Lesson 5 - Mendelian Genetics

Question 1

What is Genetics?

Answer 1

The explanation of the transmission of character traits is the basis of the branch of science called;

Genetics → the study of heredity

The idea that biological traits are inherited existed long before the mechanisms of inheritance and gene interactions were understood

Question 2

Who is Gregor Mendel

Answer 2

The Pioneer of Genetics (1822-1884)

Austrian monk

Believed to be the first to scientifically attempt to explain inheritance

Worked extensively with garden pea plants… WHY?
- Reproduce quickly
- Cheap
- Sexually reproducing → pollination
- Traits are expressed in 2 ways

Question 3

The Science OF MENDEL’S
EXPERIMENTS

Answer 3

Pea plants can be reproduced by:
- self-fertilization and
- cross-fertilization.

Purebred seeds always give rise to phenotypes that resemble the parent plant (ex, Seeds from tall plants only produce tall plants)

Question 4

Mendel’s Hypothesis and Conclusion

Answer 4

Hypothesized that the crossing of plants with different traits would create a blend

For example, crossing a purebred wrinkled-seeded plant with a purebred round-seeded plant would produce a slightly wrinkled-seeded pea plant

However, Mendel disproved his initial thoughts. His experiments resulted in all round seeded plants

He then repeated this experiment for the other traits and found the same

He concluded that:

For each trait, an individual carries two genes, one from male parent, one from female parent.

The dominant gene can “mask over” the recessive gene when both of them exist.

He also concluded that there were alternative forms of a gene (alleles) where the one that appeared the most often was dominant and the ones that occur less frequent was recessive.

round seed = dominant (upper case) R

wrinkled seed = recessive (lower case) r

Question 5

Mendel’s Generational Names

Answer 5

P generation: parents that are donating the
gametes

F1 generation: first generation of offspring produced from parents

F2 generation: second generation of offspring produced from F1 generation

P generation – crossing purebred of round
seed plant with purebred of wrinkled seed plant

F1 generation – all round seeds

F2 generation – cross 2 round seeds from F1 generation and results in ¾ round and ¼ wrinkled seeds

Question 6

MENDEL’S LAW OF
SEGREGATION

Answer 6

Members of a pair of alleles for a given trait are separated when gametes are formed (meiosis)

A Punnett Square is used to predict the genotype and phenotype of the next generation.