chromosomes - Life Science Academy

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3.1 Essential Questions & Key Terms
1. What is sickle cell disease?
2. Why does the sickling of red
blood cells cause health
problems?
3. What is sickle cell anemia?
4. How is anemia diagnosed?
5. How does sickle cell
disease affect daily life?
Key Terms
Anemia
Blood Plasma
Erythrocytes (Red Blood Cells)
Hematocrit
Leukocytes (White Blood Cells)
Sickle Cell Disease
Thrombocytes (Platelets)
Sickle Cell Disease
• Disease passed down through families
• Caused by an abnormal type of hemoglobin called
hemoglobin S
• Affects red blood cells
• Red blood cells (normally shaped like a disc) form an
abnormal sickle/crescent shape
Hemoglobin
• Protein
• Primary component
of red blood cells
• Composed of four
sub-units
• Each carries one
oxygen molecule
• People with sickle
cell have abnormal
hemoglobin
Sickle Cell Disease
• Sickled Red Blood Cells
1. Deliver less oxygen
2. Get stuck more easily
in small blood vessels
3. Fragile- break into
pieces that can
interrupt healthy blood
flow
• Decrease the amount of
oxygen flowing to body
tissues even more
• …feedback loop?
The Affects of SCD
• Millions of people throughout
the world- major public health
concern
• 3% of people with SCD die
annually- sudden death
• More prone to blood clots
• Heart attacks
• Strokes
• Pulmonary embolisms
• Increased susceptibility to
bacterial and viral infections.
Anemia
• Blood is deficient in
red blood cells, in
hemoglobin, or in
total volume
• SCD often causes
anemia
• Referred to as Sickle
Cell Anemia
Activity 3.1.1: Blood Detectives
• Anna Garcia’s autopsy report shows she had SCD
• You will learn the components and function of blood in order
to better understand SCD and it’s impact on the body
1.
2.
3.
You will examine Anna’s blood with a microscope
You will design an experiment to see how cell shape impacts
movement
You will complete a hematocrit blood test to determine whether
Anna’s SCD was causing other related health problems
3.1.2 Sickle Cell Diaries: @ Home
• Almost every patient with SCD
experiences painful episodes
called crises
• The crises can be severe
enough to require a hospital
stay
• Anna’s doctor asked her to
keep a diary documenting all of
her crises
• In this activity you are going to
investigate what life is like living
with SCD…
3.1.2 Sickle Cell Diaries: @ Home
• All docs are online
• 2 Tables
• One before you collaborate
• One after
• Collaborate online
• Over the phone
• 2 Journal Entries
• Pick any patient
• Pick one career journal
• Due Friday January 17th
Blood Plasma
• The pale yellow fluid portion of whole blood
Erythrocytes (Red Blood Cells)
• Hemoglobin-containing cells that carry oxygen to tissues
and take carbon dioxide back to your lungs to be exhaled
• Responsible for the red color of vertebrate blood
Leukocytes (White Blood Cells)
• Colorless blood cells that lack hemoglobin and contain a
nucleus: lymphocytes, monocytes, neutrophils,
eosinophils, and basophils
• Destroy bacteria
• Produce antibodies against bacteria and viruses
• Fight malignant diseases
Thrombocytes (Platelets)
• A minute colorless anucleate (no nucleus) disk-like body
of mammalian blood
• Main function is to interact with clotting proteins to stop or
prevent bleeding
Hematocrit
• The percent of the volume of whole blood that is
composed of red blood cells
• Determined by separation of red blood cells from the
plasma usually by centrifugation
Hematocrit Results
Anna’s hematocrit
is approximately
30% red blood
cell volume.
Anything less
than 35% for a
female is
considered a low
hematocrit
3.1 The Disease: Review
1. What is sickle cell
2.
3.
4.
5.
disease?
Why does the sickling of
red blood cells cause
health problems?
What is sickle cell
anemia?
How is anemia
diagnosed?
How does sickle cell
disease affect daily life?
Key Terms
Anemia
Blood Plasma
Erythrocytes (Red Blood Cells)
Hematocrit
Leukocytes (White Blood Cells)
Sickle Cell Disease
Thrombocytes (Platelets)
3.2 It’s in the Genes: Essential Questions
Key Terms
& Key Terms
Amino Acid
1.
2.
3.
4.
5.
6.
7.
8.
9.
What is the DNA code?
What is the connection between
genes and proteins?
How are proteins produced in a cell?
How does the sequence of
nucleotides in DNA determine the
sequence of amino acids in a
protein?
What is a mutation?
What determines the shape of a
protein?
Is the shape of a protein affected by
its surrounding environment?
How does a change in the DNA code
affect the shape of a protein?
Can changing just one nucleotide in a
gene change the shape of a protein?
Anticodon
Codon
Hydrophilic
Hydrophobic
Messenger RNA (mRNA)
Mutation
Nucleotide
Protein
Protein Synthesis
Ribonucleic Acid (RNA)
Ribosome
Transcription
Transfer RNA (tRNA)
Translation
Proteins
• What we know…
• DNA codes for proteins
• Proteins produced all our genetic traits
• Responsible for just about everything our bodies do
• Amazingly…
• All the proteins we need are manufactured based on
a code of four letters: A,T, C and G
• The arrangement of these nucleotides dictates
everything we are genetically and runs our whole
bodies, because they dictate what proteins our bodies
produce
3.2.1 Protein Synthesis
1. The information on DNA is copied onto an mRNA strand
2. As, Cs, Gs and Us (in place of Ts)
3.
4.
5.
6.
7.
mRNA leaves the nucleus and moves into the
cytoplasm
A ribosome attaches to the mRNA
tRNA molecules bring amino acids (there are 20) into
the ribosome
The amino acid sequences match up with mRNA
sequences- 3 at a time (codons)
The ribosome assembles the amino acids into the
specific protein originally coded for by the gene on the
DNA
Transcription & Translation
WATCH VIDEO
From DNA to mRNA
to Amino Acid:
A= U
A= U
C= G
G= C
A= U
T= A
A= U
C= G
C= G
Structure of Proteins
• Polymers of amino acids
• Joined by peptide bonds
Activity 3.2.1 Protein Synthesis
• You will explore how the body uses DNA to produce proteins
More on translation…
More on transcription…
What’s Due?
• Friday- Activity 3.2.2 Decoding- Presenting at end of
class, conclusion questions due
• Tuesday- Activity 3.1.2 SC Diaries (all work and
conclusion questions), answer conclusion questions on
separate sheet, and pick one CJ
Activity 3.2.2: The Genetic Code
• Decode messages
• Transcription and
translation
• Effect of mutations on
protein production
• Genetic mutation that
causes SCD
• Chose 1 to illustrate with
any supplies you chose
• Decode the others in
your lab book
Activity 3.1.1: Blood Detectives
• Anna Garcia’s autopsy report shows she had SCD
• You will learn the components and function of blood in order
to better understand SCD and it’s impact on the body
Complete Microscopy- Part 1
Experiment- Part 2
1.
2.
1.
3.
Determine the tipping point of sickle cell disease. What percentage of red
blood cells must have a sickled-shape to impede blood flow? Design your
own experiment using materials provided. Record design and results in
your manual and put results on board.
Hematocrit- Part 3
Hematocrit
• The percent of the volume of whole blood that is
composed of red blood cells
• Determined by separation of red blood cells from the
plasma usually by centrifugation
Hematocrit Results
Anna’s hematocrit
is approximately
30% red blood
cell volume.
Anything less
than 35% for a
female is
considered a low
hematocrit
Activity 3.2.3: Does Changing One
Nucleotide Make a Big Difference?
Nova Documentary
The sickle form of the hemoglobin gene:
1. A is changed to a T
2. 6th amino acid in the b-globin protein
from GAG to GUG
3. 6th amino acid in the protein to
become valine instead of glutamic
acid
That single amino acid replacement
1. Alters the shape and the chemistry of
the hemoglobin molecule
2. Causing it to polymerize
3. Distort the red blood cell into the sickle
shape
Genetic mutation to hemoglobin, causing
sickle cell disease
Activity 3.2.3: Does Changing One
Nucleotide Make a Big Difference?
Glutamic Acid:
Hydrophilic or hydrophobic? ____Hydrophilic______
Positive, negative or neutral? ___Negative_______
Valine:
Hydrophilic or hydrophobic? _____Hydrophobic_______
Positive, negative or neutral? ____Neutral____________
Protein shape dictates function! What
dictates shape?
1.
•
•
2.
3.
•
•
Amino acids present
Charge- positive vs.
negative amino acids
Hydrophobic vs.
hydrophilic
The order of amino acids
Surrounding Environment
Oil
Water
3.2 It’s in the Genes: Review
1.
2.
3.
4.
5.
6.
7.
8.
9.
What is the DNA code?
What is the connection between
genes and proteins?
How are proteins produced in a cell?
How does the sequence of
nucleotides in DNA determine the
sequence of amino acids in a
protein?
What is a mutation?
What determines the shape of a
protein?
Is the shape of a protein affected by
its surrounding environment?
How does a change in the DNA code
affect the shape of a protein?
Can changing just one nucleotide in a
gene change the shape of a protein?
Key Terms
Amino Acid
Anticodon
Codon
Hydrophilic
Hydrophobic
Messenger RNA (mRNA)
Mutation
Nucleotide
Protein
Protein Synthesis
Ribonucleic Acid (RNA)
Ribosome
Transcription
Transfer RNA (tRNA)
Translation
3.3 Chromosomes
1.
2.
3.
4.
Key Terms
Allele
Autosome
How is DNA passed to new Chromosome
Dominant trait
cells during cell division?
Gene
What is a chromosome?
Genetic Material
How are traits passed
Genotype
Heredity
through the generations?
Homologous
Should a person have rights Chromosomes
to their organs and tissues? Karyotype
(Optional)
Meiosis
Mitosis
Mutation
Pedigree
Phenotype
Recessive Trait
How do you get Sickle Cell Disease?
• Caused by an abnormal
gene
• Inherited Disease
• E.g., Tay Sachs,
hemophilia, cystic
fibrosis, and
Huntington’s disease
• Vs. Infectious (like…)
• How are mutations in DNA
passed down from one
generation to the next?
Activity 3.3.1: How is DNA Passed
Through the Generations?
• Chromosomes contain the
codes for how to make
specific proteins
• Determine the organism’s
traits
• Chromosome Compaction
• Specific instructions for a
protein are on sections of
the chromosome called
genes
Chromosomes
• DNA is stored in a
•
•
•
•
•
compact form
called chromosomes
46 chromosomes in
somatic (body) cells
23 chromosomes in sex
cells
Egg cell from the mother
fuses with the sperm cell
from the father (zygote)
= 46 chromosomes, 23
pairs
One from mother and one
from father in each pair
Early Zygote
Nuclei from
egg and
sperm fusing
Chromosomes and Sickle Cell
• Chromosome 11
carries the
instructions (genes)
to make the
hemoglobin protein
• There are different
versions of these
genes:
• Normal – healthy
• Mutated or changed –
Sickle cell or other
hemoglobin disorder
Mitosis (video)
1. The chromosomes coil up
2. A mitotic spindle moves them to the
3.
4.
5.
6.
middle of the cell
The sister chromatids then separate
Move to opposite poles of the cell
Two nuclei form (1 at each pole)
Cytokinesis, in which the cell divides in
two
LM 250
INTERPHASE
Centrosomes
(with centriole pairs)
Chromatin
PROPHASE
Early mitotic
spindle
Centrosome
PROMETAPHASE
Fragments
of nuclear
envelope
Kinetochore
Nucleolus
Nuclear
envelope
Chromosome, consisting
Plasma
membrane of two sister chromatids
Centromere
Spindle
microtubules
ANAPHASE
METAPHASE
Metaphase
plate
Spindle
Daughter
chromosomes
TELOPHASE&CYTOKINESIS
Cleavage
furrow
Nuclear
envelope
forming
Nucleolus
forming
Under the scope…
Meiosis (video)
◦ Meiosis, like mitosis, is preceded by chromosome
◦
◦
◦
◦
duplication
But in MEIOSIS:
The cell divides twice to form four daughter cells
Four DIFFERENT CELLS with HALF the genetic
information
Half the number of chromosomes
◦ The first division, meiosis I
 Starts coping (sisters chromatids) and with synapsis-
the pairing of homologous chromosomes
◦ In crossing over
 Homologous chromosomes exchange corresponding
segments
◦ Meiosis I separates each homologous pair
 produce two daughter cells, each with one set of
chromosomes
◦ Meiosis II is essentially the same as mitosis
 The sister chromatids of each chromosome separate
 The result is a total of four haploid cells
Meiosis
MEIOSIS I: Homologous chromosomes separate
INTERPHASE
Centrosomes
(with centriole
pairs)
Nuclear
envelope
PROPHASE I
METAPHASE I
Sites of crossing over
Spindle
Chromatin
Sister
chromatids
Tetrad
Microtubules
Metaphase
attached to
plate
kinetochore
Centromere
(with kinetochore)
ANAPHASE I
Sister chromatids
remain attached
Homologous
chromosomes separate
Prophase l of Meiosis
Sites of crossing over
Spindle
Sister chromatids
Homologous Chromosomes
Tetrad: via synapsis
Tetrad
Chiasma
Centromere
Meiosis Continued…
MEIOSIS II: Sister chromatids separate
TELOPHASE I
AND CYTOKINESIS
PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II
AND CYTOKINESIS
Cleavage
furrow
Sister chromatids
separate
Haploid daughter cells
forming
Possibility 1
Possibility 2
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Gametes
Mitosis
Meiosis
Parent cell
(before chromosome replication)
Meiosis i
Prophase I
Prophase
Duplicated
chromosome
(two sister chromatids)
Metaphase
Anaphase
Telophase
Tetrad formed
by synapsis of
homologous
chromosomes
Chromosome
replication
Chromosome
replication
2n = 4
Chromosomes
align at the
metaphase plate
Sister chromatids
separate during
anaphase
2n
Daughter cells
of mitosis
2n
Tetrads
align at the
metaphase plate
Metaphase I
Homologous
chromosomes
separate during
anaphase I;
sister
chromatids
remain together
No further
chromosomal
replication; sister
chromatids
separate
during
anaphase II
Anaphase I
Telophase I
Haploid
n=2
Daughter
cells of
meiosis I
Meiosis ii
n
n
n
n
Daughter cells of meiosis II
What happens to chromosomes throughout?
It’s all in the name…
• Start as chromatin
• Duplicate
• Thicken and clump into chromosomes
• Consist of two sister chromatids- replicates
• In meiosis…
• Chromosomes (sister chromatid duplicates) find their
other half (maternal and paternal)
• They make homologous pairs, forming an tetrad
• One chromosome carrying info from the mother, the
other carrying info from the father
 Mutations are the original
source of genetic variation
 Raw material for natural
selection
1. Synapsis and crossing
over during prophase
2. Independent assortment
(orientation) of
homologous
chromosome pairs along
the metaphase plate
(during metaphase)
3. Random Fertilization of
eggs by sperm
3.3 Chromosomes Review
1. How is DNA passed to new
cells during cell division?
2. What is a chromosome?
3. How are traits passed
through the generations?
4. Should a person have rights
to their organs and tissues?
(Optional)
Key Terms
Allele
Autosome
Chromosome
Dominant trait
Gene
Genetic Material
Genotype
Heredity
Homologous
Chromosomes
Karyotype
Meiosis
Mitosis
Mutation
Pedigree
Phenotype
Recessive Trait
3.4 Inheritance
1. Why does sickle cell
disease run in families,
yet is not present in every
generation?
2. How can doctors and
genetic counselors
calculate the probability
of a child inheriting a
disease?
3. How does the presence
of malaria in a region
affect the frequencies of
normal versus sickle cell
alleles?
Key Terms
Allele
Chromosome
Dominant Trait
Gene
Genotype
Heredity
Pedigree
Phenotype
Punnett Square
Recessive Trait
How do we know all this stuff?
• Experimental genetics began in
an abbey garden
• Father of modern genetics
• Gregor Mendel’s quantitative
experiments
• Parents pass on to their
offspring discrete heritable
factors, which maintain
individuality
• 7 years after Darwin’s Origins in
1859
• Pea plants
The Humble Pea
• Easy to grow, came
in many varieties,
easy to ensure self
or cross fertilization
• Crossed plants that
differed in certain
characteristics
• Traced traits from
generation to
generation
•
P(parental
generation)
• F1 generation
• F2 generation
Different alleles of 7 genes
Flower color
Flower position
Purple
Axial
Seed color
Yellow
Seed shape
Round
Pod shape
Pod color
Inflated
Green
White
Terminal
Green
Wrinkled
Constricted
Yellow
Stem length
Tall
Dwarf
P generation
(true-breeding parents)
F1 generation

Purple flowers
White flowers
All plants have
purple flowers
Fertilization among F1
plants(F1  F1)
F2 generation
3
4
of plants
have purple flowers
1
4
of plants
have white flowers
Mendel found for each characteristic…
•
An organism inherits two alleles, one from each
parent
• If the two alleles of an inherited pair differ
• Then one determines the organism’s
appearance and is called the dominant allele
• The other allele as no noticeable effect on the
organism’s appearance and is called the
recessive allele
Genetic makeup (alleles)
pp
PP
P plants
Gametes
All p
All P
F1 plants
(hybrids)
All Pp
1
2P
Gametes
1
2p
Sperm
P
F2 plants
Phenotypic ratio
3 purple : 1 white
p
P
PP
Pp
p
Pp
pp
Eggs
Genotypic ratio
1 PP : 2 Pp: 1 pp
• Homologous chromosomes bear the two alleles for each characteristic
• Alternative forms of a gene reside at the same locus on homologous
chromosomes
1. Homozygous recessive
2. Homozygous dominant
3. Heterozygous
Dominant
allele
Gene loci
a
B
P
a
b
PP
Homozygous
for the
dominant allele
aa
Homozygous
for the
recessive allele
Bb
Heterozygous
P
Genotype:
Recessive
allele
Back to…How do you get SCD?
• It is an inherited blood disorder
• Both parents have to have it to pass on
the abnormal gene
• If you inherit the problem gene from one
parent and a normal gene from the other
• ‘Sickle cell trait' or be a Carrier
• Doesn't usually cause any symptoms
• Can be passed on to the next generation.
Chromosomes and Sickle Cell
• Chromosome 11 carries
the instructions (genes)
to make the hemoglobin
protein.
• There are different
versions of these
genes:
• Normal--healthy
• Mutated or changed-Sickle cell or other
hemoglobin disorder.
3.4.1: Family Inheritance
• Pedigrees show the occurrence of a particular trait from
one generation to the next
• P, F1 and F2 generations
• Males are represented by squares
• Females are represented by circles
• Relationships are represented with lines
• Make it easier to visualize relationships within families
• Used to determine the mode of inheritance (dominant
versus recessive) of genetic diseases
• Pedigrees illustrate what is or has been
• Vs. Punnett Squares & probability (next)
With two carriers= 25% Chance SCD
• For every pregnancy when both parents have sickle trait,
there is a 1in 4 chance that their offspring will have sickle
cell anemia.
3.4.1: Family Inheritance & Pedigrees
• How does analyzing pedigrees help
doctors, epidemiologists, researchers, and
other scientists understand how diseases
are inherited?
• How are pedigrees used to track diseases?
• Why does sickle cell disease run in
families, yet is not present in every
generation?
Mendel’s Laws
Law of Dominance
• In a cross of parents that are pure for contrasting traits, only one form of the
trait will appear in the next generation. Offspring that are hybrid for a trait will
have only the dominant trait in the phenotype.
• Dominant vs. recessive traits
Law of Segregation
• During the formation of gametes (eggs or sperm), the two alleles responsible
for a trait separate from each other. Alleles for a trait are then "recombined" at
fertilization, producing the genotype for the traits of the offspring.
• Which of the two alleles ends up in which gamete (monohybrid cross in
Punnett square)
Law of Independent Assortment
• The different traits do not influence the inheritance of each other. They are
inherited INDEPENDENTLY.
• When looking at multiple traits, alleles segregate separately (dihybrid cross in
Punnett square)
Punnett Squares
Reginald Punnett
A
DIHYBRID
CROSS!
• Something
a bit more
challenging
• Uses
Mendel's 3rd
Law as well
3.4.2 What’s the Probability?
• How can doctors
and genetic
counselors calculate
the probability of a
child inheriting a
disease?
3.4.2 What’s the Probability?
Punnett Squares
• Create your own handout for this activity
• Write four word problems that require Punnett squares
• Be creative!
• Set up one question with chromosomes
• Use a pedigree for at least one
• Always ask for the genotypic and phenotypic ratio
• Always ask a “what’s the percent chance that..” question
• Be sure to have an answer key
• Work in 1s or 2s, but you’ll need to type and print one handout
each
• TRADE- Due Monday!
• Let’s complete some examples
Example with chromosomes
• Complete a Punnett square
for these parents.
Determine the genotypic
and phenotypic ratios.
Determine the percent
chance a child has of
having sickle cell anemia
from this reproductive
pairing
Example with pedigree
• Anna’s mother passed
away three years ago, so
she was unavailable for
genetic testing. Based upon
Anna’s family pedigree that
you created in the previous
activity, determine her
mother’s possible
genotypes and phenotypes
related to sickle cell
anemia. Explain your
reasoning and describe the
information you used to
make your prediction.
Example word problem
• Juan’s family has a history of sickle cell disease. His father died
of sickle cell disease complications when Juan was six years
old. He remembers his father being in great pain. Juan marries
Gina. Gina’s maternal grandmother and paternal grandfather
had sickle cell disease, but neither of her parents has the
disease. Juan does not want to have children because he is
convinced they will have sickle cell disease. Gina is not so
sure. They have come to you for advice about having whether
or not to have children. Based on your calculations of the
probability of their child getting sickle cell disease, what is your
advice? Show your calculations and explain your reasoning for
your response. It may be helpful for you to draw pedigrees and
possible Punnett squares for both Juan’s and Gina’s families.
Read Survival of the Sickest
• Read- Introduction, Ironing It Out
and Hey, Bud, Can You Do Me a
Fava?
•
This is a book about mysteries and miracles.
About medicine and myth. About cold iron, red
blood, and neverending ice. It’s a book about
survival and creation. It’s a book that wonders
why, and a book that asks why not. It’s a book in
love with order and a book that craves a little
chaos. Most of all, it’s a book about life—yours,
ours, and that of every little living thing under
the sun. About how we all got here, where
we’re all going, and what we can do about it.
Welcome to our magical medical mystery tour.
Genetic Basis for Sickle Cell Disease
• PBS Sickle Cell Link (Video)
• A bit on evolution….
What were Darwin’s Main
ideas anyway???
1. Species change over time
2. Living species have arisen
from earlier life forms
(descending from a
common ancestor)
 Close ties between
organisms and their
environments*
 Can be traced back to the
ancient Greeks
Evolution is the greatest unifying theme in
biology, and The Origin of Species fueled an
explosion in biological research and knowledge
that continues today.
Evolutionary theory continues to expand beyond
Darwin’s basic ideas.
Nonetheless, few contributions in all of science
have explained so much, withstood as much
repeated testing over the years, and stimulated
as much other research as those of Darwin.
• Natural Selection
1. Produce more
offspring than the
environment can
support
2. Individuals of a
population vary in
their characteristics
3. Many characteristics
can be inherited
4. Beneficial
characteristics are
preferentially
passed down
•
•
Darwin found convincing evidence for his ideas in the results of
artificial selection
With humans playing the role of the environment
Hundreds to thousands of years
of breeding (artificial selection)
Ancestral dog (wolf)
Throughout Human Evolution
• The best genes survive
from one generation to next
• Why do we still have some
deleterious genetic
mutations?
• Various mutations have
provided a benefit
• Extra Iron
• Sickle Cell
• We continue to see these
mutations in modern day
humanity even when the
benefit no longer exists
(leftover)
The Immortal Story of Henrietta Lacks
• The first cell line,
cultured more than 60
years ago
• The HeLa Cell-Line
has been reproducing
independently, fueling
biological research
• Bioethics- The study of
controversial ethics
brought about by
advances in biological
or medical research
The Great Debate
• Two sides of the
argument
• Henerietta’s
• Dr. Gey’s
• Prep time
• Design opening and
closing statement
• Make THREE KEY
arguments
• Plan a defense against
your opponent
• H: Opening statement (1 minutes) •
• G: Opening statement (1 minutes)
• H: Key Point 1(one minute)
• G: rebuttal
•
• H: rebuttal
• G: Key Point 1(one minute)
• H: rebuttal
•
• G: rebuttal
•
• H: Key Point 2 (one minute)
• G: rebuttal
• H: rebuttal
• G: Key Point 2 (one minute)
• H: rebuttal
• G: rebuttal
H: Key Point 3 (one minute)
• G: rebuttal
• H: rebuttal
G: Key Point 3 (one minute)
• H: rebuttal
• G: rebuttal
H: Closing (one minute)
G: Closing (one minute)
3.4 Inheritance Review
1. Why does sickle cell
disease run in families,
yet is not present in every
generation?
2. How can doctors and
genetic counselors
calculate the probability
of a child inheriting a
disease?
3. How does the presence
of malaria in a region
affect the frequencies of
normal versus sickle cell
alleles?
Key Terms
Allele
Chromosome
Dominant Trait
Gene
Genotype
Heredity
Pedigree
Phenotype
Punnett Square
Recessive Trait

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