DNA is our genetic “code”.

Our code is located on our chromosomes inside the nucleus of our cells.

One chromosome is made up of many genes.

One gene has information for one trait.

http://www.thetech.org/genetics/zoomIn/index.html

HOW DO SCIENTISTS KNOW WHAT OUR CHROMOSOMES LOOK LIKE? Karyotype – when we organize our

chromosome in pairs and organize them from biggest to smallest. The last pair are the sex chromosomes (determine sex). The sex chromosomes are not organized by size.

WHICH SEX IS THIS PERSON?

INHERITANCE Sex-linked genes – Carried on the X or Y (sex

chromosomes) chromosome (usually the X), most are recessive and usually seen only in males (ex: balding).

X- X- X-Y B b b

Female Male

B - normal hair

(with hair) (bald)

b – bald

MENDEL AND HEREDITY

Gregor Mendel

ORIGIN OF GENETICS Heredity – Passing traits from parents to

offspring. Genetics –The branch of biology that focuses

on heredity. Monohybrid Cross – a cross that involves only

one pair of contrasting traits. True-breeding – all of the offspring of a cross

will display only one form.

GREGOR MENDEL• An Austrian monk who carried out experiments

with pea plants to formulate theories on heredity.• He was the first to establish rules that predict

patterns of heredity.• Mendel crossed varieties of garden peas with

contrasting traits, counted the number of each kind of offspring and collected data.

Cross means the breeding of 2 individuals

MENDEL'S EXPERIMENTS Mendel preformed monohybrid crosses

using pea plants.

P generation

On1 of the 2 colors is in the F1 generation (dominant form). The other (recessively) will reappear in the F2 generation (in a 3:1 ratio).

WHAT MENDEL STUDIED

Alleles – the different versions of a gene, each is inherited from one parent. (so there are 2 alleles for each gene). There can be dominant or recessive alleles.

Homozygous – when 2 alleles in an individual are the same.

Heterozygous – when the 2 alleles in an individual are different.

Genotype – the set of alleles organism has

Phenotype – physical appearance of a character

STUDYING HEREDITY Punnett square – used to predict the outcome

of a genetic cross.

The two colors of flower (purple and white) -

Alleles

Both parents have 2 different alleles – (Bb)

Heterozygous

MONOHYBRID CROSSES Monohybrids are

when we use Punnett Squares to compare only one trait.

Ratios

DIHYBRID CROSSES Can You Guess

what these are?Two traits at a

time Ratios

INCOMPLETE DOMINANCE The traits will

blend together. This is because once trait cannot mask (cover) the other trait.

CODOMINANCE Each allele is

shown to it’s fullest abilities

MENDEL'S THEORIES Law of Segregation – two alleles for a

gene will separate when gametes are formed. (you get one from each parent)Meiosis

It’s like mitosis but it happens twice. When the cells undergo PMAT for the second time they never have as S phase where the chromosomes are copied. In the end, the two cells (gametes) have only half the number of organisms.

Remember it’s here where nondisjunction and chromosomal mutations occur.

MEIOSIS

MENDEL’S THEORIES Law of Independent Assortment – two or

more pairs of alleles will separate independently of one another during gamete formation. For example a cat with brown hair will not always have long hairTraits are given independently

Hair Eye Color Height

POPULATION GENETICS Genetic variation

within a population

Caused by mutations

Anything that changes the gene pool results in evolution.

HARDY-WEINBERG PRINCIPLE The frequency of

an allele in a stable population will not vary.

P+Q=1 orP+PQ+Q=1

Genotypes will tend to remain the same

Used to determine recessive alleles

Used to see natural selection.

HARDY-WEINBERG A randomly mating population must be free

from mutations, migrations and natural selection

Frequencies of alleles will not change over time

And populations match the equationP+PQ+Q=1Remember mutations are a good thing too or

else we wouldn’t walk on two legs. It drives evolution.

Certain genes are more prevalent in a population than others (because they are more helpful for the survival of an organism) can’t survive - can’t reproduce