Download MENDEL & HEREDITY

A. Where did I get these
freckles?
B. Why is my brother so
athletic and I’m so
clumsy?
C. Why do diseases show up
in some generations and
not others?
The answer…
Heredity!!!
Mating Game Activity
HEREDITY
A.Heredity—the passing of
traits from parents to
offspring
B.Traits—the physical or
behavioral characteristics
passed to offspring
MENDEL & HEREDITY
For thousands of
years people have
noticed that offspring
resembled their
children…Could this
man have the
answer?
MENDEL & HEREDITY
A.Gregor Mendel, an
Austrian monk, studied
garden peas for 14 years.
B.He would cross “pure”
plants of opposite traits
and observe their
offspring.
MENDEL & HEREDITY
C. Gametes—male and
female sex cells (sperm and
egg)
1. Mendel chose pea plants
because each plant has
male and female gametes.
MENDEL & HEREDITY
D. Pollination—the transfer of
pollen grains (containing
sperm) to the female
reproductive organs in the
same flower
1. Mendel used crosspollination (2 flowers)
MENDEL & HEREDITY
E. Fertilization—the joining of
male and female gametes.
F. Zygote—a fertilized cell
1. Every living thing begins
as a zygote!
MENDEL & HEREDITY
G. Hybrid—the offspring of
parents that have different
traits
1. Tall x Short
H. Monohybrid Cross—only
ONE trait is different
MENDEL & HEREDITY
I. Mendel was a careful
researcher
1. Studied one trait at a time
2. Used “pure” plant lines
3. Used a large # of plants
and many trials
MENDEL’S RULES
a)Genes are sections of DNA
located on the
chromosome
b) Genes are like ice cream,
alleles are the different
a
A
flavors
MENDEL’S RULES
B. The Rule of Dominance
1. When one trait covers up
another trait it is said to be
“dominant”
a) Write in capital letters
b) AA
MENDEL’S RULES
2. The trait that is covered up is
“recessive”
a) Trait only shows up when 2
recessive alleles are inherited
from parents
b) Write in lower case letters
b) aa
MENDEL’S RULES
3. When one dominant allele
(A) and one recessive allele
(a) is inherited, the dominant
allele shows up
a) AA=Tall
b) aa=Short
c)Aa=Tall
MENDEL’S LAWS
C. The Law of Segregation
1. Since each gene has two
alleles, it can produce two
different gametes
2. The alleles separate
3. Male and female gametes
pair up randomly creating 4
possible combinations
GENOTYPE
A. Genotype—the combination
of alleles in the organism
1. AA or Aa or aa
2. The letters!
GENOTYPE
B. Homozygous—both alleles
are dominant or recessive
1. AA or aa
C. Heterozygous—one allele is
recessive and one is dominant
2. Aa
PHENOTYPE
A. Phenotype—the outward
appearance or behavior of
the organism
1. Tall or Short
2. What it looks like!
MENDEL’S EXPERIMENT
A. Tall x Short
1. All tall plants were > 6 ft
2. All short plants were < 2ft
3. The original generation is
called “P1”
4. See page 255
MENDEL’S EXPERIMENT
B. Results: The offspring
were ALL Tall!!!
1. This generation were
called “F1”
MENDEL’S EXPERIMENT
C. Next, he crossed the F1s
D. Results: ¾ were Tall and
¼ were short (3:1 ratio)
1. The short plants
reappeared from nowhere!
2. This generation was called
“F2”
MENDEL’S RULES
A. The Rule of Unit Factors
1. Each organism inherits
one possibility for a trait
from each parent
2. Alleles—Different form
of a trait
PUNNETT SQUARES
A. Punnett Squares are used
to predict the probability of a
genotype to occur
PUNNETT SQUARES
B. Probability can be written
as a fraction, ratio or
percent
1. ¾ , ¼
2. 3:1
3. 75%, 25%
PUNNETT SQUARES
C. Can also be
used for
dihybrid
crosses (2
traits)
_________________________
RR & Rr=round
rr= wrinkled
YY & Yy= yellow
yy= green
RY Ry
RY
Ry
rY
ry
rY
ry
MENDEL’S LAST LAW
A. The Law of Independent
Assortment
1. Genes for different
traits, for example shape
and color, are inherited
independent from each
other.
MENDEL’S LAST LAW
2. The two different genes
have nothing to do with each
other.
3. Exception: Unless the
genes for the two traits are
on the same chromosome!!!
REVIEW
What is a hybrid?
THE OFFSPRING OF
PARENTS THAT HAVE
DIFFERENT
TRAITS/ALLELES
REVIEW
What is the name for the
parent generation? The
offspring?
P1
F1
REVIEW
What happens to a
recessive trait when a
dominant allele is
present?
IT DOES NOT SHOW UP!
REVIEW
Give an example of a
heterozygous organism
using the letter Q.
Qq
REVIEW
What’s the difference
between genotype and
phenotype?
G=combination of alleles
P=the outward appearance
REVIEW
If the results of your
punnett square were 1 AA,
2 Aa and 1 aa, what is
probability ratio?
1:2:1