Your “Do Now” 1/30

1. Complete the weekly Pre-Quiz (up front)2. Write our next 2 learning targets:

– I can describe and explain the differences between dominant and recessive traits

– I can explain Mendel’s laws of segregation and independent assortment

Agenda 1/30

• Exploring different types of traits• Ch 11 Notes #3• Traits activity (online)

Exploring different types of traits

• Work with a partner• We’ll discuss results in 7 minutes

Exploration Discussion

• What was the baby left handed?

• When was the baby right handed?

• Can two right-handed people have a left-handed baby?

CH 11 Notes #3 1/30Traits & Inheritance

Starting on the back of Notes #3

Dominant Trait• Description: An allele that hides another

allele for the trait– Example in Humans: Being right-handed– Symbol: Capitol letters (R, B, T)

Right-handed

Left-handed

Baby is Right-handed

Recessive Trait• Description: An allele that gets hidden when

it’s paired with another allele for the trait– Examples in humans: being left-handed– Symbol: lowercase letters (r, b, t)

Right-handed

Left-handed

Baby is Right-handed

Dominant or Recessive?

Blue-eyed allele + Brown-eyed allele = Brown-eyed person– Blue-eyed is ___________________– Brown-eyed is __________________

Front Side of Notes #3

Describing an organism• GENOTYPE: The letters coding for a trait (“Bb”)

The genes present in the DNA of an organism – Example: bb, Rr, Tt– Represented by 2 letters for a gene: “bb” for blue eyes

Blue eyesBlue eyes

Describing an organism

• PHENOTYPE: The appearance of a trait– Example: Having blue eyes

What’s the difference?

• An organism can have a gene for a trait without showing it!– Allele for left-handed doesn’t mean person will be

left-handed

So what?• This means we can’t always tell genotype by

observing phenotype!– Example: A right-handed person can carry a gene

for being left-handed

Describing genotypes

• If an organism has two of the same allele for a trait it’s called HOMOZYGOUS– Example: Right-handed allele + Right-handed allele

Right-handed

Right-handed

2 types of Homozygous

• Homozygous dominant– Two dominant alleles. – Example: RR for right-handed

• Homozygous recessive– Two recessive alleles– Example: rr for left-handed

Heterozygous

• Rr

Describing genotypes• If an organism has two different alleles for a

trait it’s called HETEROZYGOUS– Example: Left-handed allele + Right-handed allele– Genotype: Rr

Right-handed

Left-handed

What would it be? homozygous dom., homozygous

rec., or heterozygous?• Brown eye allele + Brown eye allele• Brown eye allele + Blue eye allele• Left-handed allele + Right-handed allele• Right-handed allele + Right-handed allele

Gregor Mendel

• An Austrian monk known as the father of genetics.

Gregor Mendel• Experimented with

pea plants– Easy to care for– Simple traits to

observe

Mendel’s Laws1. LAW OF SEGREGATION: When gametes are

formed, the two alleles responsible for the trait are separated from each other.

Allele for Brown eyes

Allele for Brown eyes

Allele for Brown eyes

Allele for Brown eyes

Mendel’s Laws2. LAW OF INDEPENDENT ASSORTMENT: As

gametes form, alleles on different chromosomes sort independently from each other.

Brown eyes

Left-handed

Brown eyes

Left-handed

<-OR->

Mendel’s Laws2. LAW OF INDEPENDENT ASSORTMENT: As

gametes form, alleles on different chromosomes sort independently from each other.

Brown eyes

Left-handed

Brown eyes

Left-handed

<-OR->

Practice Time!

• Work alone or with a partner• If it’s not done, it’s due tomorrow