MENDEL & GENETICS Peas, Peas, Peas, Peas Studying Mendel’s Peas (Sing to tune of “Eating Goober Peas”) Peas, Peas, Peas, Peas Studying Mendel’s Peas (Sing to tune of “Eating Goober Peas”)

Gregor Mendel Austrian monk High school science teacher Discovered laws of inheritance

Gregor Mendel Studied pea plants Easy to study Many traits only have 2 forms 7 different traits Stem height Seed shape Seed color Seed coat color Pod shape Pod color Flower position

A Closer Look at Pea Traits Stem Height 2 forms Tall stems Short stems All traits have 2 forms, a dominant & a recessive

2 types of Alleles (forms of a trait) Dominant allele Always shows up if present Dominant allele Always shows up if present Recessive allele May be present but masked if paired with a dominant allele Only shows up if paired with another recessive alleles

Examples of common traits Tongue rolling Can roll tongue - dominant Can’t roll tongue - recessive You have 2 alleles for this trait Tongue rolling Can roll tongue - dominant Can’t roll tongue - recessive You have 2 alleles for this trait

Where do your alleles come from? One from mom One from dad One from mom One from dad

What does this mean? If you can roll your tongue, you have either 2 dominant alleles Or 1 dominant and 1 recessive If you can roll your tongue, you have either 2 dominant alleles Or 1 dominant and 1 recessive

What does this mean? If you can’t roll your tongue, you have 2 recessive alleles If you can’t roll your tongue, you have 2 recessive alleles

MENDEL & GENETICS PART 2

CHROMOSOMES & YOUR CELLS Where do they come from?

Chromosomes & Body cells All cells have chromosomes Number of chromosomes for an organism is unique Humans - 46 chromosomes Dogs - 78 chromosomes Silkworms - 56 chromosomes All cells have chromosomes Number of chromosomes for an organism is unique Humans - 46 chromosomes Dogs - 78 chromosomes Silkworms - 56 chromosomes

How do they get there? By mitosis, of course! Remember - mitosis creates new cells that are identical to the original cell So that means a cell with 46 chromosomes will create a new cell with 46 chromosomes! By mitosis, of course! Remember - mitosis creates new cells that are identical to the original cell So that means a cell with 46 chromosomes will create a new cell with 46 chromosomes!

But what about our sex cells? Sex cells are created through a process called meiosis New cells have half the number of chromosomes New cells are not identical to original cells Sex cells are created through a process called meiosis New cells have half the number of chromosomes New cells are not identical to original cells

Why is this important? Remember, all organisms have a unique number of chromosomes On offspring may not survive if the number of chromosomes is incorrect Remember, all organisms have a unique number of chromosomes On offspring may not survive if the number of chromosomes is incorrect

Why is this important? (con’t) Think about how you were created, a sperm fertilized an egg. The sperm donated half the chromosomes (23) The egg donated the other half of the chromosomes (23) Think about how you were created, a sperm fertilized an egg. The sperm donated half the chromosomes (23) The egg donated the other half of the chromosomes (23)

So why is it important that sex cells have half the number of chromosomes? Your turn to write an answer