BMS04 Flashcards
Name 4 ways anti-biotics prevent transcription/translation occuring
Mimic tRNA to AA can’t be added
Inhibit peptidyl transferase enzyme
Block the tRNA binding site so AA can’t be added
Distort the shape of the ribosome so mRNA can’t bind to it
What does peptidyl transferase do?
Forms peptide bonds between AA and moves the chain along through the ribosome
What is the 3rd base wobble?
When if the 3rd base changes to a different on but the first 2 remain the same the AA won’t change
What is a codon?
The 3 bases used to choose an AA
What is the genetic code?
How each genetic codon makes an AA
What is the central dogma?
Going from DNA to RNA
What is an anticodon?
The 3 bases held in tRNA
What does aminoacyl-tRNA synthetase do?
Charges tRNA by using ATP to add the AA to it
How does the ribosomal unit form?
Initiation factors attach a tRNA to the 30s subunit, the 50s subunit the joins releasing the initiation
How does the AA chain stop getting longer?
Release factor reads a stop codon
What happens in the E site of the ribosome?
Where tRNA leaves the ribosome
What happens in the P site of the ribosome?
Holds tRNA on the mRNA chain
What happens in the A site of the ribosome?
A holds the tRNA which is going to be added to the chain next
How is bacteria translation different to ours? (2)
The chain is translated as it is being made and one chain codes for multiple peptides not just one
Describe the 4 areas of the mRNA chain
5 untranslated region, open reading frame (mRNA), 3 untranslated region and a polyA tail
What does untranslated region mean?
This section is transcribed but not translated
What is the purpose of the polyA tail? (3)
Stop enzymes degrading it and helps transportation/translation
What does the untranslated region do?
Regulate translation
Name a start codon
AUG
Name 3 stop codons
UAA, UAG and UGA
In basic terms what is mitosis?
Chromosomes separating and being duplicated
What is cytokinesis?
Cell dividing into 2
What is interphase?
The from one batch of mitosis to the next
What happens in G1?
Deciding whether to divide or not
What happens in S?
Chromosomes duplicate
What happens in G2?
Chromosomes move to the other side of the cell ready to decide
If the cell is resting what is this called?
Quiescent
What do centromeres do?
Hold 2 chromatids together to make a chromosome
What is the purpose of the kinetochore?
Binds to the centromere so the microtubules have something to attach to
What makes up a centrosome?
Centriole and microtubules
What 2 key words are associated with heteroploid?
Polyploid when there are too many chromosomes in a diploid set
Aneuploid is the wrong number of chromatids in a haploid set
What is a karyotype?
The number type and shape of chromosomes unique to and defining each species
What makes up chromatin?
DNA and protein
What is heterochromatin and which 2 places is this found?
highly condense DNA at the ends of chromosomes and at the centromere
What is a telomere made of and what does it do (3)?
G rich sequence stopping deterioration, fusion and increasing the length of the chromosome as DNA polymerase doesn’t translate until the end
When are telomeres made?
In the embryo and no more after that- they are responsible for ageing
What happens in prophase? (3)
Chromosomes condense, nucleolus disappears and spindles form
What happens in prometaphase? (2)
Envelope disintegrates and spindles attach to the kinetochore
What happens in metaphase?
Chromosomes line up
What happens in anaphase? (2)
Chromatids separate and actin causes cytokinesis
What happens in telophase? (4)
The envelope reforms, chromosomes de-condense, spindles vanish and the nucleolus reforms
What is the place where crossing over occur called?
Chiasmata
Single stranded binding protein
Bind single strands of DNA so they then can’t bind to eachother
DNA ligase
Links strand together by joining the back bones from 5 to 3
RNaseH
Removes RNA primers
RNA primers
Initiate the start of translation
Primase
Makes RNA primers
DNA helicase
Unwinds the double stranded DNA
Topoisomers
Releases the supercoils in DNA
How does DNA polymerase proof read?
Has exonuclease hydrolysing enzyme within it
What can’t DNA polymerase do?
Start strand synthesis, it merely extends strands
How does DNA polymerase hold the strand?
Sliding clamp
Name the lagging strand fragments
Okazaki fragments
Where does the strand split?
At the replication fork
Why can’t the lagging strand be continuously replicated?
The 5 end is never truly accessible
Explain why DNA is replicated 5 “ 3
It starts on the 3 of the template strand meaning the strand it makes starts with the 5 therefore is 5 to 3
Describe DNA replication (7)
Proteins anneal to the binding site, helicase unwinds the strain, SSB bind the single strands, RNA primers bind so DNA polymerase can bind at the 3’ end, DNA ligase joins the fragments and then rNaseH removes the primers
What are CpG islands?
Areas of lots of methylated C and G
What does SAHA do?
It is an inhibitor stopping acyl groups being removed from histones
What does 5-azacytidine do?
Stops methylation by inhibiting methyltransferase
What forms chromatin?
DNA and histones
What forms a histone? (3)
Globular head, 8 nucleosomes and N terminal tail
What part of chromatin is affected to change transcription?
Histone tails
Name the 4 ways the tails are affected
Acylation turns DNA off, methylation on, phosphorylation on and proteins can attach to them
What else can be acylated?
Nucleosomes
What is epigenetics? (3)
The fact that the genes are the same but its the expression that changes, how genes interact with the environment to make the phenotype, they are passed down
Which AA gets methylated?
Cytosine
How do proteins access DNA?
From methyl groups sticking out of the major groove
What can prevent transcription?
Sequence specific DNA binding transcription factors
Where does transcription start?
At the TATA box a non coding promotor
How does polyadenylation work?
Binds to the polyA tail on the mRNA so it can’t swim around
What 2 things decide gene expression?
Trans regulatory proteins and cis acting gene sequences
What do trans regulatory proteins do?
Bind to the DNA promotor to allow DNA polymerase to bind
What do cis acting gene sequences control?
Control transcription initiation
What are the difference between purines and pyrimidines?
Purines are bigger; A and G
Pyrimidines; C, T and U
Which directions do enzymes work on DNA?
Antiparallel
What makes DNA polar?
Phosphodiester bonds
What makes a nucleoside?
Base and sugar
What makes a nucleoside monophosphate?
Base, sugar and phosphate
What’s the difference between RNA and DNA pentose sugars?
RNA is deoxy and DNA is oxy
What is at the 3 end and 5 end of DNA?
3: sugar
5: phosphate
