Structure of genes

Question 1

The central dogma describes…

Answer 1

a flow of information in an
organism

(DNA -> RNA -> protein)

Question 2

In eukaryotes genes are transcribed as …

Answer 2

…signle units

Question 3

In eukaryotes genes are transcribed as single units however in bacteria genes involved in the same pathways are often arranged linearly as an…

Answer 3

…operon

Question 4

When the operon is transcribed all of the genes are transcribed in …

Answer 4

…one continuous mRNA known as a
polycistronic mRNA

Question 5

In eukaryotes genes are transcribed as single units however in bacteria genes involved in the same
pathways are often arranged linearly as an operon

When the operon is transcribed all of the genes are transcribed in one continuous mRNA known as a polycistronic mRNA.

What does this increase the efficiency of?

Answer 5

This increases the efficiency of gene regulation.
– for instance if the bacterial cell needs to make biotin it makes sense to transcribe all of the genes involved in this process together
–means there can be a simple genetic switch to turn the process on.

Question 6

Eukaryotic genes are more complex than those of…

Answer 6

…prokaryotes.

Question 7

Typically the open reading frame (ORF) which is composed from the exons within the gene is split by…

Answer 7

…intervening non-coding DNA in the form of introns

Question 8

In order to be expressed a transcript from a eukaryotic gene has to be…

Answer 8

…processed to remove the introns.

Question 9

what is the flow of information in an organism?

Answer 9

DNA -> RNA -> protein

Question 10

where is prokaryote dna?

Answer 10

prokaryotes have their genomic DNA naked in the cytoplasm (no nucleus)

Question 11

prokaryote dna does not require…

Answer 11

… polyadenylation or intron removal.

Question 12

Because prokaryotes have their genomic DNA naked in the cytoplasm (no nucleus) and doesn’t require polyadenylation or intron removal, transcription and translation are…

Answer 12

… coupled

Question 13

When does translation begin in prokaryotes?

Answer 13

Translation begins as the mRNA molecule is being transcribed, note that a
number of genes in the same operon are being transcribed together from the same mRNA (polycistronic).

Question 14

Because the eukaryotic cell has a nucleus – mRNA needs to be…

Answer 14

…transported into the cytoplasm to be translated into protein by the ribosome.

Question 15

What are mRNAs marked for export by?

Answer 15

by the interaction of specific proteins:

• cap-bindings protein
• Poly-A-binding protein
• Exon junction complex (EJC).

Question 16

Slide 11=

Answer 16

=the differences between gene expression in eukaryotes and prokaryotes.

Question 17

eukaryotic transcripts need to be transported from…

Answer 17

… the nucleus, where they are transcribed to the cytoplasm where they are translated - uncoupled.

Question 18

Many eukaryotic genes contain…

Answer 18

…untranslated sequences - introns - these need to be removed before translation.

Question 19

eukaryotic transcripts are polyadenylated at which end?

Answer 19

at the 3’ end.

Question 20

mRNA transcripts are capped at…

Answer 20

…the 3’ end

Question 21

eukaryotic transcripts are monocistronic. What does this mean?

Answer 21

they do not contain the transcripts of several genes.

Question 22

eukaryotic transcripts do not contain the transcripts of several genes. What is the word thats used to describe this?

Answer 22

monocistronic

Question 23

What is the core promoter?

Answer 23

TATA box

Question 24

How many bases in the TATA Box?

Answer 24

25 bases

Question 25

What is consensus 5’ TATAWAAR -3’ (W = A or T, R = A or G)?

Answer 25

TATA Box

Question 26

What is known as the mammalian consensus?

Answer 26

Inr (initiator)-0987

Question 27

Whats DPE?

Answer 27

downstream promoter element.

Question 28

How many bases in the initiator?

Answer 28

1 bases

Question 29

How many bases in the DPE?

Answer 29

28 to 32 bases

Question 30

What does DPE bind to?

Answer 30

TFIID

Question 31

where is 7bp GC Box?

Answer 31

immediately upstream of TATA Box

Question 32

What does 7bp GC box bind to?

Answer 32

TFIIB

Question 33

PSE is only in…

Answer 33

snRNA genes.

Question 34

Function of RNA polymerase I ?

Answer 34

Transcription of ribosomal genes

Question 35

What is the function of RNA polymerase II ?

Answer 35

Transcribes all eukaryotic protein-coding genes

Question 36

Whats the function of RNA polymerase III type 1, type 2, and type 3?

Answer 36

transcribes DNA to synthesize
ribosomal 5S rRNA, tRNA and
other small RNAs

Question 37

What do elements located upstream of the core promoter do?

Answer 37

allow interaction with RNA polymerase

Question 38

The complexity of promoter elements varies hugely in …

Answer 38

… eukaryotes

Question 39

Simple single-celled eukaryotes commonly have promoters that are…

Answer 39

… simple and proximal to the gene itself.

Question 40

Simple single-celled eukaryotes commonly have promoters that are simple and proximal to the gene
itself whilst multicellular organisms may have…

Answer 40

… regulatory elements that are many kilobases away from the gene itself.

Question 41

A mixture of small nuclear RNA molecules (snRNA) and proteins are
responsible for…

Answer 41

… excising of introns and joining together the 3’ and
5’ ends of exons to form the mature transcript

Question 42

Sometimes the exons of genes with multiple introns can be spliced together in different ways. What is this called?

Answer 42

alternative splicing

Question 43

define alternative splicing

Answer 43

Sometimes the exons of genes with multiple introns can be spliced together in different ways, meaning that the coding sequence of the transcripts can differ and results in different proteins which may be involved in different processes.