Biochem Chapter 7 Flashcards by Sanjene Sidhu

What is the same language DNA and RNA use

They both use sequences of nitrogenous bases

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What is the central dogma of molecular biology , what are the 3 steps

Describes the flow of genetic information

Info Is stored in DNA
transcribed into RNA
translated into protein

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What are the 3 main types of RNA

mRNA
tRNA
rRNA

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What is mRNA for

Carries genetic code from DNA to ribosome where proteins are made

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What is mRNA transcribed by

Form DNA by RNA polymerase

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What is monocistronci and polycistronic in mRNA

In terms of protein , and eukaryotes vs prokaryotes

In eukaryotes , each mRNA codes for one protein so it is monocistronic

In prokaryotes, each mRNA codes for more than one protein so its polycistronic

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What do tRNA do

Converts nuclei acids to the language of amino acids and peptides

Bring amino acid to ribosome during protein synthesis

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What shape is tRNA

Clover shape

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What is on tRNA
On both ends

What does it do for your codon

Anticodon on one side, allows you to bind to codon
Amino acids on one side, as a gift

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When tRNA binds to a codon, what catalyses this , what enzyme

Aminoacyl - tRNA. Synthetase

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What does aminoacyl tRNA synthestase do

Make sure you’re blinded to right codon

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What is rRNA for (3)

Structural and enzymatic component of ribosome
Helps position mRNA and tRNA properly during translation
Catalyses peptide bond formation between amino acids

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Because ribosome rna works as an enzyme, what’s another name for it

Ribozymes

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How many codons are there

64 codons

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Start codon what is it

Aug methionine

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What are the stop codons

UGA
UAA
UAG

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On tRNA , how would it relate to codon of mRNA

It would be a complimentary anti codon

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Why is the genetic code degenerate

Because multiple codons can code for the same amino acids

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Third base of codon can often change wihtout affecting the amino acids, what is this position called

Wobble

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What re the 3 point mutations

Silent
Missense
Nonsense

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What are silent point mutations

The mutation has no affect on protein change

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What is missense point mutations mean

Results in amino acid substitution

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What is nonsense point mutations

When codon turns into stop codon so shortens or non functional protein

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What are frame shift mutations

Insertion or deletion shifts the reading frame downstream, so completely different proteins are made or stop codons generated too early

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What is the main player in transcribing mRNA

RNA polymerase II

The binding site in the promoter region is called

TATA box

What does RNA polymerase I do

Make rRNA

What does rna polymerase II do

Make mRNA

What does rna polymerase III do

Make tRNA

Transcription starts at what site Positive or negative

Positive

Let’s say rna polymerase reaches end of dna sequence and leads to termination of transcription. And the DNA helix is reformed, the primary transcript that is formed is called - like the immature version mRNA

Heterogenous nuclear RNA (HnRNA)

HnRNA has to go though posttranslational processing, why

To become mature mRNA

What are 3 pposttranslational processing to make mature mRNA

Splicing 5’ Cap 3’ tail

What is splicing

Introns are removed, exons and joined together

What thing does splicing

Spliceosome

What type of cap is added for mRNA

5’ cap Methylguanosine

Why is 5’ cap added on mRNA (2)

Helps ribosome recognize mRNA Protects it from degradation

What tail is added to mRNA

3’ poly AAA tail

What is poly AAA tail for (2)

Protects degradation and helps with export from nucleus

What is alternative splicing in HnRNA

Different exons can be included or skipped to make multiple versions of mRNA

What is alternative splicing for

You don’t need more genes but t get the diversity More proteins with limited amount of genes

For translation , what is it doing

Converting mRNA into a protein

Where does translation occur

Cytoplasm of ribosome

What are size of prokaryote and eukaryote ribosome , how many s

Prokaryote 70s Eukaryote 80s

Ribosome has 3 sites

APE

What happens in the A site of ribosome

Holds new aminoacyl tRNA

What happens in p site in ribosome

Holds growing peptide chain

What happens in E site of ribosomes

Where empty tRNA exists

What are the 3 mechanisms of translation

Initiation Elongation Termination

For initiation step in translation , what happens

Smal ribosomal subunit binds to mRNA

In prokaryotes and eukaryotes, where does intitation step of translation occur

Prokaryotes: ions to shine - dalgarno sequence Eukaryotes: binds to 5’ cap

How does intitation work in translation, like what happens step by step - in terms of start codon and methionine

The start codon (AUG ) is recognized, and the first tRNA that carries methionine binds at the P site.

What do intitation factors do

Help guide ribosomes and stabilize the interaction between tRNA and start codon

How does elongation work in translation

A is where tRNA with amino acid corrrespodning to codon in the position Peptide chain forms in A site and is held in P site Inactivated tRNA pause and then exit the ribosome from the E site

How do release factors come into play in translateion

Stop codon entered the A site, no codon binds Release factors binds, causing protein to release Th protein is released and translation is done

Eukaryotic proteins have signal sequences at the end of translation, what are they fo

To designate a particular destination for the protein

What are the two forms of possttranaltional modifications needed

Structural changes Chemical changes

Why do we need to do posttranslational modifications

Because we need to make sure protein folds correctly, reaches right place and performs job

Protein folding process as a posttranslational modification to make sure everything is okay, what are the proteins used in this process called

Chaperones

What are some structural changes in possttranlational modifications What are these - cleavage -signal sequence removal - subunit assembly

Cleavage: part of protein is cut off to activate protein or allow to change shape Signal sequence removal: cutting off some part of peptide that help direct protein to proper destination Subunit assembly: multiple protein chains come together to make functional complex

What are the 4 chemical posttranslational modifications

Phosprylation Carbolyation Glycosyaltion Prenylation

What does phosphorylation, mean in posttranslational modifications

Adding phosphate group to turn proteins on and off

What does carboxylation , mean in posttranslational modifications

Stabilize protein structures Especially those binding with calcium Adding carboxylo group

What does glycosyaltion in posttranslational modification

Add sugar chain to help protein reach right place

What does prenylation, mean in posttranslational modifications

Adding lipid groups to anchor proteins into membranes

What do operons do Is it in eukaryotes of prokaryotes

Proakaryotes Has inductively and repressible systems Offer simple on and off switch for gene control

What model is used to describe operons

Jacob -Monod model

Operons have 4 structures that make it up

Regulator gene Promoter Operator Structural genes

What are these in the operon, like what they do Regulator gene

Makes repressor protein

What this do in operon Promoter

RNA polymerase binds here

What this do in operon Operator

Where the repressor binds

What this do in operon Structural genes

Actual genes being transcribed

What is inducible system in prokaryotes and operon What is the default state What is usual state with the repressor and transcription What happens when the inducer is present

Default state is off Repressor is bound to operator to block transcription Inducer is present, binds to repressor, repressor falls off, transcription happens

What are inducible effects when seen with lac operon In terms of lac repressor, operator and rna polymerase

When there’s no lactose, lac repressor tightly binds to operator. RNA polymerase can’t go into job so transcription doesn’t happen Allolactose/lactose binds to lac repressor and makes it let go of operator. RNA polymerase can now transcribe operon.

Inducible effects are positive or negative control

Negative control

What is CAP site When does it become active - glucose levels, cAMP, CAP site, helps what - is it positive or negative control

Glucose is low, cAMP increases, it binds to CAP site, binds to site near promoter, helps rna polymerase This is positive control

What is repressible system in operons Default state: How is repressor like

On The repressor in active by itself, so genes are usually transcribed

How does repressible systems work - corepressor, repressor,operator,transcription

Corepressor is present Binds to repressor Repressor becomes active Binds operator Blocks transcription

What’s a type of operon that does repressible system

Trp operon, turned off when tryptophan is abundant

What would a coreepressor be in tryptophan operator

If the tryptophan is already high in local environment

Control of gene expression in prokaryotes is done with

Operons

What are cis regulators in eukaryotic gene expression Why are they this

Promoter enhancers and response elements Because they are in the vicinity of the gene they control

What are trans regulator of gene expression in eukaryotes Why is it this

Transcription factors Because they travel through the cell to their point of action

Is heterochomatin or euchromatin more dense and which ones more active

Euchromatin is less dense, more open so more active Heterochromatin is silent and shut down for transcription

What does acetyaltion (HAT) do to chromatin

Loosens it, increasing transcription

What does deactelyation (HDACs) do to chromatin

Tighten it , decrease transcription

What odes methylation do to chromatin

Adds methyl groups to dna , long term silencing

What do transcription factors do

Determine which genes get transcribed, helps rna polymerase bind to DNA

Transcription factor has 2 domains called what

DNA binding domain Activation domain

What are enhancers

They are distract dna sequences that help boost transcription Bind to activators and dna loops to bing enhancer near promoter

Transcription factors bind to what elements in dna

Activator and repressor

What is gene amplification for

Some genes need to be expressed at high levels or in response to distant signals

What is gene duplication

Gene is copied and duplicated the relevant gene to increase expression

Gene expression in eukaryotes happens at different levels (3)

Chromatin - acetylation and decetylation Transcription factors - promoter and enhancer Amplification - gene amplification and duplication

Biochem Chapter 7 Flashcards

(94 cards)