GENETICS - CHAPTER 10.2 - 10.3 and 11.2
GREGOR MENDEL (1822-1884) Born in Austria - monk - loved nature
 interested in plants, meteorology and theories of evolution
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Mendel studied ____________________ observed _____________________________________________

by tracing these 7 traits, Mendel discovered 3 basic laws which govern the passage of traits
Before Mendel could start his experiments….. he had to get ______________________________________
always__________________________________________________________________________
Mendel got pure plants by ________________________________________________________________

eventually, he had 14 pure strains (7 traits X 2 contrasting forms of each trait)
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each pure strain he called a ________________________________________
MENDEL’S EXPERIMENTS
Mendel crossed …. pure P X contrasting pure P = F1 (first filial generation)
results: __________________________________________________________________________
Mendel then crossed…. F1 x F1 = F2 (second filial generation)
results: __________________________________________________________________________
MENDEL CONCLUDED …..that the patterns of inheritance are governed by 3 principles
1. Principle of Dominance and Recessiveness
Mendel concluded…_______________________________________________________________
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2. Principle of Segregation
Mendel concluded…_______________________________________________________________
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3. Principle of Independent Assortment
Mendel concluded…_______________________________________________________________
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Even though Mendel discovered many of the basic mechanisms of how traits are transmitted
from parent to offspring, his principles cannot be applied to all inheritance patterns.
IMPORTANT TERMS TO KNOW:
Genetics: ____________________________________________________________________________
Gene: _______________________________________________________________________________
Allele: ______________________________________________________________________________
ALLELES CAN BE…
Dominant ___________________________________________________________________________
represented by ____________________________________________________________
Recessive ____________________________________________________________________________
represented by ____________________________________________________________
BECAUSE CHROMOSOMES OCCUR IN PAIRS, ALLELES ALSO OCCUR IN PAIRS.
Homozygous: ________________________________________________________________________
examples______________________________________________________________________
Heterozygous: _______________________________________________________________________
examples______________________________________________________________________
Phenotype: _________________________________________________________________________
Examples: _____________________________________________________________________
Rule: _________________________________________________________________________
Genotype: __________________________________________________________________________
Examples: _____________________________________________________________________
Rule: _________________________________________________________________________
MENDEL’S STUDIES…..
Studied garden peas because: ______________________________________________________________
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7 well-defined traits – exhibited COMPLETE DOMINANCE
Counted offspring of each phenotype and… _______________________________________________
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Trait
Flower color
Flower position
Seed color
Seed texture
Pod color
Pod texture
Height
Dominant
Recessive
PRACTICE ASSIGNING ALLELES:
1. Homozygous purple flower __________
5. Homozygous wrinkled seed __________
2. Homozygous tall __________
6. Homozygous axial flower __________
3. Homozygous green pod __________
7. Heterozygous axial flower __________
4. Heterozygous green pod __________
8. Homozygous terminal flower __________
PROBABILITY: _____________________________________________________________________
Probability =
# of 1 kind of event
total # of events
PUNNETT SQUARE - a grid used to help in completing a genetic cross
Dr. Punnett - early 1900s - graphical way to show probability
5 STEPS
1. ___________________________________________________________________
2. ___________________________________________________________________
3. ___________________________________________________________________
4. ___________________________________________________________________
5. ___________________________________________________________________
TYPES OF CROSSES
Monohybrid Cross - ___________________________________________________________________
Dihybrid Cross - _____________________________________________________________________
LET’S PRACTICE – Cross a homozygous smooth seed with a wrinkled seed
Step 1. P genotypes = SS x ss
Step 2. split alleles
Step 3: perform Punnett
Step 4: F1 genotypes ______________________
Step 5: F1 phenotypes _____________________
Monohybrid Cross #1 – show all 5 steps
In gerbils, brown fur (F) is completely dominant over white fur (f).
Cross a heterozygous brown-furred gerbil with a white-furred gerbil.
P genotypes? _____________________
F1 genotypes _____________________
F1 phenotypes ____________________
S = smooth
s = wrinkled
Monohybrid Cross #2 – show all 5 steps
In pigs, curly tails (T) are completely dominant over straight tails (t).
Cross a homozygous curly-tailed pig with a heterozygous curly-tailed pig.
P genotypes? _____________________
F1 genotypes _____________________
F1 phenotypes ____________________
BEYOND MENDELIAN GENETICS
Some inheritance patterns are more complex than what Mendel studied.
INCOMPLETE DOMINANCE - ________________________________________________________
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Example –
CODOMINANCE - ____________________________________________________________________
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Example SEX-LINKED GENES ….are genes that are linked to (found on) the sex chromosomes – X and Y
X chromosome is LARGE and ___________________________________________
Y chromosome is small and ______________________________________________
discovered by ________________________________________________________
when _______________________________________________________________
sex chromosomes of females are ___________ males are __________
SEX-LINKED TRAITS – can be Y linked or X linked
Y linked traits _________________________________________________________________________
X linked traits _________________________________________________________________________
Examples of X linked RECESSIVE traits …..
Red/Green Colorblindness - ________________________________________________________
Hemophilia - ____________________________________________________________________
Duchenne Muscular Dystrophy - ___________________________________________________
MULTIPLE ALLELES - ________________________________________________________________
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Example - ___________________________________________________________________________
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4 possible blood types – ___________________________________________
What is a person’s blood type if their allele pair is? AA ___ Ao ___ BB___ Bo ___ AB ___ oo ___
POLYGENIC TRAITS - _______________________________________________________________
Examples: ______________________________________________________________________
 DIHYBRID PUNNETT SQUARES - Same steps as a monohybrid cross with one exception
1. ______________________________________________________________
EXTRA STEP – FOIL the alleles (First, Outside, Inside, Last)
2. ______________________________________________________________
3. ______________________________________________________________
4. ______________________________________________________________
5. ______________________________________________________________
Practice with FOILing – CROSS #1
smooth seeds = S
wrinkled seeds = s
yellow seeds = Y
green seeds = y
P = homozygous smooth & homozygous yellow crossed with
heterozygous smooth & heterozygous yellow
P= _________________________________
FOIL = _____________________________
F1 genotypes:
____________________________________
F1 phenotypes:
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CROSS #2
green pod = G
yellow pod = g
inflated pod = I
constricted pod= i
P = heterozygous green & heterozygous inflated pods crossed with
heterozygous green & heterozygous inflated pods
P= _________________________________
FOIL = _____________________________
F1 genotypes:
____________________________________
F1 phenotypes:
____________________________________
*There should always be a 9:3:3:1 phenotypic ratio in a heterozygous x heterozygous dihybrid cross.
SOME WAYS TO CHECK YOURSELF….
In monohybrid crosses of…..heterozygous x heterozygous crosses:
Genotypic ratio ALWAYS = ______________________________
Phenotypic ratio ALWAYS = ______________________________
In dihybrid crosses of….heterozygous x heterozygous crosses:
Phenotypic ratio ALWAYS = ______________________________
TRY SOME INTERACTIVE PUNNETT SQUARES @
http://glencoe.mcgraw-hill.com/sites/dl/free/0078695104/383934/BL_05.html
POLYPLOIDY….
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Triploid (3n) = _____________ diploid (2n) = ______________ haploid (1n or n) = ________________

Rarely occurs in animals – always fatal in humans

Plants often exhibit polyploidy – exhibit more vigor and size
GENETIC RECOMBINATION .…
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GENE LINKAGE
REMEMBER, chromosomes contain many genes!!!
Genes located on the same chromosome are “linked together”
and make up a LINKAGE GROUP.
Genes that are located close together on the same chromosome are likely
to be inherited together.
The linkage of genes on a chromosome is an exception
to Mendel’s law of __________________________
CHROMOSOME MAP (Gene Map)
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The “Human Genome Project”
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