U1.3 Gene expression

Question 1

What does gene expression involve?

Answer 1

Transcription and translation of DNA sequences.

Question 2

Are a lot or a few of the genes in a cell expressed?

Answer 2

A fraction (a few).

Question 3

What are the three types of RNA?

Answer 3

Messenger (mRNA), transfer (tRNA), and ribosomal (rRNA).

Question 4

What do RNA nucleotides comprise of?

Answer 4

Ribose sugar, phosphate, and one of four bases: cytocine, guanine, or uracil.

Question 5

What is the function of mRNA?

Answer 5

To carry a copy of the DNA code from the nucleus to a ribosome.

Question 6

What happens to mRNA in the nucleus?

Answer 6

It is transcribed from DNA.

Question 7

What happens to mRNA in the cytoplasm?

Answer 7

It is translated into proteins by ribosomes.

Question 8

What is a codon, and what does it code for?

Answer 8

A triplet of bases on mRNA, codes for a specific amino acid.

Question 9

Why is tRNA folded?

Answer 9

Due to the complementary base pairing.

Question 10

State the function of tRNA.

Answer 10

To carry a specific amino acid to a ribosome.

Question 11

What two things are attached to the ends of tRNA?

Answer 11

An anticodon at one end and an attachment site for a specific amino acid at the other.

Question 12

What do ribosomes comprise of?

Answer 12

rRNA and proteins.

Question 13

What is transcription?

Answer 13

The production of a copy of the genetic code on DNA as mRNA which can move out of the nucleus.

Question 14

What does RNA polymerase do?

Answer 14

It moves along DNA, unwinding the double helix and breaking hydrogen bonds between bases.

Question 15

How is the primary transcript of mRNA made?

Answer 15

From RNA nucleotides using complementary base pairings.

Question 16

What base is complementary to adenine in RNA?

Answer 16

Uracil- it replaces thymine.

Question 17

How is a mature transcript formed?

Answer 17

The primary mRNA transcript is spliced to remove the introns and join the remaining exons together.

Question 18

What are introns?

Answer 18

Non-coding regions of the primary mRNA transcript.

Question 19

What are exons?

Answer 19

Coding regions of the mRNA primary transcript.

Question 20

What sequence are exons found in the mRNA mature transcript?

Answer 20

They remain in the same sequence.

Question 21

Where does translation of mRNA into a polypeptide occur and what does it involve?

Answer 21

At a ribosome and it involves tRNA

Question 22

What does sequential translation of mRNA codons ensure?

Answer 22

The correct sequence of amino acids in a polypeptide.

Question 23

Where does translation start and end?

Answer 23

Starts at a “start” codon and ends at “stop” codon on the mRNA mature transcript.

Question 24

How do tRNA anticodons bind to mRNA codons?

Answer 24

By complementary base pairings.

Question 25

What is the genetic code translated into?

Answer 25

A sequence of amino acids which are joined by peptide bonds.

Question 26

What do the tRNA molecules with ribosomes after delivering a specific amino acid?

Answer 26

They leave them.

Question 27

What does alternative RNA result in?

Answer 27

Different proteins being produced from one gene.

Question 28

How are different mature RNA transcripts produced from the same primary transcript?

Answer 28

Depends on which exons are retained and which are removed.

Question 29

What does the folding of polypeptide chains result in?

Answer 29

A three dimensional protein molecule held together by hydrogen bonds and other interactions between individual amino acids.

Question 30

What does the shape of a protein determine?

Answer 30

Its function.

Question 31

What is phenotype determined by?

Answer 31

Proteins produced by gene expression.

Question 32

What can influence phenotype?

Answer 32

Environmental factors.