Download How do multiple alleles control the gene expression?

Date: March 4, 2016
Aim #58: How do multiple alleles control the gene
expression?
Do Now: Warm-Up Notebook
Date
Title of Activity
3/4
Dihybrid Cross
Page #
101
HW:
1) Classical Genetics Quiz Thursday (p.5) and Friday (p.1 & p.7)
2) Complete Practice Worksheet
3) Human Phys. Unit 7b Packet due Friday (March 18th)
Aim #58: How do multiple
alleles control the gene
expression?
Which side of your family is
responsible for your good looks?

Characteristics you
might think of as
single traits like eye
color or nose shape
are controlled by not
a single gene, but by
many genes.
 Traits are
determined by both
your genes and the
environment.
Human genetics is not this simple!
IsFor
There
only one
skin
color!
example:
Skin
Color
There is a brown pigment
called melanin. We basically
all have the same skin color,
just different amounts of
melanin. Albinos have no
melanin, so they have very
white skin.
Skin Color Genetics
Multiple genes control an individual’s skin
color.
1) Polygenic Traits
Most traits are the result of the action of
many genes (One trait = many genes).
For example, skin color & height depend
upon the interaction of many
independent genes.
2) Multiple Alleles

More than two alleles control the phenotype in
some cases.

Like other traits, a person’s blood type is inherited
from their parents. But unlike other traits, blood
type is controlled by three alleles:
A, B, and O.
* Remember alleles are different forms of a gene.
Blood Types
A & B alleles are codominant, they both can
appear in an individual’s phenotype.
AA or Ao
BB or Bo
AB
oo
o is recessive to A & B
3) Blood Types
4) Pleiotropy
Pleiotropy
One gene can
produce many traits
Sickle Cell
5) Polygenic vs. Pleiotropy
 Polygenic
effect: many genes = 1 trait
 Pleiotropic effect: 1 gene = many traits
6) Genes vs. Environment
 Many
traits are strongly influenced by
environmental factors, including
nutrition and exercise.
 Phenotype = Genes + Environment
Nature
Nurture
Disease
Disease is
due to
genetics and
environment

Example: While diabetes might be due to a
“bad” gene, our environment (personal habits &
diet) can be important in its severity.
7) Which of these traits is least
affected by nurture?
 Height
 Artistic
ability
 Intelligence
 Eye color
8) Why are they different?
These seeds carry
the same genes for
chlorophyll:
CC
Grown in dark
Grown in light
ENVIRONMENT AFFECTS
GENE EXPRESSION
Date: March 7, 2016
Aim #58: How do multiple alleles control the gene
expression?
Do Now: Warm-Up Notebook
Date
Title of Activity
3/7
Codominance
Page #
102
HW:
1) Practice Problems
2) Classical Genetics Quiz Thursday (p.5) and Friday (p.1 & p.7) Aim #’s
57-59
– Review Session Wednesday morning Room 142
3) Human Phys. Unit 7b Packet due Friday (March 18th)
Practice Problems II
packet page 10
1) In summer squash, white fruit color (W) is dominant over
yellow fruit color (w) and disk-shaped fruit (D) is
dominant over sphere-shaped fruit (d). If a squash plant
true-breeding for white, disk-shaped fruit is crossed with a
plant true-breeding for yellow, sphere-shaped fruit, what
will the phenotypic and genotypic ratios be for:
a) The F1 generation?
b) The F2 generation?
2) A man with group A blood marries a woman with group B
blood. Their child has group O blood.
– What are the genotypes of these individuals?
– What other genotypes and in what frequencies, would you
expect in offspring from this marriage?
3) A woman with type AB blood marries a man whose
mother was type O and father type A. They have a son
with type B blood. What are the possible genotypes of the
father?