GENETICS: Our Family Tree

It’s all Relative!

--Did you know we share 99.9% of our genes with other humans?

--95% of our genes with chimpanzees?

--92% of our genes with a mouse?

--So was Dr. Seuss thinking about genetics?

It’s all in the genes!

Genes-- the unit of heredity--carry the information

about our traits--found in the

chromosomes --pass trait information

from parent to offspring

Combination PlatterEgg + Sperm = YU

--You inherited 23 chromosomes from each parent.

--Each of those chromosomes contained ALLELES.

--Allele = different form of same gene.

--The combination of those alleles = YU!

Who’s the daddy?

--Genetics is the study of heredity.

--Gregor Mendel is the father of genetics.

--He was a priest in a monastery who enjoyed gardening.

--He was interested in the different characteristics of pea plants (yuck ).

The Birds and the Peas

--Mendel cross-pollinated 2 purebred pea plants.

--He took the pollen from one plant and fertilized it with the other plant.

--WHY? To see what he could see – the characteristics of the offspring!

Mendel’s Peas

--Mendel noticed the size of pea plants varied.

--He wondered what would happen if he crossed purebred plants?

--Purebred – Tall or Short (no in betweens—ex. mediums)

Mendel’s cross between tall pea plants yielded all tall pea plants. His cross between small pea plants yielded all small pea plants.

Tall x Tall = Tall Small x Small = Small

X X = =

P P

P P F 1

F 1

Mendel’s cross of tall plants with small plants resulted in tall plants.

X

= F 1

P P

Mendel then crossed the first generation (F1) tall plants and the results (F2) were 1 out of 4 Small.

X = F1

F 2

F2 Second Generation

Mendelalian Genetics

--What did Mendel learn from his experiments?

1) Alleles are different forms of a gene.

2) Alleles are either DOMINANT or Recessive.

3)Phenotype = physical characteristic shown is a result of at least 2 alleles.

Mendelian Genetics

--DOMINANT allele is the trait that ALWAYS shows up in the Phenotype.

--DOMINANT allele is ALWAYS represented by a CAPITAL letter (T= Tall)

--GENOTYPE = combination of alleles

--Purebred Tall Pea Plants have GENOTYPE TT

--TT = HOMOZYGOUS DOMINANT

--HOMOZYGOUS = SAME--Both alleles inherited are DOMINANT or the same

Mendelian Genetics

--Recessive alleles are weak and hidden by dominant allele.

--Recessive alleles DO NOT show up in Phenotype UNLESS two are together*.

--Recessive alleles are represented by a lower case letter

--Purebred short pea plants have GENOTYPE tt

--tt is HOMOZYGOUS Recessive.

--Both alleles are Recessive or the same.

Mendelian Genetics

• So what was the GENOTYPE of the first generation Tall plants from Slide 9?

• Tall x Small = Tall

• Tt = HETEROZYGOUS Dominant

--HETEROZYGOUS = two alleles are NOT the same

--One allele is DOMINANT the other Recessive

--HETERO = different--Phenotype = DOMINANT trait ALWAYS shows up

--Plants are tall.

Say What?

Do you know ….

• Gregor Mendel• Heredity• Trait• Genes• Cross Pollination• Alleles• GENOTYPE• Phenotype• Purebred

• HOMOZYGOUS• HETEROZYGOUS

• DOMINANT• Recessive• How to write the GENOTYPES ?

• P generation• F1 generation• F2 generation

To be continued . . .

Punnett Squares, Codominance,

Probability, and Blood Typing . .

OH MY!!!!