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GENETICS
Chapter 11 – NOT SECTION 4!
GENETICS
People
use the term genetics all
the time
What
does the word genetics
mean to you?
What
do you believe influences
your genetics?
GENETICS
Field
of Biology based on
understanding how
characteristics are passed along
from parents to offspring.
Founded
by the work of Gregor
Johann Mendel
MENDEL’S WORK
 Entered
the monastery in 1842, his
job was to tend the garden- Austria
 In
1851, entered University of
Vienna to study science and math
 Returned
to the monastery after
college and became famous for his
work with garden peas!
PLANT PARTS
 Use
handout of plant parts as a
refresher!
 Female

Ovary, Style, Stigma, Ovule
 Male

plant parts- PISTIL
plant parts- STAMEN
Filament, Anther, Pollen
PLANT STRUCTURE
HOW DOES PLANT
FERTILIZATION OCCUR?
 The
pollen attached to the anther
comes into contact with the stigma
 The pollen is the plant’s sperm, so a
pollen tube forms in the style.
 The pollen tube will take the pollen
to the ovary, or fertilize the female
egg (ovule)
 When the pollen comes into contact
with the ovule, fertilization takes
place.
PLANT POLLINATION
ON YOUR SHEET
Color
the following parts on your
plant parts worksheet
 Filament
 Anther
 Pollen
 Ovary
Ovule
Pollen Tube
Stigma
Style
GENETICS VOCABULARY
 Traits-
alternate characteristics are
available. Ex: height, eye color.
Traits can be observed.
 Heredity-
the transmission of traits
from parent to offspring.
 Gregor
Mendel- Father of modern
day genetics.
MENDEL’S PLANTS
 Observed
seven characteristics of pea
plants. Each had 2 traits!







Plant height- long or short stem
Flower Position- axial or terminal
Pod Color- Green or yellow
Pod Appearance- inflated or constricted
Seed texture- smooth or wrinkled
Seed color- Green or yellow
Flower color- Purple or white
 Mendel
used his knowledge of statistics to
observe these 7 traits in his plants.
FIRST YEAR WITH PLANTS
 Observed
that purple flowering
plants grew from seeds obtained
from purple flowering plants.
 BUT, some white-flowering plants
also grew from purple-flowering
plants.
 Some tall plants grew from seeds
from tall plants, some short plants
grew from tall plant seeds.
PLANT POLLINATION
 Remember
the steps from earlier!!!
 Self-Pollination- pollen is
transferred from the anthers of a
flower to the stigma of either the
same flower of the same plant.
 Cross-Pollination- involves flowers
of 2 separate plants.
 Pea plants normally reproduce
through self-pollination
POLLINATION CONTINUED
 Self-pollination
can be interrupted, and cross
pollination performed.
 Cross
pollination is completed by removing the
anthers from a flower and manually transferring
the anther of a flower on one plant to the stigma
of another plant.
 By
using cross pollination Mendel was able to
protect his flowers from receiving any other
pollen that might be transferred by wind or
insects, giving him more control over his plants.
MENDEL’S EXPERIMENTS
 Began
by growing plants that were pure
for each trait. Meaning that plants that
are pure for each trait will only produce
plants with that trait.
 Strains are plants that are pure for a
specific trait.
 Mendel allowed plants to self-pollinate
for several generations.
 Had 14 strains- 1 for each of the 14
traits he was observing.
MENDEL’S EXPERIMENT
 Each
strain was called a parental
generation or P1 generation
 He then cross-pollinated each strain
with its contrasting trait.

Ex: Yellow pea pods were crossed with
green pea pods
 The
first generation produced was
referred to as the F1 generation
 Second generation= F2 generation
MENDEL’S FINDINGS
 Hypothesized
that something within the
pea plants controlled the characteristics
he observed.
 Mendel
believed each trait was inherited
by means of a separate factor.
 Mendel
reasoned there must be a pair of
factor controlling each trait
MENDEL’S VOCAB





Heterozygous- 2 different alleles (2 traits different)
 Ex: Males are XY
Homozygous- 2 same alleles (2 traits same)
 Ex: Females are XX
Allele- alternate form of a gene
Phenotype- External appearance of an organism, determined by
the genotype
 EX: Female
Genotype- Genetic make up of an organism
 EX: XX
MENDEL’S VOCAB




Monohybrid Cross- A cross between individuals that
involved one pair of contrasting traits
Punnett Square- Model used to establish the
probabilities of the results of genetic crosses
Dominant- An allele masks the presence of another
allele for the same characteristic. ALWAYS
EXPRESSED!
Recessive- An allele that is masked by the presence of
another allele for the same characteristic. Needs 2 of
same trait to be expressed.
MONOHYBRID CROSS
In humans Brown eye color is dominant over
Blue eye color. What are the possible offspring of
a heterozygous brown eyed father and a
homozygous blue eyed mother?
 SET-Up

B=
 b=

Father’s Genotype =
 Mother’s Genotype=
 Set up cross.

TEST CROSS
-Introduced by Mendel
-Used to determine if an individual exhibiting a
dominant trait is homozygous or heterozygous
for the trait.
-If ALL offspring exhibits ONLY dominant genes
than parents are homozygous
-
If offspring show both dominant and recessive
genes then heterozygous.
DIHYBRID CROSS

A cross between individuals that involves two
pairs of contrasting traits.
DIHYBRID CROSS EXAMPLE
PRACTICE DIHYBRID PROBLEMS
Problems on worksheet
 Complete #1 together
 Complete the rest with ONE other partner.

DOMINANCE RELATIONSHIPS
 1.
Complete Dominance- one allele
completely hides the other. (What we have
been working on)
 2.
Incomplete Dominance- both alleles
influence the phenotype (BLENDING)
 3.
Codominance- neither allele
completely hides the other, both alleles
are seen (SPOTTING)
INCOMPLETE DOMINANCE
CODOMINANCE
Inheritance
relationship in
which neither
alleles totally
masks the
other.
Roan Cattle- Shows both red hair and white hair
allele. (shows both red and white hair color)
RR= Red hair
rr= white hair
Rr= Roan
BOTH
TRAITS ARE
SEEN
(SPOTTING)