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• Can 2 dwarfs have a tall child?• Why are more boys color blind than girls?• Does having blonde hair mean getting blue

eyes too?• If someone is bald what’s the chance their

children will go bald too?• If a couple has 5 girls, what’s the chance

the next child will be a boy? Inquiring Minds Want to KNOW!!

Mendel’s experiments showed that the inheritance of traits is predictable

Gregor Mendel was an Austrian monk who wore many hats –

Chief monk High school science teacher Monastery’s vegetable gardener

While working in his garden, Mendel noted that the pea plants had a 7 traits that only came in two forms

Mendel’s purpose in carrying out 1000’s of experiments on pea plants to study the process of heredity – the passing down of traits from parents to offspring.

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Pea plants reproduce sexually which involves ??? Parents Flowers contain both male and female

reproductive organs Stamen – Male Pistil – Female Makes Pollen/Sperm Makes Eggs

Mendel developed a method to cross-pollinate or “cross” two plants with different forms of the same trait.

He started with purebred plants. Purebred plants produce plants that look identical to the parent plant.

He called the Parent generation the “P generation” for short.

When Mendel crossed pure-bred tall plants with purebred short plants. ..

All of offspring were Tall!

100% Tall : 0% Short

The offspring generation are called “F generations.”

The “F” stands for filial –Latin for “child”

Each successive generation of offspring are noted by a little number after the letter “F” (F1).

The second generation (from mating the F1’s together) form the F2 generation.

When the plants in the F1 generation were full grown, Mendel allowed them to self-pollinate which formed seeds he then planted.

The F2 generation plants that grew from the seeds were, surprisingly, a mix of tall and short plants!

The shortness trait had reappeared after skipping a generation!

Approx. 3/4 (75% ) were tall

The remaining 1/4 (25% ) of the plants were short.

• Mendel observed patterns in the first and second generations of his crosses.

6.3 Mendel and Heredity

• Mendel observed patterns in the first and second generations of his crosses.

Mendel reached several conclusions on the basis of his experimental results.

Heredity is predictable and not caused by chance alone.

Heredity is controlled by 3 principles

1. Law of Segregation Organisms inherit one of each gene, from each parent During sex cell formation, the 2 genes get separated into different sex cellsToday we know that what Mendel hypothesized actually occurs when chromosomes separate in anaphase I and 2 of meiosis.

2. Dominant gene forms can “mask” or “hide” the expression of recessive forms of the same gene.

3. Law of Independent Assortment•Each trait is controlled by separate genes which are passed from parents to offspring independently of one another.•Ex. Just because a person inherits red hair doesn’t automatically mean they’ll have freckles too.

Though his work was unrecognized during his lifetime, today he’s known as ”The Father of Genetics” for developing the Laws of Inheritance Genetics is the scientific study of heredity - the

process of passing down genetic information

Mendel’s experiments showed that the inheritance of traits from parents to offspring was _____________________.

Why is this finding so important – what are its implications?

When you have two genes that are different (not purebred) then you are called a Hybrid!› Name another thing you think about when

you hear the word “Hybrid.” What does it mean in your example?

Geneticists use letters to represent alleles.

A Dominant allele is ALWAYS represented with a capital letter!› Tall plants = T

A recessive allele is ALWAYS represented by a lowercase version of THE SAME LETTER OF THE DOMINANT ALLELE!› Short plants = t

This way, you always know that the “T’s” go together!

When a plant inherits two Dominant alleles for tall stems, its alleles are written as TT.

When a plant inherits two recessive alleles for short stems, its alleles are written as tt.

When a plant inherits one allele for tall stems and one allele for short stems, its alleles are written as Tt.

An organism’s traits are controlled by the alleles it inherits from its parents.

Some alleles are Dominant, while other alleles are recessive.

A Dominant allele is one whose trait is ALWAYS “expressed “ or seen

A Recessive allele is “masked” or hidden by a dominant trait. It is only expressed when no dominant allele is inherited too.

Unfortunately, the importance of Mendel’s discovery was not recognized during his lifetime.

Then, in 1900, three different scientists rediscovered Mendel’s work.

These scientists quickly recognized the importance of Mendel’s ideas.

Because of his work, Mendel is often called the Father of Genetics.

Today, we use the word “Gene” instead of “factor.”

Alleles are the different forms of the same Gene.

Gene – Determines trait ex.Plant height Alleles – Determine the FORM of the

trait• ex. Tall or

Short