Chapter 8 Flashcards
Studying gene expression
What is RISC?
RNA-induced silencing control
Multiprotein complex, which incorporates one strand of a single-stranded RNA (ssRNA) fragment, such as miRNA, siRNA.
The single strand acts as a template for RISC to recognize complementary mRNA transcript. Once found, Argonaute in RISC activates and cleaves the mRNA.
This process is called RNA interference (RNAi) and it is found in many eukaryotes; it is a key process in gene silencing and defense against viral infections.
Involved in post-transcriptional control
What is the spliceosome?
A spliceosome is a large and complex molecular machine found in the cell nucleus of eukaryotic cells.
The spliceosome removes introns from a transcribed pre-mRNA, a type of primary transcript.
Involved in post-transcriptional control
What is a dicer
Dicer cleaves dsRNA into short double-stranded RNA and pre-miRNA into microRNA
Dicer facilitates the activation of RISC, which is essential for RNA interference.
Involved in post-transcriptional control
What is a mediater?
Multiprotein complex that functions as a transcriptional coactivator in all eukaryotes.
What is miRNA and how does it regulate gene expression?
MicroRNA
Can form RISC to recognize target RNA based on base pairing
Binds to complementary sequences of mRNAs and silencing the mRNA by cleaving into two pieces or destabilization through shortening of its poly(A) tail.
What is siRNA and how does it regulate gene expression?
Small interfering RNA
Double stranded RNA molecules
Can form RISC to recognize target RNA based on base pairing
Interferes with expression of specific genes with complementary sequences by degrading mRNA after transcription, preventing translation
What is a coactivator?
A coactivator is a type of transcriptional coregulator that binds to an activator (TF) to increase the rate of transcription of a gene or set of genes.
What is RNAi?
RNA interference is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules.
What is RITS?
RNA-induced transcriptional silencing complex
Triggered by short RNA molecules like siRNA, which functions as guide RNA recognizing complemenrary transcripts to help position the RITS complex near chromatin
When included in RITS, siRNA directs heterochromain formation.
Recruits writer proteins, which modify histone tails with a repressive chromatin mark
What is a genetic screen?
A search through a large collection of mutants for a mutant with a particular phenotype.
What is polymophism?
One of a number of common sequence variants that coexist in the population
What is an allele?
One of a set of alternative forms of a gene
What is a phenotype?
The observable character of a cell or an organism
What is Epistasis analysis?
Comparing the phenotypes of different combinations of mutations to determine the order in which the genes act
What is a haplotype?
Ancestral chromosome segment that has been inherited with little genetic rearrangement across generations
What is a transgenic organism?
Animal or plant that has been permanently engineered by gene deletion, gene insertion, or gene replacement
What is a genotype?
The genetic constitution of an individual cell or organism
What defines a gain-of-function mutation?
A gain-of-function mutation increases the activity of the protein product or gives it novel activity.
The change in activity following a gain-of-function mutation happens even when the normal version of the protein is present therefore such mutations are often dominant.
What defines a loss-of-function mutation?
Mutation that causes a gene product having less or no function
What defines a dominant-negative mutation?
A dominant-negative mutation gives rise to a protein product which interferes with the function of the normal protein and therefore gives rise to a loss-of-function phenotype despite the presence of a normal version of the protein.
What are single-nucleotide polymorphisms (SNPs)?
SNPs are single nucleotide differences between individuals.
What is genome-wide associated study (GWAS)?
Genome-wide association study (GWAS) link SNPs (that represent haplotypes) with a specific trait, for example a disease and determine the probability of having a certain trait or developing a disease for carriers of different SNP variants.
What is Cre-lox recombination?
Used to carry out deletions, insertions, translocations and inversion at specific sites in the DNA
Allows the DNA modification to be targeted to a specific cell type or trigger by a specific external stimulus.
Define knockout of a gene
An existing gene is inactivated, “knocked out”, by replacing it or disrupting it with an artificial piece of DNA
Define knock-down of a gene
RNA interference (RNAi) is silencing of genes with mRNA degradation.
siRNA are introduced into the cytoplasm.
What are deletions?
Part of a chromosome or a sequences of DNA is lost during DNA replication
What are insertions?
Addition of one or more nucleotides into a DNA sequence
What are chromosomal translocation?
Chromosomal segment is moved from one location to another, either within the same chromosome or to another chromosome
What are inversions?
Chromosome arrangement where a chromosome is reversed end to end, inverted.
How does Cre-lox recombiantion work?
An enzyme, Cre recombinase, recombines a pair of short target sequences called “lox sequences”.
Cre recombinase catalyses a site specific recombination event between two loxP recognition sites.
What happens depends on the position ond directions of the loxP sites
Insertion - turn toward each other
Deletion - Turned same direction
Translocation - Same direction of different strands.
What is Holliday Junctions?
Cross-shaped structures that forms during genetic recombination, when two double-stranded DNA become seperated into four strands in order to exchange information
What is recombination?
Two molecules of DNA exchange pieces of their genetic material with each other
Pieces of DNA are broken and recombinated to produce new combination of alleles.
Causes offspring with traits that can differ from those found in the parents.
What is alternative splicing?
Process during gene expression that results in a single gene coding for multiple proteins.
Exons may be included or excluded from the final mRNA
Describe PCR
Polymerase Chain Reaction
Laboratory technique to amplify a single copy or copies of a segment of DNA
PCR uses a DNA polymerase from a thermophilic bacterium
Most of the resulting pool of dsDNA molecules will have DNA from primers at the 5’ ends
What does it take to drive the expression of a gene?
Physical contact between a regulatory region and a gene is sufficient to drive the expression - but only if the regulatory gene is active
