BIOL 2500 - Topic 3 (part 2)

Who is Gregor Mendel

The father of genetics, born in the Czech republic

Story of Gregor Mendel

1.) He initially studied chemistry, but failed all his first year classes, then turned to priesthood

2.) They wanted him to teach, so they sent him back for a degree at the university of Vienna, where he studied plant physiology and plant biology

What did Gregor Mendel teach

Natural sciences at a middle school in the local town

What specific plant did Gregor Mendel study

Peas, which have dichotomous traits (i.e. all of its traits only have two forms)

What did Mendel’s research on peas show?

That inheritance was particulate and not blended.

Importance of Mendel’s experiments

It opened up the field of genetics

Mendel’s experiment (method)

He followed the standard scientific method:

Observation —> Hypothesis —> Quantitative test

Initial thoughts on Mendel’s experiment

People thought that it was too good to be true and that he faked it

Why did people think Mendel faked his experiments

He kept getting the same results over and over again

Why made Mendel’s experiments so effective

Everything was well thought out, with replicates and deliberate testable hypotheses, as well as multiple tests to confirm the results

What did Mendel do to confirm his results

1.) Controlled crosses

2.) Used pure-breeding strains, with dichotomous traits

3.) Quantified results

4.) Used replicates

5.) Did reciprocal crosses and test-crosses

Why did Mendel use peas?

1.) They have flowers that have both male and female structures (i.e. it is bisexual)

2.) It can self-fertilize

3.) But you can also do artificial cross-fertilization

4.) It has short life cycles

Artificial cross-fertlization

You can manually fertilize pea plants by removing the male anthers

Which characters did Mendel look at

1.) Round or wrinkled

2.) Seed colour

3.) Petal colour

4.) Ripe pods shape

5.) Unripe pods colour

6.) Flower position

7.) Stem length

Mendel starting lines

He used pure lines for each trait that he examined (aka true-breeding)

Pure lines

The genotype of the individual is homozygous

Mendel performing crosses

He performed crosses to produce various generations of plants

1.) The parental generation (P)

2.) First filial generation (F1)

3.) Second filial generation (F2)

Parental generation

1.) Cross pure-breeding parents with each other, with each parent having an alternative form of the trait

2.) The resulting progeny is the F1 generation

F1 generation

1.) The progeny produced from the parental cross

2.) They are then self-fertilized or crossed to produce the F2 generation

F2 generation

The progeny producing from the crossing of F1

What did Mendel do for the F1 and F2 that he did not do with the P generation

He measured the phenotypes of the resulting offspring, using multiple replicates