Genetic code (BIOL5)

Question 1

Describe DNA

Answer 1

• Polynucleotide - many nucleotides joined
  
  • Nucleotides made up of :
    
    • pentose sugar/deoxyribose
    • phosphate group
    • nitrogenous base
  • Nucleotides join, form polynucleotide strands:
    
    • join up b/w phosphates to sugar of another - creates sugar-phosphate backbone
    • 2 DNA polynucleotide strands join by H bonds b/w bases
  • Bases only join w/ one particular partner:
    
    • Spec. base pairing
    • A-T
    • C-G
• Forms a double-helix

Question 2

Describe DNA in protein synthesis

Answer 2

• Proteins made from amino acids
• Order of nucleotide bases in gene determines order of amino acids in protein
• Each amino acid coded for by 3 bases (triplet/codon)

Question 3

Describe DNA and RNA in protein synthesis

Answer 3

• DNA too big to leave nucleus; section copied into RNA
• RNA made of nucleotides containing 1 of 4 bases
• Differences b/w DNA and RNA:
  
  • sugar in RNA - ribose sugar
  • nucleotides form single strand
  • uracil (U) replaces T - pairs w/ A

Question 4

What are the 2 types of RNA?

Answer 4

mRNA

tRNA

Question 5

Describe mRNA

Answer 5

• Single polynucleotide strand
• Groups of 3 adjacent bases (codon/triplet)
• Made in nucleus during transcription
• Carried genetic code from DNA in nucleus to cytoplasm where used to make protein during translation

Question 6

Describe tRNA

Answer 6

• Single polynucleotide strand, folded into a clover shape
• H bonds b/w base pairs
• Sequence of 3 bases called anticodon; amino acid binding site on other end
• Found in cytoplasm
• Carries amino acids used to make proteins

Question 7

Genetic code is overlapping…

Answer 7

Base triplets don’t share their bases

Question 8

Genetic code is degenerate…

Answer 8

There’re more possible combinations of triplets

Some amino acids coded for by more than one triplet

Question 9

What are start/stop codons?

Answer 9

Some triplets used to tell cell to start/stop production of protein

Question 10

Genetic code is universal

Answer 10

Same specific triplets code for same amino acids in all living things