Mendel's Experiments and Principles of Genetics
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B
IOLOGY
C
HAPTER
8
Heredity
8.1 O
BJECTIVES
Discuss Mendel’s experiments and his results.
Explain the three principles of genetics Mendel
obtained through his experiments.
Solve genetics problems using Punnett Squares.
8.1 P
RINCIPLES
OF
G
ENETICS
Discuss Mendel’s experiments and results.
Explain the three principles of genetics Mendel
obtained through his experiments.
Solve genetics problems using Punnett squares.
P
RINCIPLES
OF
G
ENETICS
The passing of traits from parents to offspring is
termed heredity.
Can we predict certain traits?
Can we determine what types of genetic
information parents have by looking at certain
traits of the offspring?
We can answer these questions through genetics
– the science of heredity.
O
RIGIN
OF
G
ENETICS
Father of genetics: Gregor Mendel (1882-1884)
Tended to a garden of pea plants in a monastery.
Published results from 8 years of research, only
to be ignored until 1900.
M
ENDEL
’
S
E
XPERIMENTS
Peas are grown easily and produce large numbers
of offspring in a short time.
Chose 7 traits to study:
M
ENDEL
’
S
P
ROCESS
Mendel crossed pea plants w/ different traits.
Offspring of parental cross were called F
1
Offspring of F
1
crosses called F
2
.
He noted for each trait, there was a dominant
and recessive form.
In his crosses, recessive trait disappeared in F
1
generation and then reappeared in F
2
.
M
ENDEL
’
S
H
YPOTHESIS
He reasoned that for every trait, there must be a
pair of factors.
He called them characters, but we now know
them as genes.
One gene came from each parent.
P
UNNETT
S
QUARES
P
UNNETT
S
QUARES
P
UNNETT
S
QUARES
T
HE
T
EST
OF
S
EGREGATION
He predicted if the F1 purple flowered plants
were crossed with white flowered plants, he
would get ratios different from any of his
previously obtained ratios.
T
ERMINOLOGY
Each alternative form of a gene for a certain trait
are called alleles.
Combination of genes for a given trait referred to
as genotype. Example: WW and Ww
The physical appearance of a trait is the
phenotype. Example: Blue and brown eyes.
Homozygous = two of same alleles: WW or ww
(homozygous dominant and homozygous
recessive)
Heterozygous = two different alleles: Ww
T
WO
T
RAITS
(D
IHYBRID
C
ROSSES
)
T
WO
T
RAITS
(D
IHYBRID
C
ROSSES
)
T
WO
T
RAITS
(D
IHYBRID
C
ROSSES
)
8.2 S
OLVING
G
ENETICS
P
ROBLEMS
Objectives:
Apply the rules of probability to solve genetics
problems.
Demonstrate the inheritance of traits resulting
from incomplete dominance, codominance, and
multiple alleles.
P
ROBABILITY
What is the probability of getting heads or tails
when you toss a coin?
There is a list of steps to follow on page 208 in
text, but we have already been doing this.
Remember, we can find either genotypic or
phenotypic ratios.
I
NCOMPLETE
D
OMINANCE
: 4
O
’
CLOCK
PLANTS
AS
AN
EXAMPLE
M
ULTIPLE
A
LLELES
: H
UMAN
B
LOOD
T
YPES
8.3 T
HE
C
HROMOSOME
T
HEORY
OF
H
EREDITY
Walter Sutton’s work showed good evidence that
genes reside on chromosomes.
Some genes appear only on sex chromosomes.
XX = female and XY = male in humans.
Different combinations for different species.
Example: Grasshoppers X = male and YY =
female.
Sex-linked traits are traits that result from genes
on the sex chromosomes.
S
EX
-L
INKED
T
RAITS
IN
H
UMANS
Hemophilia – gene is a recessive gene found on
the X chromosome. Mostly, males get the
disease.
Color-blindness is the same way.
M
ANY
G
ENES
– O
NE
E
FFECT
Height, hair, eye, and skin color all controlled by
multiple alleles.
Sample genotypes:
AABBCCDD
AaBbCcDd
Aabbccdd
Modifier genes can also impact things like eye color.
Brown, blue, hazel, green, mixed etc.
Delve into the pioneering work of Gregor Mendel, the father of genetics, as he conducted groundbreaking experiments with pea plants, identified key principles of genetics, and introduced the concept of dominant and recessive traits. Explore how Mendel's work laid the foundation for our understanding of heredity and the passing of traits from parents to offspring.
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Presentation Transcript
BIOLOGY CHAPTER 8 Heredity
8.1 OBJECTIVES Discuss Mendel s experiments and his results. Explain the three principles of genetics Mendel obtained through his experiments. Solve genetics problems using Punnett Squares.
8.1 PRINCIPLES OF GENETICS Discuss Mendel s experiments and results. Explain the three principles of genetics Mendel obtained through his experiments. Solve genetics problems using Punnett squares.
PRINCIPLES OF GENETICS The passing of traits from parents to offspring is termed heredity. Can we predict certain traits? Can we determine what types of genetic information parents have by looking at certain traits of the offspring? We can answer these questions through genetics the science of heredity.
ORIGIN OF GENETICS Father of genetics: Gregor Mendel (1882-1884) Tended to a garden of pea plants in a monastery. Published results from 8 years of research, only to be ignored until 1900.
MENDELS EXPERIMENTS Peas are grown easily and produce large numbers of offspring in a short time. Chose 7 traits to study: Seed Shape Seed Colo r Yello w Green Flowe r Color Purple Flower Position Pod Color Pod Shape Plant Heigh t Long Dominant Trait Recessive Trait Round Axial (side) Green Inflated Wrinkled White Terminal (tips) Yellow Constricted Short
MENDELS PROCESS Mendel crossed pea plants w/ different traits. Offspring of parental cross were called F1 Offspring of F1crosses called F2. He noted for each trait, there was a dominant and recessive form. In his crosses, recessive trait disappeared in F1 generation and then reappeared in F2.
MENDELS HYPOTHESIS He reasoned that for every trait, there must be a pair of factors. He called them characters, but we now know them as genes. One gene came from each parent.
THE TEST OF SEGREGATION He predicted if the F1 purple flowered plants were crossed with white flowered plants, he would get ratios different from any of his previously obtained ratios.
TERMINOLOGY Each alternative form of a gene for a certain trait are called alleles. Combination of genes for a given trait referred to as genotype. Example: WW and Ww The physical appearance of a trait is the phenotype. Example: Blue and brown eyes. Homozygous = two of same alleles: WW or ww (homozygous dominant and homozygous recessive) Heterozygous = two different alleles: Ww
8.2 SOLVING GENETICS PROBLEMS Objectives: Apply the rules of probability to solve genetics problems. Demonstrate the inheritance of traits resulting from incomplete dominance, codominance, and multiple alleles.
PROBABILITY What is the probability of getting heads or tails when you toss a coin? There is a list of steps to follow on page 208 in text, but we have already been doing this. Remember, we can find either genotypic or phenotypic ratios.
INCOMPLETE DOMINANCE: 4 OCLOCK PLANTS AS AN EXAMPLE
8.3 THE CHROMOSOME THEORY OF HEREDITY Walter Sutton s work showed good evidence that genes reside on chromosomes. Some genes appear only on sex chromosomes. XX = female and XY = male in humans. Different combinations for different species. Example: Grasshoppers X = male and YY = female. Sex-linked traits are traits that result from genes on the sex chromosomes.
SEX-LINKED TRAITS IN HUMANS Hemophilia gene is a recessive gene found on the X chromosome. Mostly, males get the disease. Color-blindness is the same way.
MANY GENES ONE EFFECT Height, hair, eye, and skin color all controlled by multiple alleles. Sample genotypes: AABBCCDD AaBbCcDd Aabbccdd Modifier genes can also impact things like eye color. Brown, blue, hazel, green, mixed etc.
