Genetics
Objectives
 ________’s
Experiments and Laws Inheritance
 ________ Square to determine genotype and
phenotype ratios of a cross
 Types of Inheritance:






.
.
.
.
.
.
Heredity and Genetics
 Heredity
is the passing of traits from _________ to
_________
 Traits are controlled by _________, so…
 Genetics is the study of how traits are _________
through the action of _________
Gregor Mendel: Father of Genetics
 Mendel,
an Austrian
monk (born in1822) is
responsible for the laws
governing the i
_________ of traits
 Mendel cultivated
and tested over 28,000
_________ plants
 Mendel performed
_______________ by
transferring pollen from
one plant to selected
ova of other plants,
thereby controlling
which plants mixed
Traits Observed
Traits Continued
Genetics Vocab
 Traits:
any characteristic that can be passed from
parents to _________
 Heredity: the _________ of traits from _________ to
offspring
 Alleles: a type of gene, either _________ or
_________
Complete (Single) Dominance
 Complete
Dominance: _________ gene with the
possibility of _________ alleles


_________
_________
Dominant vs. Recessive
 Dominant:
an allele whose effects mask the effects
of a _________ allele


represented by a _________ letter.
Ex: Brown hair: _________
 Recessive:
an allele whose effects are masked by
the _________ allele


represented by a _________ letter
Ex: blond hair: _________
Heterozygous v. Homozygous


“Purebred” species
have two of the
same alleles; this is
also called
_________
Homozygous:
species with two of
the _________
alleles:



_________
(homozygous
dominant)
_________(homozyg
ous recessive)
Heterozygous:
Species with two
_________ alleles

_________
Genotype v. Phenotype
 Genotype:
the alleles present in the organism, i.e.,
_________ , _________ or _________
 Phenotype: the physical expression of the genes;
what is _________
Genetic Crosses

Monohybrid Cross: cross
involving _________ trait


Dihybrid Cross: cross
involving _________ traits


Ex: eye color
Ex: Shape and Color of
Fruit
Offspring’s genotype
and phenotype is
determined using a
_________ square
Punnett Squares
 Punnett
squares can be used to determine the
probabilities for _________ (genetic information) and
_________ (expression of gene) combinations in
_________ crosses.
Genotypes and Phenotypes in
Flowers

All genes occur in pairs, so _________ alleles affect a trait.

Possible combinations if:
R = Red flower
r = Yellow flower

Possible Genotypes
Phenotypes

_________
_________
_________
_________
_________
_________
Punnett Square: Example

A father has brown hair and is heterozygous


What is his phenotype?_______
What is his genotype? ________


He is ________________________
A mother has brown hair and is homozygous


What is her phenotype?_______
What is her genotype? ________

She is ________________________________
Punnett Square: Example
 What
are the possible phenotypes and
genotypes for their child?
 Genotypic
Ratio: ________
 Phenotypic
Ratio: __________
More Punnett Square Examples
Incomplete Dominance and
Codominance
Incomplete Dominance
 Incomplete
Dominance: _________ allele for a trait
(gene) is completely dominant over the other
_________ Results in the heterozygous genotype
having a _________ phenotype
Incomplete Dominance
 F1
hybrids have an appearance somewhat
_________ the phenotypes of the two parental
varieties.
 Example: snapdragons (flower)
red (RR) x white (WW)
RR = red flower
WW= white flower
Incomplete Dominance
r
R
RW
R
RW
r
RW
RW
produces the
All RW = _________
(_________ pink)
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Incomplete Dominance
Codominance
 Both
alleles for a gene are expressed in the
phenotype of an individual with the _________
genotype
 Example: Coat color in cattle
Codominance Example

In some cattle, the
genes for brown hair (B)
and for white hair (W)
are codominant. Cattle
with alleles for both
brown and white hair,
have both brown and
white hair. This condition
is this combination of
two separate hair colors
is called Roan. It’s
genotype is BW. Cross a
Roan Cow and a white
bull. Give the
phenotypic and
genotypic ratios for the
offspring.
Codominance Example Cont.
 Genotypic
Ratios: __________________
 Phenotypic Ratios: ___________________
Multiple Alleles
 Multiple
Allele Traits: The trait is determined by
genes that have more than _________ alleles
 Ex:


Humans: _________ blood groups
Rabbits: Fur Color
Multiple Alleles


Blood type in humans is determined by one gene and three
alelles
Each person inherits 2 alleles







_________ : IA
_________ : IB
_________ : i
Possible Combinations:
1.
type A = _________ or _________
2.
type B = _________ or _________
AB = _________
4.
type O = _________
3.
type
Multiple Alleles Problem 1
A
man with Type AB blood is marries to a
woman who is also Type AB blood. What is
the potential of each of the following
blood types?




Type A:
Type B
Type AB:
Type O:
Multiple Alleles Problem 2
A
man who is homozygous for Type B
blood is married to a woman who is Type
O blood.

What blood type will all of the children
have?
Multiple Alleles Problem 3
A
woman with Type O blood is claiming that a man
with Type AB blood is the father of her child who is
Type AB blood. Could this man be the father of her
child? Show the Punnett square and explain your
result.
Sex Linked Traits





Genes Reside on
Chromosomes
Sex-Linked Traits: the trait is
determined by the gene on
the _________ chromosomes
Most are located on the
_________ chromosomes
Sex-linked traits in humans
are usually defects or
diseases that are _________
Ex: _________, _________,
_________
Ex: Sex-Linked Traits
 Hemophilia
(H: Normal blood clotting, h: hemophilia)
Hemophilia
XX chromosome - female
Xy chromosome - male
Sex-Linked Traits
 Sex-Linked

Genes and Traits
Because males have only one X chromosome, a male
who carries a recessive allele on the X chromosome
will exhibit the sex-linked trait.
 Many
sex-linked traits carried on X chromosome
Sex Linked Trait Example
 Cross
a homozygous normal
female with a male who
has hemophilia.





Female Genotype:
Male Genotype:
Probability of Producing female child
with hemophilia?
Probability of Producing female child
with hemophilia?
Probability of Producing female child
with hemophilia
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Sex-Linked Problem 2

Cross a carrier female with a normal
male?
 Female Genotype:
 Male Genotype:
 Probability
of Producing female
child with hemophilia?
 Probability of Producing female
child with hemophilia?
 Probability of Producing female
child with hemophilia
Female Carriers
 In
sex- linked traits (ie. hemophilia), women are
_________ (they have the gene, but it is not
expressed) and men have the phenotype more
often. Can you explain why?
Polygenic
 Polygenic:



_________ than
two genes
control a trait
(“_________
genes”)
Results in a wide
range of
_________
Ex: _________,
_________,
_________
Mendel’s Law of Segregation
 Mendel’s
Law of Segregation: _________ of alleles
during _________ formation
 This is seen with _________ squares
Mendel’s Law of Independent
Assortment
 Mendel’s
Law of Independent Assortment Genes
for different traits are inherited _________ from each
other (ie. your eye color does not depend on the
shape of your eyes)
Dihybrid Crosses
A
breeding experiment that tracks the inheritance
of _________ traits
 Mendel’s “Law of Independent Assortment”


Each pair of alleles segregates _________ during
gamete formation
Formula: 2n (n = # of heterozygotes)
Example:
1. RrYy: 2n = 22 = _________ possible gametes
_________
_________
2. AaBbCCDd: 2n =
_________
2__ = ____
_________
gametes
_________
_________
_________
_________
_________
_________
_________
_________
Dihybrid Crosses
 Traits:
Seed shape & Seed color
 Alleles:
R round
r wrinkled
Y yellow
y green

RrYy x RrYy
___ ___ ___ ___
____ ___ ____ ____
All possible gamete combinations
Dihybrid Cross: With Ratio
RY
Ry
rY
ry
RY
Ry
rY
ry
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Dihybrid Cross
RY
Ry
rY
ry
RY
Ry
rY
ry
RRYY
RRYy
RrYY
RrYy
RRYy
RrYY
RrYy
RRyy
RrYy
Rryy
RrYy
rrYY
rrYy
Rryy
rrYy
rryy
copyright cmassengale
Round/Yellow:
9
Round/green:
3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic
ratio
43
Dihybrid Cross
Round/Yellow: 9
Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1
Inheritance of Traits
 Pedigrees


Geneticists use _________ to trace _________ or traits
through families.
Pedigrees are diagrams that reveal _________
patterns of _________
Pedigree for Cystic Fibrosis
Some Important Genetic Disorders