Download Patterns of Heredity

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Not
 ______
all traits are simply
inherited by dominant and
recessive alleles (Mendelian
Genetics). In some traits,
neither allele is dominant or
many alleles control the trait.
There are different ways in
which traits can be inherited
from parents to offspring.
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1. Incomplete Dominance
 Definition:
dominates
allele for a gene ____________.
 Phenotype of the heterozygous
blend of the two
offspring will be a ________
homozygous parents.
 Neither
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Incomplete Dominance
homozygous white flower crossed
A _____________
homozygous red flower will
with a _____________
heterozygous pink flowers.
produce all _______________
 Ex.
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Incomplete Dominance
NOTATION:
Alleles
are all capital letters
because NEITHER one
dominates the other. So
____________
one of the alleles has a
________
prime (‘) on it to
represent an alternate
expression of the gene.
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KEY to show
make a _____
the genotypes and the
resulting phenotypes.
Still supports Mendel’s Law of
Independent Assortment.
Always
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 Ex.
1)
 In a certain species of snapdragons,
the combined expression of both
alleles for flower color produces a new
phenotype – pink. A red snapdragon
is homozygous and is crossed with a
homozygous white snapdragon. What
are the genotypic and phenotypic
ratios of this cross?
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Key:
Red = RR
White = R’R’
Pink = RR’
P cross = RR x R’R’
100%
RR’
G:
__________
R
R
R’ RR’ RR’
Pink
P: 100%
__________
R’ RR’ RR’
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 Ex.
2)
 Then cross the F1 generation and what
are the genotypic and phenotypic
ratios of this cross?
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Key:
Red = RR
White = R’R’
Pink = RR’
P cross = RR’ x RR’
G: 1RR:2RR’:1R’R’
__________
R
R’
_____________
R RR’ RR’ P: 1Red:2Pink:1White
R’ RR’ R’R’
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2. Codominance
 Definition:
alleles are expressed
__________
EQUALLY
__________
 Both
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Codominance
 Phenotypes
of heterozygous offspring
are showing both traits!
 Ex. Red cows crossed with white will
Roan refers to
generate roan cows. _______
cows that have red coats with white
blotches.
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Codominance
NOTATION:
different
Two ____________
alleles
(capital letters) are used.
Always
make a _____
KEY to
show the genotypes and
the resulting phenotype.
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 In
chickens, black-feathered is not
wholly dominant over whitefeathered, so heterozygous
chickens are black and white
checkered. Cross two heterozygous
chickens. What would the
appearance of their offspring be?
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Key:
Black = BB
White = WW
Checkered = BW
P cross = BWxBW
B
B BB
W
BW
W BW WW
Phenotype:
1 Black
2 Checkered
1 White
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 In
shorthorn cattle, the hybrid
between red and white is called a
roan. What phenotypes would result
in the cross of a roan and a white?
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Key:
Red = RR
White = WW
Roan = RW
P cross = RW x WW
Phenotype
R
W
W RW WW
2 Roan: 2 White
W RW WW
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3. Multiple Alleles
Definition:
two alleles
More than ______________
for
a single gene can control a
trait.
Multiple alleles must be
studies by looking at the
entire population of species.
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Multiple Alleles
Each individual carries only two
alleles for any gene (one on
each homologous
chromosome).
In this form of inheritance, a
trait can have one gene, but
100 alleles for that gene.
______________
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Multiple Alleles
Ex: The human blood group
can be any combination of A,
B, and O.
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Multiple Alleles
The alleles are IA, IB and i.
A and ___
B are
Alleles ___
CODOMINANT
________________.
RECESSIVE
i (“O”) is ____________.
Alleles ___
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NOTATION:

The possible genotypes/phenotypes.
GENOTYPES
Homozygous type A
Heterozygous type A
Homozygous type B
Heterozygous type B
Codominant type AB
Recessive type O
IAIA
IAi
IBIB
IBi
IAIB
Ii
PHENOTYPES
Type A blood
Type A blood
Type B blood
Type B blood
Type AB blood
Type O blood
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Multiple Alleles
NOTE:
the “i” is dropped from
the genotype of A and B when
phenotype is written.
the ____________
(Genotype IAI
is type A blood)
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Interesting Fact
 In
the US, about 45% of the
population is type O, 42% type A,
10% type B and only 3% type AB.
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The ABO Blood System
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 The
positive and negative of a
blood type is called the
Rh factor
____________,
it is totally a
gene with RH+ (RR or
separate _______
Rr) and Rh- alleles (rr).
 If
you have the protein = Rh+
 If you DO NOT have the protein = Rh28
Interesting Fact
 In
the US, about 85% of the
population is Rh+ and 15% Rh-.
 Thus the chances of someone
being O- (having both ii and rr)
would be 45% X 15% = 6.75%.
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 The
most rare blood type would
AB
be ______, about 0.45% if the
population.
O is the universal donor.
_____
AB is the universal recipient.
_____
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P cross = IAIB x ii
i
i
IA
IB
A
I i
IBi
A
I i
IBi
Genotypes:
2 IAi : 2 IAIB
Phenotypes:
2 Type A: 2 Type B
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A
father is homozygous blood
type A and the mother is
heterozygous blood type B, what
could be the possible genotypes
and phenotypes of their
offspring's blood types?
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P cross = IAIA x IBi
B
I
i
IA
IA
A
B
I I
IAIB
A
I i
IAi
Genotypes:
2 IAi : 2 IAIB
Phenotypes:
2 Type A: 2 Type AB
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Two Types of Chromosomes
Sex chromosomes last
1. _____________________:
pair of chromosomes - 23rd
pair for humans.
XX = female
_________
male
XY = _________
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Two Types of Chromosomes
Autosomal chromosomes or
2. _________________________
Autosomes
___________
All other pairs of chromosomes
– 1st – 22nd pairs in humans.
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4. Sex-Linked Traits (X-Linked)
Other
genes besides the alleles
for sex are located on the sex
chromosomes.
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Definition:
Those
traits will occur _______
MORE
frequently in males than
females, such as color
blindness and hemophilia.
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Why?
Alleles
on a gene may be
present on the X chromosome
absent on the Y. These
but _________
are called sex-linked traits.
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This
means that ________
males may
one allele for a
inherit ______
characteristic and that allele
will be expressed, whether it is
dominant or recessive, because
only allele present on
it is the _______
their X chromosome.
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X-Linked
traits most likely will be
RECESSIVE to the normal
____________
condition and the Y
chromosome lacks the gene for
a trait, so males have a higher
chance of having the disorder.
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These
traits generally do NOT
females since
show up in __________
females have genes on both
their X chromosomes.
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Notation:
The
alleles for these traits are
superscripts on
written as ______________
X chromosome ONLY.
the ___
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No
______
alleles are written on the
Y chromosome!
Ex: Colorblind male = XbY
B
Normal male = X Y
Heterozygous FEMALES are
_______________
carriers
known as __________
XBXb
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Ex.
1) Color blindness is a sexlinked trait that is caused by a
recessive allele
______________________.
A
colorblind man marries a
woman that is homozygous for
normal vision.
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P cross =
N
N
n
X X xX Y
What possible
types of vision
could be found if
they had boys?
__________
Normal
N
X
N
X
Xn XNXn XNXn
Y XNY XNY
What possible
types of vision
could be found if
they had girls?
__________
Normal
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Ex.
2) A girl of normal vision,
whose father was colorblind,
marries a colorblind man. What
types of vision could be found
in their children?
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P cross =
N
n
n
X X xX Y
N
X
n
X
Xn XNXn XnXn
What types of
vision could be
found in their
children?
50% Normal vision
and 50%
colorblindness.
Y XNY XnY
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5. Polygenic Inheritance
Traits
are determined by
MANY genes
___________________.
They may or may not be found
on the same chromosome.
Each gene may have more
than 2 alleles.
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The
phenotypes may vary
depending on the number of
dominant and recessive alleles
in the genotype.
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Traits
that show
great variability are a result of
________________
polygenic inheritance.
Ex.
Eye color, skin color,
height, facial features.
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Environment & Genes
environment can
______________
determine whether or not a
gene is fully expressed or
expressed at all.
The
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Environment & Genes
Internal
and external
environments can
affect phenotypes:
1.Influence of
Internal
environment
____________________:
Hormones based on sexes
~___________
(testosterone, estrogen)
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2. Influence of
External
environment
_____________________:
~ temperature
~ light
~infectious agents
(viruses, bacteria)
~chemicals
~nutrition
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Environment & Genes
All
of these can influence
the expression of genes.
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Karyotype
 ___________
= a test to identify
and evaluate the size, shape and
number of chromosomes in a
sample of body cells.
 Homologous chromosomes are
arranged by ______,
size __________
banding
patterns and centromere
____________
placement.
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 Extra,
missing or abnormal
positions of chromosome pieces
can cause problems with a
person’s growth, development,
and body functions.
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Normal Female
Normal Male
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1.
2.
3.
Determine whether the
chromosomes of an adult have an
_____________
abnormality that can be passed
on to a child.
Determine whether a chromosome
defect is preventing a woman from
becoming pregnant or causing
miscarriages.
Determine whether a chromosome
________
defect is present in a fetus.
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4.
5.
6.
Determine the cause of a baby’s
birth defects or disability.
Identify the _____
sex of a person by
determining the presence of the Y
chromosome.
This may be done when a
newborn’s sex is not clear.
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•
Two copies of an autosomal
chromosome fail to separate
during meiosis so three copies of
that chromosome are made.
• Trisomy 21
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Cause: nondisjunction of the sex
chromosomes during meiosis so
individuals are missing one copy of
the X chromosome
• Affects ONLY females
• Women are usually short, sexually
underdeveloped and sterile.
• Women with this syndrome function
well within society and are not
diagnosed until they are assessed for
infertility as adults.
•
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Cause: nondisjunction of sex
chromosomes during meiosis so individuals
have an extra X chromosome.
• Affects ONLY males
• Males are often tall, sexually
underdeveloped and may have slight
intellectual impairment.
• Many males with this syndrome function
well within society and are not diagnosed
until they are assessed for infertility as
adults
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•
•
•
•
Occurs when a male inherits TWO Y
chromosomes from his father
instead of one.
Cause: unknown.
Symptoms: learning difficulties at
school and delayed emotional
maturity.
Males are tall, thin, have acne,
speech problems and reading
problems.
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Pedigree
 ___________
= a valuable tool for
anyone working in the field of
genetics.
relationships in
 Used to show _______________
families, and resemble a ________
family
______.
tree
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A circle represents
a female
A horizontal line connecting a
male and a female represents
a marriage
A square represents
a male
A vertical line and a bracket
connect the parents to their
children.
A circle or square that is
not shaded indicates that
a person does not
express the trait.
A shaded circle or square
indicates that a person
expresses the trait.
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