Lecture 8 - 3/5/10 Cys$c
Fibrosis 
 • 

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Unformatted text preview: 3/5/10 Cys$c
Fibrosis 
 •  Most
common
gene$c
disease
 Chapter
20
 Inheritance,
Gene1cs,

 and
Molecular
Biology
 –  5%
of
popula$on
are
carriers
 –  Life
expectancy
5‐30
years
 –  CF‐
what
happens?
 –  CF‐
gene$c
disease
 Traits,
appearances,
and
even
intellect
can
 be
aEributed
to
our
genes
 Genes
 DNA
is
made
up
of
genes
and
“other
stuff”
 Gene$c
factors
are
important
in
determining
our
individuality
 Your
individual
DNA
sequence
codes
for
the
specific
arrangement
of
 amino
acids
in
each
of
the
millions
of
proteins
in
your
body
 –  the
3‐billion‐plus
individual
base
pairs
in
the
nucleus
of
the
 human
cell
spell
out
everything
you
need
to
become
a
human
 DNA
exists
in
trillions
of
cells,
and
it
can
be
copied
thousands
of
$mes
 with
liEle
or
no
appreciable
error
 DNA
 Genes,
made
of
strings
of
DNA,
contain
 the
direc$ons
for
making
the
millions
of
 proteins
that
your
body
uses
 Genes
and
DNA
are
found
in
the
nucleus
 of
almost
every
cell
in
your
body
 The
number
of
es$mated
genes
in
the
 human
body
is
about
20,500
 Chromosomes
 Humans
have
23
pairs
of
chromosomes,
for
a
total
of
 46
individual
units
of
organized
DNA
 Genes
are
located
on
chromosomes
 Chromosome
11,
for
example,
carries
the
same
basic
 informa$on
in
all
of
us
 –  it
contains
genes
that
code
for
some
blood
 proteins,
insulin,
and
the
milk‐diges$ng
enzyme
 lactate
dehydrogenase,
and
regula$ng
factors
 Mendel
began
studying
inheritance
by
iden$fying
traits
in
 the
pea
plant
that
existed
in
only
two
forms
and
did
not
 blend
 ‐Why
the
pea
plant?
 Self‐pollina$ng
and
cross‐pollina$ng
his
plants
 Studied
individual
traits
as
they
appeared
in
offspring:
 “heritable
unit”
 First
use
of
the
terms
“dominant”
and
“recessive”

 However,
Mendel
didn’t
know
about
the
existence
of
genes
 or
chromosomes
or
the
details
of
cell
division

 Gregor
Mendel
 1 3/5/10 Gregor
Mendel
 Mendel’s
Laws
 Law
of
segrega$on:
random
separa$on
of
parental
 “heritable
units”
during
gamete
forma$on
 We
now
know
this
random
separa$on
is
possible
 because
of
the
special
type
of
cell
division
called
 meiosis
 Law
of
independent
assortment:
states
that
each
trait
is
 carried
in
the
egg
and
pollen
as
a
separate
en$ty,
 with
no
effect
on
any
other
trait
 Cell
Division
 Cell
Division
 Modern
Gene1cs
 Genotype
is
your
complete
set
of
genes
 Phenotype
is
all
your
observable
traits
or
characteris$cs,
 including
ones
that
are
not
easily
seen,
like
blood
type
or
 color
blindness

 –  phenotypic
differences
emerge
from
subtle
differences
 in
genotype
 –  phenotype
is
the
result
of
our
genotype
and
all
the
 environmental
influences
on
us,
including
the
quality
of
 our
food,
the
type
of
shelter
we
live
in,
and
even
our
 financial
“health”
 Alleles
 Each
member
of
the
gene
pair
is
called
an
allele
 –  an
allele
is
an
alterna$ve
form
of
a
gene
 Differences
in
alleles
give
rise
to
different
genotypes
 –  alleles
may
have
differences
in
the
sequences
of
only
 one
or
a
few
DNA
base
pairs
 Each
soma$c
cell
contains
two
copies
of
every
gene,
one
 obtained
from
each
parent
 2 3/5/10 Two
alleles
are
iden$cal
=
homozygous
for
the
trait
that
is
controlled
by
 those
alleles
 –  a
homozygous
gene
is
usually
denoted
by
two
iden$cal
leEers,
 such
as
AA
or
aa
 –  homozygous
dominant,
meaning
both
alleles
code
for
the
 dominant
trait
(AA),
or
homozygous
recessive
(aa)
 If
one
allele
codes
for
the
dominant
trait
and
the
other
codes
for
a
 recessive
trait,
the
genotype
is
heterozygous
 –  if
one
allele
is
dominant,
the
dominant
phenotype
must
be
 expressed
 Only
homozygous
recessive
individuals
express
a
recessive
phenotype
 Alleles
 Dominant
and
Recessive
Traits
 3 ...
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