Unit 1: Human Cells - Key Area 3 - Gene expression

Question 1

What is RNA?

Answer 1

A nucleic acid with a similar structure to DNA.

Question 2

What are the three types of RNA?

Answer 2

• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)

Question 3

What is the function of transfer RNA?

Answer 3

Picks up a SPECIFIC amino acid from the cytoplasm and brings it to the ribosome.

Question 4

What is the function of messenger RNA?

Answer 4

Carries the genetic code from the nucleus to the ribosome.

Question 5

What is the function of ribosomal RNA?

Answer 5

Along with protein, it gives structure to the ribosome.

Question 6

Where is mRNA made?

Answer 6

In the nucleus.

Question 7

When is mRNA’s function used?

Answer 7

The first stage of protein synthesis.

Question 8

When is tRNA’s function used?

Answer 8

The second stage of protein synthesis.

Question 9

What does RNA consist of?

Answer 9

Nucleotides.

Question 10

In RNA what are the four types of bases?

Answer 10

Adenine, cytosine, guanine, and uracil replaces thymine.

Question 11

What is the complementary base pair for adenine in RNA?

Answer 11

Uracil.

Question 12

How are proteins made?

Answer 12

Proteins are made by joining together amino acids in a specific sequence.

Question 13

What does the protein produced by protein synthesis rely on?

Answer 13

The order of amino acids which is dictated by the order/sequence of the bases on the DNA.

Question 14

What are the two main stages of protein synthesis?

Answer 14

Transcription and Translation.

Question 15

What are the stages of transcription?

Answer 15

• The section of DNA which codes for the desired protein unwinds and unzips. This is carried out by an enzyme called RNA polymerase.
• Free RNA nucleotides enter the nucleus and RNA POLYMERASE joins them with their complementary DNA base starting at the 3’ end.
• Only one strand is copied.

Question 16

What is the strand of mRNA produced by transcription called?

Answer 16

The Primary Transcript.

Question 17

Why is only one gene transcribed to form mRNA?

Answer 17

So the Primary Transcript only codes for one protein.

Question 18

What does the primary transcript contain?

Answer 18

It contains regions that code for the production of the protein called Exons and regions which are non-codingwhich are calledIntrons.

Question 19

What are the introns of the primary transcript?

Answer 19

Introns are non-coding regions that have to be removed.

Question 20

What are the exons of the primary transcript?

Answer 20

Exons are coding regions and are joined together to form the mature transcript.

Question 21

What is DNA splicing?

Answer 21

DNA splicing is where introns are removed and the exons are joined together to form a mature transcript of mRNA.

Question 22

What happens once the mature transcript of mRNA is produced?

Answer 22

The mature mRNA leaves the nucleus and enters the cytoplasm.

Question 23

Where is tRNA found?

Answer 23

In a cells cytoplasm

Question 24

What is the function of tRNA?

Answer 24

To pick up a specific amino acid and bring them to the ribosome.

Question 25

What is the **structure of tRNA**

Answer 25

**The tRNA is a strand of RNA which is folded** due to the hydrogen bonds. **The folding forms an anticodon** and an amino acid binding site. _The amino acid bonding site can only pick up one specific amino acid_.

Question 26

What is **translation**?

Answer 26

**Translation is the synthesis of a protein** in the form of a **polypeptide chain** of amino acids.

Question 27

What is **translation** under **the control of**?

Answer 27

**Translation is under the control of and dictated by mRNA** as it carries the genetic code from the DNA.

Question 28

What does each **codon** contain?

Answer 28

**Each codon** contains the **code** for **one amino acid**.

Question 29

What are **amino acids** often referred to?

Answer 29

The **building blocks** of a **protein**.

Question 30

**Where** does **translation** occur?

Answer 30

**Translation** occurs on the **ribosome**.

Question 31

What is the start codon for translation?

Answer 31

AUG is the start codon.

Question 32

What does the start codon indicate?

Answer 32

The start codon indicates to the tRNA where to add the first amino acid.

Question 33

What happens to the tRNA after the polypeptide is formed?

Answer 33

It leaves the ribosome once the polypeptide has been formed.

Question 34

What are amino acids linked by and what does this form?

Answer 34

Amino acids are linked by peptide bonds to form polypeptides.

Question 35

What does the polypeptide fold to form and how is this held together?

Answer 35

Polypeptide chains fold to form the three-dimensional shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids.

Question 36

What do proteins have a large variety of and what does this do?

Answer 36

Proteins have a large variety of shapes which determines their functions.

Question 37

What is the phenotype determined by?

Answer 37

Phenotype is determined by the proteins produced as the result of gene expression.

Question 38

How can different proteins be expressed form one gene?

Answer 38

Different proteins can be expressed from one gene, as a result of alternative RNA splicing.

Question 39

What are the bonds between the amino acids in a polypeptide chain?

Answer 39

Hydrogen bonds

Question 40

What is gene expression?

Answer 40

The switching on or off of a gene to make a specific protein.