1. Genetics & Inheritance

2. Something to Think About…
A cow has horns and a bull does not. Would their offspring be born with or without horns?

3. It all started with one man…

4. Gregor Mendel (1822 – 1884) One of the first to study genetics
Started his observations with pea plants
Color Variations
Smoothness/Roughness of Seed Coats
Length of Stems
Color of Flowers
Created pure-bred plants then crossbred
Crossed two plants in the P generation
Observed plants from first crossing- F1 generation
Observed plants from second crossing- F2 generation

5. Definitions Genetics - study of heredity
Heredity – passing of traits from one generation to another
Trait – distinguishing quality or characteristic
Genes- working subunits of DNA
Genome- all of an organisms genes; all of an organisms DNA
Cross- mating of two organisms

6. Mendel’s Laws Dominant factors make recessive traits disappear.
Each trait has two alleles; one from each parent.
There are two forms of a gene; dominant and recessive.
Dominant factors make recessive traits disappear.
Recessive traits will appear when there are two recessive alleles.
Chance determines which factor the offspring will inherit.

7. Dominant Traits Covers/hides the recessive trait.
Represented by a capital letter.
Example: Red flowers are dominant, R would be the allele for Red.
Rr would mean the dominant trait is visible.

8. Recessive Traits Hidden by the dominant trait.
Represented by a lowercase letter.
Example: Red flowers are dominant (R). White flowers are recessive (r).
For a recessive trait to show, the offspring must inherit two recessive alleles (rr).

9. Genotype Gene/allele combination for a trait (RR, Rr, rr)
Mendelian Genetics
5/15/2018
Genotype
Gene/allele combination for a trait (RR, Rr, rr)
Homozygous genotype - 2 dominant or 2 recessive genes (RR or rr); also called pure  or purebred
Homozygous dominant- RR
Homozygous recessive- rr
Heterozygous genotype - gene combination of 1 dominant & 1 recessive allele (Rr); also called hybrid

10. Phenotype The physical feature resulting from a genotype (red, white)
Mendelian Genetics
5/15/2018
Phenotype
The physical feature resulting from a genotype (red, white)

11. Genotype Produces Phenotype
Mendelian Genetics
5/15/2018
Genotype Produces Phenotype
Possible Alleles: R = red flower r = white flower
Possible Outcomes:
Genotypes RR Rr rr
Phenotypes RED RED WHITE

12. Co-Dominance
Sometimes an organism has heterozygous alleles and both show up.

13. So……..
A cow has horns and a bull does not. Would their offspring be born with or without horns?