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) *Is inherited from parents ( ½ mom + ½ dad) and creates variation*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 TG always binds with C

B. Genes A small section of the DNA spiral Each gene creates a protein which produces

our traitsEx. 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) Grow2) Create cells for reproduction

Two types of cell division are:1)Mitosis2)Meiosis

A. 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) Black b) White c) Purebred d) 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