DNA &Role In Hereditary Flashcards
Genetic of nonviolent pneumococci?
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
C chemical nature
Bacteriophage T2: reproduction cycle
Nucleotide
Base + ribose I deoxyribose = nucleoside + base
+Phosphate → nucleotide
What types of bases are there?
Pyridines → cytosine & thymine
Purines → adenine & guanine( 2RINGS)
What is chargraffs rule?
Amount of a= amount of T
Amount of c= amount of G
Purines = pyramidines
X-ray crystallography how ?
The a-ray source is
How is base pairing in DNA complimentary?
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
What ave the three possible models for DNA replication?
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
The meselston-stahl experiment
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 -
Results of meselson- stahl experiment?
This pattern could only have been observed if each DNA molecule contains a template strand from parental DNA this DNA replication is semi - conservative
How does a new DNA strand grow?
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
What is the key enzyme for the replication process?
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
The new DNA strand requires what?
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
What other proteins collaborate in the replication process?
DNA helices
Single-strand binding proteins
Okazaki fragments
What does DNA helices do?
Uses energy from ATP to unwind the DNA
What do single strand binding proteins do?
Keep the strands from getting back together
What is the Leading strand?
Only leading strand is pointing in the right direction
What is Okazaki fragments?
Synthesis of logging strand occurs in smallp discontinues stretches *
How do the 2 new strands form in different way?
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
DNA replication
Leading and lagging strand synthesis video
What do telomeres do?
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
What is telomerase?
Telomerase= catalyses the addition of extra telomere sequence to lengthen lagging strand again after replication to prevent telomeres lost
How does telomerase work?
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.
What function does DNA polymerase?
DNA polymerase has a proofreading function
If bases are paired incorrectly the nucleotides are removed
DNA proofreading
What is a mismatch repair?
Mismatch repair enzymes con tell newly synthesised stands strand, from old one, when they detect mismatches
They replace mismatched bases on the New strand
What is long-after copying?
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)
