Gene Expression

Question 1

Gene Expression

Answer 1

Process of synthesizing proteins

Question 2

Gene

Answer 2

A segment of DNA that specifies the amino acid sequence of a polypeptide

Question 3

DNA’s role

Answer 3

Doesn’t directly control protein synthesis; merely a template to be transcribed into RNA

Question 4

Transcription

Answer 4

• takes place in nucleus

- portion of DNA serves as template for mRNA formation

Question 5

Transcription Steps

Answer 5

-segment of DNA (a gene) serves as template

• RNA polymerase binds to promoter
• DNA helix unzips as RNA polymerase travels along and zips back up
• RNA polymerase joins new RNA complimentary nucleotides to that on DNA

Question 6

Translation

1. The Genetic Code

Answer 6

• Codon: triplet code of 3-nucleotide unit of mRNA
• 64 diff mRNA codons
• 1 start codon (AUG - meth)
• 3 stop codons (termination of polypeptide chain)

Question 7

Translation

2. tRNA

Answer 7

• tRNA transports correct amino acids specified in mRNA codon
• amino acid at the top of tRNA; bottom of tRNA has complimentary anticodon to mRNA codon
• order of mRNA codons determines order in which tRNA brings in amino acids

Question 8

Translation

3. Ribosome & rRNA

Answer 8

• ribosome has binding site for mRNA & 2 tRNA
• facilitate complimentary base pairing (btwn codon & anticodon)
• (1+) ribosome moves along & ‘reads’ mRNA & new tRNAs w/correct anticodon enter ribosome sites
• brings specified amino acids from mRNA to bond together in center slot to elongate into a polypeptide chain

Question 9

Translation Steps

Answer 9

1. Initiation (requires energy)
   - start codon AUG
   - P (peptide) site, A (amino acid) site, E (exit) site
2. Elongation (requires energy)
   - start from center, then left; then enter from right to center to left
3. Termination
   - stop codon
   - requires a release factor
   - no tRNA anticodon for end