Mendelien genetics - week 14 Flashcards
What is a gene
Unit of heridetitary info consisting of a specific nucleotide sequence in DNA (ran in viruses)
Model organism (non-human studied species)
Short gen time
many offspring
easy/ cheap to grow
easy to cross/ fertilize
Homozygous
Both alleles at locus are the same
Heterozygous
Both alleles at locus are different
The standard 3;1 ratio produced by Rr x Rr shows what
Alleles involved show complete dominance or recessiveness
Mandels 1st law
The two alleles for a heritable characterist segregate during gamete formation and end up in different gametes
Mandels 2nd law
Each character is independantly inherited during gamete formation
Law of independent assiotment
Exceptions to mandels law
Incomplete dominace and co-dominance - interactions at same loci
Epistasis - interactions at different loci
What is incomplete dominance
Both alleles are domiant so there’s a blending of the two traits
What is co-domiance
both alleles contribute to the phenotype of the organism by showing up simaltaniously
What is epistasis
Interactions between alleles at different loci
-the expression of one gene affect the other
Instead of 9;3;5;1 you get 9;4;3
How to test is an allele is recessive or dominate
Pure breeding
Breed new mutant (ob ob) with pure wild type (OB OB) if mutant shows up in F2 then mutant dominate
Nomenclature
Genes are usaully named occording to their function
Law of segregation
The two alleles for each gene seperate
Law of independant assiortment
Alleles of genes on non-homologous chromosomes assort independently
-Alleles on different chromosomes have a 50% chance of ending up in the same gamete
What does genetically linked mean
loci physically close together stay together during meiosis, autosomal linkage
What’s wrong with mandels laws
they only considered segregation (genes on different chromosomes) which meant he could consider traits completely independent
if b and vg genes are physically linked what does that mean for F1 generation
Most offspring b+ vg+ or b vg
With b vg+ and b+ vg being rare
Small area/ very close together so less chance of genotypes crossing over, most offspring match parents
What is the recombination frequency ?
How often recombination/ crossing over occurs between genes.
Measure by fraction/ % of offspring inherit recombinant chromosomes
(recombinates / total offspring) x 100
Compared to the x chromosome the y is what?
very reduced carries 200 genes including SDY (sex-determining region Y)
What is SDY or TDF?
testies determinding factor, transcription factor that initiates male sex determination like testies (6-8 week)
What are sex linked genes
genes on sex chromosomes
X linked genes are what
father only pass to daughters who are carries not sons
carriers mothers have 50% pass on rate
X inactivation
inactivation of 1 of 2 copies of x chromosome
- early in development one x chromo condenses into BARR BODY where genes are not expressed
- which is barr body made on cell by cell basis in first 100 cells
