Download ORIGIN OF GENETICS

Today 1/25
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Take a seat.
What is the difference between
heredity & genetics?
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The passing on of
characteristics
from parents to
offspring is called
heredity.
The study of
heredity is
genetics.
GREGOR MENDEL
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Austrian monk who
worked in the
monastery gardens.
One of the first to
study heredity using
pea plants from the
gardens
“Father of genetics”
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He studied 7 traits- one at a
time.
seed
seed
seed
shape color coat
pod
pod
flower
plant
shape
color
arrangmnt
height
MENDEL’S EXPERIMENTS
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P-Generation- parent generation
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F1 Generation- first filial generation
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Pollen from pure yellow seed plant crossed
with egg of pure green seed plant
First set of offspring from parent generation
All offspring were yellow.
Where did the green trait go?
Developed Rule of Dominance- one trait will
overpower another even if both are present.
F2 Generation- second filial generation
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Two offspring from first generation are
mated
¾ of offspring were yellow, ¼ were green
How did the green trait reappear?
Developed two laws:
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Law of Segregation
Law of Independent Assortment
MENDEL’S
CONCLUSIONS
Rule of Unit Factors
1.
A.
B.
C.
D.
Inheritance is determined by
genes passed from parent to
offspring
The different forms a
gene can take are
called alleles.
You get one allele from
mom & one allele from
dad.
EX:
GENE- seed color
ALLELES- for seed
color are yellow
& green
MENDEL’S CONCLUSIONS
2. Rule of Dominance: Some
alleles are dominant and others
are recessive.
A. DOMINANT ALLELE
•Gene that is shown
•Represented by capital
letter
•EX: Yellow is
dominant- Y
B. RECESSIVE ALLELE
•Gene that is hidden when a
dominant allele is present
•Represented by a lowercase
letter
•EX: green is recessive- y
MENDEL’S
CONCLUSIONS
3.
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Law of Segregation:
Each pair of genes
separates when
gametes are formed
during meiosis.
Explains the
disappearance of a
trait in the F1
generation and its
reappearance in the
F2 generation.
MENDEL’S CONCLUSIONS
4. Law of Independent
Assortment- The genes
for different traits are
inherited independently
of each other b/c there
is no specific way the
chromosomes must line
up during metaphase of
meiosis
PUNNETT SQUARES
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Diagram that shows
possible offspring
that would result
from two parents.
Shows probability
that a allele will be
passed to offspring
TT
Tt
Tall
Tall
Tt
tt
Tall
short
HOMOZYGOUS
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When two alleles in a
pair are the same.
Also called purebred.
Can be either:
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Homozygous dominant
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Two dominant traits
YY- yellow
Homozygous recessive
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Two recessive traits
yy- green
HETEROZYGOUS
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Have one dominant
and one recessive
allele.
Dominant allele is
always expressed.
Person is a carrier
for the recessive
trait.
Also called hybrids
EX: Yy- looks yellow
but carries a green
trait
Compare phenotype and genotype
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Genotype: gene
combination of
organism
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ex: tt, TT, Tt, GG,
gg
Phenotype:
physical
appearance of
the organism
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ex: short, tall,
green, yellow
How do you set up a Punnett
Square
1.
2.
3.
4.
5.
6.
7.
8.
READ the word problem.
Underline the parent’s phenotype.
Determine the parent’s genotype
Put one parent’s genotype on the
top of the Punnett and other
parent’s genotype down the left side.
Pull letters down into the boxes to
show possible genotype
combinations of offspring.
Determine the offspring phenotypes
and write those in the boxes.
Determine genotype & phenotype
percents/ratios for the offspring
Each box is worth 25% or ¼
Cross a homozygous dominant tall plant
with a homozygous recessive short plant
Parent 1- TT
Parent 2- tt
Genotype Phenotype
TT- 0% Tall- 100%
Tt- 100% Short- 0%
Tt- 0%
Types of Punnett Squares
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Monohybrid Crosses
determining offspring’s
chances of inheriting a
single trait
Dihybrid Crossesdetermining offsprings
chances of inheriting
two traits together.