Gene Expression

Question 1

Transcription

Answer 1

the process by which an mRNA strand forms a complementary strand to the DNA template

Question 2

Translation

Answer 2

the process by which an mRNA strand is read by a ribosome, and rRNA is used to build a protein based on the mRNa coding

Question 3

Codon

Answer 3

three base sequense of mRNA that corresponds to a specific amino acid

Question 4

How many codons and amino acids are there?

Answer 4

61 codons
20 amino acids

Question 5

What is the 1st step in forming mRNA?

Answer 5

RNA polymerase opens up the DNA helix so that complementary base pairing can occur

Question 6

Why is the 2nd step in forming mRNA processing it?

Answer 6

the newly transcribed complementary strand needs to be packaged and edited before it is considered mature mRNA and it is released from the nucleus

Question 7

Exon

Answer 7

parts of the genome that are ultimately expressed

Question 8

Intron

Answer 8

parts of the genome that are not part of any gene and are ultimately NOT expressed

Question 9

What are the ends of the pre-mRNA given?

Answer 9

an altered guanine cap and a multi-adenosine tail

Question 10

After the introns are removed, how are the exons joined?

Answer 10

spliceosomes

Question 11

What does tRNA provide in this situation?

Answer 11

A binding site for an amino acid

Question 12

Anti-codon

Answer 12

the part of tRNA that binds to the complementary mRNA codon

Question 13

How does elongation work in translation?

Answer 13

1. tRNA with anticodon moves into the P site carrying a methionine amino acid, and binds to the mRNA codon
2. the next tRNA with an anticodon moves into the A site, and binds to the mRNA codon
3. the methionine binds to the amino acid in the A site and detaches from the tRNA in the P site
4. the ribosome moves to the right, placing the first tRNA in the E site, the second tRNA in the P site, and leaving the A site open
5. The E site is vacated by the tRNA, and new tRNA carrying an amino acid enters the A site
6. The amino acid binds to the tRNA in the P site, and attaches to the amino acid on the tRNA in the A site
   **Repeat until STOP codon **

Question 14

How does termination work in translation?

Answer 14

When one of the three STOP codons enters the A site, a protein called a “release factor” binds to the stop codon, and cleaves the polypeptide from the last tRNA

Question 15

Pretranscriptional Control

Answer 15

the DNA and the transcription enzymes have to get together in the nucleus

Question 16

Transcriptional Control

Answer 16

a number of mechanisms regulate which genes get transcribed, and how quickly they get transcribed

Question 17

Posttranscriptional Control

Answer 17

how mRNA is processed, and how fast it is processed before it leaves the nucleus can be altered to influence gene expression

Question 18

Translational Control

Answer 18

small RNAs may attach to the mRNA to enable it to bond to the ribosomes faster or slower (or not at all)

Question 19

Posttranslational Control

Answer 19

After the protein is formed, it may need to be adjusted before it is biologically functional

Question 20

Transcription Factors

Answer 20

DNA-binding proteins that regulate how genes are expressed