Unit Title: Patterns of Inheritance
Course: Biology
Patterns
of Inheritance
Essential Questions:
Enduring Understandings:
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DNA (and sometimes RNA) is the
primary source of heritable genetic
information necessary for cells (and
organisms) to survive, grow and
reproduce.
Organisms typically have two alleles for
every gene; one copy of each gene
randomly inherited from each parent.
Organisms resemble family members
because they share common genes, but
are not identical to relatives because
alleles may be mutated, shuffled, and
randomly recombined during sexual
reproduction into trillions of possible
variations.
Alleles follow somewhat predictable
patterns of inheritance.
Probabilities are only predictions about
likelihood, NOT necessarily the outcome.
Phenotypes are a product of genotypes
but are influenced by environmental
factors.
While all DNA is composed of the same
materials, each individual’s DNA is
completely unique and determines how
cells function to produce individual
characteristics.
Many human disorders are genetic, and
therefore, heritable and to some extent
predictable.
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What is the role of DNA/genes in
determining cell characteristics and
organism characteristics?
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How are genes from parent
organisms passed on to offspring?
Why do organisms resemble family
members yet are never identical
(unless identical twins or clones)?
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Why are identical twins genetically
identical yet not totally identical
physically?
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How do we use known patterns
of inheritance to predict offspring
traits?
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Do the principles of genetics apply
to all organisms?
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How are genetic disorders
diagnosed and treated?
Unit Title: Patterns of Inheritance
Course: Biology
Patterns of
Inheritance
Critical Skills:
Critical Content:
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Mendelian genetics
Dominant v recessive
Genes v alleles
Genotype v phenotype
Homozygous v heterozygous
Allele segregation
Independent assortment
Crossing over
Sexual recombination
Punnett squares & probability
Patterns of inheritance
Sex-linked traits
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Apply mathematical models to
analyze data from Mendel’s
experiments
Use principles of Mendelian genetics
to demonstrate how alleles are
sorted, segregated and randomly
passed on to offspring during sexual
reproduction.
Analyze scientific data via
calculations and inference
Use punnett squares to predict the
probability of phenotypes and
genotypes for offspring.
Determine and compare ratios
Analyze and solve genetic story
problems
Analyze and construct simple
pedigrees
Interpret graphs, tables, and charts
Record investigations clearly and
accurately
Connect the effects of abnormal
chromosome segregation with
changes in phenotype and issues
surrounding human genetic diseases
Read scientific text for meaning
Write effectively
Unit Title: Patterns of Inheritance
Course: Biology
Big Idea:
The chromosomal basis of inheritance dictates the passage of genes
and traits from parent to offspring at both the cellular and organism levels.
Synopsis: Mendel applied mathematical reasoning to describe a simple model
of inheritance. Genetic molecules contain the instructions necessary for survival,
growth and reproduction. The expression of genetic material directs cell function
and determines the properties of not only the cell, but also the organism.
Approximate Instructional Days: 18
Learning Targets
3.1.3
3.1.6
3.2.2
Cells store and use information stored in DNA to guide their
function.
Cells can differentiate, and complex multicellular organisms
are formed as a highly organized arrangement of
differentiated cells.
Most of the cells in a human contain two copies of each of
22 different chromosomes.
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Focused Assessed
Unit Title: Patterns of Inheritance
Course: Biology
Suggested Learning Experiences with Ideas for Differentiation
R)=Remediation E)=Extension
Cracking the code: peas in a pod introduction to unit
Vocabulary: Use literacy strategies such as Four Square, mind
mapping, word wall, flashcards, graphic organizer, etc.
R: Vocabulary
matching or cards with
drawings
Genetic problems – Mendel’s peas, phenotypes and
genotypes, punnetts and probability, genotype/ phenotype
ratios, dihybrid crosses and ratios, other patterns of
inheritance, pedigree analysis
R: Review Meiosis to
show how gametes
formed.
R: Extra practice with
phenotypes and
genotypes
R: Focus on
monohybrid crosses
R: Use beans or other
manipulatives to show
possible gametes and
offspring
combinations.
R: Biology by Miller &
Levine. Pearson (2010)
Workbook A or B
E: Finding Patterns in
Mendel’s data
E: More complex
pedigree analysis
E: Gene linkage
mapping
Problem sets (need practice with genotypes v phenotypes,
monohybrid punnett squares and probability at a minimum)
Describe the inheritance pattern, diagnosis and treatment for
at least one human genetic disorder
Human genetic disorder project –cooperative poster,
presentation or report
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Unit Title: Patterns of Inheritance
Course: Biology
Labs with data collection and analysis (at a minimum need lab
on probability v actual data)
Resources
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Biology by Miller & Levine. Pearson (2010) Chapter 11.1-11.3 text Mendel & Patterns
of Inheritence; Chapter 14.1 – 14.2 Human Heredity
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All genetic problem sets and labs mentioned above can be made available in a
database.
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Dragon genetics and blood testing labs are excellent at
http://serendip.brynmawr.edu/sci_edu/waldron/
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Utah has a very comprehensive site on genetics at http://teach.genetics.utah.edu/
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Cracking The Code: The Continuing Saga Of Genetics is an animated video series
with excellent introductions to mendel and genetics in history – teaching resource
found at http://www.crackingthecode.ca/ctc1.html
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Remedial tutorial on genetic variation created from meiosis http://bcs.whfreeman.com/pierce1e/pages/bcsmain.asp?v=chapter&s=02000&n=00020&i=02020.03&o=|00010|00020|&ns=0
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Extension projects - http://library.thinkquest.org/19037/teach_links.html
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Unit Title: Patterns of Inheritance
Course: Biology
Unit Outline
Genetics Outline
A. Mendel’s Experiments and Principles
1. Principle of dominance—when two contrasting traits of the parent generation (P)
are crossed, the dominant trait appears in the first generation (F1, or filial one)
a) Dominant trait—symbolized with a capital letter (A)
b) Recessive trait—symbolized with a lowercase letter (a)
2. Law of segregation—for each character an organism inherits two factors, one from
each parent, that separates during gamete formation
a) Homozygous - having a pair of identical alleles (alternative version of a gene)
b) Heterozygous - having two different alleles for a trait
3. Punnett Squares - a tool used to determine the probability of inheriting traits
a) Monohybrid cross
i. Genotype—actual genetic information v Phenotype—expression of the
genes
b) Probability (the likelihood that a specific event will occur)
i. Expressed as a decimal, percent, or fraction
ii. Expected ratios are most likely to occur when the population size in the
study is very large.
iii. chance that two or more independent events will occur simultaneously
is equal to the product of their chances occurring separately
iv. Rule of addition—to determine the probability of an event occurring in
two or more different ways, add the separate probabilities of each way
that the event can occur.
c) Genotype and phenotype ratios
4. Law of independent assortment—genes located on different chromosomes assort
independently of one another
a) Dihybrid crosses—mating that involves two traits
i. Use parent genotypes to determine possible gametes for punnett square
ii. Classic 9:3:3:1 phenotype ratio supports independent assortment
iii. Analyze genotype and phenotype ratios
B. Non-Mendelian inheritance patterns (not complete dominance)
1. Incomplete dominance - blending of traits; partial expression of two alleles in the
offspring creates intermediates
2. Codominance - distinct expressions of both forms of an allele in the phenotype of
the offspring
3. Multiple allele traits – single gene may have more than two alleles and
demonstrate more than one pattern of inheritance
a. Blood typing – A & B codominate and both dominant to O
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Unit Title: Patterns of Inheritance
Course: Biology
4. Polygenic traits - requires the additive effects of two or more genes for the
expression of a phenotype (e.g., height, skin color in humans, etc.)
5. Environmental factors - both genes and environment collectively influence
phenotype.
C. Pedigree analysis
1. Pedigree—a family tree describing the interrelationships of parents and children
across several generations
a) Male = square
b) Female = circle
c) Affected = shaded square or circle
d) Unaffected = unshaded square or circle
e) Mating = horizontal line
f) Descendents = vertical line
D. Human genetic disorders - Many human disorders are genetic, and therefore,
heritable. They demonstrate a variety of inheritance patterns
1. Examples: downs, achondroplasia, sickle cell anemia, cystic fibrosis, tay sachs,
huntingtons, PKU, klinefelters, progeria, turners, marfan, duschennes
2. Technology to diagnose human genetic disorders
a) Amniocentesis—between the fourteenth and sixteenth weeks of gestation,
a physician inserts a needle into the uterus and extracts about 10 mL of
amniotic fluid (the fluid that bathes the fetus). Tests are performed on the
then-cultured cells. Complications include maternal bleeding and fetal
death.
b) Karyotype—a picture of the metaphase chromosomes
c) Chorionic villus sampling (CVS)—a physician suctions off a small amount of
fetal tissue from the placenta, usually getting enough mitotic cells to
perform a karyotype immediately
d) Ultrasound—a noninvasive procedure that uses sound waves to produce
an image of the fetus
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Genetics Vocabulary List
Genetics
Trait
Gene
Allele
P Generation
F1 Generation
F2 Generation
Law Of Segregation
Homozygous
Heterozygous
Genotype
Phenotype
Probability
Punnett Square
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Dihybrid Cross
Independent Assortment
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits
Linked Genes
Unit Title: Patterns of Inheritance
Course: Biology
Dominant Allele
Recessive Allele
Principle of Dominance
Genotype Ratio
Phenotype Ratio
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Sex Linked Genes