Transcript Mendelian (“Simple”) Genetics Chapter 11

Mendelian (“Simple”)
Genetics
Chapter 11
Objectives:
7.0 Apply Mendel's law to determine phenotypic
and genotypic probabilities of offspring.
7.1 Defining important genetic terms, including
dihybrid cross, monohybrid cross, phenotype,
genotype, homozygous, heterozygous, dominant
trait, recessive trait, incomplete dominance,
codominance, and allele
7.2 Interpreting inheritance patterns shown in
graphs and charts
7.3 Calculating genotypic and phenotypic
percentages and ratios using a Punnett square
Important Terms
• Define and explain relationships
between terms:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Genetics
10. Incomplete dominance
Trait
11. Codominance
Allele
12. Monohybrid cross
Dominant trait
13. Dihybrid cross
Recessive trait
Genotype
Phenotype
Heterozygous
Homozygous
Bozeman Biology on
Mendelian Genetics
• http://www.youtube.com/watch?fe
ature=player_detailpage&v=NWqg
ZUnJdAY
• Video quiz
Video Quiz
1. What organism did Mendel
study?
2. How many different traits of the
pea plant did Mendel study?
3. What is the first cross of a
genetic cross called?
4. What do we call a cross of the
offspring?
5. What do we now call what
Mendel called a “trait”?
6. What is shown across the top
and down the side of a
Punnett square?
7. What is shown in the boxes of
a Punnett square?
8. What does Mendel’s law of
segregation say?
9. Law of independent
assortment?
Genetics:
• The study of heredity (how
traits, or specific
characteristics, are passed
from one generation to
another)
Gregor Mendel
• Mendel (1822-1884) was an
Austrian monk trained in
science and mathematics at
the University of Vienna.
• He was a teacher, and was in
charge of the monastery’s
gardens.
Mendel’s Peas
• He used true-breeding plants -plants that had been allowed to
self-fertilize for generations,
producing offspring identical to
themselves.
• The plants had the following
traits with differences: height,
pea (seed) color, pea shape,
seed coat color, pod color, pod
shape, and flower position.
• By using purebred plants,
Mendel could cross-pollinate
purposely and purposefully to
see what would happen.
• Mendel used a paint brush to
transfer pollen from one type
of pea plant to another.
• Parent plants are called the P
generation.
• Offspring are called the filial,
or F1, generation.
• These offspring plants would
be hybrids (vs. purebreds).
• What would the offspring of a
cross between two F1 plants be
called?
Results of Mendel’s F1 CrossPollinating Experiments
• Rather than the plants showing
blended characteristics of the
parents, the F1 plants showed
characteristics of only one
parent.
Source:
http://scientopia.or
g/blogs/guestblog/
2012/08/03/mudsticks-especially-ifyou-are-gregormendel/
• What Mendel called characteristics,
or traits, scientists now call genes.
• The different forms of these traits
(i.e., green peas vs. yellow peas)
are called alleles.
• If an allele is dominant, an
organism with that allele will
always exhibit that form of the
trait.
• Recessive alleles are only exhibited
when dominant alleles are absent.
Results of Mendel’s F1
Crosses
• Mendel took F1 plants and
allowed them to self-pollinate.
• What would you naturally
expect the offspring of a selfpollinated plant to look like?
• Actual results: Traits controlled
by recessive alleles reappeared
in some of the F2 offspring.
Explanation of Results
• Law of Segregation:
– Mendel assumed the recessive
allele was masked by the
dominant allele in the F1 offspring.
– At some point, the two alleles
were separated. (At what point
was this????)
– How would the traits exhibited by
the recessive alleles show back
up?