Chapter 17: Gene Expression From Gene to Protein

Question 1

What is transcription?

Answer 1

Conversion of DNA to RNA

Question 2

What is translation?

Answer 2

Conversion of RNA to Protein

Question 3

How does DNA encode information for a protein?

Answer 3

Uses nonoverlapping nucleotide words (3 letters each)

Question 4

What is a template strand?

Answer 4

The strand that is looked at when making an RNA match

Question 5

What is a codon?

Answer 5

A sequence of 3 DNA or RNA nucleotides

Question 6

In what direction is DNA read?

Answer 6

3’ —-> 5’

Question 7

In what direction is mRNA made?

Answer 7

5’ —-> 3’

Question 8

In what direction is mRNA read?

Answer 8

5’ —-> 3’

Question 9

What is the start codon?

Answer 9

Where you start reading from

• AUG

Question 10

What is the stop codon?

Answer 10

Where you stop reading from

• UAA
• UAG
• UGA

Question 11

What are the 3 stages of transcription and what happens in each one?

Answer 11

1. Initiation
   
   • RNA polymerase binds to the promoter on the DNA
   • the double helix opens so that the template strand can be read to make mRNA
2. Elongation
   
   • mRNA is made in the 5’ to 3’ direction
3. Termination
   
   • after the polyadenylation signal (AAUAA) is reached, RNA polymerase detaches
   • complete mRNA transcript is released

Question 12

What are the two things required for mRNA to complete translation in eukaryotes?

Answer 12

A 5’ cap and a Poly-A Tail

Question 13

What is a 5’ cap?

Answer 13

• extra nucleotides that consist of phosphates

- It is attached to the 5’ end of mRNA

Question 14

What is a Poly-A Tail?

Answer 14

• a long chain of A nucleotides
• AAAAAAAAA
• It is attached to the 3’ end of mRNA

Question 15

What’s a secondary purpose of the 5’ cap and the Poly-A Tail?

Answer 15

To protect the protein content within the mRNA strand from degradation

Question 16

What is the UTR?

Answer 16

Untranslated region

It’s on both sides of the coding sequence (start and stop codons).

These are buffers that are not read.

Question 17

What happens after an eukaryotic mRNA is processed?

Answer 17

It’s ready for RNA splicing

Question 18

What are exons?

Answer 18

Section of mRNA that will undergo translation and decode a protein.

Question 19

What are introns?

Answer 19

Noncoding sections of RNA transcript

Question 20

What is RNA splicing and how does it work?

Answer 20

Introns are removed before the mRNA undergoes translation.

A protein comes along and removes the introns. The exons then join together to make one long protein mRNA.

Question 21

If a protein contains multiple exons, how many proteins can be made from a single mRNA transcript?

Answer 21

7

Possible proteins made:
1, 2, 3, 1+2, 2+3, 1+3, 1+2+3

Question 22

Where does translation occur?

Answer 22

Ribosomes in the cytoplasm

Question 23

Explain the steps of translation in the ribosome.

Answer 23

1. The mRNA strand starts going through the ribosome. Once it reads an AUG, tRNAs come along and deposits corresponding codons (UAC etc).
2. As the mRNA strand moves through the ribosome, the APE conveyer belt releases the E rRNA (no longer useful) and the P and A tRNAs start making a growing polypeptide.
3. This will continue until a stop codon is reached.

Question 24

What is an anticodon?

Answer 24

3 nucleotides located on a tRNA

The sock thingy

Question 25

What is the tRNA anticodon that would bind to the sequence GUU on an mRNA molecule?

Answer 25

CAA

Question 26

If a tRNA anticodon is complementary to the mRNA codon GGG, what amino acid would you expect it to carry?

Answer 26

The amino acid on the chart that corresponds to GGG NOT CCC!

Question 27

If the questions asks for an amino acid, use the mRNA codon, not the tRNA anticodon. When do you use the anticodon to read the chart?

Answer 27

Only when she asks for it.

Question 28

What is a point mutation?

Answer 28

When one letter changes in the sequence

Question 29

What is insertion and deletion mutation?

Answer 29

Addition of deletion of single or grouped nucleotides

Question 30

What is a silent point mutation?

Answer 30

There's a mutation but it does not affect the amino acid chosen from the table (No change seen)

Question 31

What is a missense point mutation?

Answer 31

The letter changed caused the table to give a different amino acid. (Noticeable change)

Question 32

What is a nonsense point mutation?

Answer 32

This is when a letter change causes a stop codon in the sequence. (Noticeable change because the protein stops)

Question 33

What is a wild type?

Answer 33

Normal allele at the locus

Question 34

Which is more important, the first position or third position of a single codon?

Answer 34

1st