GEGE Flashcards
Haplosufficient
When one allele is sufficient to produce a phenotype.
Haploinsufficient
When one allele is not sufficient to produce a phenotype –> must be homozygous
Loss of Function Mutations
Null/ amorphic mutation
Leaky/ hypomorphic mutation
Amorphic mutation
Complete loss of gene function.
Hypomorphic mutation
Partial loss of gene function
Dominant -ve mutation
Mutation in polypeptide which interferes with a protein’s functioning.
Incomplete dominance
Will show a mix of the two phenotypes e.g flower colour
Co-dominance
Will should both phenotypes e.g blood type
Pleiotrophy
When a single gene affects two or more characteristics.
Incomplete Penetrance
Individual with mutant allele may not show the mutant phenotype
Variable expressivity
The extent to which the phenotype is expressed varies
Complementary Gene Interaction (form of epistasis)
Recessive mutation in two different genes acting in the same pathway produce the same phenotype
Wild type alleles for both genes need to be present for both genes to produce the wild type phenotype.
Duplicate Gene Interaction (form of epistasis)
Only homozygous mutation in both genes produce a mutant phenotype
Dominant Gene Interaction (form of epistasis)
Two genes contribute to a phenotype
Phenotype 1 = both genes have a dominant allele
Phenotype 2 = either gene is recessive
Phenotype 3 = both gene are recessive
Dominant Supression (form of epistasis)
The dominant allele of one gene supresses the phenotypic expression of alleles of a second gene
Dominant Epistasis (form of epistasis)
A dominant allele of one gene supresses or masks the phenotypic expression of alleles of a second gene.
Recessive Epistasis (form of epistasis)
Homozygous recessive alleles for one gene masks the phenotypic expression of alleles at a second gene.
Cell Cycle
Interphase -> Prophase -> Prometaphase -> Metaphase -> Anaphase -> Telophase
Interphase
Chromatin condense and transition to polar ends of the cell
Prophase
Chromosomes condense and spindles attach
Prometaphase
Nuclear membrane dissolves
Metaphase
Spindle fibres align chromosomes along equatorial plate
Anaphase
Sister chromosomes pulled apart
Telophase
Nuclear membrane reforms and cytoplasm begins to divide
Metacentric chromosomes
Centromere in middle of chromosome
Acrocentric chromosomes
Centromere towards one teleomere
Telometric chromosomes
Centromere right at the end of the chromosome
Aneuploidy
variation in chromosome dose e.g downs sydndrome
Polyploidy
Variation in sets of chromosomes
Allopolyploidy
Sets of chromosomes come from different species –> sterile hybrid produced.
Haplotypes
A block of genes located together which are inherited together
Tautomers
Alternate forms of the nucleotide bases
i.e C+A and T+G
Indels
Addition or deletion of bases
Transitions
Purine replaced with another purine and a pyrimidine is replaced with another pyrimidine
Transversions
Purine replaced with a pyrimidine and a pyrimidine is replaced with apurine
Silent Mutation
bp change –> no AA change
Missense mutation
bp change –> AA change
Non-sense mutation
bp change –> early stop codon
Frameshift
bp deletion/addition –> alters reading frame
Mutant Screening Strategies
Forward genetic screen
Genome-wide screen
Reverse genetic screen
Forward Genetic Screen
Take organism -> mutate -> look at individual mutants which alter function/development
Genome-wide screen
Target all of genes using CRISPR -> get mutations -> identify what gene it is based on the mutation
Reverse Genetic Screen
Guess which gene is causing a mutation -> directly target that gene and mutate it -> see if the two mutations are the same.
Genetic Variation Comes From?
Mutation
Sexual Reproduction
Migration
Changes in allele frequency due to…
Mutation
Migration
Selection
Inbreeding
Inbreeding depression
Decrease in growth, fertility and survival following inbreeding and an increase in homozygosity
Hybrid Vigor
increase in vigor often after crossing inbred lines
Qualitative Traits
Controlled by a few genes of large effect
Phenotype determined by simple crossing experiment
E.g eye colour in drosophila
Quantitative Traits
Controlled by many gene of small effect
Environmental factors contribute to phenotype
E.g IQ
Structural Genomics
Sequencing and analysis of genome infromation
Comparative Genomics
Infer sequence function, understand genome evolution
Functional Genomics
What genes do and their link to phenotype
Evolutionary Genomics
Identifies similarities/differences between individuals/species
Interspecific Comparison
Between members of the same species
Identify sequences conserved over evolutionary time
Intraspecific Comparison
Identify sequence polymorphisms responsible for genetic differences between individuals
Paralogs
Genes which have originated from the duplication of an ancestral gene -> functions distinct but related
Orthologs
Genes in different species derived from a single ancestral gene -> have equivalent functions in different species
Phylogenetic footprinting
identify conserved regions in diverse species
Phylogenetic shadowing
look at sequences which have been conserved and try to determine why
