#5 – CHOOSE ALL THE EXAMPLES OF A GENOTYPE BELOW

A. Brown hair B. BB C. Xx D. Green eyes

WHAT’S THE DIFFERENCE?

Genotype:

TWO Alleles TWO Letters 3 “types”

AA, Aa, aa

Phenotype:

Trait you see Determined by

the genotype

Ex: Red socks, brown hair, tall, short, round eyes

Punnett Square: A tool used to predict the probability of genotypes and phenotypes of offspring

Why would we need/want to know this info?

Genetic Counselor = Analyzes parent’s DNA for possible traits/diseasesWould you??

#6 How would a child have a trait NEITHER parent has?

(Hint: Think of a genotype)

Answer must include a minimum of:

2 green words (in back) 2 yellow words (in back)

#6 How would a child have a trait NEITHER parent has?

(Hint: Think of a genotype)

Parents are HETEROZYGOUS One dominant & 1 recessive

allele Child inherits 2 recessive

alleles

Punnett Square: A tool used to predict the probability of genotypes and phenotypes of offspring

Why would we need/want to know this info?

Genetic Counselor = Analyzes parent’s DNA for possible traits/diseasesWould you??

WRITE A….. 1. Dominant allele 2. Add a recessive allele 3. Is this a genotype or

phenotype? 4. How would you abbreviate??

WRITE A….. 1. Dominant allele 2. Add a dominant allele 3. Is this a genotype or

phenotype? 4. How would you abbreviate??

ATTACHED EARLOBES Genotype OR Phenotype?

WRITE THE GENOTYPES Mom has freckles (F) and Dad

has no freckles (f). Each parent has a homozygous genotype.

Mom: Dad:

HOW DO I USE A PUNNETT SQUARE??

Step 1….. Determine the

genotypes of both parents.

Ex: Parent 1 is homozygous dominant for brown eyes (A) and Parent 2 is heterozygous

Homozygous = Same Dominant = Capital

Parent 1 = AA

Heterozygous = Different

Parent 2 = Aa

HOW DO I USE A PUNNETT SQUARE??

Step 2…. Make a Punnett Square – Leave

room on top & bottom1 2

3 4

Step 3…. Write the first genotype (AA) next

to box # 1 and box # 3 of the Punnett Square

IMPORTANT!!! Only one allele next to each box!1 2

3 4

AA

Step 4…. Write the second genotype (Aa) on

top of the box # 1 & # 2 of the Punnett Square

1 2

3 4

A

A a

A

Step 5…. “Multiply” the alleles together

starting with box #1 Outside In Top Bottom

1 2

3 4

A

A a

A AA

1 2

3 4

A

A a

A AA Aa

1 2

3 4

A

A a

A AA Aa

AA

1 2

3 4

A

A a

A AA Aa

AA Aa

NOW FOR MATH….IN SCIENCE CLASS GENOTYPES PHENOTYPE

S Box #1 = AA Box #2 = Aa Box #3 = AA Box #4 = Aa

Brown eyes are dominant to blue eyes.

AA = Brown eyes Aa = Brown eyes AA = Brown eyes Aa = Brown eyes

2 of 4: AA 50% Brown Eyes

2 of 4: Aa 50% Brown Eyes

WHAT ARE THE CHANCES? ….PROBABILITY….

The 4 boxes = 100%

What % does box #1 represent? 25% or 1 of 4 probability of brown eyes

What % does box #2 represent? 25% or 1 of 4 probability of brown eyes

What % does box #1 & #2 represent? 50% or 2 of 4 probability of brown eyes

NOW….FOR MATH IN SCIENCE! Genotype Phenotype Ratio

AA Brown eyes 50% OR 2:4

Aa Brown eyes 50% or 2:4

Total = 100% BROWN eyes

PRACTICE!!! The dominant allele (T) is long whiskers & the recessive allele (t) is for short whiskers.

a) Both parents are heterozygous (hybrid)

Step 1: Tt and Tt

PRACTICE!!!a) Both parents are heterozygous

TT Tt

Tt tt

T t

T

t

TT: Long whiskers25% OR 1:4

Tt: Long whiskers 50% OR 2:4

tt: Short whiskers25% OR 1:4

Total = 75% long 25% short

In purple people eaters, one-horn is dominant (H) and no horns is recessive (h).

Cross a heterozygous purple people eater with a purple people eater that has no horns.

Step 1: Tt and tt (no horns is recessive)

Cross a purple people eater that is heterozygous with a purple people eater that has no horns.

Hh hh

Hh hh

H h

h

h

Hh: One horn 50% OR 2:4

hh: No horns 50% OR 2:4