IA4 Genetics
Grades are due tomorrow:
The only thing that I haven’t put
in are your projects. I am working on
them today.
1/8/14
• BR6: Using the Carbon Cycle poster next to
the board, describe the flow of carbon
through the cycle. Use the words: carbon
dioxide, photosynthesis, respiration,
combustion, plants, animals, atmosphere.
• Agenda:
– Human Genetics Survey
Darwin’s Point
1/10/14
• Pretest IA4
Sharpen pencils, have IA numbers ready
Mark E if you don’t know/have to guess
Pick up Vocab/I Can sheet when you turn in scantron/test
Agenda:
PIA4
Look up traits on Human Genetics homework –
what is the “dominant trait”
Vocab/I Can for Genetics
1/13/14
• sub - Mythbusters
1/14/14
• BR 7:
What factors affect whether or not children look
like their parents?
Agenda:
Blue People!!
Vocab Notes
Vocabulary
• Genetics – the study of heredity
• Heredity- the passing of genes or traits from
parent to offspring
• Genes – segments of DNA along
chromosomes that contain the chemical
message that governs a trait
• Trait- an inherited characteristic
Blue People of Troublesome Creek
Vocabulary
• alleles – different forms of a gene in a gene
pool
• genotype – genetic makeup of an individual
• phenotype – physical characteristics of an
individual
• homozygous – two identical alleles for a trait
• heterozygous – two different alleles for a trait
I can recognize the contributions of Redi, Needham, Spallanzani, and Pasteur.
1/15/14
• BR 8: In humans, the allele for free hanging
ear lobes is dominant (F) over attached
earlobes (f). Predict the genotypic ratio of
offspring produced by crossing two
heterozygous for this trait. Draw a punnett
square to illustrate your prediction.
• Agenda:
– Genetic Scientists’ Contributions
Pedigree of Methemoglobinemia – The Blue People Pedigree Chart
Pedigree information graciously provided by Mary D. Fugate, publisher of The Fugate Family Newsletter.
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People/Scientist
Belief/contribution to Genetics
Greeks
-Both Male and Female contribute a fluid to
create children
-Each body part contributes fluid to create
that part in children
Leeuwenhoek
-Made improvements to microscope
-First to observe sperm
Mendel
-Developed law of heredity
-Father of modern genetics
-Worked with pea plants
Middle Ages
-Thought there was spontaneous generation
Harvey
-Women have eggs b/c chickens have eggs
-Proposed epigenesis
Fusion b/w egg and sperm
Spontaneous Generation Beliefs
• Maggots and worms came from decaying food, urine,
and manure
• Animals that lived in mud (salamanders, frogs, etc.)
were generated by the mud
• Rats were spontaneously generated in piles of garbage or
created from magical recipes. One seventeenth-century
recipe even called for the creation of mice from sweaty
underwear and wheat husks placed together in a jar for
twenty-one days.
• pieces of cheese and bread wrapped in rags and left in
a dark corner, for example, were thus thought to
produce mice, because after several weeks there were
mice in the rags
I can recognize the contributions of
Redi, Needham, Spallanzani, and Pasteur.
• Open book to pages 9-12 and read about the
4 remaining scientists.
• Using the descriptions and pictures in the
book I want you to make a table showing their
ideas/contributions to genetics, and then
draw a picture of their experiment for each of
the scientists.
Scientist
Redi
Needham
Spallanzani
Pasteur
Ideas/Contributions to
Genetics
How Experiment
was set up
Keep working on NovelStar if you didn’t finish. We have another week or so!
See me for questions…
1/16/14
• BR9: For each image, record which scientist
created the experiment.
• Agenda:
– Mendelian Genetics Notes
– Anyone not read “Desiree’s Baby”?
Gregor Mendel
• Austrian monk
• garden peas – why?
– small
– easy to grow
– short growing season
– lots of results quickly
– more results = ???
Pollination/Fertilization in Peas
• Pea flowers are normally self-pollinating, which means that sperm
cells fertilize egg cells from within the same flower.
• true-breeding - self-pollinating plants that would produce offspring
with identical traits to themselves generation after generation
(purebred)
Recall from elementary science classes: What are the male and female parts of the
flower called? male _______________ female _____________
The Role of Fertilization
• Mendel decided to “cross” his stocks of true-breeding
plants—he caused one plant to reproduce with another
plant.
• This process, known as cross-pollination, produces a
plant that has two different parents.
• The offspring of crosses between parents with
different traits are called hybrids.
Genes and Alleles
• When doing genetic crosses, we call the original pair of
plants the P, or parental, generation.
• Their offspring are called the F1, or “first filial,”
generation.
• For each trait studied in Mendel’s experiments, all the
offspring had the characteristics of only one of their
parents, as shown in the table.
Mendel’s Laws of Genetics
1. Law of Dominance
2. Law of Segregation
3. Law of Independent
Assortment
Dominant and Recessive Traits
•
Mendel’s principle of dominance states that
some alleles are dominant and others are
recessive.
•
An organism with at least one dominant allele for
a particular form of a trait will exhibit that form of the
trait. Dominant “masks” recessive.
•
An organism with a recessive allele for a
particular form of a trait will exhibit that form only
when the dominant allele for the trait is not
present.
Dominant and Recessive Traits
• In Mendel’s experiments, the allele for tall plants was
dominant and the allele for short plants was
recessive.
• Likewise, the allele for yellow seeds was dominant
over the recessive allele for green seeds
Dominant and Recessive Human Traits
Dominant Recessive
Cheek Dimples No Dimples
Cleft Chin Smooth Chin
Freckles No Freckles
Free Earlobes Attached Earlobes
Wet Ear Wax Dry Ear Wax
Straight thumb Hitchhiker's thumb
Widow's peak Straight hairline
Polydactyly 5 fingers/toes
Mendel’s Laws of Genetics
1. Law of Dominance
2. Law of Segregation
3. Law of Independent
Assortment
Segregation
• Mendel wanted to find out what
had happened to the recessive
alleles.
• Mendel allowed all seven kinds
of F1 hybrids to self-pollinate.
The offspring of an F1 cross are
called the F2 generation.
Explaining the F1 Cross The Formation of Gametes
• One fourth of the F2
generation were short.
• Mendel suggested that the
alleles for tallness and
shortness in the F1 plants
must have segregated from
each other during the
formation of the sex cells,
or gametes.
• Each gamete carries only
one allele for each gene.
The Formation of Gametes
• A capital letter represents a
dominant allele.
• A lowercase letter represents
a recessive allele.
• Assume each F1 plant had a
T(Tall) allele and a t(short)
allele or gametes.
• When they crossed, they
produced three different mixed
pairs…
TT, Tt, and tt.
The Formation of Gametes
 Whenever the pair was TT
(both dominant)…the plant
was tall.
 When the pair was Tt (one
dominant, one recessive)
…the plant was tall.
 When the pair was tt (both
recessive)…the plant was
short.
Mendel’s Laws of Genetics
1. Law of Dominance
2. Law of Segregation
3. Law of Independent
Assortment
Independent Assortment
• Mendel wondered if the segregation of one pair of alleles
affects another pair.
• Mendel performed an experiment that followed two different
genes as they passed from one generation to the next.
• Because it involves two different genes, Mendel’s experiment is
known as a two-factor, or dihybrid, cross. Single-gene crosses
are monohybrid crosses.
• The principle of independent assortment states that genes for
different traits can segregate independently during the
formation of gametes.
The DiHybrid (Two-Factor) Cross: F1
• Lets look at pea color (green or yellow) and
shape (round or wrinkled.
• The round yellow peas had the genotype
RRYY, which is homozygous dominant.
• The wrinkled green peas had the genotype
rryy, which is homozygous recessive.
• The Punnett square shows that the
genotype of each F1 offspring was RrYy,
heterozygous for both seed shape and
seed color.
The Two-Factor Cross: F2
In the F2 offspring:
 Mendel observed that the alleles for seed shape segregated
independently of those for seed color.
 Genes that segregate independently—such as the genes for seed
shape and seed color in pea plants—do not influence each
other’s inheritance.
 Mendel’s experimental results were very close to the 9:3:3:1 ratio
that the Punnett square shown predicts.
 Mendel had discovered the principle of independent
assortment. The principle of independent assortment states that
genes for different traits can segregate independently during
gamete formation.
PUNNETT SQUARE – DIHYBRID CROSS
YYRR x YyRr
– Separate the alleles in
all possible combinations
YYRR
YR YR YR YR
YyRr
YR Yr
– Set up the square
YR YR YR YR
YR
Yr
yR
yr
yR
yr
YR
YR
YR
YR
YR YYRR
YYRR
YYRR YYRR
Yr
YYRr
YYRr
YYRr
YYRr
yR
YyRR
YyRR
YyRR
YyRR
yr
YyRr
YyRr
YyRr
YyRr
Mendel’s Principles continued…
 Before long, Morgan and other biologists had tested
every one of Mendel’s principles and learned that they
applied not just to pea plants but to other organisms as
well.
 At the beginning of the 1900s, American geneticist
Thomas Hunt Morgan decided to use the common
fruit fly as a model organism in his genetics
experiments because it could produce plenty of
offspring, and it did so quickly in the laboratory.
Beyond Dominant and Recessive Alleles
 In most organisms, genetics is more
complicated, because the majority of
genes have more than two alleles.
 Some alleles are neither dominant nor
recessive.
 Mendel’s principles alone cannot
predict traits that are controlled by
multiple alleles or multiple genes.
Other Inheritance Patterns
• Incomplete
Dominance –
Flower Color
• Polygenic Skin Color
• Codominance Speckled Feathers
• Multiple Alleles Blood Type
• Sex-LinkedColor blindness
Incomplete Dominance
• A cross between two four o’clock plants
shows a common exception to Mendel’s
principles.
• The F1 generation produced by a cross
between red-flowered (RR) and whiteflowered (WW) plants consists of pinkcolored flowers (RW), as shown.
• In this case, neither allele is dominant. Cases
in which one allele is not completely
dominant over another are called
incomplete dominance.
• In incomplete dominance, the heterozygous
phenotype lies somewhere between the two
homozygous phenotypes.
Codominance
• Cases in which the phenotypes produced by both alleles
are clearly expressed are called codominance.
• For example, in certain varieties of chicken, the allele for
black feathers is codominant with the allele for white
feathers.
• Heterozygous chickens have a color described as
“erminette,” speckled with black and white feathers.
Multiple Alleles
• A single gene can have many
possible alleles.
• A gene with more than two alleles
is said to have multiple alleles.
• Many genes have multiple
alleles, including the human
genes for blood type. This chart
shows the percentage of the U.S.
population that shares each
blood group.
American Red Cross
Info on Blood Types
http://www.redcrossblood.org/learn-aboutblood/blood-types
Polygenic Traits
• Traits controlled by two or more genes are said to be
polygenic traits. Polygenic means “many genes.”
• Polygenic traits often show a wide range of phenotypes.
• The variety of skin color in humans comes about partly
because more than four different genes probably control
this trait.
Genes and the Environment
• Environmental conditions can affect gene
expression and influence genetically determined
traits.
• Genes provide a plan for development, but how
that plan unfolds also depends on the
environment.
• For example, consider the Western white butterfly.
Western white butterflies that hatch in the summer
have different color patterns on their wings than
those hatching in the spring.
Genes and the Environment
• Scientific studies revealed that butterflies hatching in
springtime had greater levels of pigment in their wings than
those hatching in the summer.
• In order to fly effectively, the body temperature of the
Western white butterfly needs to be 28–40°C.
• More pigmentation allows a butterfly to reach the warm
body temperature faster. Similarly, in the hot summer
months, less pigmentation prevents the butterflies from
overheating.
1/17/14
Bellringer 10: (Turn in when done)
Fill in the blanks using vocabulary words. Just write the word.
1. The _________ is used to describe the physical traits shown in the punnett
square.
2. The _________ is used to describe the genes shown in the punnett square.
3. The allele type that will usually mask or “cover up” the effect of another
allele is called _____________.
4. The allele type that is usually not expressed when masked or “covered up”
is called ____________.
Agenda:
“Desiree’s Baby”
1/27/14
BR 1:
Use this Word Bank to complete the
sentences on the right.
Word Bank:
• Independent assortment
• Sex-linked
• Polygenic traits
• Codominance
• Laws of segregation
Agenda:
Desiree’s Baby
Work on Spongebob Genetics Assignment
1. When both traits show up, like black
with white spots, it is called
______________________.
2. Traits that are found on the X or Y
chromosome are called __________.
3. Traits controlled by two or more
genes are______________________.
4. The independent segregation of genes
is ____________________________.
5. The defined separation of alleles is
called_________________________.
Desiree’s Baby
• Summary of the story?