Download Unit 7 Heredity: Chp 11 Non-Mendelian Genetics Notes

NON-MENDELIAN GENETICS
Simple Mendelian Inheritance = controlled by dominant and recessive paired alleles.
Many inheritance patterns are more complicated than those in Pea plants.
INCOMPLETE DOMINANCE
Appearance of a 3rd phenotype
Complete Dominance = TT, Tt same phenotype
Incomplete Dominance = intermediate phenotype for Tt
Red flower and White flower
F1 all pink = Rr
Neither allele is COMPLETELY dominant
Combine to give a new trait
Rr x Rr
1:2:1
RR = Red
Rr = Pink
rr = White
CODOMINANCE
Expressed both alleles
Black x White feathered birds
B and W (both capital)
They would be Black if Mendel’s worked
They would be Gray if Incomplete dominance
Heterozygous have some black and some white feathers
MULTIPLE PHENOTYPES FROM MULTIPLE ALLELES
More than 2 alleles control a trait in a population
4 alleles for a single gene in Rabbit color
Each rabbit only has 2 of the 4
SEX DETERMINATION
Human = 23n
46 = 2n
22 pairs of matching homologous chromosomes called = Autosomes
Look exactly alike
23rd pair differs in Male and Female = Sex Chromosomes
Female = XX (1 kind of Gamete)
Male = XY (2 kinds of Gametes)
A punnett square shows a 50/50% chance of either sex
ENVIRONMENTAL INFLUENCES
When you solve puzzle of dominant and recessive and understand other patterns of
heredity = still not complete
As organisms develop, many factors can influence how the gene is expressed
Internal Environment
-
Age or Gender can affect gene function
Color of feathers in birds = male breeding plumage
Horns on Buck deer
Controlled by different hormones
These hormones are controlled by different sets of genes
External Environment
-
Temperature, nutrition, light, chemical and infectious agents influence gene
expression
Temp has affect of color in Rabbit coats
Bacteria color Fig 14.9
Light affects leaf size and shape
APPLIED GENETICS
DETERMINING GENOTYPES
Recessive traits = Homozygous recessive
Same phenotype = TT, Tt
Testcross = cross individual unknown genotype with an individual of known genotype
Test organism = usually homozygous recessive for trait
SELECTIVE BREEDING
Selective Breeding = breed domesticated animals and plants for desired traits
Cattle, Fruit, Vegetables
“True Breed”
Don’t want a heterozygous if it is a weak gene
Pedigree = graphic representation of an individual’s family tree (patterns of inheritance)
Poor hips in a Lab = don’t breed
TT x TT
tt
x tt
Hybid = cross two types of fish
- one might be disease resistant
- Bass = Florida stain is bigger
Cattle not resistant to heat but good meat
Cross with cattle resistant = Hybrid
Takes a while to get a “pure bred” hybrid