Inheritance – characteristics are passed through generations by genetic material (traits) Gregor Mendel - discovered the pattern of inheritance by studying pea plants. How are characteristics passed down through generations? How Do We Know?

The Principle of Segregation 1) Inherited traits are determined by distinct units named genes 2) Each gene carries two factors, one inherited from each parent (alleles) 3) The two alleles separate from each other and end up in gametes during meiosis. What did Mendel discover?

NUCLEUS CHROMOSOMES GENES ALLELES SMALLEST size DNA Largest Size Contains Interaction between two Made of

In each of our cells (except or gametes) we have 23 pairs of chromosomes One member of the chromosome pair comes from our father, the other from our mother. Largest Structure: Karotype

Genes are regions of DNA within the chromosome pair that code for a particular trait. Each gene is made up of two factors, one from each chromosome pair. These factors are called alleles How are genes arranged on chromosomes?

The two alleles that make up each gene may be the same or different. If the alleles are the same they are called homozygous If the alleles are different they are called heterozygous Are an individual's alleles the same? heterozygous homozygous

Each trait is determined by the interaction between the two alleles of a gene and several interactions are possible. The genetic make up of a trait= genotype The physical appearance of a trait= phenotype How do alleles determine the trait of an individual?

1.Complete Dominance – when one allele completely masks the other. Dominant Alleles – only one allele needed to express trait. Recessive Alleles – need two recessive alleles for trait to be expressed. Recessive trait : Sugary kernels are recessive Genotype= Phenotype= Dominant trait: Yellow kernels Genotype= Phenotype= Ex: Y = yellow y= sugary

2. Incomplete dominance When the alleles are blended and the offspring have a mix of their parent traits. ex. Snap Dragons R = red r = white Offspring can be pink!

3. Codominance – in this case both alleles are expressed. BB= black corn YY= yellow corn BY = black and yellow corn Heterozygous genotype

Genotype codes for phenotype

GENOTYPE - the two letters that represent the alleles of a gene EX. RR, Rr, rr Phenotype - the outward appearance of an organism (what it looks like) Ex. If a farmer has a red flower (RR) - the genotype is RR - the phenotype is red

1. A brown dog (bb) the genotype ________ the phenotype _______ 2. A long haired cat (Hh) the genotype _______ the phenotype _______ bb brown Hh Long haired

3. A spotted owl (SS) the genotype _____ the phenotype _____ SS spotted

(Review) Remember The Principle of Segregation? Mendel learned that the alleles of each individual seperate and end up in gametes (meiosis)

Ex. A female pure brown dog (bb) b b bb

PRACTICE 1. A hybrid male yellow canary (Yy) Yy

2. A pure female white flower (rr) rr

If a male red flower (Rr) and a pure white flower from above got their gametes together (fertilization ) what kind of combinations could be formed? X

Male red flower (Rr)Female white flower Rr Sperm 1Sperm 2 rr Egg 1Egg 2

= = = = GenotypePhenotype