Lecture 17 - Genetic Variation & Disease #1 Flashcards
What is an allele?
An allele is an alternative form of genetic variant located at the same position on a gene
How many copies of each gene does a diploid organism have?
Two copies, one from each parent, called the homologous paid
What is a phenotype
The observable characteristics or traits in an individual, determined by their genotype i.e. physical appearance
What is a genotype?
The combination of alleles a person has for a particular genetic variant
What is the inheritance pattern of dominant alleles?
Only one dominant allele is needed for the trait to be expresses, either in homozygotes dominant (RR) or heterozygote (Rr)
What is the inheritance pattern of recessive alleles?
Two copies of the recessive allele (rr) are required for the trait to be expressed
What is a gain-of-function allele?
An allele that causes protein to work too well or to perform a new function, often showing dominant inheritance
What is a loss-of-function allele?
An allele that results in a non-functional protein, often showing recessive inheritance because the other allele can compensate for the loss
What are monogenic traits?
Traits controlled by a single gene, often following simple dominant/recessive inheritance patterns
What are polygenic traits?
Traits controlled by multiple genes, typically showing complex inheritance patterns influenced by both genetics and environment
Two monogenic diseases
- Retinitis Pigmentosa
- Phenlyketonuria (PKU)
What is the role of Rhodopsin receptor in retinitis pigmentosa?
Genetic variants disrupts its ionic lock, causing the receptor to remain constantly active, leading to retinal degeneration and blindness overtime
What causes PKU?
A recessive genetic condition where non-functional phenylalanine hydroxylase leads to the build up of phenyalanine, causing brain damage if untreated.
How can PKU be managed?
Through a low phenylalanine diet to prevent the harmful accumulation of phenylalanine in the body
What is genotyping?
The process of determining the specific alleles present in an organism’s DNA
What are some methods used for genotyping organisms?
- PCR-RFLP
- Fluorescence-based methods
- Sequencing
What is genetic testing used for?
To identify specific alleles in an individual’s DNA, which can predict the risk of diseases or confirm a diagnosis
What are the steps in the Polymerase Chain reaction (PCR) process?
- Denaturation - separating DNA by heating to very high temperature
- Annealing - Cooled, so DNA primers can attach to target sequence.
- Elongation - heat increased slightly so heat-tolerant DNA polymerase can bind primer and replicate DNA.
What does genotyping usually rely on?
PCR - Polymerase chain reaction
What are reaction components for PCR?
- DNA sample - extracted
- Primers - Small segment of DNA, complementary to DNA of interest
- Polymerase - Heat tolerant DNA enzyme
- Nucleotides (dNTPs) - DNA nucleotides to build new DNA strand
What is PCR-RFLP used for?
It’s a genotyping technique that uses PCR, restriction enzymes, and gel electrophoresis to identify genetic variants by cutting DNA at specific sites.
What is the role of restriction enzyme in PCR-RFLP?
They cut DNA at specific sequences, allowing researcher to distinguish between different alleles based on fragments size after gel electrophoresis
What is a fluorescence - based genotyping method?
A technique that uses fluorescent probes specific to genetic variants, detected during PCR to determine the presence of certain alleles
What is whole - genome sequencing used for in genotyping?
To determine the complete DNA sequence of an organism, allowing identification of genetic variants across the entire genome
