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Chapter 11 Notes - Introduction to Genetics
What is Inheritance?
•Every living thing has a set of characteristics inherited from its parent
or parents.
•Genetics ____________________________________________.
11-1 The Work of Gregor Mendel
•He was an Austrian monk
•He worked with different ________________________ (pure bred) ____________________ .
•Pea plants were a good choice because:
•They were ___________________________
•Seed in _____________________
•________________________________________________________
•Mendel worked with 7 different traits:
•___________________________________
•___________________________________
•___________________________________
•___________________________________
•___________________________________
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Genes and Dominance
•What is a trait?
•___________________________________
•Example:
•Tall vs.. Short – _______________
•Round vs. Wrinkled – _______________________
•Mendel called the original plants the ______(parent) generation
•Offspring =______ generation
•If you cross two parents with different traits, the offspring are called
_______________.
Mendel’s F1 Cross
This is what Mendel saw.
The offspring had the characteristics of only
one of its parents
Mendel concluded:
1. Inheritance is determined by ____________ that are passed from one generation to the next
2. Chemical factors that determine traits are called ___________
3. Different forms of the same gene are called ____________
Example: Gene for ___________
Alleles: _______________________
4. _______________________________________________ : Some alleles are dominant and
some alleles are recessive.
•_________________________________ are always expressed
•_________________________________ are can only be expressed when the dominant allele
is not present
•Mendel wondered if the recessive alleles had dissapeared or were they still present in the F 1 plants
•He decided to allow all seven kinds of F1 hybrids to produce F2 offspring.
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Segregation
•Mendel looked at the results of his F1 and F2 crosses:
P1
F1
tall plants x short plants
_______________________
( ____________________________________________________________ )
P2
F2
tall plants x tall plants
________________________________________
This is What Mendel Saw
•Because the trait, _________, ___________________, Mendel reasoned that the ____________ for
tallness and shortness had ______________________ from each other when gametes
(__________________) form.
T = Tall
t = short
F1 : the F1 plant
produces 2 kinds
of sex cells
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11-2 Probability and Punnett Squares
•The chances that a particular event will happen is called ______________________.
•The principles of probability can be used to ________________ the outcomes of
__________________________________.
Punnett Squares
•_________________________ can be used to determine the genetic _____________________ that
might result from a ________________________.
•The _______________ in a Punnett Square represent ______________:
•Capital Letters = ________________________________ (____)
•Lowercase Letters = ________________________________ (____)
Punnett Square Terms
•___________________________ = True Breeding (__________)
•___________________________ = Hybrid
(___________)
•___________________________ = Physical Characteristics
•___________________________ = Genetic Makeup
(__________________________)
(___________)
Predicting Averages
•Probabilities can _____________ the average outcome of ______________________________.
•The larger the number of offspring resulting from a cross, the closer the results will be to the
expected values.
Ratios:
P - _________________
G – ____________
Offspring
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11-3 Independent Assortment
•What happens if there is ________________________________?
•Does inheriting a certain gene for seed color affect the inheritance of another trait like plant height?
2 Factor Crosses
•Mendel performed experiment to follow ______________________________ as they passed from
one generation to the next.
•These experiments are known as ___________________ (__________________) crosses.
•Mendel crossed plants that were true-breeding for two different traits.
•Round, yellow peas
•Genotype ______________
•Wrinkled green peas
•Genotype ______________
Which traits are dominant and which traits are recessive?
RRYY x rryy
ry
ry
ry
ry
RY
RY
RY
RY
Why are there so many boxes?
•Each parent can produce ______________________ kinds of sex cells (________________)
•Each gamete has an _________________________ of combining with each of the other parents 4
types of gametes.
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F2: Dihybrid Cross
•Each of the offspring in the example are hybrids for _____________________ - ________________
•Mendel crossed these offspring to produce another generation of plants (F2)
•If the genotype of each parent is RrYy, What kinds of gametes will each parent produce?
Gametes
•Parent 1: RrYy
•_____ _____ _____ _____
•Parent 2: RrYy
•______ ______ _____ _____
•The results of the F2 cross showed that the alleles for the two different traits segregated
________________________ into the gametes.
•The offspring from this cross showed a _______________________ of the different
________________________.
Summary of Mendel’s Principles
•Inherited traits are determined by __________. Genes are passed from parents to offspring
•Some forms of the gene may be _________________ and others may be _________________
•The genes ___________________ during meiosis so only one copy of a gene goes into the gamete
•Alleles for different genes usually segregate _______________________ of one another.
Exceptions to Mendel’s Principles
•Some alleles are _______________________________________________________, and many
traits are controlled by ______________________________ or _____________________________.
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Incomplete Dominance
•One allele is ______________________________ dominant over another.
•The heterozygous phenotype is somewhere _______________________ the two homozygous
phenotypes.
Example:
•R = red flowers
•r = white flowers
•Rr = pink flowers.
•
Codominance
•___________ alleles ___________________ to the phenotype of the organism
•Example: Horses, allele for red hair is codominant with allele for white hair.
Animals with both alleles ___________________ red and white hairs. The color
is called roan.
Multiple Alleles
•A particular trait has ____________________________________ alleles.
•You only inherit two of those alleles at a time.
•Examples: coat color in rabbits, hair color in humans, and _________________________________.
Human Blood Types ;
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Polygenic Traits
•Traits produced by the interaction of _______________________.
•Examples: _______________________________, height, cystic fibrosis
Applying Mendel’s Principles
•Albinism in humans is caused by a __________________ trait.
•If two people with normal skin color have a child with albinism, what are the odds that a second child
will also have albinism?
A = normal, a = albino
•Chances for a normal child?
•___________
•Changes for an albino child?
•___________
11-4 Meiosis
Introduction
•Multicellular organisms use ____________ to _____________________ that lost due to
_______________ or damage or to ___________.
•These cells (_____________________) are identical to the parent cells because all of the DNA is
first copied and then two copies of the DNA separate when the daughter cells form.
•______________________________________________________________________________ .
Meiosis is Different
•Multicellular organisms _____________________________.
•In order to keep the number of chromosomes the same from generation to generation, the
_________________ have to reduce the number of chromosomes to one half of the number that you
find in a somatic cell (body cell)
•_______________________________________________________________________________.
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Meiosis I
•The chromosomes have replicated during S phase of the cell cycle.
•During _______________, the chromosomes become visible and the
chromosomes pair off--that is chromosomes that carry the same information
called ________________, and form structures called ____________.
•Something important happens during this process--the homologous chromosomes can twist around
each other and some times they break off. When they re-attach, they may attach to the other
chromosome.
•This event is called ________________________ and is an important
process in genetics.
•After prophase I, the tetrads of chromosomes line up at
the equator of the cell for ________________
•In _________________________, the pairs of chromosomes separate from each
other. _________________________________________________________of
each type of chromosome.
•In __________________, two daughter cells form. Each of these cells have
__________________ _______________ of chromosomes that we wstarted
with.
Meiosis II
•In this second cell division, the two daughter cells from meiosis I undergo one more cell division
•The steps in this cells division are very much the same as mitosis except the DNA is _______ copied
again
• ___________________:
• ___________________:
• ___________________:
• ___________________:
chromosomes become visible
chromosomes line up at the equator
centromeres split, and the copies of the DNA are pulled apart
4 daughter cells form.
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Products of Meiosis
• _______________________
• Cells are ___________________________________________ to the parent cell
• _________________________ may have ________________________________ from the
maternal and paternal chromosomes.
________________________________________________________________________________
Additional Notes:
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