aa. brown hair bb. bb cc. xx dd. green eyes
DESCRIPTION
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/diseases Would you??TRANSCRIPT
#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