6.3 Continued: The Genetic Code

Question 1

DNA contains the sequence of nucleotides that code for proteins. The sequence is read in groups of ___ called the ___ ____.

Answer 1

• three

- triplet code

Question 2

During transcription, only one DNA strand is being transcribed, this is known as the ___ strand.

Answer 2

• template strand

AKA noncoding strand, minus strand, or antisense strand

Question 3

mRNA molecules formed are _____ and _____ to the DNA molecules.

Answer 3

• antiparallel and complimentary

- base pairing A=U and C=G

Question 4

What are the mRNA nucleotide triplets called? What do these code for?

Answer 4

• Codons

- code for amino acids

Question 5

How many different codon combinations are there? How many of these codons code for amino acid? How many of these are stop codons?

Answer 5

• 64 different codon combinations
• 61 code for amino acids
• three or stop codons
  Codons are universal to all life

Question 6

How many amino acids are in nature?

Answer 6

20

Question 7

What is redundancy?

Answer 7

• more than one codon code for each amino acid

Question 8

Which is a start codon? What does it do?

Answer 8

• AUG is the start codon, it codes for Methionine

- initiates translation at a ribosome

Question 9

What is a reading frame? (2)

Answer 9

• The codons of the mRNA must be read in the correct grouping during translation to synthesize the correct proteins
• if the reading frame shifts even by one letter, it will produce a completely different outcome

Question 10

What are the three stop codons?

Answer 10

• UAA
• UAG
• UGA

Question 11

Do stop codons code for amino acid?

Answer 11

No

Question 12

The genetic code has redundancy, but no ambiguity. What does this mean? (3)

Answer 12

• It means that the genetic code has more than one codon that can code for the same amino acid (redundant)
• but one codon cannot code for different amino acids
• ex. UCC and UCA both code for serine, but neither of them will never code for a different amino acid