Mendelian Genetics Flashcards
Gregor Mendel
“The father of Modern Genetics”
–> Started out as a monk growing peas
–> In 1865, he published a paper that reported on his pea plant experiments that suggested a model for how traits are inherited
Mendel was the first to…
Deduce clear laws that explained the process and patterns of inheritance (through experimental observations and mathematics)
2 major hypotheses existed for inheritance of traits:
1) The “Blending” Hypothesis
2) Inheritance of Acquired Characters Hypothesis
Blending Hypothesis
Genetic material contributed by BOTH parents MIX together (blend)
Ex: Black + White Sheep = Grey Sheep
Inheritance of Acquired Characters Hypothesis
Experience Dependent Inheritance
–> An organism passes on traits that the parent acquired through use/disuse in its lifetime
EX: The passing down of long necks in giraffes due to parents stretching to reach high hanging fruit
Benefits of the pea plant model (5)
1) Easy + Inexpensive to cultivate
2) Reproduce Quickly (short generation time)
3) Lots of variety in pea plants that are easily distinguishable
4) Pea physiology lends itself to genetic analyses
5) Each plant could be easily mated and this mating could be well controlled (allowing for certainty of parentage)
Character
A heritable feature that varies among individuals
Ex: Flower Color
Trait
Each variant of a character
Ex: Red or White (flower color)
7 Characters Observed by Mendel
1) Seed Color
2) Seed Shape
3) Pod Color
4) Flower Color
5) Flower Position
6) Stem Length
7) ?? Didn’t write it down
Each character Mendel studied had…
2 distinct forms/variants
How did Mendel begin his experiments?
True Breeding Lines
True Breeding Lines
Plants whose offspring resembles the parent over many generations
How are true breeding lines obtained?
Self-Pollination
Pea plants make both…
Male and female gametes
Anther
The plant part where pollen (male gamete) is kept
Pollen
Male plant gamete
Self-Fertilization
Pollen from within the same plant enters its own stigma
What was a commonality between the true breeding plants Mendel created?
All the true breeding plants he made were HOMOZYGOUS for the give trait that he was isolating/studying
Cross Pollination Process
1) Took one pea plant and cut its anthers (removed the male gamete parts –> Preventing self-pollination)
2) Collected some pollen from the other plant in the cross onto a brush
3) Brushed this pollen onto the plant that had its anthers cut to initiate fertilization
4) Waited for the seeds in the plant to mature and then planted the seeds to grow the crossed plants and assess their phenotypes
Hybridization
The mating or crossing of 2 true-breeding varieties
–> Producing a hybrid (mixed variety) AKA heterozygote
Mendel’s First Experiment (cross)
Cross pollinated true breeding lines with different traits for the same character
–> Produced the F1 generation of plants
P Generation
Parental Generation (True breeding parents)
F1 Generation
First Generation derived from P generation
–> The hybrid offspring of the true breeding P-generation
Results of Mendel’s First Experiment (flower color trait)
Crossed true breeding pea plants with purple flower to plants with white flowers
Result –> All offspring had purple flowers (white trait “disappeared”)
Mendel’s Second Experiment (cross)
Cross pollinated and allowed for self pollinated of plants in the F1 generation
–> Produced the F2 generation
F2 Generation
2nd generation derived from P-generation
–> Made through crossing F1 plants
