Transcript 2 cp u9 inheritance notes

If a woman is a carrier of an
X-linked recessive allele for
a disorder and her mate
does not, their sons have a
______ chance of inheriting
the disorder. ______ of their
daughters will have it, but
______ of them are likely to
be carriers.
5-12
5-13
If a man has an X-linked
recessive disorder and
his mate does not carry
the allele for it, _____ of
their girls will be carriers.
_____ of their boys will
inherit the harmful allele.
• Why are there more X sex linked
traits?
• Linked genes are usually …
• Mutations in an organisms gametes
=?
• Mutations that cause death = ?
Example from class = ?
• What type of mutation causes Down
syndrome (2 correct answers)?
5-12
Read 12.2 and answer #s 1-8
on the bottom of page 248 – DUE
tomorrow (Friday 5-13)
Pedigree – diagram that shows how a
trait is
inherited
over several
generations
Squares = ?
Circles = ?
• Study the simple
pedigree. The man
is red (pink)
because…?
• The daughters are
blue because …?
• Is it possible to get a
son that has
Hemophilia or is a
carrier? Explain!
• If one of the sons
hooks up with a
female carrier, what
will happen?
Hemophilia (X-linked recessive)
Pedigree from Queen Victoria
How did she become a carrier? 1.
________________ 2.___________
___________ 3.________________
X-Linked Traits
• Traits carried on the X chromosome
– Who will show more X-linked disorders,
males or females? Why?
• Males – b/c they only have one X (XY)
so it doesn’t matter if trait is dominant
or recessive
– Examples:
• Colorblindness – carried
on X-chromosome
• Hemophilia – impaired
blood clotting
• Carriers – people who carry an allele
for a disorder, but do not have the
disorder (Heterozygous)
• Genetic disorders – any disease /
disorder that has a genetic basis
• Polygenic – characteristics that are
influenced by several genes
– Examples:
• Skin color – six genes
• Other examples – eye color, height,
hair color
• Complex characters - characteristics
that are influenced strongly by
both environment and genes
• Sun = darker skin
• Height = several genes but also
nutrition and disease
An example of a human trait that is 5-16
polygenic and a complex character =
_____ because...
• Who will show more X-linked
disorders, males or females? Why?
• Linked genes are usually …
• Germ-cell mutations = ?
• Chromosomal mutations cause
changes to chromosome ___ or ___.
Example from class = ?
• What is a pedigree?
• Multiple Alleles – genes that have three
or more alleles (usually 2)
– Example: Blood Type
– What are the blood types?
• ABO
– Three alleles – IA, IB, i
• Blood Types – A, B, AB, O
• Antigens – proteins, carbs etc on outside of red blood cells
• Antibodies – immuno proteins that destroy unrecognized
antigens
• http://nobelprize.org/educational_games/
medicine/landsteiner/
• “Blood typing activity” google – first link
5-17
How do you identify a dominant
genetic disorder on a pedigree?
5-17
Quizish Questish type deal on
Friday 5-20. Also bring your binder
 last binder check likely.
• Codominance – when both alleles are
expressed in the phenotype (IA, IB –
neither is dominant over the other – both
carbs are produced on cell surface)
• In codominance, you see both traits
Red cow x white cow = roan cow
Codominance
• Incomplete dominance – mix between two
parents (blend)
• In incomplete dominance, you see a mix or
blend of both traits
• Example:
– straight hair mom X curly hair dad = wavy
haired child
– Red flower x white flower = pink flower
Incomplete Dominance
X-Linked Traits (review)
• Traits carried on the X chromosome
– Who will show more X-linked disorders,
males or females? Why?
• Males – b/c they only have one X (XY)
(doesn’t matter if trait is dominant or
recessive)
– Examples:
• Colorblindness
• Hemophilia
X-linked Dominant
• If mother affected
 equal chance of
sons / daughters
affected
• If father affected 
All daughters will
have, sons ok
• No carriers
possible
X-Linked Recessive
• If mother carrier 
50% chance son will
be affected, no
daughters will have
(females can be
carriers)
• If father affected 
Sons will be ok, All
daughters are
carriers
Autosomal Dominant
• Affected
individual  50 /
50 chance of
producing
affected children
• No carriers
possible
Autosomal Recessive
• Occurs if both
parents are
carriers (only
25% of the time)
• Carriers possible
• Single-Allele Traits – traits caused by
one dominant allele
• Huntington’s Disease –
– caused by one dominant allele. Onset is
30-40 so parents have children before
they realize they have it
– Forgetfulness, irritability, muscle spasms
and mental illness, then death
– Genetic testing now beginning to be
used to determine if either parent has
disease