Genetics!

Heredity is the passing of traits from parent to offspring.

These traits are controlled by genes.

Traits are observable characteristics we inherit from our parents

Genes are found on chromosomes. They are sections of the DNA.

When pairs of chromosomes separate into sex cells during meiosis, pairs of genes also separate from one another.

As a result, each sex cell ends up with one form of a gene for each trait that an organism shows.

The different forms a gene may have for a trait are its alleles.

Example: straight or widow’s peak are the alleles for hairline.

Gregor Mendel (1822-1884). Mendel is considered the father of genetics..

Mendel conducted the first studies on how traits pass from one generation to the next.

He worked with pea plants

Mendel’s Experiments:

Mendel chose to experiment with peas because they possessed four important qualities:

1.Peas are true-breeding (all offspring will have the same

characteristic generation after generation).

2. (purple vs. white flowers; round vs. wrinkled seeds).

3. Peas reproduce by self-pollination, in which pollen produced

by a flower fertilizes eggs in the same flower.

4. Pea plants grow quickly and do not require much space.

There are 7 Different Traits to Consider With Peas:

1.Pea shape (round or wrinkled)

2.Pea color (green or yellow)

3.Pod shape (constricted or inflated)

4.Pod color (green or yellow)

5.Flower color (purple or white)

6.Plant size (tall or dwarf)

7.Position of flowers (axial or terminal)

The dominant allele is the form of a trait that appears to dominate or mask another form of the same trait.

The recessive allele is the form of the trait that seems to disappear in a population but can reappear depending on the way the alleles combine.

An organism that always produces the same traits in its offspring is called a purebred. (purebred tall, purebred short)

Probability is a form of mathematics that helps predict the chance that something will happen.

Mendel’s experiment utilized this.

To predict what the offspring will look like without actually making the cross, scientists use Punnett squares.

1)Capital letter stands for a dominant allele

2)Lower case letter stands for recessive allele

Every trait has two alleles- this is the genotype!

Ex) TT Tt tT tt(homozygous) (heterozygous) (heterozygous) (homozygous)

The physical trait that shows as a result of a particular genotype is its phenotype.

In a Punnett Square, the letters representing the two alleles from one parent are written along the top and those of the second parent on the side.

Each section of the square is filled in like a multiplication problem with one allele donated from each parent.

The letters that fill in each inside square represent the POSSIBLE genotypes of offspring those parents could produce.

T = Tall pea plantt = Short pea plant