

Transcription vs. Translation

A

Transcription is used to make a copy of one gene
Translation is to create protein from the copied gene

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30
Q

Where is gene expression done in eukaryotes?

A

TXN: nucleus
TSN: cytoplasm (ribosome/RER)

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31
Q

Where is gene expression done in prokaryotes?

A

TXN and TSN done in cytoplasm (ribosomes)

32
Q

What is gene expression?

A

how genetic information in DNA is expressed as a trait
- how DNA is read to create a protein

33
Q

What is transcription?

A

Synthesis of a complementary strand of RNA (mRNA) from a DNA template

34
Q

What makes up one transcription unit?

A
35
Q

RNA polymerase function

A

uses DNA as template to synthesize RNA
- strand made in 5’ -> 3’
- binds promoter region, copies gene, detaches at terminator

36
Q

What are the three steps of transcription?

A
  1. initiation
  2. elongation
  3. termination
37
Q

What happens during transcription initiation?

A

RNA polymerase binds promoter
- dsDNA unwinds, exposing gene

38
Q

What happens during transcription elongation?

A

RNA polymerase creates RNA strand by adding complementary nucleotides in 5’ -> 3’ direction

39
Q

What happens during transcription termination?

A

RNA polymerase reaches terminator and detaches from DNA template
- DNA rewinds

40
Q

What happens during translation?

A

mRNA chain is used as template to synthesize amino acid strand
- protein synthesis
- Begins at start codon. ends at stop codon

41
Q

Where does translation occur?

A

Ribosomes in cytoplasm

42
Q

What components are involved in translation? What are their functions?

A

mRNA - the code
Ribosome - organelle that synthesizes the protein
tRNA - delivers amino acid to ribosome. matches the AA to correct codon using anticodon

43
Q

What are your stop codons?

A

UAA, UAG, UGA

44
Q

What is a codon?

A

3 base sequence that codes for specific amino acid
- 64 combinations, 20 AAs

45
Q

Why is their redundancy within codons?

A

protects from mutation

46
Q

What happens in step 1 of protein synthesis?

A

Initiation step
- the two subunits assemble around the mRNA with the start codon in the P-site

47
Q

What happens in step 2 of protein synthesis?

A
48
Q

What happens in step 3 of protein synthesis?

A

tRNA comes in at A-site

49
Q

What happens in step 4 of protein synthesis?

A

Elongation step
- ribosome forms bond

50
Q

What happens in step 5 of protein synthesis?

A
51
Q

What happens in step 6 of protein synthesis?

A

Termination: stop codon reaches A-site
no tRNA to bind, Polypeptide chain is released

52
Q

How is gene expression regulated in eukaryotes?

A

complicated process :p

53
Q

How is gene expression regulated in prokaryotes?

A

many genes co- regulated in operon system -> one promoter for multiple genes

54
Q

What are three types of genes?

A
  1. constitutive
  2. repressible
  3. inducible
55
Q

What are constitutive genes? Give an example

A

gene product is always needed so txn is always “on” (e.g. glycolytic proteins)

56
Q

What are repressible genes?

A

txn is normally “on” but can be turned off

57
Q

What are inducible genes?

A

txn is normally “off” but can be turned on

58
Q

What is an example of an inducible gene in bacteria?

A

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
Q

What is the function of an operator in an operon?

A

Can block txn

60
Q

What is lacI’s function in this image?

A

encodes for a lac repressor, a constitutive gene, to bind to the operator to inhibit the transcription of lac operon

61
Q

What is allolactose’s function in this image?

A

It is an inducer that denatures the lac repressor to turn lac operon on

62
Q

How do mutations in DNA sequence occur?

A

Can be spontaneous or induced

63
Q

What is a point mutation?

A

single base change

64
Q

What is frameshift mutation?

A

insertion or deletion of a base, shifting the reading frame down

65
Q

What kind of mutation is shown?

A

Silent mutation: base doesn’t result in AA sequence change

66
Q

What kind of mutation is shown?

A

Missense mutation: base change results in a single AA change

67
Q

What kind of mutation is shown? Give an example

A

Nonsense mutation: base change results in introduction of a premature stop codon
e.g. sickle-cell anemia

68
Q

What are three types of chemical mutagens?

A
  1. base-pair mutagens
  2. base analogs
  3. frameshift mutations
69
Q

What are the types of radiation mutagens?

A
  1. ionizing radiation
  2. non-ionizing radiation
70
Q

What do base pair mutagens do? Give an example

A

alter base-pairing rules
e.g. nitrous acid causes A to pair with C during DNA replication

71
Q

What do base analogs do?

A

incorporated as one nucleotide but have altered base-pair rules
e.g. 5-bromouracil replaces T but base-pairs with G

72
Q

What do frameshift mutations do? Give an example

A

usually intercalate into DNA and cause DNA polymerase to make small insertions or deletions
e.g. aflatoxin from peanut mold

73
Q

What does ionizing radiation do?

A

Damages DNA and creates free radicals
e.g. X-rays , gamma rays, Chernobyl

74
Q

What does nonionizing radiation do?

A

Creates thymine-thymine dimers
e.g. UV light
- bacteria have created ways to get around it

75
Q

How do we detect mutagens?

A

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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