Punnet Squares

!  Objective: SWBAT explain what a punnett square is and use a punnett square.

!  Warm Up: Why do sex cells (Sperm, eggs) only have 23 chromosomes and not 46 like the rest of our cells?

Career of the Week!

!   a scientist who modifies the genes of organisms to

help diagnose diseases, develop new crops, and better medications.

!   Education- Bachelors Degree (Science) Doctoral Degree (Ph.D.) !   Average Salary- $65,110 per year !   Duties- working in a team, doing labs everyday,

experimenting on animals before people.

Genetic Engineer

Quick Review

!  Dominant vs Recessive !  If one parent gives you the allele for blue

eyes, and another parent gives you the allele for brown eyes, you will most likely have brown eyes.

!  Why?

Time to be VAIN together!

What about you?

!  Widow’s Peak

!  Earlobes

!  Dimples

!  Taco Tongue?

Notes

Phenotype: Latin Root:

“Pheno” means “to show”

An organism’s physical appearance or visible trait. *you CAN see this!

Notes

Genotype: An organism’s allele combination.

*you can’t see this, it’s in the nucleus

Writing Genotypes

(1). The first letter of the dominant allele is the letter used.

(2). The capital letter represents a dominant allele.

(3). The lower case letter represents a recessive allele.

Example: Brown and Blue Eyes

(1). If brown is the dominant allele, which letter are we going to use?

(2). Does brown get a capital or lower

case letter? (3.) Does blue get a capital or lower case

letter?

Writing Genotypes

If a person has two alleles for brown, the genotype is: BB

If a person has two alleles for blue, the

genotype is: bb If a person has one allele for brown, one

for blue, the genotype is: Bb

Quick Check (Think-Pair-Share)

!  Why do we have two alleles for each gene?

Quick Check

!  Which one describes the phenotype (PHYSICAL trait you can see), brown or BB?

!  Which describes the genotype (GENETIC makeup that you can’t see), brown or BB?

!   If the genotype is Bb, what is the phenotype?

Trait: Dimples

Dimples are dominant over No dimples. 1. What letter will we use to represent the

dimples trait? 2. For the Dimples allele, do we use D or

d? 3. For the No Dimples allele, do we use D

or d?

Trait: Dimples

4. If you get a Dimples allele from your dad and a No Dimples allele from your mom, what is your genotype?

5. If you get a Dimples allele from your

dad, and a No Dimples allele from your mom, what is your phenotype?

Trait: Nose Shape

Pointy nose shapes are dominant over round nose shapes.

1. If you get a Round nose allele from your dad and a Round nose allele from your mom, what is your genotype?

2. If you get a Round nose allele from your dad and a Round nose allele from your mom, what is your phenotype?

New Vocabulary:

!  Hybrid or Heterozygous: when the 2 alleles

are different •  Ex. Bb, Rr, Ww

!  Homozygous: when the 2 alleles are the same

•  Ex. BB, bb, WW, ww, RR, rr

Punnett Squares

!  Punnett Square: a tool used to see all the possible combinations of alleles from the parents.

Here is how Punnett Squares work…

•  Mom’s alleles (PP: Purple flowers) •  Dad’s alleles (pp: white flowers)

P P

p p

!   All four offspring would be Purple flowers (Pp) (4/4=100% Pp)

Pp

Pp

Pp

Pp

Example:

!  Freckles (F) are dominant over no freckles (f). The mother is a heterozygous freckled woman (Ff) and the father is a homozygous non-freckled man (ff). They have a baby. What is the likelihood that the baby will have freckles?

!  Mom: (Ff) Dad: (ff)

What did you get? !   Freckles (F) are dominant over no freckles (f). The mother is a heterozygous

freckled woman (Ff) and the father is a homozygous non-freckled man (ff). They have a baby. What is the likelihood that the baby will have freckles?

!   Mom: (Ff) Dad: (ff)

Example # 2:

!  Curly hair is dominant to straight hair. If a HETEROZYGOUS Curly haired man had a baby with a HYBRID Curly Haired woman, what is the likelihood that the babies will have curly hair?

What did you get? !   Curly hair is dominant to straight hair. If a HETEROZYGOUS Curly haired

man had a baby with a HYBRID Curly Haired woman, what is the likelihood that the babies will have curly hair?

Video

!  http://www.brainpop.com/science/cellularlifeandgenetics/heredity/

Homework

!  Complete the two punnett square questions on the back of your notes.

November 21, 2011 (Page 73)

!  Objective: SWBAT predict the outcome of a genetic cross using a punnett square.

!  Catalyst: Write a heterozygous genotype: Write a homozygous genotype:

Punnett Square Review

!  What is the difference between dominant and recessive alleles?

Punnett Square Review

!  Why is a genotype always written with two alleles?

Punnett Square Review

!  What is a phenotype?

Punnett Square Revew

!  How is the genotype related to the phenotype?

Punnett Square Review

!   Freckles are dominant over no freckles. The mother is a heterozygous freckled woman (Ff) and the father is a homozygous freckled man (FF). They have a baby. What is the likelihood that the baby will have freckles?

Homework Review

!  Question #1. Brown eyes (B) are dominant over blue eyes (b). A blue-eyed woman (bb) and a brown-eyed man (BB) have a child.

(1). What is the genotype of the woman? (2). What is the phenotype of the woman? (3). What is the genotype of the man? (4). What is the phenotype of the man?

Homework Review !   (6) How many boxes have BB? __________

Bb? __________ bb? __________ !   (7) Of the four boxes, how many show brown-eyed babies? !   (8) Of the four boxes, how many show blue-eyed babies? !   (9) What is the probability of this couple having a brown-

eyed baby? (give a fraction) !   (10) What is the probability of this couple having a blue-

eyed baby? (give a fraction)

Homework Review

!  Question #2. Freckles (F) is dominant over no freckles (f). Juan (FF) and Carolina (Ff) have a baby.

(13). What is Juan’s phenotype? (14). What is Carolina’s phenotype?

Homework Review

(16) How many boxes have FF? _____ Ff? _____ ff? ______

(17) Of the four boxes, how many show freckles? (18) Of the four boxes, how many show no freckles? (19) What is the probability of this couple having a

freckled baby? (give a fraction) (20) What is the probability of this couple having a

non-freckled baby? (give a fraction)