Genetics Honors bio

Genetics

branch of biology that is concerned with how characteristics are transmitted from parents to offspring

Heredity

passing on of a characteristic from parents to their offspring

traits

consist of two genes

1 from each parent

gene

segment of DNA that codes for a trait

Allele

a single gene

Gregor Mendel

used pea plants

they're able to self pollinate and cross pollinate

reproduce very quickly

can study several generations in a short period of time

They had 7 contrasting traits

1. pea textures ( smoothed or winkled)

2. Flower color (purple or white)

3. Color of pod (green or yellow)

4. Pea height (height of plant )(tall or short)

5.Pea color (Green or Yellow)

6. Pod Texture (inflated or Constricted)

7. Flower Position (axial or deminal)

very accessible to him

Mendel's Experiments

1. He grew plants that were pure for each trait by allowing them to self pollinate through several generations

2. He crossed a pure tall plant and a pure short plant

P1 generation

the original parents

The results

offspring's were all tall

Tall was dominant

All tall is P1 generation

F1 Generation

offspring of the P1 generation

3. Cross two plants from the F1 Generation

Results

offspring's were 3/4 tall, 1/4 short

Recessive gene have been hidden

F2 Generation

offspring of F1 Generation

Mendel called genes factors or units

Dominant gene

represented by a capital letter

Dominant trait

if the dominant gene is present, the dominant trait will show

Ex

RR or Rr

recessive gene

represented by a lowercase letter

Recessive trait

only expressed if two recessive genes are present

Ex

rr

Homozygous trait (purebred trait)

trait that contains two genes that are the same

Heterozygous trait (hybrid trait)

a trait that has two different genes

Phenotype

actual visible physical characteristics a genotype produces

ex

Brown hair, Blue eyes, Purple flowers, wrinkled pea, green pea

Genotype

the actual allele combination

Mendel's Laws

Law of Dominance

if the dominant gene is present, the dominant trait will show

ex

Bb

law of seggregation

during gamete formation gene pairs for every trait will separate

gamete

sex cells (egg in sperm)

law of independent assortment

during gamete formation genes for every trait will separate independently from one another

Probility

The chance will or will not happen

1. Percent

2. Fraction

3. Ratio

ex

chances of coin being heads

product rule

probability of more then one thing happening at the same time

Punnett square

used to determine the probability of possible genotypes and phenotypes of the offspring

Monohybrid cross

cross that involves one trait

Genotype ratio

Number of offspring with the same allele combination

Phenotype ratio

Number of offspring that look the same physically

Dihybrid cross

cross that involves two different traits