2. Ch4_Ch_2_-_probabilities_Sept_23_corrected

2. Ch4_Ch_2_-_probabilities_Sept_23_corrected - 9/29/09

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Unformatted text preview: 9/29/09 Chapter
2
–
Mendelian
GeneCcs
&
More! 
 •  Alleles
–
different
versions
of
a
gene
 •  Different
traits
of
same
character
(e.g.,
hair
colour
=
character;
red
&
brown)
 •  If
genes
encode
proteins
 •  Then
alleles
encode
slightly
different
proteins
 •  Proteins
produced
by
some
alleles
funcCon
beDer
than
others;
some
 alleles
may
produce
completely
non‐funcConal
proteins
 •  Do
alleles
for
the
same
gene
(thus
on
homologs)
interact
with
each
 other?
 •  Alleles
do
NOT
interact;
however,
the
products
of
alleles

 DNA protein organismal traits Expression
of
Genes 
 1 9/29/09 •  There
are
40
different
alleles
for
an
enzyme
involved
in
liver
 metabolism.

What
is
the
maximum
number
of
alleles
that
1
 individual
can
have?
 A.  B.  C.  D.  E.  1
 2
 20
 40
 80
 Not posted Transmission
of
alleles 
 Individual
heterozygous
at
 1
gene
(locus)
 •  What
if
there
are
10
alleles
for
eye
colour
in
a
populaCon?
 •  What’s
the
maximum
#
of
alleles
an
individual
can
have
for
eye
colour?
 •  What
are
the
gametes
this
individual
could
produce?
 Principle
of
Segrega/on
 Brown eyes Green eyes 2 9/29/09 Principle
of
SegregaCon 
 •  When
do
the
2
alleles
 segregate
from
1
another?
 Chromosome got from dad Chromosome got from mom A1 A2 Transmission
of
alleles
&
probability 
 •  ProbabiliCes
–
predicted
on
scale
of
0
to
1
 •  Outcome
that
can’t
possibly
happen
is
0;
outcome
that
it
certain
is
1
 •  If
>1
outcome
possible
–
sum
of
all
probabiliCes
of
all
possible
 outcomes
must
equal
1
 •  E.g.,
coin
toss
 •  What
are
the
possible
outcomes?
_________
 •  What
are
the
probabiliCes
of
these
outcomes?
________________
 •  What’s
the
chance
(probability)
of
flipping
2
heads
at
same
Cme?
 3 9/29/09 Transmission
of
alleles
&
probability 
 •  Product
Rule
(‘AND’)
–
used
when
events
are
independent
 •  Individual
probabiliCes
are
MULTIPLIED
 Gamete Gamete
 Offspring Offspring Gamete Offspring Offspring Gamete Transmission
of
alleles
&
probability 
 •  E.g.,
Individuals
with
the
following
genotypes
mate:
 
 
 
12 AA 
x




A1A2
 •  What
gametes
do
they
each
produce?
 •  Product
Rule
(‘AND’)
–
used
when
events
are
independent
 •  Individual
probabiliCes
are
MULTIPLIED
 A1 A1
 A1A1 A2A1 A2 A1A2 A2A2 •  MONOHYBRID
CROSS
 • 1
gene
 • Both
parents
heterozygous
 A2 4 9/29/09 Some
terminology
about
crosses 
 •  E.g.,
Individuals
with
the
following
genotypes
mate:
 
 
11 AA 
x




A1A1

















OR









A2A2 
x




A2A2
 •  Pure
(or
true)‐breeding
lines

homozygous
for
gene
of
interest
 •  Produce
offspring
with
constant
traits

(e.g.,
webbed
wings)
 •  Many
of
crosses
we’ll
perform
–
pure‐breeding
PARENTAL
(P)
generaCon
 True-breeding A1 A2
 True-breeding A2 A2A1 A2A1 A1 A2A1 A2A1 A1
 A1 A2 A2 All offspring (F1) are hybrids CORRECTED SLIDE MONOHYBRID
CROSS
 Not posted Principle
of
SegregaCon
&
Probability 
 A1 A2 Here - only looking at gamete formation; not yet looking at a mating Chromosomes replicate A1 A1A2 A2 Meiosis I - alleles segregate A1 A1 A2 A2 Meiosis II 1/2 A1 A1 A2 A2 1/2 Each gamete carries only one (1) allele for each character because the alleles segregated during meiosis. 5 9/29/09 Transmission
of
alleles
&
probability 
 •  E.g.,
Individuals
with
the
following
genotypes
mate:
 
 
 
12 AA 
x




A1A2
 •  What
is
the
chance
that
they
will
produce
a
heterozygous
offspring
(A1A2)?
 •  Same
as:
What’s
the
chance
of
flipping
a
head
&
a
tail
in
any
order?

 •  Sum
Rule
(‘OR’)
–
used
when
events
are
mutually
exclusive
 •  Individual
probabiliCes
are
ADDED
 A1 A1
 A1A1 A2A1 A2 A1A2 A2A2 A2 Principle
of
SegregaCon
&
Probability 
 •  E.g.,
Individuals
with
the
following
genotypes
mate:
 
 
 
12 BB 
x




B1B2
 •  What
gametes
do
they
each
produce?
(I.e.,
What
are
the
game8c
 genotypes?
 
 
 
 
 B1
and
B2 

 •  What’s
the
chance/probability
of
an
egg
with
B1?
 •  Chance/probability
of
an
egg
with
B2?
 •  What’s
the
chance/probability
of
a
sperm
with
B1?
 •  Chance/probability
of
a
sperm
with
B2?
 What about for this cross? A1A1 x A1A2 6 9/29/09 Principle
of
SegregaCon
&
Probability 
 •  Genes
A
&
R
are
located
on
different
chromosomes.
A
male
is
 heterozygous
for
both
genes.
Which
of
the
following
processes
 would
generate
different
combinaCons
of
alleles
of
these
2
genes?
 1.  2.  3.  4.  RecombinaCon
 Independent
Assortment
 Sister
chromaCd
segregaCon
 Two
of
the
above
 Not posted 7 9/29/09 Transmission
of
alleles 
 Individual
heterozygous
at
2
 genes
(loci)
–
genes
are
on
 different
chromosomes
 •  What
are
the
gametes
this
individual
could
produce
wrt
eye
&
hair
colour?
 •  Would
X.O.
have
any
effect?

 Brown eyes Black hair Green eyes Black hair Brown eyes Red hair Green eyes Red hair Principle
of
Independent
Assortment
 Principle
of
Independent
Assortment 
 Eye colour Hair colour 2
chromosomes/gamete

 4
different
combinaCons
 possible
 PotenCal
gametes
of
ONE
 individual
 8 9/29/09 Principle
of
Independent
Assortment 
 Individual with genotype: R1R2A1A2 (Chromosomes are already replicated.) R1 R1 2 R2 R A1 A1 A2 A2 R1 R1 A1 A1 R1 R1 R2 Chromosomes can line up 2 ways in MI R1 R1 2 R2 R A2 A2A1 A1 R2 R2 A1 A1 R2 A2 A1 R2 MI - homologues segregate R2 R2 A2 A2 R1 R1 A2 A2 R1 A2 MII A1 A2 R2 A2 R1 A1 A1 The genes for these two (2) traits assort independently, because they are located on different chromosomes. For two or more genes 9 ...
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This note was uploaded on 01/10/2010 for the course BIOLOGY biol2040 taught by Professor Tamarakelly during the Fall '09 term at York University.

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