Section 8:Gene Expression Flashcards
Define both types of mutation
Gene=A change in the base sequence of DNA
Chromosome=A change in the structure or number of chromosomes
What are the overall effects of mutation?
- Production of new/superior protein=Gain reproductive advatage
- Neutral mutation=No change
- Production of inferior or no protein=Fatal and/or disease causing
What are the three possible subsitiution mutation?
- Formation of stop codon~Polypeptide stops prematurely
- Formation of codon for codon for AA~Polypeptide differs which can change the protein shape
- Formation of codon for same AA~No change to polypeptide
How does a deletion mutation affects polypeptides?
Causes a frame shift~Each base triplet is read differently
The impact can differ based on where the mutation occured
What are the four other types of mutations and give a basic description
- Addition~Usually frameshift=Whole new sequence of triplets (If 3 added there will be no frameshift)
- Duplication~One or base repeated=Frameshift to the left
- Inversion~group of DNA bases become seperated from the DNA sequence=Rejoin at the same position in reverse order
- Translocation~group of bases seperated from DNA sequence on one chromosome=Inserted into DNA sequence of another chromosome
Define mutagenic agents and give two examples
Increases the mutation rate e.g UV light or nitrogen dioxide
Describe how two examples of mutagenic agents work
- UV light=affects thymine~disrupts DNA replication
- Nitrogen Dioxide=disrupts DNA replication
What are transcription factors?
specific molecules with a sequence of bases that will bind to its complementary bases in DNA ~stimulates and ‘switches on’ genes
How do transcription factors work?
- They bind to its complementary bases in DNA
- Causes transcription to start as RNA polymerase is stimulated
- mRNA is produced and undergoes translation to form a polypeptide
How does oestrogen affect gene transcription?
Oestrogen is a smal,lipid soluble hormone which can diffuse through the phospolipid bilayer
1. Once in cytoplasm it binds to the receptor which is on a transcirptional factor
2. Oestrogen causes the transcriptional factor to chang shape
3. The transcriptional factor binds with DNA and begins to process of transcription
What is siRNA?
Small interfering RNA-double stranded RNA which destroys mRNA
How does siRNA control translation?
- Double stranded RNA cut into segments (siRNA) by an enzyme
- One of siRNA strands combines with an enzyme~bases on siRNA pair with complementary bases on mRNA
- The enzyme then cuts mRNA into smaller parts~this prevents translation
- The gene will not be expressed
How could siRNA be used in medicine and science?
Able to treat genetic diseases or diseases caused by mutation~if siRNA is present it can stop the gene causing the disease from bein expressed
Define genome and proteome
- Genome=all the genes/alleles of an organism
- Proteome=all of the proteins produced by the gamete
Why is it easier to determine the genome and proteome of simpilar organisms?
- Vast majority of prokarotes have just one,circular piece of DNA (not associated with histones)
- There are no introns
What are the sources of stem cells in mammals?
Embryonic,Umbilical cord blood,Placental and Adult
Placental stem cells with develop into specific cell types
Adult stem cells are specific to a particular tissue/organ and mantain & repair throughout life
Give a basic description of each
What are the different types of stem cells?
- Totipotent(early embryo)=differentiate into any type of cell
- Pluripotenet(after early embryo has divided and matured)=can differentiate into almost an type of cell~slightly more specialised than totipotent
- Multipotent(adult)=differentiate into a limited number of types of cells
- Unipotent(adult tissue)=differentiate into only one type of cell~derived from multipotent
What is iPS?
Induced pluripotent stem cells
Pluripotent cells that are produced from unipotent stem cells
* Cell is made to have ability to express genes that are usually not expressed
* Similar to embroynic stem cells but are capable of self renewel
What human diseases/injuries could be tretaed by growing:
* blood cells
* heart muscle cells
* skin cells
- Leukemia
- Heart damage e.g as a result of a heart attack
- Burns and wounds
How are stem cells grown?
- Early embryo is cultyred in a nutrient medium
- Outer layer collapses + inner cell mass is freed from embryo
- Chemicals added to break up cell mass into smaller groups
- Colonies of embryonic stem cells form
- Differentiation factor~transfer differentiated cells to damaged tissues
