BiologyLaw of Heredity
Ms. Yang
02.07.2013
ObjectivesSWBAT…
1. Set up and solve a Punnett square
2. Review key concepts of heredity.
CatalystTurn the following into a ratio:
1. 6 white eyes to 7 red eyes
2. 9 pink to 8 purple to 6 blue
3. 10 oranges to 10 apples to 10 bananas
Date: 02/06/2013
Catalyst Response
1. 6 white eyes to 7 red eyes
2. 9 pink to 8 purple to 6 blue
3. 10 oranges to 10 apples to 3 bananas to 3 grapes to 10 peaches
6:7
9:8:6
10:10:3:3:10
Group RolesRole Duties
Manager * Reads directions and keeps group on task
Recorder * Turns in worksheet and makes sure everyone agrees on answers
Reporter * Presents answers to class
Technician * Gets materials and asks questions to teacher or other groups.
It is EVERYONE’s duty to contribute to the group and learn the material!
Model 3
• Send TECHNICIAN to get penny.• Complete Model 3.
Model 3
R Rr r
R rR r
Possible combination of alleles:Rr
Phenotype:round
Possible combination of alleles:RR, Rr, rr
Phenotype:round, round, wrinkled
Model 4
Mendel’s Law of Heredity
Review Notes!
• Crossed pea plants
• Tested for different traits
Mendel’s Pea Experiments
Mendel’s Pea Experiments• Why pea plants?
– Easy to grow– Don’t take up a lot of space– Grows fast– Easy to “mate” together– Makes lots of offspring
(seeds)
Mendel’s Pea Experiments
ParentsFirst generation,
Offspring of Parents
Second generation,Offspring of F1 mating
with another F1
Mendel’s Conclusions• Heredity = traits are transmitted
from 2 parents to their offspring• Trait = a characteristic that is
based on genetics• Hybrid = offspring of parents that
have different forms of a trait• Purebred = offspring of parents
have the same form of a trait
Genetics
Offspring get two copies of genes
for a trait (ONE FROM MOM, ONE FROM
DAD), sometimes one copy
dominates over the other copy.
Genetics• Gene = section of chromosome that tells
cell what to do• Allele = a variant of a gene• Dominant = an allele that dominates over
the recessive allele, only need one copy to be expressed
• Recessive = an allele that gets masked if a dominant allele is paired with it, must have two copies to be expressed
Genetics• Homozygous = 2 identical alleles
for a trait• Heterozygous = 2 different alleles
for a trait• Genotype = combination of alleles• Phenotype = expression of the
genotype, the way the genotype is expressed
Monohybrid Cross
• Making a cross for ONE trait
A Punnett square for a MONOHYBRID CROSS
looks like:
Steps to solve Punnett Square Cross
1. What are the parent alleles?
2. What size Punnett square?
3. Where do the parent gametes go?
Example #1
In pea plants….
Tall (T) is dominant over short (t)
Make a cross between
Homo tall X Homo shortTT tt
GENOTYPE _____ PHENOTYPE _______
_____ of the offspring
____ %
___/4
will be _______
T T
t
t
T t T t
T t T t
Tt TALL
ALL
100
4
TALL
_____ of the offspring ___/4 or ____ %will be _________
GENOTYPES _______ PHENOTYPES _______________
WHAT ARE THE POSSIBLE…
Tt
4 100
4
tall
Tall
Example #1
In humans….
Brown eyes (B) is dominant over blue eyes (b)
Make a cross between
Hetero X Hetero Bb Bb
Try the Cross!
B b
B
b
B B B b
B b b b
_____
of the offspring ___/4 or ____ %will have _________
GENOTYPES _______ PHENOTYPES _______________
_______ _______________
_______ _______________
WHAT ARE THE POSSIBLE…
_____
of the offspring ___/4 or ____ % will have _________
BbBB
253 75
13
brown eyes1
blue eyes
bb Blue eyes
Brown eyes
Brown eyes
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