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Why is he considered the father of genetics?
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Born in Heinzendorf Austria in 1822
Grew up on a family farm and learned about cultivating
flowers and fruit trees.
He went to college. He was brilliant. He struggled with
scientific reading.
After college he entered a monastery 1843.
He used plants to study the way traits are passed from
parents to offspring. He grew almost 30,000 pea plants.
In 1865 he presented his work.
 2 lectures and only 40 copies made.
1868 Elected Abbot of Monastery and his duties prevented
him from sharing his work.
In 1900 his work was rediscovered.
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He wanted to know why traits sometimes
appear in one generation but not the next. He
also wanted to know why the missing traits
seemed to reappear in future generations.
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Timeline
Timeline 2
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Trait = A distinguishing quality that can be passed from
one generation to the other (i.e. cleft or smooth chin).
Dominant Trait = The trait observed when at least one
dominant allele for a characteristic is inherited (i.e. Cc =
cleft chin).
Recessive Trait = The trait that is apparent only when two
recessive alleles for the same characteristic are inherited
(i.e. cc = smooth chin).
Genes = Segments of DNA that carry hereditary
instructions and are passed from parent to offspring.
DNA (click to see video) = Deoxribonucleic Acid
Alleles = Different forms of a single gene (i.e. Cc
where C is for cleft chin and c is for smooth chin)
 Genotype = The inherited combination of alleles
(i.e. CC Cc or cc).
 Phenotype = An organisms inherited appearance
(i.e. cleft chin or smooth chin)
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Ratio: is the comparing how many there are of
one kind of something to how many there are of
another (i.e 3:1). Ratios can be represented by
fractions and reduced by dividing the fraction (2/4
= ½).
 Probability: is the mathematical chance that an
event will occur (i.e. a coin toss = 50/50).
 Generation : is a group of organisms living during
roughly the same time period.
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Dominant Trait: is the trait observed when
there is at least one dominant allele
inherited (i.e. Cc = cleft)
Recessive Trait: is the trait observed only
when there two recessive allele for the
same characteristic are inherited (i.e. cc =
smooth)
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Self –Pollinating = A plant that contains
male and female parts and can fertilize its
own eggs (see picture page 107)
Cross – Pollinating = Two different plants
reproducing by sending the pollen from one
plant to the eggs of another (see picture
page 108).
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Homozygous (True Breeding) = Is when an
organism carries only one form of a gene
governing a characteristic. Always produces kids
with the same traits as the parents because the
parents pass on only one kind of instructions or
genes (i.e. CC or cc).
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Heterozygous (not true breeding) = Is when
an organism carries two different forms of a
gene governing a characteristic ( i.e. Cc)
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His work was not widely accepted until 16
years after his death.
DNA and Genes really hadn’t been discovered
yet.
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They grow quickly
Usually self - pollinating
They have several inherited characteristics
that can be studied (flower color, seed color,
seed shape, pod color, pod shape, flower
position and plant height).
What are inherited characteristics?
They are inherited features, such as flower
color that can vary among individuals.
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Self pollinating (male and female
reproductive cells are on the same
flower)
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Cross pollinating (male and female
reproductive cells are on different
plants.
1.
2.
3.
4.
Different forms or versions of genes account for variations in
inherited characteristics.
For each character, an organism inherits two genes, one
from each parent.
If two alleles differ, then one, the dominant allele, is fully
expressed in the organism’s appearance; the other, the
recessive allele, has no noticeable effect on the
organism’s appearance.
During gamete (haploid 1n) production the egg and sperm
each receive only one of the genes that are present in two
copies in normal body cells (diploid 2n)
SELF POLLINATION
Plant carries male and
female structures. Pollen
from one flower or plant
can fertilize the eggs of the
same flower or another
flower on the same plant. 1
Parent
CROSS POLLINATION
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Pollen is taken from one
plant’s anther’s (male) and
placed on other plant’s
stigma (female).
Two Parents
The two versions of a gene that govern the same
characteristic are known alleles. (For example the gene for
flower color exists in two different forms ………..
Purple ( Dominant (P) ) and white (recessive (p) ). These
different forms of the gene are known as alleles.
Parents could be PP, Pp or pp
so let’s imagine PP x pp ……….
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Dad
P
P
Mom
p
p
Mendel performed crosses to study seven different characteristics of pea plants.
Each cross was between the two traits or forms of the characteristic.
 For example see page 109 fig.6.
 A true breeding cross RR x rr (true breeding round x true breeding wrinkled)
produced the 1st generation of all round peas.
 Show punnett square to show why.
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Mendel chose to call the trait that seemed to show the DOMINANT trait and the
one that did not show the RECESSIVE trait.
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Mendel repeated this same experiment with at least 6 other crosses and found
the same results each time.
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Mendel allowed the 1st generation from each of the 7 crosses
to self-pollinate.
This time the plant that showed only the dominant trait in
the first experiment (i.e roundness) reproduced within itself
(self – pollination) and the recessive trait showed up again in
the offspring in exactly 3:1 ratio for each of the 7
characteristics he studied.
Look at table on page 110.
Try Math Break
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A ratio is comparing how many there are of one kind of something
to how many there are of another. Ratios can be represented by
fractions and reduced by dividing the fraction.
 What is the ratio of boys to girls in this class?
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Probability is the mathematical chance that an event will occur.
 What is the chance of flipping tails on one toss of a
two-sided coin?
▪ ½ or 50%
 What is the chance of flipping tails 3 times in a row?
▪ ½ x ½ x ½ = 1/8
DOMINANT
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RECESSIVE
The big letter represents
the dominant or stronger
form of a gene for a
characteristic.
R
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The small letter represents
the recessive or weaker
form of a gene or
characteristic.
r
Each parent donates one set of instructions, known as genes to
the offspring. The Zygote (fertilized egg) would have at two least
genes for each characteristic (one from mom and one from dad).
The two genes that govern the same characteristic are known as
alleles. A punnett square is used to visualize all possible
combinations of alleles from parents.
 PP = alleles for a true breeding (homozygous) purple pea plant
 pp = alleles for a true breeding (homozygous) white pea plant.
 PP x pp = all four possibilities of Pp = (non-true breeding
heterozygous)
* Note: Only some traits are single gene traits as explained above.
Many traits turn out to be controlled by several genes from mom
and dad.
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HETEROZYGOUS
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Would be one big letter (R)
representing a gene (allele)
and one small letter (r).
HOMOZYGOUS
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Rr
Would be two big letters
(RR) or two small letters
(rr).
RR or rr
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Also referred to as True –
Breeding or Pure Bred.
GENOTYPE
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Inherited alleles or forms of
a gene for a characteristic
PHENOTYPE
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Organism’s inherited
appearance (how it looks)
Mendel published his work and presented his
findings in two lectures. He had only 40 copies of his
results published.
 He was elected abbot of the monastery in 1868. His
duties prevented him from visiting scientists and
attending conferences where he could have
discussed the results.
 He died in 1884. His work was rediscovered in 1900.
 His results were used to justify Darwin’s Theory of
Evolution.
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Darwin came up The Theory of Evolution. He
had questions that he could not answer.
 How did organisms pass traits on to their
offspring?
 Why did some traits seem to be passed on and
others not?
 How did the traits of the parents work together in
the offspring -- did they compete, or combine?
When scientists today work to decode the
human genome, they use high-tech methods to
view the microscopic chromosomes and even pluck
individual genes out of a cell. But in Darwin's time, it
was impossible to see any of that. No one was sure
how animals or plants passed down traits. And
Darwin knew that the lack of an explanation
forheredity left a big gap in his theory of natural
selection.
 Source:
http://www.pbs.org/wgbh/evolution/library/06/1/l_0
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Practice