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Monday3/19/12
• AIM: What is heredity?
• Homework: Handout Section 11.2 Read
pages 288-291. Reading check on page
288.
• 2- Use figure 11.7 and in your own words,
summarize steps A-C
• 3- Answer question 1 page 295 of the
handout
Transcribe and translate
DNA: TACGTTTGCGACACCACT
What do genes do?
Units of heredity that are passed down
from generation to generation
Hold the code to build physical traits
Where are genes located?
On DNA which builds
chromosomes which are in the
nucleus
How many codons are there in
total? 64
How many amino acids are there
in total? 20
Why is it a good thing to have
multiple codons specify the same
amino acid?
Because if the gene is mutated there is
still a chance the protein therefore
physical trait will be unaffected!
• If a person with brown eyes has a baby
with a person with green eyes? What
color eyes do you think their baby will
have and why do you think that?
Light blue
0 dominant alleles
Blue
1 dominant allele
Blue-green
2 dominant alleles
hazel
3 dominant alleles
Light brown
4 dominant alleles
Brown
5 dominant alleles
Dark brown / black
6 dominant alleles
What is Heredity?
• The transfer of characteristics from one
generation to the next
Human heredity
• Chromosomes are built from DNA wrapped
around proteins
• Genes are parts of DNA
– Specific nucleotide sequences
• Therefore genes are found on
chromosomes
• One chromosome might have 1000 genes
on it
• Your cells have more genes than
chromosomes
Thursday 3/22/12
• AIM: Why is Gregor Mendel the “father of
Genetics”?
• DO NOW: If a person with brown eyes
has a baby with a person with green eyes?
What color eyes do you think their baby wil
have and why do you think that?
• HOMEWORK: Text page 265 Inquiry Lab.
Page 266 using words question 2
What are Traits?
• A characteristic that is determined by
your genes
• A pair of genes will determine the trait
– Examples:
• Tongue rolling
• Earlobes
• Widow’s Peak
• Hair Whorl
• Dimples
What is genetics?
• The science of how traits are inherited
Who is Gregor Mendel?
• “Father of Genetics”
• Studied pea plants
• He crossed pea plants with different
characteristics and studied their offspring
• He was able to determine how
traits get passed on from
generation to generation
Gregor Mendel
• Father of genetics
• Looked at the pea
plant
• Specifically 7 visible
traits
• Followed their
inheritance over many
generations
• The pea plant displayed one of 2
possible characteristics for each trait
How did Mendel experiment
with the pea plant?
Mendel’s pea plant
• Key feature:
reproduction can be
controlled and
manipulated
• Self- fertilization and
cross-fertilization
were easily obtained
Fertilization
• Self-fertilization: egg
in the flower is
fertilized by the sperm
of the same flower
• Cross-fertilization:
sperm from a foreign
plant fertilizes an egg
Friday 3/23/12
• AIM: How did Gregor Mendel develop his
3 laws of heredity?
• DO NOW: Explain the difference between
self and cross fertilization.
• Homework: Complete any assignment
you missed this week
• Last nights hw. 1- Page 265 Inquiry Lab
• 2- page 266 Understanding words # 2
Mendel’s work
• At first Mendel self fertilized plants in order
to create true breeds
• True breed or pure breed has only one
trait to pass on
– Ex: Seed color
– Yellow seed yellow seed
• True breeds are homozygotes
Monday 3/26/12
• AIM: How did Gregor Mendel develop his
first two laws of heredity?
• DO NOW: Explain why Mendel choose to
work with pea plants
• HOMEWORK: textbook read pages 267269. questions 1 and 3 on page 270
Mendel’s work
• Mendel did not know anything about
dominant or recessive behavior
• He did know how to make pea plants
reproduce
Definitions
• Genes: instructions to build physical
characteristics
• Chromosome: large unit of DNA and
protein that carry genes on them
• Human cells:
– Somatic cells: body cells: diploid(2n)
– Gametes: sex cells: haploid(n)
Somatic Cells
• ALL somatic (body cells) have the same
46 chromosomes
• Each cell is different due to the genes that
get turned on or off
How is a cell’s DNA like a library?
Wednesday 3/28/12
• AIM: How did Gregor Mendel develop his
law of dominance?
• DO NOW: Explain the difference between
diploid and haploid and give an example of
each
• HOMEWORK: Textbook page 270
questions 2 and 4
• I AM CHECKING 1-4 TOMORROW
Diploid (2n) vs haploid (n)
Mendel’s work
• He self fertilized plants for several
generations to ensure that all were pure
breeds
• True breed or pure breed: plants with a
trait such as purple flowers that is always
inherited by all offspring
– Only have 1 type of allele for a specific gene
(homozygous)
Mendel’s work
• Cross fertilized plants that were true
breeding for 7 specific traits
• Hybrid: The offspring of a cross
fertilization
– 2 parents similar to sexual reproduction
– Has genetic information from both parents
Mendel’s work
• Crossed two true
breed parents that
displayed opposite
traits.(P or Parental
generation)
• All First filial or F1
offspring were purple
Genetics vocabulary
• Gene: part of DNa which holds the
instructions to build a protein
• Allele: copy of a gene
– Specific directions
• Genotype: genetic makeup of an
organism
• Phenotype; resulting physical
characteristics
What happened to the white
color?
Self-fertilized F1
• Second filial or F2
generation yielded
about ¼ white and ¾
purple
Mendel’s conclusion
• When the white flowered plants showed
up in the F2 generation, Mendel concluded
that the white characteristics must have
been hidden in the F1
Self-fertilized F2
• Saw that all white flowered F2 yielded all
white F3 but the purple still yielded 3:1
ratio of purple to white
• Therefore the white allele was not lost but
rather hidden or masked by the purple
allele
From these experiments, Mendel
concluded:
• Traits are determined by physical unit that come
in pairs
• Pairs are separated during gamete formation
• Gametes only 1 allele each
• The particular allele that ends up in a gamete is
caused by chance
• One allele is dominant and one recessive
• From Mendel’s Monohybrid cross he developed
the law of dominance and the law of segregation
3/29/12 Thursday
• AIM: how did Mendel develop his law of
Independent assortment?
• DO NOW: Explain why ALL of the F1
generation had purple flowered plants.
• Homework: Textbook
Mendel’s Law of segregation
• Pairs of alleles on homologous
chromosomes separate from each other
during gamete formation
• Gametes receive only one allele from a
homologous pair.
• Fertilization produces offspring with a copy
of one allele from mom and one from dad
Mendel’s Law of dominance
• When two different alleles are present, the
dominant alleles gives the resulting trait
and masks the trait of the recessive allele
• However the recessive allele is still
present
Friday 3/30/12
• AIM: how did Gregor Mendel develop his
law of independent assortment?
• DO NOW: Explain the difference between
genotype and phenotype
•
•
•
•
• Which two laws did Mendel Develop from
his Monohybrid crosses?
Answer
• Law of segregation: alleles separate
during gamete formation
• Law of Dominance: when two different
alleles for a trait are present, one is
expressed (dominant) the other is masked
According to Mendel why do
homozygote dominant and
heterozygote genotypes show
the same phenotype?
Both have a copy of the dominant
allele
Monohybrid cross
• ONLY tracks one physical trait at a time.
• From Mendel’s monohybrid crosses, he
developed:
– Law of segregation
– Law of dominance
Mendel was not satisfied
• He wanted to see if alleles could be
inherited together
• He looked at two traits at the same time
• Ex: seed shape and seed color
• His results were inconclusive
•
•
•
•
•
R-round
r-wrinkled
Y-Yellow
y-green
•
Mendel’s dihybrid cross
• P: true breed RRYY x rryy
• All F1: RrYy
• Allowed F1 to self-fertilize which yielded the
following phenotypic ratio
• F2: 9:3:3:1 ratio of
Round Yellow: Round green: wr Yellow: wr,green
•
•
•
•
•
•
•
•
•
Law of independent assortment
• Multiple traits are inherited independently
of each other because alleles of genes are
distributed independently during gamete
formation
• Genes for different traits are inherited
independently
•
Mendel’s laws
•
•
•
•
Law of segregation
Law of Dominance
Law of independent assortment
Still used today they paved the foundation
for genetics
• Although his observations and laws
explain the simplest form of genetics
Monday 4/3/12
• AIM: What are some exceptions to
Mendel’s laws?
• DO NOW: Why did Mendel perform his di
hybrid cross and what were his results?
• Homework: Textbook read page 282-284.
questions 1-3 page 284. Write out the
question followed by the answer
• Mendel gave us a foundation to build on
genetics
• Without his experiments and discoveries,
we may not have known anything about
heredity
According to Mendel,
phenotypically how does a
homozygote dominant and a
heterozygote react?
Answer: Law of dominance: if the dominant
allele is present it will be expressed
They will both display the same phenotpye
Incomplete Dominance
• Incomplete
dominance is
basically just a
blending of traits
• The heterozygous
form is a blend of the
dominant and the
recessive traits
Wednesday
• AIM: how can more than one allele code
for the same trait?
• DO NOW:Explain how the pink snap
dragon defies Mendel’s law of dominance
How does this happen?
Usually the law of dominance: if the
dominant allele is present it is
expressed. So the Rr snapdragon
would be Red BUT instead it is pink
due to incomplete dominance.
The heterozygote Rr is a combination
of the dominant R and recessive r
phenotypes
Homozygous
Dom
Homozygous
recessive
Heterozygous
• Usually alleles code for
enzymes which in turn
code for chemical
reactions to occur.
• In the case of the snap
dragon, R allele codes
for an enzyme which
catalyzes a reaction
which makes the red
pigment
• r- white pigment
• Both are made and mix
just like mixing red and
white paint
•
Tuesday 4/3/12
• AIM: How are two alleles expressed at the
same time?
• DO NOW: Explain HOW the snap dragons
of a red and white cross yielded all pink
snap dragons
• HOMEWORK: Textbook page 284
questions 4-6
Wednesday 4/4/12
• AIM: How does human blood type defy
Mendel’s laws?
• DO NOW: Explain how human blood type
is determined.
• HOMEWORK: Read page 284. reading
Check on 284
•
Question
• 1- A woman with blood type A and a man
with blood type B have a child with blood
type O. How did this happen?
• 2- Baby daddy DRAMA! A woman claims
her son is Mr. Clide’s. The woman has
blood type O Mr. Clyde has blood type AB
and the child also has blood type O. Is Mr.
Clyde the boy’s father Explain why or why
not
•
Codominance
• There is more than one dominant allele
• Ex: Human blood Type
• There are 3 alleles that code for the
antigen protein found on the surface of the
Red Blood Cell
Blood type is an example of
codominance
• A person with blood type AB is showing
the results of having both the IA and IB
codominant genes
• 3 alleles code for blood type
• Specifically blood typing alleles code for
antigens
• Antigen: specific recognition protein found
on the surface of red blood cells
Antibody
• A protein that defends the body against
foreign antigens
• In relationship to blood type, each antigen
has the opposite antibody floating in the
plasma
•
Rh factor
• Determines if blood is + or –
• It is a completely different protein and has
NO connection to antigens
List and explain the 2 exceptions
to Mendel’s laws we have
discussed so far
Incomplete Dominance
COdominance
Monday 4/16/12
• AIM: How does one gene control several
characteristics?
• DO NOW: Explain the difference between
codominance and incomplete dominace
• HOMEWORK: textbook page 280 sex
linked traits. Answer the Reading check
on page 280
• Incomplete dominance;
• The heterozygote is a
combination of the
dominant and recessive
allele
• Codominance: There
is more than one
dominant allele and
both are fully
expressed when
present at the same
time
SO FAR
• EXCEPTIONS to Mendel’s 3 laws of
Inheritance
– Incomplete dominance (pink snap dragons)
– Codominance (Blood type AB)
– Multiple allele inheritance: more than one
allele determines a trait. (human blood type)
Polygenic Inheritance
• More than one gene coding for the same
trait
• Eye color is known to have a polygenic
inheritance pattern, possibly governed by
6 or more genes.
• There are also 6 different described eye
colors.
• Basically, dark is dominant at each of the
6 genes. The more dominant alleles that
you have the darker your eyes are.
Light blue
0 dominant alleles
Blue
1 dominant allele
Blue-green
2 dominant alleles
hazel
3 dominant alleles
Light brown
4 dominant alleles
Brown
5 dominant alleles
Dark brown / black
6 dominant alleles
•
Pleiotropy
• Single gene influences
several traits
• Ex: SRY gene on the Y
chromosome
• Sex determining region
• SRY gene: initiates
sequence of events that
affects many different
body structures
• Specifically during
development it turns the
gonads into testis and is
responsible for all male
charatceristics
Chromosomes are inherited
• Mendel did not know the difference
between a gene and chromosome
• Thomas Hunt Morgan: worked with
Drosophila fruit flies
– He figured out that genes are the inherited
unit
Remember
• Chromosomes are the inherited unit
– Humans have 22 pairs of Autosomes
– 1 sex pair
– Totaling 23 pairs = 46
• Genes are carried on chromosomes and
contain the directions to build a protein
• One gene codes for one protein
The chromosomal basis of
inheritance
• Genes are located on
chromosomes
• Inheritance pertains to the
behavior of chromosomes
during meiosis and fertilization
• Gene locus: the actual
position of an allele on a
chromosome
Some gene loci are very close
together
Tuesday 4/17/12
• AIM: How are some traits inherited together?
• DO NOW: Explain the difference between
polygenic inheritance and pleiotropy.
• Homework: textbook Read page
335.Explain how DNA helped to identify
unknown individuals whose coffins floated
out of burial sites
What did Mendel’s Law of
independent assortment say
• According to Mendel, genes or alleles
found on different chromosomes cannot
be inherited together
Remember Mendel’s Law of
Independent assortment
• Independent Assortment of Alleles
Wednesday 4/18/12
• AIM: How can genes be inherited
together?
• DO NOW: List ALL of the exceptions to
Mendel’s laws that we discussed.
• HOMEWORK: Reading check page 283
and Monday’s Reading check page 280
will be collected tomorrow
Gene linkage
• Some alleles are so
close to each other on
a chromosome that
they are inherited
together
• This defies Mendel’s
law of independent
assortment
• Gene linkage only
occurs when loci is
close
Genetic linkage
• When two genes are very close on the same
chromosome they do not segregate
independently, they are said to be linked.
• Linkage is a powerful tool in modern genetic
counseling.
• Autosomes (chromosomes 1-22) do display
linkage however it is most understood in the sex
chromosomes(X and Y)
• Since most X-linked traits are seen in males
Sex-linked genes
• Found on the X chromosome
• Are easy to track because traits are often
seen in males due to males having only
one X chromosome
Thursday 4/19/12
• AIM: What are some of the human genetic
disorders?
• DO NOW: Explain why sex linked
disorders are easier to trace in males over
females
• Homework: textbook page 339-340
questions: 1,2,3,4,5,6,9,14,17. write out
the question followed by the answer
except for # 14.
Sex-linked genes
• Found only on X chromosome
• Specifically Y chromosome holds only
about 20 genes
• Where as the X chromosome has about
1500 genes
How do our chromosomes
determine sex?
Formation of a zygote
Genetic makeup of your cells
• Whatever chromosomes and genes the
zygote receives, EVERY cell is genetically
identical to it
• Cell differentiation: when cells become
specialized
Friday 4/20/12
If all of our cells are genetically
identical, then why does a neuron
transmit electrical impulses while
a muscle cell provides
movement?
Cells become specialized by turning
on specific genes while turning other
genes off
Apoptosis
• Programmed cell death
Mutation
• Any change in the coding sequence that
causes a change in the physical
characteristic.
• Chromosomal mutations: loss or gain of a
complete chromosome
– Usually chromosomal mutations lead to
miscarriage
• The baby does not develop to be born
– There are only a few chromosomal mutations
that will lead to full term development but the
child will have severe abnormalities
Mutations continued
• Genetic mutations: occur at a single gene
– Change in the “reading frame” or nucleotide
sequence that causes a change in the
physical characteristic
– Much more common than chromosomal
mutations
Human Genetic disorders
• Sex-linked genetic disorders
– Only on the X chromosome
– Seen more in males than females
• Examples:
– Red-green colorblindness
– Hemophilia
Red Green Colorblindness
Hemophilia:
• Inability for blood to clot
• People do not produce one of the proteins
necessary for proper blood clotting
Females exhibit normal
dominant or recessive
expression
• As long as the
dominant allele is
present, it will be
expressed
•
Sex Linked traits
• Females must be homozygote recessive in
order to display the sex linked disorder
Sex-linked dominant disorder
• Vitamin D resistant
Rickett’s
• Ingestion of Vitamin D
is ineffective
• Causes bone
deformity and bow
leggedness
Human Recessive Genetic
disorders
• Homozygote Recessive is the only way to
display
• Heterozygotes are carriers
• Sickle Cell Anemia
• Albinism
• Cystic fibrosis
Sickle cell anemia
• Homozygote recessive disorder
• Causes the hemoglobin protein to sickle in
shape
• Hemoglobin can not carry oxygen
Cystic Fibrosis
• European descent
• 1:2500
• Lack of a
membrane protein
that transports Cl• Accumulation in the
extracellular matrix
leads to cells
producing a thick
sticky mucous
Renal cystic fibrosis
Albinism
• Albinism:
homozygous
recessive allele for
the enzyme
tyrosine which
builds melanin
Human Dominant Disorders
• Both Homozygote
Dominant and
Heterozygote
display trait
Huntington Disease
• People usually have symptoms for up to 10 years before they find
out they have Huntington's disease.
• Most people are diagnosed between the ages of 30 and 50,
although this can happen much earlier or later.
• Symptoms are often overlooked, as they are mild and commonly
experienced by well people
• mild tremor
• clumsiness
• lack of concentration
• difficulty remembering things
• mood changes, including depression
• sometimes, aggressive antisocial behavior
Huntington’s disease: dominant
allele causes slow deterioration of brain
and nervous system
Achondroplasia
• Dwarfism
• “without cartilage
formation”
• the defect is not in
forming cartilage but
in converting it to
bone
Hypertrichosis
Excessive hair growth
over and above the
normal for the age,
sex and race of an
individual
Exact cause is
unknown but has
been linked to a
spontaneous
mutation
Nondisjunction and Down’s
syndrome
•
• In Down syndrome, 95% of all cases
are caused by this event: one cell
has two 21st chromosomes instead
of one, so the resulting fertilized egg
has three 21st chromosomes.
• Recent research has shown that in
these cases, approximately 90% of
the abnormal cells are the eggs.
• The cause of the nondisjunction
error isn't known, but there is
definitely connection with maternal
age
Trisomy
• Trisomy 13
• Trisomy 18
Nondisjunction
•
Nondisjunction leads to
abnormal numbers of
chromosomes
• Turner’s syndrome: XO: no hormones
lead to no menstruation and no secondary
sex characteristics
• Infertility
• Short stature, folds on neck, more X linked
recessive disorders, color blindness,
hemophilia etc.
Trisomy X
• 1 in every 1000 woman have 3 X
chromosomes
• Very tall
• Below normal intelligence
Klinefelter syndrome
• 1 in every 1000 males have XXY
• Most never even know they have it
• At puberty may experience mixed
secondary sex characteristics such as
partial breast development, widening of
the hips and small testis
• These men are usually infertile
XYY males
•
•
•
•
High levels of testosterone
Severe acne
More than 6 feet tall
Lower IQ
Genetic testing and counseling
• Punnett squares, testcrosses and genetic
screening helps to determine the genotype
of parents
• You can then predict the probability of
zygote receiving traits
• Medical tests that identify changes in
chromosomes, genes and proteins
Fetal Testing
•
•
•
•
•
Ultrasound
Amniocentesis
Chorionic Villus Sampling
Fetoscopy
Newborn Screening
Ultrasound
• Sounds waves are used to produce an
image
Fetoscopy
• Viewing scope is
placed into the
uterus creating an
image
• Enables blood
samples to be taken
• Detects Spina bifida
• Only done if there is
a history of birth
defects
Amniocentesis
• 14th-16th week
• 10 mL of amniotic fluid
• Looks at chemicals and molecules
present
• chromosomal disorders, including
Down’s syndrome, trisomy
13,18,Turner’s syndrome,
Kleinfelter’s syndrome
• Sickle Cell, Tay Sachs
• spina bifida and anencephaly
Chorionic Villus Sampling
8th-10th week
• Insert through the cervix
into the uterus
• Take a tissue sample
from the placenta
• Contain fetal cells which
divide more rapidly than
amniotic cells
New born Screening
• Examines newborn blood to detect genetic
disorders
• PKU: phenylketonoria
• Treated with diet regulation
Hemophilia: the inability to clot
blood
• Sex-linked disorder found on the X
chromosome
• It is a recessive trait therefor a female can
have one copy of the allele and not display
the trait however a male will always
display the trait
Females exhibit normal
dominant or recessive
expression
• As long as the
dominant allele is
present, it will be
expressed
Because males have only 1 X chromosome, if
they receive the recessive allele from mom they
show the recessive trait
•