Download CHAPTER EIGHT – HEREDITY Definition – Reason

CHAPTER EIGHT – HEREDITY
Definition –
 Reason
GENETICS
1.
2.
Definition
Work of Mendel
 His background
 What he studied:
a. significance of his
choice
b. what he wanted to
find out
 His experiments:
a.
Parental cross
b.
F1 offspring
c.
F2 offspring
 His Explanation:
a.
Law of Dominance
 how represented

b.
3.
Law of Segregation
Genetic Terms
a. Punnett Square
b. Allele
c. Genotype
d. Phenotype
e. Homozygous
f. Heterozygous
4. Probability and Genetics
a. Product Rule
 Definition
 Example
b. Probability and Large
Numbers
5. Problem Solving
 One trait cross
 Incomplete Dominance
a. Definition
b.
Example
 Multiple Alleles
a.
b.
Definition
Example
c.
Also illustrates codominance
Definition –
 Two Trait Crosses
a. Mendel wanted to see the outcome of
crosses if two
traits were
considered together:
P.C. Pure Strain Round Yellow x Pure
Strain Wrinkled Green
F1
Allowed these offspring to self-pollinate
F2
b.
Dihybrid
F2 phenotypic ratio of a dihybrid crosses:
c.
Law of Independent Assortment
THE CHROMOSOME THEORY OF HEREDITY
1.
Background: Statement
A.
proposed by Sutton in the early 1900’s as a hypothesis
 Why?
B.
supported by studies of Morgan
 worked with Drosophila
1.) Why good subject for genetic
studies
 discovered sex chromosomes
 Definition
Males =
Females =
Explains:
• 50:50 chance
• which parent determines the sex of the
offspring
• ? applies in all organisms
 Autosomes
1.
Definition
 How does this relate to the Chromosome Theory of
Heredity?
 Another Study by Morgan:
1.
Worked with eye color:
P. C. P.S. Red-eyes x P.S. White-eyes
F1
All Red-eyes
F2
3:1 (white eyes – always male)
2.
Explanation:
 Sex-linked traits:
a.
Definition
b.
Cross to explain Morgan’s
findings
3.
Solving Sex-linked Problems:
 Examples of sex-linked traits in
humans: Hemophilia, Red-Green
Color-blindness
 Carrier
 Relate to Chromosome Theory of
Heredity
B.
Study of Bridges
1.
Worked with fruit fly
2.
Found females with XXY and males with X
 Explanation: Non-Disjunction
a.
Definition
b.
Cross
 Relate to Chromosome Theory of Heredity
 Change traditional XX and XY designation:
Fruit Flies – 2nd X indicates a female
Humans – presence of Y indicates a male
 Can occur in humans: Down’s Syndrome is
caused by non-disjunction of the 21st
chromosome
2.
OTHER GENETIC CHARACTERISTICS:
a.
Gene-linkage
1.)
Definition Why?
2.) Example:
RrYy x
RrYy
Ratio if genes are linked:
3.)
b.
c.
Gene linkage and variety
 Example in Humans
 Creating variety in linked genes:
Crossing over
1.)
Definition
2.) Example
3.) Genetic recombination
 Definition
4.) Genetic Maps
 Definition
 Relationship to crossing over
Multiple Genes
1.)
Definition
2.) Examples
3.) Creates continuous variation
 Definition
d.
Modifier Genes
1.)
Definition
e.
2.) Example: eye color
Gene Expression and the Environment
1.)
New Definition of gene