U4L4 - Mutations and Gene regulation Flashcards
What are proto-oncogenes?
A group of genes that control cell growth in normal cells, but can become cancerous when they are mutated.
What are oncogenes?
When proto-oncogenes are mutated, they become oncogenes and cause uncontrolled cell division = malignant tumors,
What are Carcinogens?
Agents that cause cancer (mutations). They include radiation, smoking, and viruses (HPV).
What is a mutagen?
an environmental agent that directly alters the DNA within a cell
What is a Spontaneous mutation?
caused by error in DNA replication
EX:
Alkylation – adding alkyl groups (C-groups) to DNA
Oxidation – oxidized bases in DNA
What is a Induced mutation ?
caused by environmental agent
EX:
Radiation: UV, Gamma, Beta, Alpha,
Chemical: CO, smoke, nitrosamines (smoked meat & fish)
What is a point mutation?
replacement of a single nucleotide in a gene (substitution, insertion, deletion, inversion of base pair)
What is a silent mutation?
no change in a.a
What is a missense mutation?
codon change results in a different a.a
What is a nonsense mutation?
Codon change results in a premature stop codon
What is a Frameshift Mutation?
insertions or deletions of nucleotides that is not divisible by 3. The reading frame “shifts” which gives a completely different a.a sequence
What is controlling gene expression?
Not all proteins are needed by all cells at all times. It is Inefficient for a cell to transcribe and translate ALL of its genes at all times. Thus, some genes are turned off and on when needed = gene regulation
What are the four ways eukaryotes control gene expression?
1) Transcriptional control
2) post-transcriptional control
3) Translational control
4) post-translational control
What is Transcriptional control (as mRNA is synthesized) ?
selection of genes to be transcribed and the rate of transcription
E.g. methyl group added to promoter so RNA polymerase can’t bind and transcribe
What is post-transcriptional control (as mRNA is processed)?
processing of mRNA and the rate at which mRNA leaves the nucleus.
E.g. masking proteins bind to mRNA and inhibit further processing or alternative splicing
What is translational control (as protein is synthesized)?
how long mRNA remains in the cytoplasm
E.g. variation in length of poly-A tail related to rate of translation
What is post-translational control (after protein synthesis)?
additional processing that proteins require to be functional or through feedback inhibition.
E.g. presence of hormones lengthen or shorten time that a protein is functional, or “tagged” proteins are degraded
What controls gene expression in prokaryotes?
Gene expression is in response to the concentrations of two molecules:
Lactose (source of energy)
Tryptophan (aa used to make proteins)
What is an Operon and what is it composed of?
it is a cluster of genes code for a protein commonly regulated and transcribed into mRNA and it consists of; Structural genes (genes encoding for protein), Promoter (nucleotide sequence allows for binding of RNA polymerase for transcription to begin), Operator (base sequence controls transcription), Regulatory genes (encodes for repressor protein), Repressor and activator proteins (proteins that bind to operator to repress or activate gene
transcription)
How does Lactose metabolism in E. coli worl?
1) Transport lactose into the cell
2) Break down lactose into glucose and galactose
—-> The enzyme Beta-galactosidase breaks down lactose into glucose and galactose
Explain the role of lactose
Lactose is called an inducer molecule because it signals the production of
1) Beta-galactosidase: the enzyme that cleaves lactose into glucose and galactose
2) Galactoside permease: the transport protein that allows lactose to enter a cell
