module 10 lesson 1: Mendelian Genetics.ppt

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Module 10 Lesson 1:
Mendelian Genetics

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Inventory of my traits

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 These features you described are called
traits.
• Traits are observable characteristics that are passed
down from parent to offspring.
• An individual will have many traits they share in
common with others.
• An individual's overall combination of traits makes
them unique.
• Some traits are more common in a population than
others.

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 When traits are passed from generation to
generation it is called inheritance, or
heredity.
 The scientific study of inheritance is
called genetics.
• (The study of how characteristics are
transmitted from parents to offspring)

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• Answer these questions after the inventory:
• Do you think people may have some traits in
common?
• Do you think traits exist in the same frequency in a
certain population or some traits are more common
than others?

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Which traits are stronger &
which are weaker?
• So which are dominant?& which are
recessive
• Do you think so that the more popular
traits are dominant & the less ones are
recessive?
• A dominant trait is not necessarily more common and
a recessive trait is not necessarily rare in a
population.

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Mendel 7 traits

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Gregor Mendel, continued
• Mendel’s Garden Peas
– Mendel observed
characteristics of pea plants.
– He studied 7 traits.
– Each characteristic occurred
in two contrasting traits.
https://www.youtube.com/watch?v=3f_eisNPpnc
Till 2:44

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Section 1 Mendel’s Legacy
Chapter 9
Gregor Mendel, continued
• Mendel’s Methods
– Mendel used cross-pollination techniques in
which pollen is transferred between flowers of two
different plants.
But let’s examine the flower parts first

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Flower
Anatomy

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Types of pollination

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Mendel’s Experiments
• Mendel bred plants for several generations that were
true-breeding for specific traits and called these the P
generation.
• Offspring of the P generation were called the F1
generation. [ F stands for (filial) = generation ]
• Offspring of the F1 generation were called the F2
generation.

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Three Steps of Mendel’s Experiments

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Mendel’s Results and Conclusions
• Recessive and Dominant Traits
– Mendel concluded that inherited characteristics are
controlled by factors that occur in pairs (genes).
– In his experiments on pea plants, one factor in a
pair masked the other.
– The trait that masked the other was called the
dominant trait. The trait that was masked was
called the recessive trait.
– https://www.youtube.com/watch?v=cWt1RFnWNzk

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Allele: The alternative forms of a gene,
like the "tall" and "short" versions of
the gene for height in garden peas.

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Homozygous Vs. Heterozygous

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Genotype and Phenotype
• The genotype is the genetic makeup of an organism
(allele pairs).
• The phenotype is the appearance of an organism
(observable characteristic).

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Mendel’s Results and Conclusions, continued
• The Law of Segregation
– The law of segregation states that the two alleles for
each trait is segregated, or separated, during meiosis
(the formation of gametes). During fertilization, two
alleles for the trait unite.

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• The Law of Independent
Assortment
– The law of
independent
assortment states that
a random distribution of
alleles occurs during
gamete formation.
Genes on separate
chromosomes sort
independently during
meiosis.

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• The Law of Independent Assortment
– The law of independent assortment is observed only
for genes that are located on separate chromosomes
or are far apart on the same chromosome.

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Support for Mendel’s Conclusions
• We now know that the factors that Mendel studied
are alleles, or alternative forms of a gene.
• One allele for each trait is passed from each parent
to the offspring.

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Probability
• Probability is the likelihood that a
specific event will occur.
• A probability may be expressed as a
decimal, a percentage, or a fraction.
• The probability of inheritance of genes
can be modeled by flipping a coin.

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Predicting Results of Monohybrid Crosses
• A Punnett square can be
used to predict the
outcome of genetic
crosses.
• A cross in which one
characteristic is tracked is
a monohybrid cross.

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Punnett
Square with
Homozygous
Cross
100% Yellow

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Monohybrid Cross
of Heterozygous
Plants
-The genotypic ratio is:
1:2:1
-The phenotypic ratio is:
3:1

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Predicting Results of Dihybrid Crosses
• A cross in which two characteristics are tracked is a
dihybrid cross.

Dihybrid Crosses
•Dihybrid crosses examine
two separate traits being
inherited at the same
time.
Plant Height
Flower Color

Dihybrid Crosses
•Each parent now has two
sets of alleles…one for
each trait
•(Ex. TtPp x TtPp)
X

Dihybrid Crosses
•The Punnet Square will now be a large square
separated into 16 boxes.
•The traits for the mother will go across the top.
•The traits for the father will go across the side.

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Dihybrid Crosses

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Multiple Choice, continued
2. In a monohybrid cross of two heterozygous parents
(Pp), what would the expected genotypes of the
offspring be?
A. 1 PP : 2 Pp : 1 pp
B. 1 pp : 3 PP
C. 3 Pp : 1 pp
D. all Pp
Standardized Test Prep

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3. Which of the following is an example of a genotype of
a heterozygous individual?
A. p
B. YY
C. Zz
D. rr

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4. Homologous chromosomes are
chromosomes that carry genes
for the same characteristics,
such as eye color or hair color.
Which of the chromosomes in
the bottom row could not be the
homologous chromosome for the
single chromosome in the top
row?
A. 1
B. 2
C. 3
D. 4
Use the diagrams of
chromosomes below to answer
the question that follows.
The single chromosome below
has two genes, both of which
carry a dominant allele Q and R.

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5. Rr : genotype :: red :
A. F1 generation
B. heterozygote
C. phenotype
D. dominant

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6. The Punnett square shows the
expected results of a cross
between two pea plants. R and r
represent the alleles for round
seed and wrinkled seed traits,
respectively. What would the seed
texture phenotype of the plant in
box 4 be?
A. round
B. Rr
C. wrinkled
D. rr
Use the diagram of a
Punnett square below to
answer the question that
follows.

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Short Response
Mendel was able to observe certain traits as they
were passed on by carefully controlling how the pea
plants were pollinated. Explain why Mendel began his
experiments by allowing pea plants to self-pollinate
for several generations.

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Short Response, continued
Mendel was able to observe certain traits as they
were passed on by carefully controlling how the pea
plants were pollinated. Explain why Mendel began his
experiments by allowing pea plants to self-pollinate
for several generations.
Answer:
Mendel wanted to ensure that the plants he was
studying were true-breeding.

module 10 lesson 1: Mendelian Genetics.ppt

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module 10 lesson 1: Mendelian Genetics.ppt