Microbiology Ch.8

Front 1

genetics

Back 1

studey of what genes are, how they carry information, how information is expressed, and how genes are replicated

Front 2

gene

Back 2

segment of DNA that encodes a functional product, usually a protein

Front 3

genome

Back 3

all of the genetic material in a cell

Front 4

genotype

Back 4

genes of an organism

Front 5

phenotype

Back 5

expression of the genes

Front 6

vertical gene transfer

Back 6

occurs during reproduction, between generations of cells.

reproduction (parents to offspring)

Front 7

horizontal gene transfer

Back 7

transfer of genes between cells of the same generation

Front 8

flow of genetic information inside a cell

Back 8

DNA---DND replication---> DNA---transcription---> RNA---translations--->
protein

Front 9

DNA

Back 9

-polymer of nucleotides: adenine (A), thmine (T), cytosine (C), guanine (G)

-double helix associated with proteins

-"backbone" is deoxyribose-phosphate

-strands held together by hydrogen bonds between A-T(2) and C-G(3)

-strands are anti-parallel

Front 10

DNA Replication

Back 10

-Semiconservative: new double strand DNA contains one original and one new strand

-In the 5'-->3' direction, initiated by an RNA primer

-DNA polymerase and DNA ligase are involved

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RNA

Back 11

-polymer of nucleotides: adenine (A), uracil (U), cytosine (C), guanine (G)

-include mRNA, tRNA, and rRNA

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Transcription

Back 12

-DNA is transcribed to make RNA
-Transcription begins when RNA polymerase binds to the promotor sequence
-Transcription proceeds in the 5'-->3' direction
-Transcription stops when it reaches the terminator sequence

Front 13

Translation

Back 13

-Protein synthesis (mRNA-->protein)

-mRNA is translated in codons (3 nucleotides for 1 amino acid---degenerate)

-tRNA contain specific amino acids and anticodons

-translation of mRNA begins at the start codon: AUG

-translation ends at a STOP codon: UAA, UAG, UGA

Front 14

Regulation of gene expression

Back 14

-constitutive enzymes are expressed at a fixed rate

-other enzymes are expressed only as needed, either repressible or inducible

Front 15

mutation

Back 15

change in the genetic material. It may be neutral, beneficial, or harmful.

Front 16

The frequency of mutation

Back 16

spontaneous mutation rate = 1 in 10^9 replicated base pairs or 1 in 10^6 replicated genes.

Mutagens increase to 10^-5 or 10^-3 per replicated gene.

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spontaneous mutations

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occur in the absence of a mutagen

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base substitution

Back 18

(point mutation)

-missense and nonsense mutations are base substitutions

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Missense mutation

Back 19

base substitution

change in one base; result in change in amino acid

Front 20

nonsense mutation

Back 20

base substitution

results in a nonsense codon

Front 21

frameshift mutation

Back 21

insertion or deletion of one or more nucleotide pairs

Front 22

Mutagen

Back 22

agent that causes mutations. Ames test for identification of mutagens.

Front 23

chemicals

Back 23

base pair mutagens (nitrous acid HNO2), nucleoside analogs, and frameshift mutagens (benzpyrene)

Front 24

ionizing radiation

Back 24

(x rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone --> nucleotide excision repairs mutations

Front 25

UV radiation

Back 25

causes thymine dimers --> light-repair seperates thymine dimers

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Mutant Selection

Back 26

positive (direct) selection detects mutant cells because they grow or appear different.

negative (indirect) selection detects mutant cells becase they do not grow.

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Genetic transfer and recombination

Back 27

exchange of genes between two DNA molecules to form new combinations of genes on a chromosome

Includes: transformation, conjugation, and transduction

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transformation

Back 28

genes transferred into bacteria as 'naked' DNA in solution

-griffith experiment demonstrate genetic transformation

- using various components of the Killed S. pneumoniae proved DNA was the carrier of genetic information

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conjugation

Back 29

genes transferred through F+ pili from donor bacteria to recipient bacteria

Front 30

transduction

Back 30

genes transferred into bacteria through bacteriophage

Front 31

plasmids

Back 31

conjugative plasmid
dissimilation plasmid
R factors

Front 32

conjugative plasmids

Back 32

carries genes for sex pili and transfer of the plasmid

Front 33

dissimilation plasmids

Back 33

encode enzymes for catabolism of unusual compounds

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R factors

Back 34

encode antibiotic resistance

Front 35

Transposons

Back 35

-segments of DNA that can move from one region of DNA to another

-contain insertion sequences for cutting and resealing DNA (transposase)

-complex transposons carry other genes