3- DNA and how genes work

Question 1

What are the bases that form DNA?

Answer 1

Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

Question 2

What are the bases that from RNA?

Answer 2

Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U)

Question 3

What are the sugars that form DNA?

Answer 3

Deoxyribose

Question 4

What are the sugars that form RNA?

Answer 4

Ribose

Question 5

Sketch a DNA double helix showing base pairs and 5’ and 3’ ends

Answer 5

accurate drawing

Question 6

What direction does the DNA run?

Answer 6

5 prime end to 3 prime end

Question 7

What end of DNA are new bases added to?

Answer 7

3 prime end

Question 8

What is meant by the term “Semi-conservative” replication?

Answer 8

Each daughter strand contains one conserved strand and one new strand

Question 9

Where does the DNA unwind?

Answer 9

Replication origin

Question 10

Where does DNA synthesis begin?

Answer 10

Replication fork

Question 11

Where does DNA synthesis begin?

Answer 11

Replication fork

Question 12

What is the role of DNA polymerase?

Answer 12

Catalyses the addition of nucleotides to the growing end a new DNA molecule

Question 13

What is the 3’->5’ strand known as?

Answer 13

Leading strand

Question 14

What is the 5’->3’ strand known as?

Answer 14

Lagging strand

Question 15

How is the 5- 3 strand synthesised?

Answer 15

Short strands called Okazaki fragments are made in the 5-3 direction
These strands are made in small pieces discontinuously
DNA ligase joins them together via “backstiching”
This process takes longer hence the lagging

Question 16

What are exons?

Answer 16

The coding region of a gene

Question 17

What happens when the introns are spliced?

Answer 17

mRNA is produced

Question 18

What is transcription?

Answer 18

Copying of DNA into messenger RNA

Question 19

What is the main enzyme involved in transcription?

Answer 19

RNA polymerase

Question 20

What are the 4 key elements of the gene for transcription and what are the functions?

Answer 20

Transcription start-site-where the copying of the DNA strand into RNA begins
TATA box- signal for the start of transcription
Promoter- where transcription factors bind to regulate transcription
Terminator sequence/stop site- the signal for RNA polymerase to stop copying the DNA template into RNA

Question 21

What is translation?

Answer 21

RNA to a protein

Question 22

What happens when the genetic code loses a base?

Answer 22

There is a frame shift mutation

Question 23

What is the role of tRNA in protein synthesis?

Answer 23

Brings each of the 20 amino acids to the growing protein

Contain an anti-codon sequence that recognise the codon for each amino acid

Question 24

What happens to the proteins after translations?

Answer 24

Proteins are transferred to the golgi apparatus for final “polishing” and secretion