Genetics Notes. What is heredity? A. Traits passing from offspring to parents B. Traits passing from...

Genetics Notes

What is heredity?

A. Traits passing from offspring to parents

B. Traits passing from parents to offspring

C. Plants that are cross-pollinatedD. The ratio of dominant to recessive

traits

Heredity is

“C” - The passing of traits from parent to offspring

Who was Gregor Mendel?

Austrian Monk Conducted his research in a

monastery garden Worked with pea plants Discovered the principles of heredity

Self-pollinating Peas

Self-pollinating – when a plant fertilizes itself Results in a true-bred plant All the offspring of a true-bred plant will have

the same trait as the parent

Parent

Offspring

Cross-pollinating Peas

When one plant fertilizes a different plant

Pollen from one plant lands on the pistil and fertilizes the ovule (egg) of a different flower on a different plant

• Wind• Bees & other insects

First Generation Plants

First Generation Plants Self -Pollinated

X

F2 Second Generation

The white flowers reappeared! How did this happen?

Alleles: *different forms of a gene *exist in pairs (one from mom & one from dad)

Dominant allele– the prevailing (stronger) traitCapital Letter

Recessive allele– the (weak) hidden traitLower case letter

Genotype – the combination of alleles you have for a specific trait

• Ex: RR or Rr or rr

Phenotype – the physical feature you show or see

• Ex: Red flower petals, white flower petals

Example:

Gene: Flower Petal Color Alleles:

• Red (R)• White (r)

RR = homozygous dominantrr = homozygous recessiveRr = heterozygous

Homo – the same Hetero - different

Complete Dominance Rr = Red• dominant trait shows

Co Dominance RW = Red & White• Both traits show

Incomplete Dominance Rr = Pink• Traits are blended (mixed)

First Generation Plants Self -Pollinated

X

F2 Second Generation

The white flowers reappeared! HOW?

The parents were heterozygous (Rr).

RrRr

RRRr

Rr rr

Mendel’s Discoveries:

Each trait has two sets of instructions (alleles), one from each parent

Discovered dominant and recessive traits.

Intro. to Punnett Squares

A chart used to show all the ways genes from two parents can combine and be passed to offspring.