L5 Developmental genetics Flashcards
How are genes named?
Genes are named after a protein product or the phenotype, whichever came first
Species names and gene names are italicised
What are the main causes of random mutations?
Radiation (e.g. X-rays)
Chemical (e.g. base modifiers)
These changes can be point mutations (single base-pair), deletion, insertion, translocation
Why are naturally occuring mutations important?
Naturally occurring mutations are important for evolution, but also are a major cause of disease.
What are inherited mutations called?
Germline mutations
Inherited so from sperm or oocyte
What is somatic mutation?
Somatic mutations are just in our body.
How are mutation changed caused?
They are caused by radiation or chemicals.
What are the two types of developmental genetics?
- Forward Genetics (Mutagenesis).
- Reverse Genetics
What is forward genetics?
- Approach begins with observing a mutant phenotype
- Researchers then work to identify the gene or genes responsible for that phenotype
- Essentially, it moves from “phenotype to genotype”
What is reverse genetics?
- Approach starts with a known gene or DNA sequence.
- Researchers then manipulate that gene (e.g., by mutating it) and observe the resulting phenotype.
- Therefore, it moves from “genotype to phenotype”
What does mutagenesis mean?
This is the process of causing mutations
It can involve exposing organisms to mutagens, which are agents that cause mutations
What are the major ways of targeting specific genes in reverse genetics?
- CRISPR
- Gene Knock-out
What is gene knock-out?
Complete removal of gene to determine its function.
What is the major adavantage of CRISPR?
It works in any organisms
How does gene replacement work?
Gene replacement (knock-in) usually makes a small changes to the endogenous gene.
What is the difference between forward and reverse genetics?
Forward - Phenotype to gene
Reverse - Gene - Phenotype
What three ways of mutation that affects genes?
- Changes in regulatory sequences (in the DNA that affects transcription)
- Changes in non-coding sequences (of the transcript that may affect RNA splicing, stability or translation)
- Changes in the coding sequence (may alter an important amino acid affecting folding of the protein or may create a premature stop codon)
What do changes in regulatory sequences in DNA affects?
Transcription
What do changes in non - coding sequences of the transcript affect?
They may affect RNA splicing, stability or translation.
What do changes in coding sequence alter?
May alter an important amino acid affecting folding of the protein or may create a premature stop codon - truncated protein.
Missense = single amino acid substituted. Nonsense = stop codon
What is a domain?
A domain is a functional unit in a protein.
What is a dimer?
A dimer is when two of the same protein bind together.
What do you mean by conformational change?
A conformational change is a change in protein structure
List the processes of mutations affecting protein function.
- DNA binding
- dimerization
- conformational change
- Transcriptional activation
Give an example of amorphic/non-functioning mutation.
An example is a missense mutation that completely inactivates the DNA binding domain.
Give an example of hypomorphic/weakened mutation.
for example a missense mutation that weakens the DNA binding domain.
Give an example of antimorphic/dominant negative mutation.
for example a missense mutation that destroys the dimerisation domain.
Give an example of hypermorphic/overactive mutation.
for example a missense mutation that results in activation that is independent of dimerization.
What are the 4 types of mutations? (Muller’s Morphs)
Loss of function mutations:
1. Amorphic
2. Hypomorphic
3. Antimorphic
Gain of function mutation:
4. hypermorphic
What is Muller’s morphs?
Types of phenotypes produced by mutations
What is amorphic?
Complete loss of gene function: typically early nonsense mutations or a deletion of the entire gene
What is hypomorphic?
Partial loss of gene function/ reduction of wild type function: typically missense mutations. Usually recessive
What are missense mutations?
A “missense mutation” is a specific type of point mutation within DNA
What is antimorphic?
Acts as competitive inhibitors, typically mutations that affect one domain of a protein. Also called dominant negative
What is hypermorphic?
Over expression of the transcription unit or over activity of the gene product: for example mutation in a binding site for a repressor. Dominant
Which type of Muller’s Morphs mutations are recessive or dominant?
Amorphic - Recessive
Hypomorphic - Recessive
Antimorphic - Dominant negative
Hypermorphic - Dominant
What does mutations that result in the same phenotype despite being in different genes suggest?
Mutations that result is the same phenotype that are not in the same gene suggest that the genes function in the same pathway
What are alleles?
Mutations that result is the same phenotype may be different mutations in the same gene. Mutations in the same gene are called alleles.
What do reprter constructs help us to study?
Reporter constructs helps us to study gene and mutations in vivo.
What is GFP?
Green Fluorescent Protein
What is transfection?
The process of introducing foreign genetic material (like DNA) into cells
How do you generate a GFP transgenic line?
1) Genomic DNA with all of the regulatory elements
2) Genitcally engineer GFP onto the end of the last exon (gene fusion) or replace the gene (reporter construct)
3) Re-introduce this into the animal
What is a transgenic line?
A cell line or organism whose genome has been altered by the insertion of foreign DNA.
What are the uses for GFP transgenic lines?
To follow expression of a gene or to follow the behavior of cells in vivo.
To follow subcellular localisation of a protein.
