Factor - A factor is a gene. Organisms have 2 genes for every trait they show. Allele – An allele is a version or form of a gene (dominant vs. recessive) If an organism’s two genes are the same, it is homozygous for that trait: Ex: RR or rr If your two genes are the different, it is heterozygous for that trait: Ex: Rr

The two alleles you actually have in your DNA is your genotype. Ex: RR, Rr and rr are possible genotypes The way your alleles are shown on the outside, or expressed, is known as your phenotype. Ex: rolling or not be able to roll is a phenotype.

The Law of Dominance States that some alleles are dominant and some alleles are recessive. A dominant allele will be expressed (show up) in the phenotype if it is present in the genotype. A recessive allele will be expressed only if no dominant allele is present. Mendel’s law of segregation states that alleles will separate when gametes (sex cells) are formed, and they will go to different sex cells.

Mendel’s Experiments…continued…. Independent Assortment

Mendel’s Experiments…continued…. Independent Assortment Mendel wanted to determine if certain traits were passed along together (linked). Ex: Do yellow and round pea traits get passed along together to offspring? Do green and wrinkled traits get passed along together?

The experiment:Y=Yellow R = Round y = green r = wrinkled

The experiment:Y=Yellow R = Round y = green r = wrinkled Parents:true breeding for both traits YYRR x yyrr

The experiment:Y=Yellow R = Round y = green r = wrinkled Parents:true breeding for both traits YYRR x yyrr Poss.YR, YRyr, yr Gam.

The experiment:Y=Yellow R = Round y = green r = wrinkled Parents:true breeding for both traits YYRR x yyrr Poss.YR, YRyr, yr Gam. F1

The experiment:Y=Yellow R = Round y = green r = wrinkled Parents:true breeding for both traits YYRR x yyrr Poss.YR, YRyr, yr Gam. F1YR YR yrYyRr YyRrPhenotype ratio: yr YyRr YyRr

Did this tell Mendel whether or not traits Are passed along together or linked? No

Mendel crossed the F1 individuals: YyRr x YrRr

Mendel crossed the F1 individuals: YyRr x YrRr Poss. Gam.

Mendel crossed the F1 individuals: YyRr x YyRr Poss. YR, Yr, yR, yrYR, Yr, yR, yr Gam.

Phenotype ratio: Period 3 Bio – Wait until tomorrow for Phenotype ratios.

Did this tell Mendel wether or not traits Are passed along together or linked?

Mendel found that traits were NOT linked and alleles assort independent of one another during gamete formation: the Law of Independent Assortment What might be an exception to this law?

An exception to this would be when genes are found on the same chromosome.

Carnations: Incomplete Dominance

Snapdragon: Incomplete Dominance

Roan Cattle : Codominance (RW)

Sickle cell anemia: Codominant

clumps with: anti-A anti-B anti-A none anti-B

Genes, Chromosomes, and Heredity

In 1902, it was discovered that Mendel’s genes were found on chromosomes.

Genes, Chromosomes, and Heredity In 1902, it was discovered that Mendel’s genes were found on chromosomes. Chromosomes can be viewed in their homologous pairs by photographing them and organizing them into a picture known as a karyotype.

A normal human karyotype

Humans have 46 chromosomes in 23 pairs. The fist 22 pairs are called autosomes. The last pair are called sex chromosomes: XX = female (chromosomes are homologous) XY = male because a Y is present. (they are nonhomologous)

Sex linkage – A gene is said to be sex- linked when it is located on the sex chromosomes. These are most commonly on the X chromosome.

Sex linked traits are more commonly found in males than in females. Why??? Look at some examples

Hemophilia – Normal is dominant Normal genotype: MaleFemale Hemophilia genotype: MaleFemale

Fruit fly eye color – Red is dominant over white Red genotype: MaleFemale White genotype: MaleFemale

Draw identical twins here

Himalayan rabbitSiamese Cat

The environment can affect the way your genes are expressed. This means that the phenotype is affected.

End Result: Different polypeptide or protein chains can be made from different amino acid sequences. These proteins will have different functions! Chromosomal Mutations

Diseases associated with chromosomal mutations: - Downs Syndrome - Kleinfelters disease - Turner’s Syndrome

MUTATIONS IN THE DNA Types of mutations: Frame Shift - when either insertion or deletion of one or two nucleotide bases. When this occurs, the “reading frame” is changed so that all the codons read after the mutation are incorrect.

Disorders that result from DNA mutations: Sickle Cell Anemia PKU Cystic Fibrosis