Download 11-3: exploring mendelian genetics

11-3: EXPLORING
MENDELIAN GENETICS
TWO FACTOR CROSS: F 1
Following two different genes from one
generation to the next.
Mendel crossed true-breeding plants that
produced only round yellow peas (RRYY) with
plants that produced with wrinkled green peas
(rryy).
All F 1 offspring were round yellow peas.
RRYY x rryy
TWO FACTOR CROSS: F 2
 However, in the F 2 , not only were there round yellow
and wrinkled green peas produced, but so were round
green and wrinkled yellow peas.
RrYy x RrYy
R: round
r: wrinkled
Y: yellow
y: green
INDEPENDENT ASSORTMENT
The principle of independent assortment
states that genes for different traits can
segregate independently during the
formation of gametes.
SUMMARY OF MENDEL’S
PRINCIPLES
1. Inheritance is determined by genes, which
are passed from parents to offspring.
2. Some forms of a gene may be dominant and
others recessive.
3. You get one copy of each gene from each
parent. These genes segregate when
gametes are formed.
4. Different genes segregate independently
from one another.
THINK-PAIR-SHARE
In your own words, restate the
summary of Mendel’s principles in
your notebook.
BEYOND DOMINANT &
RECESSIVE ALLELES
Some alleles are neither dominant
nor recessive, and many traits are
controlled by multiple alleles or
multiple genes.
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits
INCOMPLETE DOMINANCE*
 Incomplete dominance: one allele is not completely
dominant over another. Two traits blend.
CODOMINANCE*
 Codominance: both alleles contribute and are
present in the phenotype of the organism. Two traits
show.
MULTIPLE ALLELES
 Multiple Alleles: genes that have more than two
alleles.
 Example: C, c ch , c h and c alleles of rabbit coat color.
POLYGENIC TRAITS
 Polygenic traits: traits controlled by two or more
genes. Often show a wide range of phenotype.
 Example: eye color, skin color etc.
THINK-PAIR-SHARE
Which concept applies to each picture?
3.
1.
2.
4.