BSI Lectures 7-10 Gene Expression Flashcards
True or False? The DNA in every cell contains all the genes to make a complete human.
True
If every cell contains all genes to make a human why does each cell have a specific function?
Because only certain genes are expressed in each cell
What are the 6 steps at which gene expression can be controlled?
- Transcription
- RNA processing (splicing)
- RNA transport and localization
- Translational control
- mRNA degradation
- Control of protein activity
DNA methylation
long tails on the histones contain lysine, which has a positive charge. These tails form ionic bonds with the negative charges on the DNA. These bonds pull the histones together and tightly pack the chromosome preventing RNA polymerase from completing transcription
Histon acetylation
Acetylation of lysine residues on histone tails leads to looser packaging of genes; therefore, RNA polymerase can make mRNA (turns genes on)
What leads to the tighter packing of genes?
methylation
T or F; Gene regulatory sequences for a specific gene can be thousands of base pairs away from the promoter.
True
_____ promote assembly of transcription initiation complex.
Activators
What effect does methylation of DNA typically have on gene expression?
It shuts genes off; leads to tighter packaging of genes
Do transcription regulators repress or stimulate transcription?
They can do both
What do transcription regulators bind to in order to regulate transcription?
Gene regulatory sequences
Are most genes regulated by one transcription regulator or many?
Many
What are the 3 ways that the process of translation can be regulated?
Translation initiation via phosphorylation of eIF-2 inhibits translation; mRNA stability/degradation;miRNA
Define: Epigenetics
Heritable changes in the genomes that are NOT due to changes in the DNA sequence
What are the types of modifications to turn off or on genes?
DNA Methylation turns genes off and Acetylation usually turns genes on
What are transcription regulators?
aka Transcription factors or gene regulator proteins are proteins that bind to gene regulatory sequences to stimulate or repress transcription.
Each gene has its own set of gene ________ sequences associated with it.
Regulatory
Phosphorylation of _____ inhibits translation initiation.
eIF-2
Where would the DNA sequence that codes for the 5’ UTR be found?
In the “transcriptional unit” toward the 3’ end.
Where would the DNA sequence that codes for the poly A tail be found?
The poly A tail is not encoded in the gene. Enzymes later adds on the poly A tail.
______ hinder assembly of transcription initiation complex.
Repressors
The combination of activators and repressors determine the level of ____ _____ of a particular gene.
Gene expression
What does alternative splicing produce?
Isoforms
What are isoforms?
multiple forms of a protein that differ slightly in amino acid sequence. Because they have different amino acid sequences they are considered different proteins and they have slightly different functions.
Alternative splicing produces _____ mRNAs from a _____ pre-mRNA
variable; single
Can one gene give rise to multiple mature mRNAs with difference nucleotide sequences?
Yes, due to alternative splicing
Alternative splicing can alter protein function by:
- Changing the chemical properties or shape of binding sites
- Adding or deleting specific domains
- Adding or deleting post-translational modification sites
Alternative splicing can alter protein function. T or F?
True. The alterations can lead to differences in where the protein functions, how it is regulated, its affinity towards a substrate, etc.
All of the mRNA molecules produced from a specific gene will always contain the same nucleotide sequence. T or F
False, due to alternative splicing
If a SNP is in the noncoding sequence, will it have any effect on the phenotype of a cell?
It could affect splicing or modification.
Control of mRNA transport
If the mRNA is not capped, polyadenylated, and spliced it will not be transported out of the nucleus
SNP’s are ____ _____ that have been evolutionaryily successful enough to recur in a significant proportion of the population.
Point mutations
Example: positions where more than 1% of the population has a G-C nucleotide pair while another has an A-T
________ are short RNA’s that bind to mRNA and inhibits translation by causing degradation of mRNA.
miRNA
Will a SNP in a specific gene be present in every cell of your body that contains DNA?
Yes, because we are born with it and every cell carries all the genetic material to make a human.
If the rate of degradation of a poly A tail increases, what will happen to the half-life of the mRNA?
It will decrease its half life
What is the function of miRNA?
They are short RNA’s (21-23 nucleotides) that binds to mRNA causing degradation to mRNA.
Define: Single Nucleotide polymorphism
Points in the genome that differ in nucleotide sequence between one portion of the population and another.
Will a SNP always change the amino acid sequence of a protein?
No, due to synonymous and non-synonymous codes
Degradation of poly A tail decreases mRNA _______
stability
_______ ______ ______ are thought to be upwards of 8000 of these RNA’s, some arise from transcription of “wrong” strand of DNA of a protein encoding gene. Some of them bind to the mRNA produced from the same gene to inhibit translation.
Long Noncoding RNAs (lncRNA)
What are the 3 control of the activity of a protein (post-translational control)?
Protein modifications, Inhibitor binding, protein degredation
Points in the genome that differ in nucleotide sequence between ONE portion of the population and another is called ______
Single nucleotide polymorphism (SNP’s)
T or F? SNP’s are only in certain parts of the genome.
False, they can be found in any part of the gene
The location of the SNP’s will determine the effect it has on the ________.
Phenotype
____ can alter susceptibility to disease.
SNPs
_____ can alter response to drugs. (Basis for pharmacogenomics)
SNPs
An SNP is a variation at a specific nucleotide in the DNA sequence between two genes on the same chromosome. T or F?
False, between one gene
