T7.2 Transcription and Gene Expression HL Flashcards
How is gene expression regulated?1
By the proteins that bind to specific base sequences in DNA
What are functions of non-coding DNA in transcription?
They can act as Promotors, Enhancers, Silencers, and Promoto-Proximal elements
What does Promotor DNA do?
it tells RNA Polymerase where to bind to the DNA and to initiate transcription. It is kind of like Primer in DNA replication
What protein binds to Promotor DNA?
RNA Polymerase (RNAP)
What does Enhancer DNA do?
Increases the rate of transcription when specific proteins, called activator transcription factors, binds to the DNA.
What does silencer DNA do?
Slows the rate or stops transcription by the binding proteins (repressors transcription factors)
What does Promot-Proximal element do?
Basically the same thing as an enhancer, but is close to the promotor sequence while the Enhancer can be hundreds of base pairs away.
How are enhancers or silencers brought close to the promoter?
- The chromatin structure of DNA makes it so there is a big loop, where the enhancer/silencer is on the end of the loop and the promoter is on the other.
- It’s kind of like a loop on a string. To make a loop, the two ends of the string need to be brought together. The two ends are where the enhancer/silencer and promoter is located, so they can be brought together even if they are hundreds of thousands of base pairs away.
How is the production/transcribing of lactase effected by environmental factors?
- When lactose is absent, repressors are bound to the DNA and prevents RNAP from binding
- When lactose is present, the repressor is not bound to DNA and RNAP can bind to start transcription.
How is developmental biology impacted by environmental factors?
- Depends on the concentration of morphogens
- Morphogens are molecules that contribute to different patterns of tissue development.
- It’s distribution by diffusion determines the development of cells that respond differently to the different concentrations of the morphogen.
- This regulates where/when genes are expressed and repressed for growing a foot or growing an eye.
- Can be seen with proteins that control when/where legs are grown on fruitflies.
How does environmental factors impact the gene expression of pigment production?
Siamese cats are the main example used
* C gene cods for tyrosine which makes pigment.
* The Cs mutant allele is in siamese cats, where tyrosine gene is expressed only at temps below body temperature.
* This is why siamese cats have coloring in cooler areas of the body, such as the tail or ears
Acetylation
A modification *of the tails of the histones in the octamer *that neutralizes positive charges on histone tails, allowing a less condensed DNA structure.
Increases transcription by increasing the accessibility of the gene to the transcription factors.
Methylation of histones
Modification of the tails of the histones in which methyl groups are added to various amino acids.
This usually decreases accessibility of the gene depending on the number of methyl group and to which amino acids they attach to.
Lasts a long time
What does methylation prevent?
Prevents transcription factors from binding to DNA
3 stages of transcription
Initiation, Elongation, Termination
Insects eat teeth idk come up with your own way to remember it
Initiation
RNAP binds to promoter
Elongation
RNA nucleotides addeed to make strand of mRNA
- uses antisense strand of DNA as a template to make a sense RNA
Termination
RNA polymerase detatches from DNA. mRNA released to go to ribsome
How do bacteria create mRNA/Proteins?
- Transcription and translation happen simultaneously
- No compartmentalization (what happens in nucleus of eukayotes happens in cytoplasm of prokaryotes)
- Polysomes attach to the mRNA as the mRNA is being transcribed, producing proteins
- Polysomes: multiple ribosome groups
Do prokayotes have introns?
no
Do Eukaryotics have introns?
yes
snRNPs
snurps
Small nuclear ribonucleic proteins, removes introns to make a functional mRNA strand
Does prokayotic mRNA require processing?
no, no introns are present, meaning what is transcribed is the finished (mature) mRNA
Exons
coding DNA (codes for proteins)
Introns
intervening sequences of non-coding DNA
Spliceosome
a large ribonucleos protein (RNP)
complex made up of five snRNPs and several proteins
Alternative splicing
Process during gene expression whereby a single gene codes for different forms of a protein
A particular exon may or may not be included in the final mRNA
What will proteins translated from alternatively spliced mRNAs differ in?
Their amino acid sequence and biological function
Example of alternative splicing
Tropomyosin
* produced from a gene with 11 exons
* can be alternatively spliced to produce 5 different forms of the protein
* Skeletal muscle exon “2” and smooth muscle exons “3” and “10 are not present in mature mRNA that produces Tropomyosin
Methylation of DNA
Methyl groups attach to cytosines on the DNA, and has the same outcome as the methylation of histones
Smaller scale of methylation of histones
