Transcript Part 5: EOC Review Power Point

Biology EOC Review
Biological Molecules and Membranes/Cell
Structure/Mitosis/Meiosis and Genetics/Evolution
Part 5
If you recall…
 …we just discussed how living things such as plant
cells can benefit from both asexual and sexual
reproduction.
 We discussed the structure of DNA and
chromosomes.
 We also discussed that genes within the DNA of a
cell have the means of potentially mutating which
may help cells and organisms adapt to a changing
environment.
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How do we know?
 How do we know that genetic mutations in the
DNA can actually help an organism survive?
 We need to simply look at something that is
referred to as Mendelian Genetics to see this
pattern.
 Mendelian Genetics, which is named afterGregor
Mendel, is a pretty old concept that humans have
been unknowingly utilizing for centuries as we have
learned to domesticate plants and animals.
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???
 Remember our little plant cells that have been
growing asexually through the process of mitosis?
 The ones that are in a plant experiencing a major
change in their environment so that they aren’t
getting enough sunlight to use photosynthesis to
make food for themselves?
 How can Mendelian Genetics help?
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Grafting
 These plant cells may experience a genetic mutation
that could change the sun-gathering pigment
chlorophyll into a new pigment that absorbs
different strengths or wavelengths of light.
 Maybe instead of absorbing red and blue light,
which is what chlorophyll normally does, maybe
this new mutated pigment absorbs green and
yellow light.
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Grafting
 This new mutated pigment will reflect red and blue
light, so we see it as a purple pigment.
 If this purple pigment now helps our little plant
cells grow by allowing it to photosynthesize, they
will continue to multiply.
 If a farmer should see this new purple part of the
plant, they could remove it, graft it on to a very
strong stalk of a different plant, and grow it.
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Grafting
 The farmer just grafted the purple part of our plant
onto the healthy stem of another plant.
 That new plant does well and all new growth is
now purple.
 The plant thrives and flowers.
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Parenting
 The flower produces male gametes or sex cells,
which we call pollen (In humans, male gametes are
called sperm.).
 The flower also produces female gametes or sex
cells, which we call oocytes, ova (ovum), or eggs
(We use the same term in humans.).
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Parenting
 Each parent (Mom = egg and Dad = sperm/pollen)
has genetic information that they will share,
through meiosis, with their offspring.
 This process is called fertilization.
 Quick recap – Remember that in meiosis, a.k.a.
sexual reproduction, that one cell produces four
completely different cells.
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Punnett Squares
 We can show this Mom v. Dad DNA genetics
sharing by using something called a Punnett
Square.
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Punnett Square
 In a Punnett square, we look at each parent’s gene
and give it an abbreviation.
 For example, let’s say that, in our purple plant, a
gene in the DNA codes for a yellow flower. We
could use Y to describe that yellow flower.
 However, we notice that sometimes these same
plants produce a red flower. We could use y to
describe that red flower.
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Punnett Square
 BTW, Y and y are called alleles.
 Since you only need one copy of the Y allele to have
a yellow flower, we can call it the dominant trait.
 While red flowers needs two y alleles, which is why
we call it a recessive trait.
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Punnett Square
 The combination of alleles is known as a genotype.
 You could have either YY or Yy or yy.
 YY can also be called a homozygous dominant
genotype.
 Yy can also be called a heterozygous genotype.
 yy can also be called a homozygous recessive
genotype.
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Punnett Square
 If Mom’s egg carries a Y and Dad’s sperm carries a
Y, the zygote or baby produced will have a YY
allele/gene combination.
 Their seed or future little baby plant will have a
homozygous dominant genotype.
 What color flower will the baby plant produce?
 The physical characteristic of flower color is called
the phenotype.
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Punnett Square DIY Videos
 In order to prove this, which is what scientists do,
you need to show the data, a.k.a. complete a
Punnett Square.
 If you need to review how to fill out a Punnett
Square please view this link before going to the next
slide.
 Monohybrids and the Punnett Square Guinea Pigs
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Punnett
Square
• Note that all of the
future seeds or baby
plants will be YY.
• The genotypic ratio
or mathematical
way to say this is
100% of the next
generation will be
YY.
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Punnett
Square
• Note that all of the
future seeds or baby
plants will also be
homozygous
dominant. 100% will
be homozygous
dominant, which is
another way to say
the genotypic ratio.
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Punnett
Square
• The phenotypic
ratio for all of the
seeds or baby plants
is 100% yellow.
• You will need to
know how to
provide all of this
information on any
Punnett Square.
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Punnett Square
 What if Mom provides a yy allele and Dad provides
a yy allele?
 Can you predict the genotypic ratio for all of their
seeds?
 Can you predict the phenotypic ratio for all of their
seeds?
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Punnett
Square
• 100% Homozygous
recessive or yy for
the genotypic ratio.
• 100% Red Flowers
for the phenotypic
ratio.
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Punnett Square
 What if Mom is Yy and Dad is YY?
 What is the genotypic ratio?
 What is the phenotypic ratio?
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Punnett
Square
• 50% YY or
homozygous
dominant and 50%
Yy or heterozygous
for the genotypic
ratio.
• What about the
phenotypic ratio?
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Punnett
Square
• You need to know if
it is a complete or
incomplete
dominant trait.
• If there is no other
color of flower other
than yellow or red,
it probably is
complete
dominance.
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Punnett
Square
• For a complete
dominant trait in
which only yellow
or red flowers are
possible, this shows
50% yellow and 50%
red flowers as the
phenotypic ratio.
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Punnett Square
 Mom is YY and Dad is yy.
 You know what to do.
 Go!
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Punnett
Square
• 100% heterozygous
or Yy for the
genotypic ratio.
• 100% Yellow
Flowers for the
phenotypic ratio
assuming complete
dominance.
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Punnett Square
 Mom is Yy and Dad is Yy.
 You know what to do.
 Go!
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Punnett
Square
• 25% YY, 50% Yy,
and 25% yy is the
genotypic ratio.
• 75% Yellow and
25% Red is the
phenotypic ratio.
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Incomplete
Dominance
• This incomplete
dominance pattern can be
identified when three
different phenotypes are
apparent.
• This occurs when RR
produces a red flower.
• RW produces a pink
flower.
• WW produces a white
flower.
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Incomplete
Dominance
• The genotypic ratio is 1 RR
to 2 RW to 1 WW.
• The phenotypic ratio is 1
red flower, 2 pink flowers,
and 1 white flower.
• Animal fur patterns can
also be explained using
incomplete dominance
patterns.
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Codominant Patterns
• Codominance patterns occur when each allele codes
for a specific phenotype.
• Human Blood Types are the most common example.
• IAIA and IAIO would have Blood Type A.
• IAIB would have Blood Type AB.
• IBIB and IBIO would have Blood Type B.
• IOIO would have Blood Type O.
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Codominance
Patterns
• Blood Type A = IAIA and
I AI O
• Blood Type AB = IAIB
• Blood Type B = IBIB and
IBIO
• Blood Type O = IOIO
• Phenotypic Ratio for this
cross is 1 Blood Type AB, 1
Blood Type A, 1 Blood
Type B, and 1 Blood Type
O.
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Sex-Linked Traits
 Genes/alleles can also be found on the sex
chromosomes, which is why they are sex-linked.
 Males have XY in which the X chromosome contains
much more genes than the Y chromosome.
 Females have XX in which both X chromosomes
contain several genes.
 This means that some genetic traits are passed
down to only certain sexes and not others.
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Sex-Linked Traits
 A common example of a sex-linked trait is red-green
color blindness.
 Male with normal vision = XRY
 Male with red-green color blindness = XrY
 Female with normal vision = XRXR
 Female carrier with normal vision = XRXr
 Female with red-green color blindness = XrXr
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Sex-Linked
Trait
• Phenotypic ratio would be:
50 % female carrier with
normal vision, 50 % male
with normal vision even
though Dad is a red-green
color blind male.
• If you need to, feel free to
view the videos using the
links on the next slide and
practice doing more of
these Punnett Squares.
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Punnett Square DIY Videos
 For more complex Punnett Squares view these:
 Dihybrid Crosses and a Cat Called "Moo”
 Multiple Alleles (ABO Blood Types) and Punnett
Squares
 Incomplete Dominance, Codominance, Polygenic
Traits, and Epistasis!
 Punnett Squares and Sex-Linked Traits
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So, what about…
 …our purple plant?
 Let’s imagine that it blooms in the Spring.
 You manage to collect the pollen from some of the
flowers and you pollinate some of the other flowers
in a process called cross-pollination.
 If purple is a recessive trait, make predictions on
genotypic and phenotypic ratios for the seedlings.
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BTW
 By the way, we call the parent generation = P1.
 The grandparent generation = P2.
 The kids/seedlings = F1.
 The grandkids/grand-seedlings = F2.
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Did you solve the crosspollination question?
 If the pollen came from a flower that had the
recessive purple trait and it was used to crosspollinate another flower that had the recessive
purple trait, you are dealing with a pp X pp Punnett
square.
 Both parents (male = pollen from the stamen; female
= stigma of the flower) are purple, which is a
recessive trait. (Assume complete dominance)
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Result
 This means that all seedlings from this crosspollination event will have purple parts.
 Now, what if that did not happen and, yet, you
would like to somehow have purple plant parts?
 Well, that’s a molecular biology thing, which we
will cover next time.
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Review
 We discussed at Mendelian Genetics and how to
complete a variety of Punnett Squares.
 We discussed genotype, phenotype, ratios, and
other little details that will hopefully let you
understand how humans have been able to
domesticate a wide variety of different species
throughout history.
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The End
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