Mmg Microbial Genetics: Dna Transfer

Front 1

What is the central Dogma of molecular biology?

Back 1

-DNA, RNA, Protein

Front 2

What are the informational macromolecules?

Back 2

-DNA, RNA, Protein

Front 3

How is information in DNA and RNA encoded?

Back 3

-by sequence of bases

Front 4

How is information in protein is encoded?

Back 4

-in sequence of amino acids

Front 5

What is a gene?

Back 5

-segment of DNA that encodes a RNA molecule
-mRNA, tRNA, rRNA

Front 6

What does polycistronic mean?

Back 6

-when more than one gene is transcribed into one mRNA of prokaryotes

Front 7

What does monocistronic mean?

Back 7

-one gene gets one mRNA (can be prokaryotic or eukaryotic)

Front 8

What does primary mRNA transcript contain?

Back 8

-exons and introns

Front 9

What are exons?
What are introns?

Back 9

-protein-coding sequences
-intervening sequences

Front 10

How are introns removed?

Back 10

-by RNA processing
-RNA must be transported out of nucleus

Front 11

What are the three stages of Transcription?

Back 11

-initiation
-elongation
-termination

Front 12

How does transcription occur?

Back 12

-in a 5' to 3' direction (concurrent in E. coli)

Front 13

What does transcription of E. coli require?

Back 13

-RNA polymerase (one in bacteria)
-multisubunit core enzyme
-sigma factor

Front 14

What is a sigma factor used for?
How about multiple sigma factors?

Back 14

-specificity of initiation
-transcription of different genes

Front 15

How does RNA polymerase (RNAP) work in transcription of E. coli?

Back 15

-binds promoter sequences 5' to mRNA start site which is determined by Pribnow box and about 35 sequences

Front 16

What are the two types of termination of transcription?

Back 16

-self-termination
-protein-dependent terminationd

Front 17

How does self-termination work?

Back 17

-only RNAP is needed for termination
-no other protein factors are required
-requires stem-loop formation in RNA and about 6 U residues

Front 18

How does protein-dependent termination work?

Back 18

-Rho protein is needed for termination
-requires DNA sequence righ in C residues
-Rho binds mRNA and unwinds RNA-DNA complex
-unwinding causes RNAP to fall off

Front 19

What is RNA processing?

Back 19

-conversion of a precursor RNA to a mature RNA

Front 20

In prokaryotes and eukaryotes, what molecules are made as precusors that are cut to make final mature RNA's?

Back 20

-tRNA's and rRNA's

Front 21

In eukaryotes, what do mRNA molecules do?

Back 21

-made as pre-mRNA precursors; introns are spliced out to make mature mRNA's

Front 22

What is capping?

Back 22

-addition of methylated guanine residue to 5' end of mRNA

Front 23

What is polyadenylation?

Back 23

-addition of long stretch of A residues to 3' end of mRNA; occurs during termination

Front 24

What is a spliceosome?

Back 24

-multiprotein complex
-splicing creates an exon-exon junction and an intron lariat

Front 25

What is a ribozyme?

Back 25

-catalytic RNA
-no proteins needed
-found in self-splicing introns

Front 26

What is a genetic code?

Back 26

-information that allows nucleic acid sequences to be translated into amino acid sequences in proteins

Front 27

What is a codon?

Back 27

-triplet of three bases encoding an amino acid

Front 28

What is degeneracy of code?

Back 28

-most amino acids are encoded by more than one codon
-codon usage varies from organism to organism

Front 29

How does translation occur in protein synthesis?

Back 29

-base pairing of codon with anticodon on specific charged tRNA molecule

Front 30

What can computer programs pick out in DNA codes?

Back 30

-the ORF's (Open-reading frames)
*doesn't prove they are expressed though

Front 31

What are open-reading frames?

Back 31

-defined by a start codon, then a number of codons, and lastly a stop codon

Front 32

What are start codons?

Back 32

-methionine (AUG)

Front 33

What are some sotp codons?

Back 33

-UAA
-UAG
-UGA

Front 34

Describe tRNA.

Back 34

-adaptor molecules that contain anticodon that base pairs with codon
-short, single-stranded RNA; 73-93 nucleotides; cloverleaf
-about 60 tRNA's in bacteria (100-110 in mamalian cells)
-each tRNA is specific for an AA that binds to ribose sugar of A residue of CCA acceptor and sequence

Front 35

What are Aminoacyl-tRNA synthetases?

Back 35

-enzymes that covalently attach amino acids to tRNA
-must recognize tRNA anticodon loop and specific amino acid
-high degree of fidelity required so that wrong amino acid doesn't get incormporated into polypeptides

Front 36

What are ribosomes?

Back 36

-sites of protein synthsis that contain multiple proteins and ribosomal RNA (rRNA)
-free or on rough ER

Front 37

What are antibiotics?

Back 37

-inhibit initiation (streptomycin) and elongation (puromycin, chloramphenical, clcyoheximide, tetracycline, kanamycin)

Front 38

What are the bacteria-specific antibiotics?
How about eukaryote specific?

Back 38

-streptomycin, chloramphenical
-cycloheximide

Front 39

How does initiation in translation occur in bacteria?

Back 39

-16S rRNA base pairs with sequences upstream of start codon

Front 40

How do eukaryotes begin initiation in translation?

Back 40

-ribosome recognizes 5' cap and starts at first AUG

Front 41

What does initiation include for translation?

Back 41

-complex of 30S small subunit, mRNA, tRNA, and initiation factors (proteins)

Front 42

What are polysomes and what are they for?

Back 42

-multiple ribosomes translate the same mRNA; independent events
-increase speed and efficiency
-some nascent proteins fold spontaneously while being synthesized

Front 43

What are molecular chaperones?

Back 43

-proteins that assist in the folding of polypeptides post-translation or after denaturation
-do NOT become part of protein
-require energy (ATP)