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HEREDITY
Why we are the way we are?
REVIEW OF MITOSIS
• Division of somatic
(body) cells
• Phases
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Interphase
Prophase
Metaphase
Anaphase
Telephase
Cytokinesis
• Produces 2 identical
diploid cells
MEIOSIS
• Division of gametes
(reproductive) cells
• Repeat all phases 2x’s,
EXCEPT for interphase
• Crossing Over
– Chromosomes exchange
parts during metaphase
- creating different
combinations of genes
• Produces 4 different
haploid cells
GENDER DIFFERENCES
• Males
– Meiosis occurs in
testes
– Starts @ puberty
– Produces 4 mature
sperm cells each time
• Females
– Meiosis occurs in
ovaries
– Begins/ends prior to
birth
– Produces 1 mature egg
& 3 polar bodies
• Shriveled cells lost their
cytoplasm to single
mature egg
CELL DIVISION T-CHART
Type cells
Same/different
# of cells
# chromosomes
Term (# chrom)
mitosis
meiosis
MENDEL’S LAWS
• Law of Dominance
– Some traits show up
throughout many
generations.
• Dominant – hide other
traits
• Recessive – can be
hidden
– Symbols
• CAPITAL = dominant
• lower = recessive
• Terms
– Genotype
• Genetic make-up
• TT, Tt = tall
• tt = short
– Phenotype
• Physical appearance
• Tall or short
MENDEL’S LAWS
• Law of Segregation
– Traits have multiple
forms (dom & rec) – also
called alleles
– Inherit one form from
each parent
– Terms:
• Homozygous (purebred)
– 2 identical alleles
– TT or tt
• Heterozygous (hybrid)
– 2 different alleles
– Tt
MENDEL’S LAWS
• Law of Independent
Assortment
– Genes not tied
together
– Allows for differences
between individuals of
same species
– Example:
• Not everyone who is
tall has to have brown
hair
GENETIC PROBABILITY
• Punnett square
– Grid used to predict
genetic probability
• Chance that offspring
will receive certain trait
• Monohybrid
– Grid that looks at only
1 trait
MONOHYBRID CROSSES
1. Identify the genotypes
of the parents
–
This will determine the
size of the square
2. Place 1 genotype on
the top of the square
& the 2nd along left
3. Fill in the center
squares
4. Determine the
genotypic &
phenotypic ratios of
the offspring
MONOHYBRIDS
Example #1
A man who is
homozygous for brown
eyes and a women who is
homozygous decide to
have children.
If brown eyes are
dominant, what color
eyes will their children
have?
MONOHYBRIDS
Example #2
If both the mother and
father are heterzygous
for eye color, what color
eyes will their children
have?
MONOHYBRIDS
Example #3
In monkeys, long tails
are dominant over short
tails. If a homozygous
recessive female mates
with a heterozygous
male, what will their
offspring look like?
DIHYBRID CROSS
1.
2.
Identify the genotypes of
the parents
Determine the possible
gametes each parent could
provide.
–
3.
Place the gametes of the
parents on the top & along
left side
–
4.
There will be 2
letters/block
Fill in the center squares
–
5.
This will determine the
size of the square
There will be 4 letters w/in
each block
Determine the genotypic
& phenotypic ratios of the
offspring
DIHYBRIDS
Example #4
Assuming that spots are
dominant over no spots &
horns are dominant over no
horns, what would the
offspring of the following
cows look like?
Male – homozygous spots &
heterozygous for horns
Female – heterozygous
spots with no horns
DIHYBRIDS
Example #5
In pigs, pink is dominant
to white and curly tails
are dominant to straight
tails.
Male –white w/ and
purebred curly tail
Female – pure pink w/
straight tail
DIHYBRIDS
Example #6
Brown eyes dominant over blue & separate
brows are dominant over unibrows
Mom & Dad both heterozygous both traits
INCOMPLETE DOMINANCE
• Dominant gene not
completely hide the
recessive gene
– Results in a blend or
mix of the two
features
– Results in 3 possible
phenotypes
– Heterozygous
genotype now has its
own physical
appearance
(phenotype)
• Often seen in shapes
& colors
– Example:
• TT  tall
• tt  short
• Tt  medium
INCOMPLETE PROBLEMS
• Example #7
In carnations, Red is
dominant over white & a
mix of the two create
pink.
What type of flowers
would be produced by
crossing a white carnation
with a pink carnation?
INCOMPLETE PROBLEMS
Example #8
Straight hair is dominant
over curly hair & a
combination of genes
results in wavy hair.
What would the children
of two wavy haired
parents look like?
CODOMINANCE
• A condition where both
alleles of a gene are
active (dominant)
• No recessive gene
• A heterozygous
individual would have
both physical features
present
• Condition is most often
seen in hair, feathers,
fur & skin color
• Example: Cows
– B  Black
– W  white
– BW  Black & White
COMDOMINANT PROBLEMS
Example #9
Tabby cats are the result
of codominance, the
genes for black and tan
are both present.
What would be the result
of a black cat & a tabby
cat having kittens?
COMDOMINANT PROBLEMS
Example #10
A roan cow is one that
has both red & white
hairs. What would the
calves of two roan cows
look like?
POLYGENIC INHERITANCE
• Poly = many
• Genic = genes
• Many physical
features are
controlled by more
than 1 gene
• What makes us look
so different
• Example:
– Eyes
•
•
•
•
•
•
Size
Shape
Slant
Distance
Color
Lash length
SEX DETERMINATION
• 22 pairs autosomes
– Same males & females
– Basic physical info
• 1 pair sex chromosomes
– XX  female
– XY  male
SEX-LINKED TRAITS
• Genes carried on x
chromosome
• Most are recessive and
so rarely seen in
females
– Males only need 1
recessive gene to show
trait (XhY)
– Females need 2 recessive
genes to show trait
(XhXh)
– Females can be Carriers
• Heterozygous, have 1
recessive gene but do
NOT exhibit the trait
• XHXh
• Examples:
– Red Green
colorblindness
– Hemophilia
– Muscular Dystrophy
– Male Pattern Baldness
– Fragile X syndrome
SEX-LINKED PROBLEMS
Example #11
If a colorblind woman is
married to a man with
normal vision, what are
the chances that their
children will be
colorblind?
SEX-LINKED PROBLEMS
Example #12
If a man with hemophilia and
a completely normal female
decide to have children, will
they have to worry about
their children having
hemophilia?
SEX-LINKED PROBLEMS
Example #13
If a bald man and a
woman who carries the
gene for baldness have
children, will all of their
children be bald?
PEDIGREE
• Family tree shows how
a trait or genetic
disorder is passed
through the
generations
• Symbols:
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–
–
–
–
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Male
Female
Marriage
Death/divorce
Relationship
Twins
Miscarriage
• Symbols:
– Traits/diseases
• Person w/ trait
• Person w/o trait
• Carrier
• Format
– Oldest  youngest
(left)
(right)
– Generations numbered
along left side
– Arrow points to
individual
PEDIGREE EXAMPLE
MULTIPLE ALLELES
• Trait that requires
more than 1 gene to
determine phenotype
• Blood types
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Type A  IAIA, IAIi
Type B  IBIB, IBIi
Type AB  IAIB
Type O  ii
• Blood types are
named by the types of
antigens found in the
red blood cells
– Antigen  protein
specific to individual
• AB  universal
receiver
– (take all types since
their blood contains all
possible antigens)
• O  universal donor
– (give blood anyone
since their blood
contains no antigens)
BLOOD TYPE PROBLEMS
Example #14
If the mother is
homozygous for A and
the father is heterozygous
for B, what possible blood
types could they provide
to their children?
BLOOD TYPE PROBLEMS
Example #15
If both mom and dad have
type AB blood, what
possible blood types could
they provide to their
children?
BLOOD TYPE PROBLEMS
Example #16
Mr. & Mrs. Doe had a
child named Jim at the
same time Mr. & Mrs. Roe
had their son Joe. The
couples thought their
children had been
switched at birth and
demanded blood tests to
prove paternity. Use the
test results to determine if
there was a mix-up.
Mr. Roe – A
Mrs. Roe – A
Joe – O
Mr. Doe – O
Mrs. Doe – AB
Jim – A