Gene Expression - Transcription + Translation

Question 1

What is Diamond Blackfan anaemia?

Answer 1

Decreased erythrocytes progenitor cells in bone marrow&raquo_space; anaemia
Mutation in ribosomal genes

Question 2

What is a gene?

Answer 2

A stretch of DNA
A unit of inheritance which is transferred from parent to offspring - determines characteristics of offspring

Question 3

Where does transcription occur?

Answer 3

In the nucleus

Question 4

Describe the start and end of protein structure

Answer 4

N terminal at start
C terminal at end

5 to 3 - N to C

Question 5

Describe the start and end of mRNA structure

Answer 5

5’ at start
3’ at end

5 to 3 - N to C

Question 6

What are the types of RNA

Answer 6

mRNA
rRNA
tRNA

Question 7

What are the 3 stages in DNA transcription?

Answer 7

1- initiation
2- elongation
3- termination

Question 8

What is needed for transcription?

Answer 8

Enzyme - RNA polymerase
Active substrate - nucleotide triphosphates
Template - DNA

Question 9

Identify 3 stop codons

Answer 9

UAA
UAG
UGA

Question 10

Identity the start codon

Answer 10

AUG
Methionine

Question 11

What is transcription?

Answer 11

DNA is copied to mRNA by RNA polymerase

Question 12

Describe initiation in transcription

Answer 12

Transcription factors bind to promote
RNA polymerase follows + binds

Question 13

Describe elongation in transcription

Answer 13

• DNA strand unwinds
• RNA polymerase reads nucleotide sequence of template strand > mRNA is made 5’ to 3’

Question 14

Describe termination in transcription

Answer 14

• RNA polymerase reaches the end of the gene
• RNA polymerase stops adding nucleotides to pre mRNA
• mRNA is released
• DNA strands reform double helix

Question 15

What is an intron?

Answer 15

Sequences in pre-mRNA that is spliced out
Not transcribed
Non coding section

Question 16

What is an exon?

Answer 16

Coding section
Sequence in pre-mRNA that is transcribed

Question 17

Outline the process of RNA splicing

Answer 17

Removal of introns from pre-mRNA to form mature RNA of only exons

Question 18

How are mRNA molecules processed?

Answer 18

• nucleotide cap - 5’ cap
• poly-A-tail - at 3’ end

Provide protection against degradation

Question 19

What is polydenylation?

Answer 19

Addition of poly A tail

Question 20

How is mature mRNA released?

Answer 20

Exported from nucleus into cytoplasm via nuclear pores for translation to occur

Question 21

What is needed for translation?

Answer 21

Enzyme - ribosome
Active substrates - amino acids
Template - mRNA

Question 22

What is translation?

Answer 22

Process in which ribosomes produce polypeptides from mRNA

Question 23

Describe the structure and function of ribosomes

Answer 23

Structure - cytoplasmic organelle with large and small subunit

Function - site of polypeptide synthesis

Question 24

What are the types of ribosomes?

Answer 24

• Free ribosomes - float in cytoplasm
• Bound ribosomes - attached to rough ER

Question 25

Explain the role of ribosomes in translation

Answer 25

- Large subunit contains rRNA which acts as an enzyme - rRNA makes peptides bonds between amino acids to form a polypeptide in translation

Question 26

What does tRNA do?

Answer 26

Brings amino acids to the mRNA ribosome complex in translation

Question 27

What are the attachment sites for tRNA?

Answer 27

- **Anticodon** - pairs with complementary codon of mRNA - **Site off attachment for amino acid**

Question 28

Describe initiation in translation

Answer 28

- 5’ end of mRNA binds to small ribosomal subunit and anticodon of initiator - tRNA brings amino acid methionine which pairs with AUG start codon

Question 29

Describe elongation in translation

Answer 29

- tRNA bring complementary amino acids to growing peptide chain - rRNA forms peptide bonds between amino acids

Question 30

Describe termination in translation

Answer 30

- occurs when ribosome reaches a stop codon - release factors binds to stop codons - polypeptide, mRNA + tRNA released from ribosome

Question 31

Distinguish between the function of DNA replication, transcription and translation

Answer 31

**DNA replication** - making DNA **DNA transcription** - making RNA **DNA translation** - making polypeptide

Question 32

Distinguish between the enzymes used in DNA replication, transcription and translation

Answer 32

**DNA replication**- DNA polymerase **DNA transcription** - RNA polymarse **DNA translation** - rRNA

Question 33

Distinguish between the active substrate used in DNA replication, transcription and translation

Answer 33

**DNA replication**- dNTPs **DNA transcription** - NTPs **DNA translation** - amino acids

Question 34

Distinguish between the template needed in DNA replication, transcription and translation

Answer 34

**DNA replication**- DNA **DNA transcription** - DNA **DNA translation** - mRNA

Question 35

What is the role of the promoter region in gene expression?

Answer 35

- required for initiation of transcription - permits RNA polymerase to bind - controls timing of transcription