Transcription I

Question 1

Describe the central dogma

Answer 1

DNA (replication) > RNA (transcription) > Protein (Translation)

Question 2

Describe DNA in terms of the central dogma

Answer 2

DNA contains original codes for making protein

Question 3

Describe mRNA in terms of the central dogma

Answer 3

mRNA is a copy of gene on DNA, it leaves nucleus of cell, ribosome read its coding sequences, putting AA together

Question 4

What does part of the DNA molecule contain?

Answer 4

Code for AA sequence of polypeptide chain and regulatory sequences needed for expression

Question 5

Describe the human genome

Answer 5

Many genes interrupted by one/more non-coding regions. Exons encode AA sequences of the protein

Question 6

What is an intron?

Answer 6

Intragenic regions inside a gene that interrupt/separate exon sequences, few genes in genome have no introns, but most have several.
Length of introns in genes larger than exons (Introns = 50bp>100bp)

Question 7

What is an exon?

Answer 7

Sequences found in both genes DNA and mature mRNA (from 50bp to few kilobases)

Question 8

Describe the effect of the dystrophin gene

Answer 8

Causes DMD which leads to muscle degenration and weakness - Those with DMD have 2500kb long length of genes

Question 9

Describe a promoter in terms of gene structure

Answer 9

Specialised DNA sequences near start of gene where transcription occurs (Specific promoters vary)

Question 10

Describe an enhancer in terms of gene structure

Answer 10

Thousands of base pairs away from promoter, often needed for efficient transcription of eukaryotic genes

Question 11

Define a gene

Answer 11

A sequence of chromosomal DNA that’s needed for production of functional product, be it polypeptide/function RNA molecule

Question 12

Describe gene families

Answer 12

Genes belong to families of closely related DNA/nucleotide sequences of genes
Largest gene family in human genome - Immunoglobulin

Question 13

Define transcription

Answer 13

Polymerisation of ribonucleotides guided by complementary base pairing producing an RNA transcript of a gene (3 stages - Initiation, Elongation, Termination)

Question 14

Describe the chromosomal organisation of 2 clusters of human globin genes

Answer 14

Many globin genes don’t produce any RNA/protein so have no function

Question 15

What are pseudogenes?

Answer 15

DNA sequences that closely resemble known genes but are non-functional

Question 16

How is energy provided for elongation?

Answer 16

Hydrolysis of high energy bonds in each ribonucleotide triphosphate

Question 17

Describe the initiation of transcription in prokaryotic cells

Answer 17

RNA polymerase binds with a sigma factor to form holoenzyme, Phosphodiester bond formed as nucleotides added to template strand
By convection, RNA molecule always depicted with its 5’ end - The first part to be transcribed

Question 18

Where is the promoter region found?

Answer 18

From -35 to -10 nucleotides before transcription site

Question 19

Why are regions upstream important?

Answer 19

For regulation

Question 20

Describe elongation of transcription

Answer 20

mRNA strand forms in replication bubble while RNA polymerase moves downstream 5’-3’
Transcription bubble ~17bp

Question 21

What are the 2 types of termination of transcription?

Answer 21

Intrinsic terminators - Rho independent termination

Extrinsic terminators - Rho dependent termination

Question 22

Describe the intrinsic terminator for transcription

Answer 22

p-independent termination facilitated by 2
sequences in RNA
1. Uracil-rich sequence located at 3’ end of RNA
2. Stem-loop structure upstream on the Us

Question 23

Describe the extrinsic terminator for transcription

Answer 23

Recognition of termination signal, cessation of transcription
Release of RNA from DNA

Question 24

Why is termination type 1 intrinsic?

Answer 24

No protein needed to remove RNA from DNA = Intrinsic