Biology Law of Heredity Ms. Yang 02.07.2013. Objectives SWBAT… 1.Set up and solve a Punnett square...

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