molecular biology2

Question 1

what are the 3 different types of DNA replication?

Answer 1

• semiconservative model
• conservative model
• dispersive model

Question 2

how long does it take to replicate the human genome

Answer 2

8 hrs

Question 3

semiconservative model

Answer 3

how our DNA is made- this was found out in the meselson stahl experiment
a strand of DNA serves as a template to make a new one

Question 4

conservative model

Answer 4

one molecule consist of both original strands and a new model consists of 2 new strands

Question 5

dispersive model

Answer 5

2 molecules that are hybrids of parental and daughter dna- patch work of original and new DNA

Question 6

how is speed achieved in DNA replication

Answer 6

because DNA replication happens at multiple places at one time with the replication fork moving in both directions

Question 7

what direction is the growing strand synthesised in? why is this?

Answer 7

in a 5’ - 3’ direction
this is because dna polymerase only works in a 5’-3’ direction

Question 8

in dna replication, what dictates what base comes next

Answer 8

the template strand

Question 9

what Is the formation of the phosphodiesterase bond catalysed by?

Answer 9

it is catalysed by DNA polymerase

Question 10

what does monomers called dNTP’S consist of
(deoxynucleotide triphosphate)

Answer 10

they consist of a deoxyribose sugar, 3 phosphates and a base.

Question 11

what is the formation of the phosphodiesterase bond catalysed by?

Answer 11

DNA polymerase

Question 12

how is DNA unwound in replication?

Answer 12

it is done by DNA helices

Question 13

describe the leading and lagging strand replication in DNA

Answer 13

the leading strand is replicated continuously towards the replication fork
the lagging strand is replicated discontinuously away from the replication fork in OKAZAKI fragments

Question 14

why is the replication fork asymmetrical

Answer 14

because the DNA replication is semi conservative, there is a leading and lagging strand that are moving in opposite directions.

Question 15

what needs to be done to allow for enough room for Okazaki fragments to be made and how is it stabilised

Answer 15

in order to provide enough for Okazaki fragments to be generated, single strands have to be exposed which is done by DNA helices. it will be stabilised temporarily by DNA binding protein

Question 16

how are new Okazaki fragments made?

Answer 16

they are made by DNA primate generating an RNA primer so a new Okazaki fragment can be made.

Question 17

what are RNA primers

Answer 17

they are short templates that provide mark the starting point for the construction of the new DNA strand

Question 18

what is required for DNA primase to produce another RNA primer to make a lagging strand

Answer 18

150 bases on the template strand

Question 19

Werners syndrome

Answer 19

premature aging

Question 20

what happens when there is not enough bases left on the template strand to produce a new RNA primer

Answer 20

usually in healthy people, telomerase will add information to the lagging strand in the form of TTAGGG repeated sequences, which allows an Okazaki fragment to be generated.

Question 21

what happens when people don’t have the mechanism to add sequences to make an Okazaki fragment

Answer 21

the dna will become unstable and degrade leading to shortening of the chromosome which lead to Werners syndrome.

Question 22

when DNA polymerase makes an error, how Is it fixed?

Answer 22

• errors can be removed during synthesis
• DNA polymerase has a site that adds bases and then an editing site which will proof read the base, the editing bade will remove the wrong base and add the right one

Question 23

what is PCR used for

Answer 23

it is used to generate lots of copies of genetic material

Question 24

how does PCR work

Answer 24

• the strands are heated to break hydrogen bonds
• RNA primers of known sequence can be added to mixture
• individual dna strands will bind to their matching RNA primers using hydrogen bonds
• DNA polymerase and monomers complementary to the DNA strand can be added to the picture, resulting in the synthesis of new dna

Question 25

how is PCR used in the presence of infectious agents

Answer 25

• take sample/blood
• centrifuge to separate infected serum
• amplify the viral rna genome
• gel electrophoresis can then be used to determine if someone is infected using a normal blood control

Question 26

how is per used to identify inheritance patterns

Answer 26

because repeated sequences on paternal and maternal chromosomes can be amplified and compared to their offspring (to see if they have inherited any particular conditions)

Question 27

what can quantitative fluorescent PCR be used for

Answer 27

• detecting large chromosomal mutations
• screening for loos of heterozygosity

Question 28

how does automated sequencing help in personalised medicine

Answer 28

because you use automated sequencing when you are looking at a particular chromosome, so it can be used to help confirm a diagnosis.

Question 29

how is the lagging strand made?

Answer 29

it is made discontinuously due to the fact that it goes in a 3-5 direction.
therefore dna polymerase can only make this in a series of small chunks from 5-3 called Okazaki fragments.

Question 30

what happens after the new DNA strands have been made on the leading and the lagging strand?

Answer 30

the enzyme exonuclease will remove the primers and DNA polymerase will fill the gaps with DNA.

Question 30

function of DNA ligase?

Answer 30

this is the enzyme used in the final step, that will seal the strands together.