RPConstruct a Punnett and cross two

heterozygous brown labs. What do we know?If the brown phenotype is heterozygous, then

we know that brown is dominant. We should use a B since brown is the

dominant color.Complete the punnett and tell % of brown.

•Bb x Bb Where are the offspring?• B b B BB Bb

• b Bb bb

%% ~ Genotypes 25% BB 50% Bb 25%bb Phenotypes 75% Brown 25% YellowProbability is that 75% of the pups will be brown.

25%25%

25%25%

Types of Inheritance NB# 16This power point make not make much sense, but read through it and then go to the online text book and read pages 120-125 in the Holt text book.

Read over the worksheet “Types of Inheritance” and do as directed on the work sheet and the power point.

I. Dominant- RecessiveMendelian

• Dominant allele masks or hides the physical expression of the recessive allele.

• bb BB, Bb

Types of Inheritance

What to notice here: That the recessive phenotype or trait is hidden by the dominant train. That is what Mendel called it.

NOW . . . Do the punnett on NB# 16Homozygous no freckles X heterozygous freckles

Offspring

50% no freckles ff

50% with freckles Ff

II. Incomplete dominance-blending

• Alleles are neither dominant or recessive. Heterozygote is “blended” - between the two traits. Ex. Red allele combined with white allele will produce a pink flower in a case of incomplete dominance.

Pg 124 R1 = red allele R2 = white allele

• R1 R1

• R2

• R1 R2 R1 R2

• R2

• R1 R2 R1 R2

• R1 R2 x R1 R2

Pg 124

• R1 R2

•

• R1

•

• R2

•

III. Codominance-no blending

• Shared expression of a trait. Each allele is expressed fully.

• An example would be a variegated red and white flower, or blood type

IV. Multiples Alleles

• More than two alleles. Suspect this when there are more than 2 phenotypes for a trait.

• Add the following to NB#16

There are 3 different alleles for blood type. A, B and O. A and B are co-dominant but O is recessive to both A and B.

Blood type - What do you already know?

Blood Types(Phenotypes)

Genotypes

1

2

3

4

AB

ABO

AA, AOBB, BO

ABOO

III. Multiples Alleles• Blood Type is

controlled by more than two alleles.

• A, B, and O- O is recessive

• See 612-614 if you want to learn more about blood type

Phenotypes Genotypes

B BB, BO I I

A AA, AO I I

O OO ii

AB AB I I

No Response Page Today 3/12Quiz over punnetts and using the words homozygous, heterozygous, genotype and phenotype is tomorrow.

Unit Test over Genetics is next Tuesday.

Open agendas and write that down.

Then silently read over #16

Sex Linked

• Genes on the x or y chromosome

• There are some recessive traits (hidden if dominant allele is present) that are found/located on the sex chromosomes. Males are determined by only one X chromosome and a Y chromosome

• Females are determined by two x chromosomes

• If a trait is passed down to offspring and is caused by a gene on the X chromosome, male offspring will express the trait whether it is dominant or recessive

Ac stopped here

PEDIGREE