Key Area 1.3

Question 1

What determines the phenotype of an organism

Answer 1

Proteins

Question 2

The processes of gene expression are?

Answer 2

Transcription

Translation

Question 3

What are proteins made of

Answer 3

Amino acids

Question 4

What type of chain is formed when amino acids link together

Answer 4

Polypeptide chain

Question 5

What type of bond links amino acids together

Answer 5

Peptide bonds

Question 6

Why is the shape of a protein important

Answer 6

Allows it to carry out its function

Question 7

How are long chains of amino acids able to form into 3D proteins

Answer 7

Hydrogen bonds form in certain places in the chain allowing them to be folded

Question 8

What name is given to the point hydrogen bonds form in a polypeptide chain

Answer 8

Cross connections

Question 9

What is the difference between RNA and DNA

Answer 9

RNA:
Single stranded
A-U C-G
Ribose sugar

DNA:
Double stranded
A-T C-G
deoxyribose sugar

Question 10

Name and describe the types of RNA

Answer 10

mRNA: carries a copy of the DNA code from the nucleus to the ribosomes

tRNA:collects amino acids and bring them to the ribosomes to build proteins

rRNA: combines with proteins to create the ribosome

Question 11

Where does does transcription take place

Answer 11

Nucleus

Question 12

Name the enzyme involved in transcription and state it’s function

Answer 12

RNA polymerase: it forms the bonds between the nucleotides to form a mRNA strand

Question 13

Describe the process of transcription

Answer 13

1) a section of DNA unwinds and weak hydrogen bonds between bases are broken, separating the strand
2) free RNA nucleotides align themselves with their complementary base pair (A-U C-G)
3) RNA polymerase forms the bonds between the sugar of one RNA nucleotide to the phosphate of the next
4) nucleotides continue to be added until that section has been transcripted. This strand is called the primary transcript
5) the primary transcript peels away from the DNA and the DNA recoils
6) primary transcript undergoes mRNA splicing and becomes a mature transcript
7) the mature transcript leaves the nucleus through nuclear membrane pores and enters the cytoplasm where it attaches to a ribosome

Question 14

What are introns and exons

Answer 14

Introns - non coding regions

Exons - coding regions

Question 15

What is alternative mRNA splicing and why it it advantageous

Answer 15

Alternative mRNA splicing is the process by which different regions can be treated as exons or introns depending on the protein being made

Advantageous:
This allows more than one protein to be made from a single gene

Question 16

Describe how a mature mRNA transcript can be achieved

Answer 16

It is formed through mRNA splicing

Different parts of the primary transcript are treated as exons and introns

The introns are removed and the exons are spliced together to form a continuous sequences

This is now called the MATURE TRANSCRIPT

The mature transcript leaves the nucleus and travels to the cytoplasm

Question 17

What is a group of 3 bases on an mRNA strand called

What is a group of 3 bases on an tRNA molecule called

Answer 17

1) codon

2) anticodon

Question 18

Where does translation take place

Answer 18

The ribosomes

Question 19

Describe the process of translation

Answer 19

1) Ribosomes bind to the 5’ end of the mRNA strand so that the start codon is at the attachment site
2) tRNA molecule with complementary anti-codon brings the specific amino acid to the ribosome
3) anti-codon and codon align and a weak hydrogen bond it formed between the two
4) ribosome moves along and reads next codon and the complementary tRNA molecule carrying the specific amino acid aligns next to the codon
5) peptide bond firms between the amino acids and tRNA molecule are released to be reused
6) the process continues until stop codon is reached
7) finally the polypeptide chain folds to become a protein

Question 20

State and describe two ways polypeptides can be altered after translation

Answer 20

Cleavage: can be cut by an enzyme to make it active

Addition of other molecules:
Carbohydrates and phosphate groups

Question 21

What allows a single gene to be expressed a several proteins m

Answer 21

Alternative mRNA splicing and post translational modification