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Microbiology > 6. Genetics > Flashcards

6. Genetics Flashcards

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Biology 101 flashcards
1
Q

nucleoside

A

sugar plus base

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2
Q

nucleotide

A

sugar, base, and phosphate

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3
Q

pyrimidine

A

guanine and adenine

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4
Q

purine

A

cytosine and thymine

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5
Q

is DNA or RNA more stable?

A

DNA is more stable
strong G=C content

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6
Q

hydrogen bonds
phosphodiester bonds

A

hydrogen bonds connect the strands through the bases
phosphodiester bonds are the phosphate to sugar groups

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7
Q

topoisomerases

A

insert and remove supercoils

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8
Q

negative supercoiling:

A

twisted in opposite sense relative to right-handed double helix; found in most cells

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9
Q

DNA gyrase

A

introduces supercoils into DNA via double-strand breaks

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10
Q

positive supercoiling

A

helps prevent DNA melting at high temperatures

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11
Q

viruses contain either RNA or DNA genomes

A

-can be linear or circular
-can be single or double stranded

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12
Q

plasmids

A

double-stranded DNA that replicate separately from chromosome
-usually circular
-generally beneficial for the cell (antibiotic resistance)
-NOT extracellular, unlike viruses
(can be lost)
plasmids are diverse- multiple can exist in one cell

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13
Q

operon

A

group of genes transcribed together

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14
Q

DNA replication

A

semi conservative
parent + daughter strand

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15
Q

DNA polymerase I

A

fills in the gaps (bw okazaki)
removes RNA primers

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16
Q

DNA polymerase III

A

replicates majority

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17
Q

DNA ligase

A

reconnects broken DNA strands

18
Q

transcription in bacteria

A

produces RNA from a DNA template

mRna
tRNA
rRNA
terminator regions
RNA contains ribose
-uracil
-less stable

19
Q

polycistronic

A

multiple ribosomes reading messenger molecule
transcript for more than one gene

20
Q

RNA polymerases in bacteria archaea and eukarya

A

bacteria
-1 RNA polymerase
-only need sigma

archaea
-transcription more complex
-require other transcription factors

eukarya
-transcription more complex
-3 RNA polymerase

21
Q

sigma subunit

A

recognizes promoter sequences
binds between the -35 region and the pribnow box in the promoter sequence

22
Q

operon parts

A

promoter
5’ leader
gene 1
gene 2
gene 3
transcription terminator

go through transcription to form a polycistronic mRNA with ORF 1, 2, and 3

23
Q

transcription in bacteria: termination of RNA synthesis is

A

governed by specific DNA sequences
EX: GC-rich sequences with inverted repeat and central nonrepeating segment

rho-dependent termination

24
Q

rho-dependent termination

A

rho protein recognizes specific DNA sequences and causes a pause in the RNA polymerase, releasing RNA and RNA polymerase

25
Q

amino acids, polypeptides, and proteins

A

proteins play a major role in cell function
-catalytic proteins (enzymes)
-structural proteins (membranes, walls, ribosomes)
-regulatory proteins
proteins are polymers of amino acids
amino acids are linked by peptide bonds to form a polypeptide
proteins are one or more polypeptides

26
Q

genetic code

A

a triplet of nucleic acid bases (codon) encodes a single amino acid
-64 possible codons
-specific codons for starting and stopping translation

27
Q

degenerate code

A

multiple codons encode a single amino acid

28
Q

wobble

A

irregular base pairing allowed at third position of tRNA

29
Q

start and stop signals

A

AUG - methionine
UAA stop
UAG stop signal

30
Q

translation

A

synthesis of polypeptide directed by sequence of nucleotides in mRNA

direction of synthesis N-TERMINAL to C-terminal

31
Q

ribosome

A

site of translation
-coupled transcription/ translation in bacterial/ archaea
polyribosome- complex of mRNA with several ribosomes

32
Q

transfer RNA

A

tertiary structure due to base pairing within the tRNA molecule
-anticodon is present
–complementary to the mRNA codon
–located on the anticodon arm

33
Q

amino acid activation

A

attachment of amino acid to tRNA
-catalyzed by aminoacyl-tRNA synthetases

at least 20- each specific for a single amino acid and for all the tRNAs to which each may be properly attached (cognate tRNAs)

34
Q

elongation of the polypeptide chain consists of three phases

A

aminoacyl-tRNA binding
transpeptidation reaction
translocation

involves several elongation factors (EFs)

35
Q

tRNA binding sites of ribosome

A

aminoacyl (acceptor; A) site
-binds incoming aminoacyl-tRNA

peptidyl (donor; P) site
-binds initiator tRNA or tRNA attached to growing peptide (peptidyl-tRNA)

exit (E) site
-briefly binds empty tRNA before it leaves ribosome

36
Q

assisted protein folding and chaperones

A

chaperones catalyze macromolecular folding events

chaperones can also refold partially denatured proteins (helper proteins)

37
Q

translocases

A

transport proteins into or through bacterial and archaeal membranes

38
Q

Sec systems

A

exports unfolded proteins and inserts integral membrane proteins

39
Q

Tat systems

A

transports folded proteins through membranes

40
Q

protein secretion: sec and tat systems
-signal sequence

A

15-20 residues
found at N-terminus
signals secretory system
prevents protein from completely folding

41
Q

antibiotics that inhibit bacterial translation

A

erythromycin prevents the shift on ribosome
tetracyline blocks tRNA attachment to mRNA
chloramphenicol prevents peptide bond formation between amino acids
gentamicin and streptomycin are aminoglycosides that distort ribosome shape

Microbiology (8 decks)

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