A. DNA (deoxyribonucleic acid)  A set of “blueprints” for the organism  Every cell in the body has the exact same DNA copies (except gametes – ½ the amount) *Is inherited from parents ( ½ mom + ½ dad) and creates variation*

A. DNA  Double helix shape (spiral ladder) which was found by Watson and Crick  Each ladder rung is made from 4 bases: ◦ Adenine (A) ◦ Guanine (G) ◦ Thiamine (T) ◦ Cytosine (C  The order that the bases are arranged is called our genetic code

A always binds with T G always binds with C

B. Genes  A small section of the DNA spiral  Each gene creates a protein which produces our traits Ex. Eye color Pigment gene – have pigment (green or brown) or not (blue eyes)  Genes are arranged in pairs; each gene is on a different chromosome ◦ There are two genes for eye color

B. Genes  One gene is given by the mother; the other given by the father  Alleles are variations of the gene ◦ Ex. Alleles of eye color are brown, blue, green ◦ Draw!

C. Chromosomes  The packages of compressed DNA  There are 2 copies of each chromosome in a body cell.  Human body cells = 46 chromosomes (2 copies)  Human gametes = 23 chromosomes (1 copy)

 Predict how many chromosomes a dog has:  How many a cat has?  Is it linked to how dominant the species is?

 Males have 1 X and 1 Y chromosome  Females have 2 X chromosomes

 Two reasons cells divide are to: 1)Grow 2)Create cells for reproduction Two types of cell division are: 1) Mitosis 2) Meiosis

A. MitosisA. Mitosis (hyper) -is when a cell creates 2 copies of its DNA so it can equally split into two identical cells Ex. Binary fission – a bacteria makes double its DNA then splits to create 2 bacteria, each with a full set of DNA  Used when species grow and during asexual reproduction

B. Meiosis  Is when a cell divides to create new cells with ½ the DNA of the original cell  Used to create gametes (sperm/egg) in sexual reproduction  Four cells are created in total

 Purebred (true breeding) – those organisms with the exact same traits as their ancestors Ex. Offspring of 2 labs  Hybrids – offspring made by mating organisms with different traits Ex. Offspring of a pug with a beagle

Hybrid Purebred

 Allele  Genotype: the letters representing the gene of an organism ◦ Ex. TT or tt or Tt  Phenotype – the appearance of an organism because of its genes ◦ Ex. TT – black fur  tt – white fur

A. Dominance  Dominant Trait- the variation of a trait which requires only 1 copy to appear ◦ Represented by capital letters  Recessive Trait – the variation of a trait which requires 2 copies to appear ◦ Represented by lowercase letters *Remember : A combination of 2 genes creates a trait*

 Punnett Squares ◦ A tool used to study the outcome of crossing two sets of genes ◦ One parent’s genes go along top; one along left side See handout worksheet

Ex. 1: Purebred black cat x Purebred white cat  Genotypes of the black parent: White parent:  What are the phenotypes of the offspring?  What are the genotypes of the offspring?  How many offspring are:  A) Blackb) White  c) Purebredd) Hybrids 

Ex. 2: Black hybrid x White purebred cat

B. Incomplete Dominance  When neither allele is dominant; they trait is a mixture of each allele Ex. White snapdragon x Red snapdragon

 Some traits are controlled by more than 1 gene ◦ Ex. Eye color, hair color, skin color  Some traits are effected by the environment ◦ Thalidomide babies