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MCR101 > Topic 7 -Microbial Genetics I & II > Flashcards

Topic 7 -Microbial Genetics I & II Flashcards

1
Q

What is genetics?

A

study of what genes are, how they carry information, how info is processed, and how genes are replicated

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2
Q

What is a genome?

A

all of the genetic material in a cell (chromosomes/mitochondria/chloroplasts/plasmids)

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3
Q

What is genomics?

A

molecular study of genomes

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4
Q

What is a chromosome?

A

structure that carries hereditary info, contains many genes. Can be circular (bacterial) or linear (humans)

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5
Q

What is a gene?

A

region of DNA that carries a function or produces a functional product (protein or RNA)

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6
Q

What is a genotype?

A

genetic makeup of an organism (e.g. all the genes)

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7
Q

What is a phenotype?

A

external manifestation of genotype or expression of genes (e.g. blue eyes)

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8
Q

Name the 3 basics categories of genes

A
  1. structural genes (code for proteins)
  2. RNA (code for)
  3. regulatory genes (control gene expression)
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9
Q

A bit about bacterial chromosomes

A

Haploid

single, circular

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10
Q

A bit about eukaryote chromosomes

A

multiple & linear

Diploid

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11
Q

Describe the structure of DNA

A 
Two stranded helix
basic unit is called a nucleotide, each consisting of:
5/3 carbon sugar (deoxyribose)
phosphate group
Nitrogenous base: A, C, T or G
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12
Q

Describe DNA replication

A

5’=>3’ direction

  1. enzymes unwind parental double helix
  2. proteins stabilise unwound parental DNA
  3. leading strand is synthesised continuously by DNA polymerase
  4. Lagging strand is synthesised discontinuously. RNA polymerase synthesises short primer, DNA polymerase extends
  5. DNA polymerase digests RNA primer and replaces it w/ DNA
  6. DNA ligase joins discontinuous ends of lagging strand
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13
Q

DNA replication is….?

A

semiconservative.

Each chromosome ends up w/ 1 new & 1 old strand

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14
Q

Describe the structure of RNA and name the 3 different types

A 
Ribose sugar & phosphate backbone
4 nucelotides - A, U, C & G
3 types:
mRNA (messenger)
tRNA (transfer)
rRna (ribosomal)
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15
Q

Describe the process of DNA transcription

A

DNA is transcribed to make RNA (m, r or t)
5’=>3’ direction
1. RNA polymerase binds to promotor, DNA unwinds
2. RNA is synthesised by complementary base pairing of free nucleotides w/ nucleotide bases on template DNA strand
3. Site of synthesis moves along DNA; DNA that has been transcribed rewinds.
4. Transcription stops when it reaches terminator
5. RNA & RNA polymerase are released and helix reforms

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16
Q

What is a codon?

A

Groups of 3 nucleotides (e.g. AUG, UUG)

17
Q

Describe the process of DNA translation

A

tRNA carrying 1st aa is paired w/ start codon on mRNA. Then tRNA carrying 2nd aa etc etc. This continues for each codon creating peptide bonds and releasing the previous tRNA until stop codon is reached. This releases & forms a new polypeptide
Consult textbook/lecture notes diagram.

18
Q

Central dogma of molecular biology?

A

DNA=>RNA=>PROTEIN

19
Q

What is an operon?

A

a set of genes; all of which are regulated as a single unit.

Consists of a promotor, operator and structural genes coding for proteins

20
Q

What are constitutive and regulative enzymes?

A

Constitutive -expressed at fixed rate
Regulative -only expressed as needed. Can be repressible (inhibit gene expression, mediated by repressors) or inducible (transcription turned on. mediated by inducers)

21
Q

Briefly describe the regulation of an operon

A

repressor active; operon off. Repressor binds to operator region, blocking transcription.

repressor inactive; operon on. Inducer binds to repressor, inactivating it, allowing transcription.

22
Q

What is a point mutation?

A

base substitution or missense mutation

23
Q

What is a nonsense mutation?

A

changes a normal codon into a stop codon

24
Q

What is a frameshift mutation?

A

insertation or deletion of 1 or more nucleotide pairs

25
Q

What is a silent mutation?

A

alters a base but does not change the amino acid

26
Q

What is a back-mutation?

A

A mutated gene reverses to its original base composition

27
Q

name the 2 kinds of mutation repair

A

Light repair or excision repair

28
Q

What is a mutagen? Give examples

A

a physical or chemical agent that increases the mutation rate above the spontaneous level.
E.g. X-rays, base analogs

29
Q

What is the purpose of the AMES test?

A

to detect if a compound is mutagenic (carcinogenic)

30
Q

Outline the procedure of the AMES test

A
  1. Indicator organism (mutant strain of salmonella) has lost ability to synthesise histidine, is added to experimental sample
  2. This culture is added to a histidine lacking media and incubated. This mutation is highly susceptible to back-mutation
  3. exposing cells of this mutant to a mutagen will produce revertants able to make histidine, which can be detected & counted
31
Q

What is horizontal gene transfer? Name the 3 mechanisms

A 
transfer of genes b/w cells of the same generation.
3 recombination mechanisms are:
1. Transformation
2. Conjugation
3. Transduction
32
Q

What is vertical gene transfer?

A

Occurs during repro: b/w (down the) generations of cells

33
Q

Describe genetic recombination

A

occurs when an organism acquires & expresses genes that originated in another organism

34
Q

Describe genetic transformation

A

chromosome fragments from lysed cell are accpeted by recipient cell; genes on DNA fragment are then acquired by recipient.
Donor & recipient may be unrelated.

35
Q

Describe genetic conjugation

A

Plasmid mediated -self replicating circular DNA
requires:
cell to cell contact (pillus)
recipient doesn’t already have a plasmid
Recipient receives a copy, so both donor/recipient have the plasmid

36
Q

Describe genetic transduction

A

Think virus reproduction!!!!!

Bacteriophage (virus that targets bacteria) serves as carrier of DNA from donor cell to recipient cell

37
Q

Describe what a plasmid is

A

small, circular DNA material found in cytoplasm. self-replicating, can move to new cells

38
Q

Name the 5 different kinds of plasmids & their functions

A
  1. Conjugative plasmid: carries genes for sex pili & transfer of plasmid
  2. Dissimilation plasmids: encode enzymes for catabolism of unusual compounds
  3. R factors: encode antibiotic resistant genes
  4. Virulence genes: pathogens
  5. Bacteriocin genes: kill competing bacteria
39
Q

Describe what a transposon is

A

Small segments of DNA that can move from one region of a DNA molecule to another.
Carry transposase gene, encode a recombinase allowing cutting/resealing DNA
Can excise out of DNA & recombine at another location

MCR101 (13 decks)

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