DNA &Role In Hereditary

Question 1

Genetic of nonviolent pneumococci?

Answer 1

Method: take livings strain s and inject in mouse
Living r strain → mouse healthy no bacterial cell found in heart
H eat s strain → turns diff
Inject in mouse = No bacterial cell found in heart

Question 2

C chemical nature

Question 3

Bacteriophage T2: reproduction cycle

Question 4

Nucleotide

Answer 4

Base + ribose I deoxyribose = nucleoside + base
+Phosphate → nucleotide

Question 5

What types of bases are there?

Answer 5

Pyridines → cytosine & thymine
Purines → adenine & guanine( 2RINGS)

Question 6

What is chargraffs rule?

Answer 6

Amount of a= amount of T
Amount of c= amount of G
Purines = pyramidines

Question 7

X-ray crystallography how ?

Answer 7

The a-ray source is

Question 8

How is base pairing in DNA complimentary?

Answer 8

DNA consists of 2 antiparrallel like a ladder
A-t pairs and g-c pairs forming the rungs
Phosphate sugar chains form the backbone s
↓ 5’ end ↑ 3’ end
Individual nucleotide subunits consist of base,etc

Question 9

What ave the three possible models for DNA replication?

Answer 9

Original DNA → after round of replication → semi-conservative replication →2 double helix 50/50 - both
2nd- original DNA strand → 2 double helix each1-originale
3rds original DNA strand → dispersive

Question 10

The meselston-stahl experiment

Answer 10

Ecoligrown in 15N medium transferred to normal 14N
E. Cool replicates every 20 min →New DNA will incorporate 14N
14N/14N DNA →sample at 0 mins parent -

Question 11

Results of meselson- stahl experiment?

Answer 11

This pattern could only have been observed if each DNA molecule contains a template strand from parental DNA this DNA replication is semi - conservative

Question 12

How does a new DNA strand grow?

Answer 12

By adding to its 3’ end
A new nucleoside triphosphate attaches to the 3 ‘ end sugar phosphate end
Energy from cleaving the pyrophosphote used to bind the nucleotide → replication complex catalyses the reaction

Question 13

What is the key enzyme for the replication process?

Answer 13

DNA polymerase binds to the template strand ensures the correct base that fits into the new strand
The template strand and KMA plume go through DNA polymerase to create a new strand

Question 14

The new DNA strand requires what?

Answer 14

The primer is made of RNA a molecule similar to DNA and is synthesised by primate
The DNA polymerase than begins adding nucléoïdes to the 3’ end of the primer
The protein → sliding DNA clamp ↑ the efficiency of DNA polymerisation

Question 15

What other proteins collaborate in the replication process?

Answer 15

DNA helices
Single-strand binding proteins
Okazaki fragments

Question 16

What does DNA helices do?

Answer 16

Uses energy from ATP to unwind the DNA

Question 17

What do single strand binding proteins do?

Answer 17

Keep the strands from getting back together

Question 18

What is the Leading strand?

Answer 18

Only leading strand is pointing in the right direction

Question 19

What is Okazaki fragments?

Answer 19

Synthesis of logging strand occurs in smallp discontinues stretches *

Question 20

How do the 2 new strands form in different way?

Answer 20

Leading strand → 3’ } nucleotides continuosly added to the Lagging strand → 5’ . end of new leading stead
* The lagging strand waits until a stretch has been unwound then a primer canbe added & nucléoïdes are added to the primer 3’ end to fill stretch

Question 21

DNA replication

Answer 21

Leading and lagging strand synthesis video

Question 22

What do telomeres do?

Answer 22

When undergoing replication → chromosomes con lose 50-200 base pairs with each replication
To stop loss of important genes → chromosomes have “ telomeres “→ repealing sequence of genes

Question 23

What is telomerase?

Answer 23

Telomerase= catalyses the addition of extra telomere sequence to lengthen lagging strand again after replication to prevent telomeres lost

Question 24

How does telomerase work?

Answer 24

Telomeres bind s an RNA template
DNA p olymerose then fills in complementary bases
Telomerase is the removed and DNA polymerase then fills in the gap with extra Okazaki fragments.

Question 25

What function does DNA polymerase?

Answer 25

DNA polymerase has a proofreading function
If bases are paired incorrectly the nucleotides are removed
DNA proofreading

Question 26

What is a mismatch repair?

Answer 26

Mismatch repair enzymes con tell newly synthesised stands strand, from old one, when they detect mismatches
They replace mismatched bases on the New strand

Question 27

What is long-after copying?

Answer 27

Newly synthesised stead becomes indistinguishable from old strand but random mutations might occur
Excision repair enzymes scan DNA for mismatches due to mutations but replacement occurs on a random strand (not always correct)