Chapter 15

Question 1

Archibald Garrod

Answer 1

1902 Recognized that alkaptonuria is inherited by recessive allele. Patients lacked enzyme
Connected genes to enzymes

Question 2

Beadle and Tatum 1941

Answer 2

Deliberately created mutations in chromosomes. Used x rays to damage DNA and looked for nutritional mutations. Used minimal media. Looked for cells lacking specific enzymes. One-gene/one-enzyme

Question 3

Media vs Rich and Minimal

Answer 3

Media is a place that have materials to grow
Rich Medium- all AA’s, chem, salt, soil etc. Everything needed to grow.
Minimal Media - Few things need to grow, sees what organism produces itself

Question 4

One-gene/One-enzyme

Answer 4

Modified to One gene/one-polypeptide. Operation on one gene=one protein. NOT How it actually works

Question 5

Central Dogma of Biology

Answer 5

DNA makes RNA makes Protein
First described by Francis Crick
Retroviruses violate this order using reverse transcriptase to convert RNA genome into DNA

Question 6

Transcription

Answer 6

DNA to RNA
Uses single strand of DNA to make RNA and then goes back together. DNA template strand
mRNA used to direct synthesis of polypeptides

Question 7

Translation

Answer 7

RNA to protein (Polypeptide)
Synthesis of polypeptides. Takes place at ribosome, requires several kinds of RNA

Question 8

mRNA
rRNA
tRNA

Answer 8

mRNA makes protein
rRNA component of ribosomes (Translation)
tRNA Link between mRNA and protein (translation) AA’s brought in.

Question 9

Francis Crick and Sydney Brenner
Genetic Code

Answer 9

Determined how the order of nucleotides in DNA encoded amino acid order. Codons. Insertions of deletions (Frameshift mutations) Indicates importance of reading frame.
Genetic code is strongest evidence of common ancestory

Question 10

Codon

Answer 10

Block of 3 DNA nucleotides corresponding to an amino acid

Question 11

Marshall Nirenberg

Answer 11

Identified the codons that specify each AA

Question 12

Stop Codon

Answer 12

UAA, UGA, UAG

Question 13

Start Codon

Answer 13

AUG

Question 14

Degenerate codon

Answer 14

Some AA’s are specified by more than one codon

Question 15

Prokaryotic Transcription

Answer 15

Single RNA polymerase only goes 5’ to 3’ as ribonucleotides are added.
Initiation of mRNA synthesis does NOT REQUIRE a primer
Termination is marked by “stop” with a Hairpin (U and A bonds together, weaken DNA/RNA binding and forces enzyme to “Fall off”.)
Requires a Promoter Site, Start Site, Termination Site
Only in prokaryote is transcription and translation coupled (No nucleus)

Question 16

Spaced vs Unspaced Codons

Answer 16

Spaced - Codon sequence in a gene is punctuated (Incorrect)
Unspaced - Condon adjacent to each other

Question 17

Promoter Site

Answer 17

Forms a recognition and binding site for RNA polymerase found upstream of start site -35 sequences and -10 sequences

Question 18

Transcription bubble

Answer 18

Small region of DNA unwinds by RNA polymerase to break H bonds and read DNA. Starts at -10 sequence

Question 19

Core Enzyme vs Holoenzyme

Answer 19

Core - 2 alphas, Beta, Beta ‘
Holoenzyme 2 alphas, Beta, Beta ‘ and Sigma subunit

Question 20

Eukaryotic Transcription

Answer 20

3 different RNA polymerases
RNA poly I transcribes rRNA
RNA poly II transcribes mRNA and some snRNA.
RNA poly III transcribes tRNA and some small RNA’s
Each RNA poly recognizes its own promoter
mRNA modifications - addition of 5’ cap (Guanine cap) to protect from degradation involved in translation initiation. Addition of 3’ poly-A tail (AAAAAA) to protect from degradation. Removal of non coding sequence (introns)

Question 21

Eukaryotic Initiation

Answer 21

Requires series of transcription factors and get the RNA poly II enzyme to promoter for gene expression. RNA Polymerase forms initiation complex

Question 22

Introns vs Exons

Answer 22

Introns are non-coding sequences
Exons are sequences that will be translated. snRNP’s recognize intron-exon boundaries and clusters with proteins to form spliceosome to remove introns

Question 23

tRNA and charging reaction

Answer 23

(Aminoacyl-tRNA synthetases- adds AA to the acceptor stem of tRNA) (Anticodon loop contains 3 nucleotides complementary to mRNA codons)
Each aminoacyl-tRNA synthetase recognizes only 1 AA but several tRNA’s
Charged tRNA has an AA added using ATP energy. Can undergo peptide bond formation without additional energy. Ribosomes do not verify AA attached to tRNA

Question 24

P site
A site
E site

Answer 24

P site - binds the tRNA attached to the growing peptide chain
A site - binds the tRNA carrying the next AA
E site - binds the tRNA that carried the last AA and exits tRNA from ribosome
First tRNA goes into P site, then all others first go into A then P then E

Question 25

Ribosomes 2 primary functions

Answer 25

1 Decode the mRNA using anticodons and codons
2 Form peptide bonds between amino acids
Peptidyl transferase - enzymatic component of ribosome and forms peptide bonds between AA

Question 26

Prokaryote vs Eukaryote
Translation

Answer 26

Pro - initiation complex initiator tRNA charged with N-formylmethionine, mRNA strand and small ribosomal subunit. Ribosome binding sequence (RBS) of mRNA positions small subunit correctly, large subunit added, initiator tRNA bound to P site with A site empty
Euk - Similar except initiation AA is methionine, more complicated initiation complex, LACKS RBS, small subunit binds to 5’ cap of mRNA.
2nd charged tRNA can bind to empty A site and requires elongation factors. 2 AA’s can form peptide bonds. Translation may occur in either cytoplasm or RER. Signal sequences at beginning of polypeptide sequence bind to SRP (Signal recognition particle). SRP recognized by RER receptor proteins. Docking holds ribosome to RER and begins protein-trafficking pathway

Question 27

Wobble

Answer 27

Pairing allows less stringent pairing between 3’ base of codon (third letter) and the 5’ base of the anticodon, this allows tRNA’s to accommodate all codons

Question 28

Point Mutations

Answer 28

Alter single base

Question 29

Base substitution

Answer 29

Substitute one base for another

Question 30

Silent Mutation

Answer 30

Same amino acid inserted with different bases

Question 31

Missense mutation

Answer 31

Changes amino acid inserted.
Transitions or transversions

Question 32

Nonsense mutation

Answer 32

Changed to stop codon before it is suppose to stop.

Question 33

Frameshift Mutation

Answer 33

Addition or deletion of a single base, much more profound consequences. Alter reading frame downstream. Triplet repeat expansion mutation - repeated unit is expanded and repeated

Question 34

Chromosomal Mutation

Answer 34

Change the structure of a chromosome. Deletions - Part of chromosome is lost
Duplication - Part of chromosomes is copied
Inversion - part of chromosomes in reverse order
Translocation - part of chromosomes is moved to a new location or different chromosome.