DNA replication and protein synthesis Flashcards
What is the other name of Griffith experiment?
Transformation process
What did Griffith do?
Infected mice with 2 strain of Pneumococcus bacteria.
Talk about S strain.
Smooth colonies. ability to cause disease
Talk about R strain.
Rough colonies, inability to produce pathogenic effects.
Why is S strain pathogenic?
Antibody couldn’t attack due to capsule like mucus surrounding the bacteria.
What happened when R strain is injected into mouse?
Survived due to no living R strain in blood.
What happened when S strain is injected into mouse?
Died due to living S strain in blood.
What happened when heat killed S strain injected into mouse?
Survived due to no living S strain in blood.
What happened when heat killed S strain and living R strain injected into mouse?
Died because blood contains S strain.
A substance from heat killed S strain transforms the harmless R strain into deadly S strain.
What is the transformation process?
Change of non pathogenic strain to pathogenic strain.
What is the conclusion of Griffith experiment?
Hereditary information can pass from dead cells to living ones, transforming them.
What was the purpose of Avery experiment?
To see which part of cell carries genetic information.
What did Avery do?
Prepares mixture of dead S strain and living R strain that Griffith used.
S cells lysed (split open) and separated cell content into several fractions.
Each fractions mixed with R living cells for transformation activity.
What was the result of Avery experiment?
Nucleic acids had transformation activity with living R strain.
What was the conclusion of Avery experiment?
DNA is the transforming principle in bacteria.
Nucleic acid carries genetic material.
What are the three hypothesis of DNA replication?
Conservative replication
Dispersive replication
Semiconservative replication
What is the conservative replication?
Parental double helix would remain intact and generate DNA copies consisting of entirely new molecules.
What is the dispersive replication?
Parental DNA would become dispersed throughout the new copy so that each strand of all the daughter molecules would be a mixture of old and new DNA.
What is the semiconservative replication?
Two strands of the parental molecule separate, and each functions as a template to synthesis of new, complementary strand.
What is the Meselson and Stahl experiment?
Determining what kind is DNA replication among three hypothesis.
What was the process of Meselson and Stahl experiment?
Grew bacteria in medium containing 15N.
Bacteria incorporated 15N into their DNA and made it denser than normal.
Some cells were then transferred to a 14N medium and allowed them to undergo cell division.
First generation of bacteria reveals newly synthesized DNA strands were less dense because they incorporated bases containing lighter 14N, forming 14N - 15N DNA strands.
After more cell divisions in 14N medium, DNA is then mixed with CsCl, placed in ultracentrifuge and centrifuged at very high speed for 48 hours.
DNA molecules move to positions where their density equals that of CsCl solution.
What was the result of Meselson and Stahl experiment?
Before transfer to DNA, heavy DNA molecules were at the bottom
One generation after transfer, hybrid DNA molecules move to the middle
Two generations after transfer, hybrid DNA molecules move to the middle and light DNA molecules at the top.
What is the conclusion of Meselson and Stahl experiment?
Replication is semiconservative.
What is the process of DNA replication?
DNA helicase separates parental DNA strands
DNA polymerase III synthesizes new DNA strands
DNA replication is continuous in one strand and discontinuous in another
Talk about DNA helicase separating parental DNA strands.
Replication begins at origin of replication.
DNA helicase separates with parental DNA, breaking H bonds.
DNA separates, unwinds, forming replication bubble with two replication forks.
RF formed at junction of single and double stranded region.
SSBP bind to single stranded DNA to prevent reformation of double helix.
Talk about DNA polymerase III synthesizing new DNA strands.
Each parental strand is now a template for new complementary strand.
DPIII synthesize new strands at RF which proceeds in 5’ to 3’ direction.
Primase synthesizes RNA primer at OR to protect new DNA strands.
Talk about DNA replication being continuous in one strand.
Leading strand is long and continuous and grows towards the main replication fork.
Lagging strand (Okazaki fragments) is short and many and grows away from main replication fork.
Each segment initiated by separate RNA primer.
What happens at the end of DNA replication?
DPI converts RNA primers to DNA nucleotides.
OF joined together by DNA ligase.
Bubbles grow simultaneously and meet each other.
Each daughter DNA molecule consist of one parental strand and one new strand.
How is protein synthesized?
Cell uses DNA information to synthesize protein on ribosome.
Ribosome consist of large and small subunits composed of RNA molecules and over 50 types of protein.
Has three sites for protein synthesis (EPA)
What is the name for 3 base on DNA?
Triplet code
What is the name for 3 base on mRNA?
Codon.
Codes for 1 amino acid.
What is the two steps in protein synthesis?
Transcription and translation.
Talk about transcription.
Transcription factors and RNA polymerase II binds to promoter site on one strand of DNA.
mRNA forms and starts to copy the bases of DNA moving from 5’ to 3’.
Transcription stop when they reach the stop codon and mRNA drops.
5’ Cap (Guanine 3 phosphate) and poly A tail at 3’ end formed.
mRNA copies both exon and intron which doesn’t code for proteins.
Primary mRNA transcript is modified before leaving nucleus by removing introns using enzyme spliceosome during post transcriptional modification.
mRNA is now matured and leaves nucleus to cytoplasm for translation.
How many codons are formed for protein synthesize?
64 codons.
What is the start codon?
AUG
What is the stop codon/nonsense codon?
UAA, UAG, UGA
What is the function of 5’ cap and Poly A tail?
To protect the newly formed mRNA.
Talk about translation.
Small subunit of ribosome binds to mRNA at start codon in cytoplasm.
First tRNA with first amino acid binds to start codon at P site and one initiation factor drops.
Initiation complex is when the large subunit binds to mRNA and the last 2 initiation factors drop.
Second tRNA with second AA enters A site and peptide bond formed between 1st and 2nd AA.
Dipeptide passed to 2nd tRNA and the first tRNA with no AA moves to E site and goes out.
Cycle repeats as ribosome moves one codon until stop codon reached on mRNA.
Release factor binds on stop codon and ribosome releases polypeptide into cytoplasm which undergoes folding to become functional.
mRNA is released and ribosome subunits separate.
What is the name for 3 base on tRNA?
Anti codon.
What is the difference between prokaryote and eukaryote protein synthesis?
No introns, have introns
mRNA transcript of several genes, one gene
translation begins before transcription complete, wait first
no PTM, has PTM and 5’ and PAT added
mRNA not modified, mRNA modified
Small ribosome, larger ribosome
