Gene Expression: From Gene to Protein

Question 1

What is transcription?

Answer 1

Synthesis of RNA using info from DNA

Question 2

What does transcription produce?

Answer 2

mRNA

Question 3

What is translation?

Answer 3

The synthesis of a polypeptide using information in the mRNA

Question 4

What is gene expression?

Answer 4

Genes specify proteins via transcription and translation

Question 5

What are codons?

Answer 5

A series of nonoverlapping, three nucleotide words (“triplet code”)

Question 6

What are codons translated into?

Answer 6

A chain of amino acids, forming a polypeptide

Question 7

What is a stop codon?

Answer 7

A sequence of three nucleotides that signal the end of protein synthesis

Question 8

What are the 3 stop codons?

Answer 8

UAA, UGA, UAG

Question 9

What is a start codon?

Answer 9

The first codon in a transcript that signals the start of transcription

Question 10

What is the most common start codon?

Answer 10

AUG

Question 11

What are the molecular components of transcription?

Answer 11

• Initiation
• Elongation
• Termination

Question 12

When do eukaryotic cells modify RNA?

Answer 12

After transcription

Question 13

What does the alteration of mRNA ends include?

Answer 13

• A modified guanine nucleotide added to the 5’ end
• 50-250 adenine nucleotides added to the 3’ end

Question 14

Why are the ends of mRNA altered?

Answer 14

• To facilitate the export of mRNA to the cytoplasm
• To protect mRNA from hydrolytic enzymes
• To help ribosomes attach to the 5’ end

Question 15

What are introns?

Answer 15

Noncoding segments in a gene, removed through RNA splicing

Question 16

What are exons?

Answer 16

Expressed regions that are usually translated into amino acid sequences

Question 17

Accurate translation requires two instances of molecular recognition?

Answer 17

• A correct match between tRNA and an amino acid
• A correct match between anticodon tRNA and mRNA codon

Question 18

What are mutations?

Answer 18

Changes in nucleotide sequence within the genetic information of a cell

Question 19

What are point mutations?

Answer 19

Changes in just one nucleotide pair

Question 20

What can lead to the production of an abnormal protein?

Answer 20

The change of a single nucleotide in a DNA template strand

Question 21

What are the two general categories of point mutations?

Answer 21

• Single nucleotide pair substitutions
• Nucleotide pair insertions or deletions

Question 22

What is a nucleotide pair substitution?

Answer 22

The replacement of one nucleotide and its partner with another pair of nucleotides

Question 23

What are silent mutations?

Answer 23

No affect on amino acids due to redundancy in the genetic code

Question 24

What are missense mutations?

Answer 24

Still codes for amino acid but not the correct amino acid

Question 25

What are nonsense mutations?

Answer 25

Changes an amino acid codon into a stop codon, typically leads to a nonfunctional protein

Question 26

Which has a more disastrous effect on the resulting protein: substitutions or insertions and deletions?

Answer 26

Insertions and deletions

Question 27

What occurs during insertion or deletion of nucleotides?

Answer 27

It may alter the reading frame, producing a frameshift mutation