INTRODUCTION TO GENETICS

INTRODUCTION TO GENETICS

Before we start, did you know….Before we start, did you know….

•Humans are 99.9% genetically identical – only 0.1% of our genetic make-up differs.

•Our genes are remarkably similar to those of other life forms. For example, we share 98% of our genes with chimpanzees, 90% with mice, 85% with zebra fish, 21% with worms, and 7% with a simple bacterium such as E. coli.

•Humans are 99.9% genetically identical – only 0.1% of our genetic make-up differs.

•Our genes are remarkably similar to those of other life forms. For example, we share 98% of our genes with chimpanzees, 90% with mice, 85% with zebra fish, 21% with worms, and 7% with a simple bacterium such as E. coli.

We share DNA…..with THEM?!We share DNA…..with THEM?!

Purpose of today’s class: Purpose of today’s class: • To understand how Mendel began the study of genetics.

• To understand how genes lead to physical characteristics.

• To understand how Mendel began the study of genetics.

• To understand how genes lead to physical characteristics.

Background to GeneticsBackground to Genetics

GREGOR MENDEL:- priest who tended to a garden at his monastery.

- Asked himself why different pea plants had different characteristics.

Ex. Color, height, seed

- THUS BEGAN GENETICS!

GREGOR MENDEL:- priest who tended to a garden at his monastery.

- Asked himself why different pea plants had different characteristics.

Ex. Color, height, seed

- THUS BEGAN GENETICS!

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Mendel’s ExperimentsMendel’s Experiments

• Mendel cross-pollinated two purebred pea plants:

=He took the pollen from one plant and used it to fertilize another plant, giving him control of fertilization.

• Mendel cross-pollinated two purebred pea plants:

=He took the pollen from one plant and used it to fertilize another plant, giving him control of fertilization.

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Crossing Pea PlantsCrossing Pea Plants

• By crossing two purebred pea plants, Mendel was able to study the heredity of certain traits.

Heredity= passing of physical characteristics from parent to offspring.

Trait= each form of a characteristic. For ex. Characteristic= seed color

Traits = yellow, green

• By crossing two purebred pea plants, Mendel was able to study the heredity of certain traits.

Heredity= passing of physical characteristics from parent to offspring.

Trait= each form of a characteristic. For ex. Characteristic= seed color

Traits = yellow, green

DIAGRAM of Mendel’s CrossDIAGRAM of Mendel’s Cross

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Parent Generation= P

= pink purebred crossed with white purebred.

1st Filial Generation= F1

= all pink flowers produced

??If parent generation had two separate traits (purple and white), why did the F1 generation have only ONE trait

(just purple)?

??If parent generation had two separate traits (purple and white), why did the F1 generation have only ONE trait

(just purple)?

What determines Physical Traits?What determines Physical Traits?

• GENE: determines/controls a physical trait.

• ALLELE= different forms of a gene. You get one allele of a gene from each parent.

• Physical traits are determined by the DOMINANT alleles= the allele that always shows up in an organism when present.

(If there is no dominant allele present, then the recessive allele is expressed.)

• GENE: determines/controls a physical trait.

• ALLELE= different forms of a gene. You get one allele of a gene from each parent.

• Physical traits are determined by the DOMINANT alleles= the allele that always shows up in an organism when present.

(If there is no dominant allele present, then the recessive allele is expressed.)

For Example, in Mendel’s Cross…For Example, in Mendel’s Cross…

Physical Characteristic= flower colorTrait= purple or whiteAlleles: purple= dominant because the F1

generation was all purple.

white= recessive because it was hidden in F1 generation (none were white).

Physical Characteristic= flower colorTrait= purple or whiteAlleles: purple= dominant because the F1

generation was all purple.

white= recessive because it was hidden in F1 generation (none were white).

Symbols for AllelesSymbols for Alleles

• Capital letters represent dominant alleles. (P= purple)

• Lowercase letters represent recessive alleles. (p= white)

*As long as one capital letter is present, the physical trait is the dominant allele.

*Same letter must be used for the same allele.

• Capital letters represent dominant alleles. (P= purple)

• Lowercase letters represent recessive alleles. (p= white)

*As long as one capital letter is present, the physical trait is the dominant allele.

*Same letter must be used for the same allele.

For Example: For Example:

The letter “P” represents flower color. PP = purple (inherited dominant alleles from both parents).

Pp= purple (inherited one dominant and one recessive, but trait is still purple).This is a hybrid= one of each allele.

pp= white (inherited recessive alleles from both parents, and trait is now white).

The letter “P” represents flower color. PP = purple (inherited dominant alleles from both parents).

Pp= purple (inherited one dominant and one recessive, but trait is still purple).This is a hybrid= one of each allele.

pp= white (inherited recessive alleles from both parents, and trait is now white).

*Look at Allele symbols in the above cross-pollinations.

Do you understand…Do you understand…

• Gregor Mendel• Heredity• Trait• Characteristic• Cross-pollination• Purebred• Gene• Allele• P generation

• Gregor Mendel• Heredity• Trait• Characteristic• Cross-pollination• Purebred• Gene• Allele• P generation

• F1 Generation

• Dominant• Recessive• Symbols for alleles

• PP• Pp (hybrid)• pp

• F1 Generation

• Dominant• Recessive• Symbols for alleles

• PP• Pp (hybrid)• pp