Lecture 8 Protein Synthesis

Question 1

Information molecules

nucleic acids

Answer 1

hold and transfer genetic information

Question 2

Structure

nucleic acids

Answer 2

chain of nucleotides

pentose sugar + phosphate + nitrogenous base (A,G,C,T or U)

Question 3

DNA

Answer 3

double stranded
double helical structure
base pairing; A-T (2 bonds), G-C (3 bonds)

Question 4

RNA

Answer 4

mostly single stranded
higher level structures in tRNA and rRNA
base pairing: A-U, G-C
major classes: mRNA, rRNA, tRNA

Question 5

Transcription

what is it? where does it happen?

Answer 5

happens in the nucleus
highly regulated
transfer of genetic information from DNA to mRNA

Question 6

Transcription steps 1-3

RNA synthesis

Answer 6

1. transcription is activated by binding of regulatory proteins to regulatory regions in DNA (promoter and enhancers) located upstream of the gene
2. DNA “unzips” in region to be transcribed
3. RNA polymerase enzyme binds to DNA

Question 7

Transcription steps (4-6)

Answer 7

4. RNA nucleotides form complementary base pairs with DNA, then RNA polymerase joins RNA nucleotides and elongates strand to form pre-mRNA
5. pre-mRNA is spliced (introns removed) and processed to form mature mRNA
6. mRNA leaves the nucleus and enters the cytoplasm

Question 8

activation of transcription requires?

Answer 8

interaction of several regulatory proteins

Question 9

transcription factors

Answer 9

proteins that bind to DNA to activate transcription of specific genes
regulates transcription
ex: liver had liver transcription factors, muscle has muscle transcription factors.

Question 10

what is a promoter composed of

Answer 10

A’s and T’s

Question 11

Translation

what is it?

Answer 11

transfer of information from mRNA to amino acid sequence of protein
genetic code contained in 3 nucleotides
-64 possible codons

Question 12

mRNA

Answer 12

contains the codons - base triplets

each codon codes for a specific amino acid (also start and stop codons)

Question 13

tRNA

Answer 13

contains the anticodon complementary to a specific codon of mRNA
each specific tRNA carries a particular amino acid
Key link between the genetic code in mRNA and the amino acid sequence of the protein

Question 14

aminoacyl-tRNA

Answer 14

tRNA linked to amino acid

Question 15

ribosome

Answer 15

key organelle for translation, binds to mRNA and tRNA

catalyzes peptide bond formation

Question 16

Translation steps 1-4

Answer 16

1. ribosome binds to mRNA
2. first aminoacyl-tRNA comes in, matches anticodon to first mRNA codon (AUG)
3. second aminoacyl-tRNA comes in, matches anticodon to next mRNA codon
4. peptide bond forms between first two amino acids

Question 17

translation steps 5-7

Answer 17

5. first tRNA releases; ribosome moves to next codon on mRNA
6. next aminoacyl-tRNA comes in, process repeats steps 3-5; growing polypeptide chain
7. last amino acids is added to chain

Question 18

rRNA

Answer 18

ribosome catalyzes peptide bond

moves three spaces down