Fnord babies DO NOW!!! (HW problem check)

Objective: Define incomplete dominance and codominance, and solve genetics problems involving both.

Task: Answer, don’t copy:

In Fnords, orange (O) skin is dominant over blue skin (o). An orange fnord and a blue fnord mate, and produce 314 orange

offspring and 307 blue offspring.

A. What is the genotype of the orange parent?

B. Two orange fnords mate, and they produce both orange and blue offspring. If they have 98 blue babies, about how many

orange ones are there?

C. Describe a cross you could make to figure out if one an orange fnord is homozygous dominant or heterozygous.

FNORDS!

A. Oo

B. about 300

C. cross with a blue fnord. If all offspring are orange, must have been a homozygote. Testcross

O o

O OO Oo

o Oo oo

Important Info from 9.1-9.2

• Generation titlesP generation =

parents

F1 generation = offspring generation 1 (Latin filial = son)

F2 generation = offspring generation 2 (from F1 self fertilization)

Beyond Complete Dominance

• In the crosses we looked at earlier, one allele (form of a gene) was completely dominant over the other.

• Ex. Tt = phenotype “T”

• Some traits are more complex however…

Codominance

For a trait that is codominant, heterozygotes display BOTH phenotypes.

Look at the example of horses

RR = Red fur

rr = White fur

Rr = Red AND White fur (roan)

Codominance – Roan Horses

Incomplete Dominance

RR Rr rr

The heterozygote genotype has a blend of both possible homozygous phenotypes.

Pink flowers = RR’

• Since one allele isn’t really dominant, the non-functional allele (white in this example) is written with a capital letter and an apostrophe (i.e. R’, Q’, etc.)

Flower Power

• If you crossed two of the pink flowers on the previous slide,– What % would be pink?– What % would be red?– What % would be white?

• What is the phenotype ratio?

Do Now 2.16 (HW check)

• Objective:– Use a Punnett square to analyze genetic

crosses involving traits that are sex-linked or multiallelic.

• Task:– Complete the following practice questions on

the back of yesterday’s notes outline: complete dominance, incomplete dominance, and co-dominance. (5 total)

Shh! Don’t say a word!

Write down what numbers (if

any) you can read in each circle

Are you color blind?

• 4 Sex-Linked Traits:

• 1. Normal Color Vision: A: 29,  B: 45,  C: --,  D: 26  

• 2. Red-Green Color-Blind: A: 70,  B: --,  C: 5,  D: --  

• 3. Red Color-blind: A: 70,  B: --,  C: 5,  D: 6  

• 4. Green Color-Blind: A: 70,  B: --,  C: 5,  D: 2

There are a LOT more color blind men than women!

Try One – as sex-linkage example in notes

• A female with normal vision that has 1 copy of a colorblindness gene (genotype X+ Xo) has children with a normal male (X+ Y).

A. What % of their male children will be colorblind?

B. What % of their female children will be colorblind?

C. Do all colorblind women have a colorblind father? Explain

3 Different Alleles: Multiple Allele Traits

• The three alleles that determine blood type are represented as IA, IB, and i.

Phenotype Genotypes

A IAIA, IAi

B IBIB, IBi

AB IAIB

O ii

Crosses

• A woman with blood type A has a baby with blood type O. The man she believes to be the father has the blood type AB. Is it possible the man is the father of the baby?

He isn’t the Father!

mom

Possible dad

IA

IB

IA

IAIA

(A)IAIB

(AB)

i

IAi(A)

IBi(B)

Multiple Allelic Traits

• Traits for which there are 3 or more alleles are said to be multiple allele traits, or multiple allelic.

• Try the example cross on your notes

Wrap up• Alleles can react in different ways, for

different genes:– Codominance: both alleles expressed (roan

horses)– Incomplete: heterozygote has blended

phenotype (pink flowers)– Sex-linkage: males only get 1 copy!

(colorblindness)– Multiple alleles: 3 or more alleles for 1 gene.

(blood type)

Homework

• Syllabus reading

• You should now be able to work on the 1,2, and 3-point problems on the “Classical Genetics Problem Set.”