GENETICS Genetics (heredity) is the study of how inborn characteristics (traits) are passed from parents to children. Gregor Mendel: 19 th century monk who studied how traits in pea plants are inherited. He made many observations.

1.Pea plants of the same species had some traits with either of two appearances: round or wrinkled peas yellow or green peas smooth or bumpy pods green or yellow pods

2.Pea plants can be pure bred. This means the offspring are genetically identical to the parents. 3.Pea plants reproduce sexually

What Mendel did: He used the pollen from a plant with green pods to pollinate a plant with yellow pods (he forced sexual reproduction), collected the seeds, and planted them. Green pods are male, yellow pods are female

So What Happened??? The plants that resulted ALWAYS had green pods. He reversed the mating: the yellow pods were male, the green pods were female. RESULT: All the offspring had green pods.

MENDEL’S CONCLUSION genes 1.Traits in living things are caused by things in the cell called genes. We now know that genes are specific pieces of DNA on a chromosome. alleles. 2.Many genes exist in two alternate forms called alleles. Alleles are two different forms of the same gene.

dominant recessive 3.When a gene has different alleles in the same organism, only one allele is expressed. The gene that is expressed is the dominant allele and the one not expressed is the recessive allele. For pea plants, green pods were made by the dominant allele, and yellow pods were made by the recessive allele.

Why two alleles? Why not one? Or three? Or 46? One allele comes from the father, one from the mother. Back to the peas: The male plant had two dominant alleles GG The female had two recessive alleles gg

What happened when Mendel crossed two of the green offspring? Mother:Gg Father:Gg Each parent produces two types of gametes: G and g.

Result: Out of 100 offspring, 75 had green pods, 25 had yellow pods. Why? G g X G g father mother Produce the following: GG green Gg green gG green gg yellow

GG:homozygous dominant: Both parents contribute the dominant allele. The plant has green pods. gg:homozygous recessive: Both parents contribute the recessive allele. The plant has yellow pods. Gg:heterozygous: One parent contributes the dominant allele, one parent, the recessive allele. The plant has green pods.

In genetics, there are certain terms that relate to mating: P generation: The original mating of purebred parents. F 1 generation:Offspring from mating the P generation. F 2 generation:Offspring of the F 1 generation.

Genotype: the alleles in an individual (GG, Gg, gg, heterozygous, etc) Phenotype:the appearance of an individual based on genotype.

The Monohybrid Cross In humans, sickle cell anemia is caused by a recessive allele in blood (h). The dominant allele is for normal blood proteins (H). Phenotypes:normal blood cells sickle cells

Genotypes:HH is normal blood Hh is normal blood hh is sickle cells

If a man who is homozygous recessive has a child with a homozygous dominant woman 1)What are the phenotypes and genotypes of the F 1 generation? 2) If a member of the F 1 generation has children with a partner with sickle cell anemia, what would the phenotypes and genotypes of their children?

P generation: h Male: produces only h sperm (he has sickle cell anemia) H Female:produces only H eggs

The results of this cross can be shown using a Punnet Square: HH x hh HH hHh h

Genotypes of all offspring: All Hh (heterozygous) Phenotypes of all offspring: All normal blood.