Transcript Slide 1

General Biology 2
A.
B.
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D.
E.
Roll
Personal Introduction
Statement about disabilities
Course Policies and Schedule
Class room management
1. cell phones
2. timeliness
3. questions
I.
Brief review of meiosis-corner stone of
Mendelian genetics
• A. Relevant terms to be used
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diploid vs. haploid
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2.
chromosome versus chromatin
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chromatid, monad, dyad, tetrad
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homologous chromosomes
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synapsis and chiasmata
B.
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Events of meiosis I
1. prophase I
2. metaphase I
3. anaphase I
4. telophase I
C.
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Interkinesis
1. some textbooks call this interphase II
2. lousy name
3. no DNA replication
4. pretty much resting stage
5. some species meiosis is arrested at this
stage
• 6. human egg is released after meiosis I and
meiosis II does not occur unless fertilization
happens
D.
Meiosis II
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prophase II
metaphase II
anaphase II
telophase II
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Biology Happens Around the World
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Early Mendel
A. Biography
1. 1822-1883
2. Moravia-Silesia
3. 1851-1853 Univ of
Vienna
4. age 29 years
5. left after two yearsepilepsy
6. entered monastery-safe
environment for health reasons
7. first organism honey
bee-practical application
• German and italian races
B.
Qualities of pea plant
• 1. who
pollinates this
flower?
• 2. arrangement
of petals
promotes selfpollination
• 3. usually true
breeding
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4. true breeding =
homozygous
5. easily recognized
traits
6. distinct traits-not
intermediate phenotypes
7. easy to generate
large numbers
8. short generation time
9. can easily manipulate
flowers breeding partners
C. Not first to study genetics
• 1. earlier geneticists studied multiple traits at one time
• 2. did not look at large numbers
• 3. did not choose traits that had distinct forms
• 4. did not follow through successive generations
• 5. predominant conclusions of time-blending theory of
inheritance-fusion of inheritance particles
• -some factor from male and female mix
-analogous to mixing paints
-would result in identical offspring
-not true
III.
A.
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Mendel’s first cross
Tall vs. short
parental generation
next generation all tall
allowed self-pollination
mixed bag 787 tall: 277
short
5. allowed this generation to
self pollinate
6. all short true breeding
7. 1/3 tall true breeding-2/3’s
of tall were not true
breeding
B.
Explanation
• 1. Law of particulate inheritance
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a. Each trait or characteristic is influenced
by two particles or factors
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b. One particle/factor comes from dad and
one from mom
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c. Particles remain separate and distinct in
cells of offspring
• 2. Law of segregation
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a. Independent factors separate during
gamete formation
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b. These factors come in more than one
flavor-one factor may overshadow the second
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c. Each gamete receives one of the two
factors that an individual carries in its cells
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d. Mendel knew nothing of chromosomes or
of meiosis
C.
Mendel’s cross with traits on chromosomes
• 1. Parental generation
forming offspring of first
generation
2. First generation meiosis
• Notice separation of
factors influencing
height in gametes
• Basically two flavors of
gametes being
produced
3.
Punnett square for second generation
• a. Notice outcome of
random mating/self
pollination
• b. All of short plants will
be true breeding
• c. 1/3 of tall will be true
breeding
• d. 2/3’s of tall will produce
a mixture as their parents
did
D.
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Vocabulary of monohybrid cross
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gene
allele
dominant vs. recessive
phenotype vs. genotype
heterozygous vs. homozygous
monohybrid vs. dihybrid
P, F1, and F2
E. Sample problem
• In humans, freckles are dominant to no freckles. Mary,
who has no freckles, is planning on having children with
Paul. Paul, who has freckles, was born to a freckless
woman. Mary wants to know the probability of her in
utero son has of having freckles.
• How do we start?
• List the symbols to be used to represent the alleles.
• What is the mother’s phenotype? Genotype?
• What is the father’s phenotype? What does his
genotype have to be?
• What alleles are carried in the eggs and sperm of the
couple?
• Create the punnett square.
• What will be the name of the son which is not born yet?
F.
An analysis of Mendelian ratios
• 1. ratios almost too good
• 2. discussion in the literature
that the numbers should not
come out as closely to
theoretical as they do
• 3. statistical probability of
such a good fit is low
• 4. other writers come to his
defense
• 5. will see other results that
look very close when we get to
the dihybrid crosses.
G.
Generalizations about Mendelian
monohybrid crosses.
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three crosses to remember
hetero X hetero
hetero X homo rec
hetero X homo dom
H.
Chi square analysis
• 1. in lab you are going to play Mendel counting the
number of kernels of corn that display certain phenotypic
ratios
• 2. trying to verify Mendelian theoretical ratios
• 3. doubtful that you will come as close as Mendel did in
your actual ratios
• 4. when will close enough be considered close enough
to agree with theory
• 5. need a statistical test to decide
• 6. the statistical test needs to be tied to sample size
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Background information
tossing a coin 100 times
Expect to get 50:50
Not going to happen very often
There will be chance variation
How close to predicted results do the actual results
have to be to accept that the coin is behaving as you
predicted
Is 70:30 close enough or do you need 60:40
Imagine doing the coin tossings is sets of 100
The ratios obtained will vary around the 50:50
expected
7.
Background information continued
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one set of tosses by chance alone might come out with 80:20
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It is not mathematically impossible that this would happen
• k. if this result occurred of 80:20 occurred 1/10th of the time, it
would be more significant than if it occurred 1/20th of the time
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in the first case we might have doubt about the coin itself
• m. 1/20 or .05 is where we draw our mathematical line between
models that fit theoretical predictions and models that don’t
• n. the number of .05 has to do with the number of “experiments”
and means that one time out of twenty the experiment will not turn
out as predicted by the hypothesis-the results will vary by chance
alone
8.
Example
• a. case one 40 tosses
30T:10H
• b. case two 200 tosses
90T:110H
• c. each case has a deviation of ten from
expected
• d. more acceptable in the second case due to
sample size
• e. chi square test determines the level of
acceptability of results
• f. chi square = (obs-exp)2/ exp
9.
Chi square calculations
Case One
Observed
Expected
(obs-exp)2/exp
Heads
10
20
(10-20)2/20 = 5
Tails
30
20
(30-20)2/20 = 5
Total
40
40
5 + 5 = 10
Heads
110
100
(110-100)2/100 = 1
Tails
90
100
(90-100)2/100 = 1
Total
200
200
1+1=2
Case Two
10.
Compare values to chi square table
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case one chi square value = 10
case two chi square value = 2
I.
Test Cross-allows determination of an
unknown genotype
• 1. You are a breeder of beagles. Barking in beagles is
a highly prized trait and is dominant over nonbarking.
• 2. Neighbor has a beautiful beagle, but wants to get rid
of animal due to a nasty habit
• 3. You own a beagle kennel-but don’t know if you want
to allow the neighbor’s beagle into your breeding stock
• 4. Don’t know his background-where he came from
• 5. Perform a test cross
– Unknown genotype X homo. recessive
J.
Intermediate inheritance/incomplete
dominance
• 1. Not all traits are inherited in Mendelian simple
dominance/recessive fashion
• 2. In some cases the hybrid heterozygote shows an
intermediate phenotype between the two extremes
• 3. Don’t confuse this with blending
• 4. Example of red and white four o’clock flowers
• 5. Heterozygote is pink
• 6. What would you expect if two pink four o’clock
flowers had offspring?