Ch. 8 Microbial Genetics

Question 1

central dogma of biology

Answer 1

DNA (transcribes into) mRNA (translates into) protein (shaped into its) function.

Mutations affect DNA, which alters mRNA, which alters proteins, which alters function.

Question 2

gene

Answer 2

sequence of bases in DNA that codes for a functional protein

Question 3

allele

Answer 3

a specific version or form of a gene

Question 4

genotype

Answer 4

all alleles in an organism

Question 5

phenotype

Answer 5

the physical expression of a genotype; characteristics of an organism determined by genetics

Question 6

vertical gene transmission

Answer 6

parent cell –> replication –> fission (daughter cells)

Question 7

horizontal gene transmission

Answer 7

recombination; gene transmission between cells of the same generation.

Question 8

DNA chemical components

Answer 8

• sugar phosphate backbone
• nitrogenous bases (GC - TA)
• “twisted ladder” structure

Question 9

DNA Polymerase

Answer 9

sets down matching nitrogenous bases, breaking H-bonds and synthesizing new strands across from the template strands.

in a bacteria, once it goes fully around the circle (circular DNA), there are 2 full identical DNA molecules

Question 10

replication fork

Answer 10

where unwinding takes place; bidirectional

Question 11

DNA transcription

Answer 11

DNA –> mRNA

Question 12

differences between DNA and RNA

Answer 12

• different sugar in backbone (ribose instead of deoxyribose)
• Uracil instead of Thymine

Question 13

RNA Polymerase

Answer 13

1) connects at the promoter
2) adds complementary base pairings of RNA
3) reaches the terminator and releases; Polymerase dissociates and mRNA is released.

Question 14

promoter

Answer 14

beginning of a gene

Question 15

terminator

Answer 15

end of a gene

Question 16

translation

Answer 16

mRNA –> amino acid sequence of a protein

Question 17

codons

Answer 17

3 bases coding for a specific amino acid

AUG: start codon (methianine)
UAA, UAG, UGA: stop codon

Question 18

steps of translation

Answer 18

1) large and small ribosomal units (rRNA) come together on the mRNA start codon
2) start codon enters the P-site
3) tRNA with the anticodon and amino acid bonding sit for that specific codon pairs (in start, methianine)
4) the next tRNA enters the A-site, bringing along its amino acid. peptide bond forms between amino acids by a ribozyme. P-site tRNA and aa separate. (CLEAVE PEPTIDE CHAIN FROM P-SITE, ATTACH TO A–SITE, TRANSLOCATE, REPEAT)
5) ribosome translocates 3 bases down. P-site codon and tRNA moves to E-site; A-site codon and tRNA move to P-site
6) new tRNA arrives with a new amino acid. empty tRNA from the E-site is ejected and may be reused. repeat until stop codon is reached. (CLEAVE PEPTIDE CHAIN FROM P-SITE, ATTACH TO A–SITE, TRANSLOCATE, REPEAT)
7) stop codon - no matching tRNA; subunits, tRNA, and polypeptide all dissociate.

Question 19

in what type of cell can coupled transcription and translation occur (translation of proteins as an mRNA is being transcribed)

Answer 19

prokaryotes. Eukaryotes need to have mRNA removed from the nuclear membrane to the rRNA in the cytoplasm; prokaryotes do not have a nuclear membrane.

Question 20

operon does what?

Answer 20

regulates bacterial gene expression

Question 21

pre-transcriptional control

Answer 21

are you going to make mRNA or nah

Question 22

constitutive genes/enzymes

Answer 22

always produced

AKA housekeeping enzumes

Question 23

operon consists of..

Answer 23

1) promoter
2) operatory
3) structural genes (code for enzymes that work together and are regulated together)

Question 24

not part of operon, but produces repressor protein:

Answer 24

regulatory or I gene (I stands for inhibitory)

Question 25

2 kinds of operons

Answer 25

inducible operon | repressible operon

Question 26

inducible operon

Answer 26

default is: OFF | inducer turns it: ON

Question 27

repressible operon

Answer 27

default is: ON | repressor turns it: OFF

Question 28

Lac operon

Answer 28

when lactose is absent, these genes are OFF, thus enzymes to catabolize lactose are not produced. When lactose is present, allolactose binds to the inducer, thus turning ON these structural genes, thus, catabolizing enzymes are produced. INDUCIBLE OPERON

Question 29

trp operon

Answer 29

when tryptophan is absent, these genes are ON, thus producing tryptophan. when tryptophan is present, it acts as a corepressor (activating the protein to bind to the O-site), thus turning OFF these structural genes. REPRESSIBLE OPERON

Question 30

mutations

Answer 30

permanent change in DNA sequence

Question 31

mutagens

Answer 31

- radiation | - chemical

Question 32

Bruce Ames

Answer 32

created the Ames test for using bacteria to screen for mutagens; if a chemical is mutagenic, it may be carcinogenic and further testing can ensue.

Question 33

Ames test

Answer 33

1) his- salmonella culture is grown in minimal culture (only has glucose and some minerals). This salmonella cannot grow since it does not have access to histidine 2) a substance is added to the culture along with rat liver extract; if the substance mutates from his- to his+, it is mutagenic

Question 34

why is liver extract used in the Ames test?

Answer 34

most carcinogenic substances only express their carcinogenic nature after being processed in the liver

Question 35

horizontal gene transfer methods

Answer 35

- transformation - conjugation - transduction

Question 36

plasmids

Answer 36

extra circular chromosomal DNA (separate from the main chromosome) - do NOT carry housekeeping genes - various kinds (a plasmid can be more than one kind)

Question 37

dissimilation plasmid

Answer 37

contain genes for breaking down unusual carbon sources

Question 38

increased virulence plasmids

Answer 38

it's in the name, bro

Question 39

R factor

Answer 39

increase resistance to different antibiotics (spread of antibiotic resistance)

Question 40

conjugative

Answer 40

can be transmitted from donor to receptor (pilus)

Question 41

transformation was discovered by...

Answer 41

Frederick Griffith (1928)

Question 42

steps of transformation

Answer 42

1) recipient cell (competent) takes up donor DNA 2) donor DNA aligns with complementary DNA 3) recombination occurs between donor DNA and recipient DNA (occurs during DNA repair; new allele or entirely new properties!)

Question 43

conjugation methods

Answer 43

A) sex pilus (gram negative) B) mating bridge (gram positive) both are hollow tubes

Question 44

donor and recipient in conjugation

Answer 44

F+ (donor) | F- (recipient)

Question 45

F-factor

Answer 45

fertility factor; makes a cell F+ and codes for a pilus or bridge

Question 46

conjugation steps

Answer 46

1) pilus or bridge forms; 2) F+ attaches to F- through signals 3) DNA in F-fact replicated and passed through the pilus/bridge; resulting in 2 F+ cells 4) Brownian motion breaks pilus/bridge F+ + F- => F+ + F+

Question 47

Hfr cell

Answer 47

high frequency of recombination cell; when F-factor becomes integrated into chromosome

Question 48

Hfr cell passes what to its recipient?

Answer 48

part of its chromosome! a piece of the F-factor translates, as well as part of its main chromosome. Brownian motion breaks the bridge before it can complete the circle and pass the entire F-factor, and thus the recipient cell remains F- as it does not have the F-factor. However, it has received some new genes!

Question 49

Hfr "equation"

Answer 49

Hfr + F- => Hfr + F- (w some new DNA)

Question 50

Can Hfr return to being just F+?

Answer 50

Yus

Question 51

generalized transduction

Answer 51

1) phage (protein coat, DNA core) infects donor bacteria by injecting its DNA 2) bacteria becomes "phage-producing factory", creating phage DNA and proetins. the bacterial chromosome is broken into pieces 3) errors -- phage capsids may pack bacterial DNA instead of phage DNA 4) donor cell lyses and releases phages, some of which contain bacterial DNA 5) phage with bacterial DNA infects recipient bacteria 6) recombination may occur; leading to a cell with a different genotype (may help it resist the bacteria? who knows)