Mendelian Genetics Assessment

Gregor Mendel

Austrian monk, father of genetics

Molecular Genetics

Study of DNA

Genetics

Study of how information is passed down

What did Gregor Mendel study?

Pea Plants

Why did Mendel think peas are a good organism to study genetics?

1. Fast Generation

2. Easy to obtain and cheap

3. Small/Take up little space

4. Have lots of offspring 

5. Very distinct/clear

6. Peas can reproduce sexually and asexually

What was the purpose of Mendel’s pea plant experiments?

To study how traits are inherited and discover inheritance patterns.

What are true-breeding plants?

Plants that always produce the same trait when self-pollinated (homozygous).

What is the P generation?

The original parental true-breeding plants in Mendel’s crosses.

What is the F1 generation?

The first offspring generation, produced by crossing P plants.

What is the F2 generation?

The offspring of F1 plants (from self-pollination or F1 × F1 cross).

In Mendel’s monohybrid cross, what ratio did he observe in the F2 generation?

About 3 dominant : 1 recessive phenotype.

Mendel’s Conclusion

1. Traits are inherited as distinct units (genes)/Traits are passed from parents to offspring as individual units (genes)

2. Organisms have 2 alleles for each gene that they inherit from their parent

3. Some factors/alleles are dominant over others (recessive)

4. Law of Segregation: During gamete function only 1 factor/allele for each gene will be carried in the sperm or egg

5. Law of Independent Assortment: Alleles for different genes will be inherited separately or independently

Gene

A unit of heredity that codes for a trait

Allele

An alternative form of a gene that determine how a trait is expressed, such as tall vs short

Genotype

The genetic makeup of an organism (the allele combination)

Phenotype

The observable physical traits of an organism, determined by genotype

Homozygous

When two alleles are the same for a given trait (ex: TT or tt)

Heterozygous

Two different alleles for a gene/trait

Gamete

A sex cell (sperm or egg) that carries only one set of chromosomes

Dominant Allele

The allele that is expressed when present, masking the other allele

Recessive Allele

The allele that is masked when the dominant allele is present

Punnet Square

A chart used to predict the probability of genetic outcomes in offspring

Law of Segregation

Principle stating that allele pairs separate during gamete formation, so each gamete carries only one allele

Law of Independent Assortment

Principle stating that genes for different traits separate independently during gamete formation (if genes are unlinked)

Hybrid

Another term for a heterozygous individual

Incomplete Dominance

When the heterozygous trait is mixed instead of either color. One allele is not completely dominant of the other.

Co Dominance

When both alleles are fully expressed in the offspring.

Ex: vitiligo

Multiple Alleles

When a gene has more than two allele forms in a population

Test Cross

Crossing a dominant phenotype with a homozygous recessive to find the genotype