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Tracking Family History
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A chart that shows multiple family generations
and relationships to track the inheritance of
genetic traits.
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Can be used to determine genotypes of family
members.
Can be used to help predict probability of
future generations expressing certain traits.
Important tool for genetic counselors

Incomplete dominance –
dominant & recessive
traits are blended

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Example: Four o’clock
flower color – red, white,
pink
Remember: Vegetable juice

Codominance – dominant
& recessive traits both
show up completely and
individually
Example: Blood types A & B,
Horse coat color
 Remember: Salad & cows

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Multiple alleles - More than 2 alleles control
the phenotype

Example: blood types A, B, O, eye color
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Polygenic traits –
more than one gene
controls phenotype

Examples: skin (4
genes), fingerprints

Epistasis = one gene
can interfere with the
expression of
another

Examples: mouse fur
color (5 genes) – one
gene overshadows the
others
Albanism – no
pigment
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The environment can influence
gene expression


Affects phenotype
Examples:
Sun exposure – affect s skin & hair
color
 Temperature – sea turtles produce
more females in warm years and
more males in cold years
 Identical twins – nutrition,
healthcare & physical activity
influence appearance

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An individual’s fingerprints are
controlled by polygenic
inheritance, but also by the fetal
environment. The ridge pattern
of a fingerprint can be altered
during weeks 6 – 13 of fetal
development as the fetus
touches the wall of the amniotic
sac with its fingertips.
Identical twins who have
identical genes have different
fingerprints.

There are three alleles
to blood
Ai (antigen for A)
 Bi (antigen for B)
 Oi (antigen that can
be changed called H)


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Ai produces the
antigen A found on
the RBC and co
dominate
Bi, antigen B, co
dominate
Oi, recessive changing
antigen
Blood Antigen Antibodies
Type
A
A, H
Anti-B
Receives Donates
To
From
A, O
A, AB
B
B, H
Anti – A
B, O
AB
A, B, H none
A, B, AB, AB
O
O
H
O
Anti-A
Anti - B
B, AB
A, B, AB,
O
Blood Type
of Parents
Possible Genotypes
of Parents
Possible Blood Types
Among Children
A and A
Ai and Ai
A and O
A and B
Ai and Bi
A, B, AB, O
A and AB
Ai and AB
A, B, and AB
A and O
Ai and ii
A and O
B and B
Bi and Bi
B and O
B and AB
Bi and AB
A, B, and AB
B and O
Bi and ii
B and O
AB and AB
AB and AB
A, B, and AB
AB and O
AB and ii
A and B
O and O
ii and ii
O
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During mitosis, the 23 pairs of human
chromosomes condense and are visible with a
light microscope.
A karyotype analysis usually involves blocking
cells in mitosis and staining the condensed
chromosomes with Giemsa dye, “G”.
The dye stains regions of chromosomes that are
rich in the base pairs Adenine (A) and Thymine
(T) producing a dark band.
These bands are not a single gene but represent
hundreds of genes.

analysis involves
comparing
chromosomes

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
length
the placement of
centromeres
the location and sizes
of G-bands (stains)