Happy Tuesday!

• Get prepared for the quiz on Mitosis vs Meiosis it

• 10 minutes to look over notes

• Clear your desks!

• Good luck

Life’s Biggest Question Solved!

Why we are the way we are…

An Inventory of your Traits!

• Take this survey on different traits on your body

• Even the littlest of traits makes you different from your classmates

• This is all due to your genetic make-up and the genes you inherited from your parents!

Mark Yes or No, I have…

• Detached earlobes

• Can roll my tongue

• Dimples

• Freckles

• Naturally curly hair

• Cleft chin

• allergies•I cross my left thumb over my right thumb when I clasp my hands•I can see the colors red and green•The hairline on my forehead is straight

Traits• Traits are observable characteristics we

inherit from our parents– Some are common while some are not– Every person has a different combination of

traits that make them unique from anyone else!

Where do these traits come from?

• Today we’re going to learn about how our genetic information (inherited from our mom and dad) turn in to observable traits on our body!

How do you know if someone is a boy or a girl?

You look in their genes!

How many chromosomes do humans have in their body cells? 46 total

or 23 sets

How many chromosomes come from mom?

23 total

Where are the genes?

Homologous Chromosome: Every organism has 2 of each chromosome, one inherited from mom and one from dad

Chromosomes contains the samegene that code for a trait

Mom & Dad may have different versions of the genes, and that difference in DNA causes different versions of the same trait to be expressed.

Mom Dad

Homologous Chromsomes

Gene for

Eye color

Different version for the same gene

Different version for the same gene

Allele: Different versions of the same gene leading to a difference in the trait expressed

Alleles are represented by letters in the alphabet, and there are always two letters together since you have one from mom AND one from dad

Ex: cc, aa, Aa, GG

Vocabulary DefinitionsPhenotype : the observable traits of an organism

Ex: Brown eyes, curly hair, short

Genotype : the genetic combination of alleles present in an organisms chromosomes

Ex: Bb; bb; BB

Mom Dad

Let’s look at the offspring these two parents made!

Phenotype is blue

Phenotype is brown

Phenotype is brown

But Genotype (genetic makeup) is Blue and Brown! Bb

Phenotype vs. Genotypedetached ear lobes

Homozygous zz

B bDominant – phenotype always represented

Recessive – loses to the dominant allele

Genotype Strongest Phenotype

BB

bb

Bb

Bb

B

• Heterozygous: 2 different alleles for a single trait– Bb or Cc or Dd– **Always a capital letter and a lower case letter

• Homozygous: identical alleles for a single trait– BB or CC or dd

– **Always either all capital letters of lowercase letters

– Homozygous dominant: DD

– Homozygous recessive: dd

• Point to remember: usually the dominant allele is what determines the letter of the alphabet– Example: if Straight hair is dominant over

curly hair– SS – straight hair– Ss – straight hair– Ss – curly hair

• Finish questions #1-#3 with a partner and we’ll go over it

• Then, we’ll build our own bunnies using genetics!

An Introduction to Punnett Squares

Punnett Square : a mathematical way to predict the genotype ratios of offspring from 2 parents

Parent #1 alleles Parent #2

alleles

AlbinismDominant: melanin is produced normally:AA or Aa

Recessive: melanin produced is messed up:aa

2 parents: Aa and Aa

Calculating Ratios

Ratio = # of offspring with trait # of possible offspring

Wanted: Ratio of expected Heterozygous Dominant offspring

Ratio = # offspring with Aa = 1/2 4 total offspring

**These ratios are what we EXPECT to happen!**

Let’s look at what actually happens in our bodies and what the punnett squares

predict will happen

Sex Determination

Whether you are a boy or a girl all depends upon the presence of a Y chromosome, inherited from your father!