Lecture 16 Flashcards
Blending Inheritance
Widespread hypothetical model never formally presented to a scientific body
Proposed that inherited traits of offspring were determined randomly from a range bound by the traits found in the parents
Blending inheritance can’t be a thing bc why
Predicts that over time it would give rise to a genetically uniform population of individuals
It’s contradicted bc it doesn’t and won’t happen
Also fails to explain traits reappearing fully developed after skipping one or more generations
Gregor Mendel
1822-1884
Mendel study
Studied 7 “characters” (each determined by a separate gene) in pea plants
Each of these genes exhibited 2 contrasting alternatives that Mendel call “traits” we call them alleles now
Monohybrid experiment: pea flower colour gene
Pea flower gene had 2 color alleles (purple and white)
Allele
Contrasting alternative of a gene
Phenotypes
Physical characteristics
True breeding phenotypes
When u cross purple flower plant with purple flower plants
U always get purple
Monohybrid cross
Crosses if true bred purple flowered plants with true bred white flower plants are a Monohybrid cross
Achieved by cross pollination
Cross pollination in flowers
Remove anthers containing male pollen from first true bred pant
Remove anther from second true bred plant and discard
Use male pollen from the first plant to pollinate the female stigma of the second plant
Flowers of the second plants were then covered so no pollen from other plants in the area could enter the flower
Result of Mendel Monohybrid cross
All offspring had purple flowered plants phenotype
Not expected if blending was true (it’s not)
Since Mendel was hybridizing a single character allele. The offspring of the F1 generation were Monohybrids for this character
Dominant allele
Allele that took precedence in the F1 generation
Recessive allele
Allele that was latent or masked in the F1 generation
Reciprocal cross
Series of matings where the mother phenotype in the first cross is the father phenotype in the second cross
And
Fathers phenotype in 1st is mother phenotype in second
Reciprocal cross results
Results from mendels pea plant crosses indicated it didn’t matter which coloured plant provided the pollen. Result were the same F1 offspring (purple)
Genotype
Genetic makeup of a cell, an individual or gamete usually with reference to a specific character under consideration
Expression of the genotype contributes to the phenotype
Gene locus
Location of a gene in a chromosome is called the gene locus
Indicated by placing a line on the chromosome
GENOME
Organisms complete set of DNA which includes all its genes and all its noncoding DNA
How to calculate ratios
Divide everything by the smallest one
For example
3:2:4:3
1.5 : 1 : 2: 1.5
Mendel Drew several important conclusions
Individual pea plants have 2 alleles for each gene (each gamete only receives in allele for each gene)
Hereditary factors remained even if they weren’t expressed
Particulate inheritance
Alleles are unchanging units that can be passed from generation to generation
Mendels 1st law of inheritance
Independent law of segregation
Alleles of a gene segregate independently of each other during gamete formation
