Download Goal 3.03A Patterns of Inheritance

Goal 3.03 Interpret and predict patterns of inheritance.
Let there be
PEAS ON EARTH!
math.uit.no
Gregor Mendel
• Modern genetics began in the
mid-1800s in an abbey garden,
where a monk named Gregor
Mendel documented inheritance
in peas
– used good experimental design
– used mathematical analysis
• collected data & counted them
– excellent example of scientific
method
Mendel’s work
Pollen transferred from white
flower to stigma of purple flower
• Bred pea plants
– cross-pollinate
true breeding parents
– raised seed & then
observed traits
– allowed offspring
to self-pollinate
& observed next
generation
When bred to themselves
will always produce
organisms with same
anthers
phenotype.
removed
EX.
White bred to white
all purple flowers result
always produces white;
purple bred to purple
always produces purple.
When a flower pollinates
self-pollinate
itself. No new genes are
introduced.
?
Mendel collected data for 7 pea traits
Each of these
traits is
represented by a
specific allele on
a specific
chromosome.
Flower color
Seed color
Seed shape
Pod color
Allele = genes
that determine a
specific trait.
Pod shape
Flower location
Plant size
Parents
1st
true-breeding
purple-flower peas
X
true-breeding
white-flower peas
100%
purple-flower peas
generation
(hybrids)
100%
self-pollinate
2nd
generation
75%
purple-flower peas
25%
white-flower peas
3:1
What did Mendel’s findings mean?
• Some traits mask others
– purple & white flower colors are separate
traits that do not blend
• purple x white = light purple
• purple masked white
allele producing
functional protein
mutant allele
malfunctioning
protein
– Dominant allele
• functional protein
– affects characteristic
• masks other alleles
– recessive allele
• no noticeable effect
• allele makes a
non-functioning protein
homologous
chromosomes
Genotype vs. phenotype
• Difference between how an organism
“looks” & its genetics
– phenotype
• Form of the trait that gets expressed
“what you see”
– genotype
• An organism’s actual alleles
X
P
Explain Mendel’s results using
…dominant & recessive
…phenotype & genotype
purple
white
F1
all purple
Environment effect on genes
• Phenotype is controlled by
both environment & genes
Human skin color is
influenced by both genetics
& environmental conditions
Color of Hydrangea flowers
is influenced by soil pH
Coat color in arctic
fox influenced by
heat sensitive alleles
Phenotype is a result of both genetics and environment.
Siamese cats that grow
up in a cold
environment are
darker…
Cold Environment
www.safeandsoundlostandfound.org
…than those that grow
up in a warmer
environment.
www.cats-central.com
Warm Environment
Inheritance of genes
• On the chromosomes passed from Mom &
Dad to offspring are genes
– may be same information
– may be different information
eye color
(blue or
brown?)
eye color
(blue or
brown?)
Remember how Meiosis separates the alleles into sex cells?
This separation is called the
Law of Segregation.
Effect of genes
• Genes come in different versions - alleles
– brown vs. blue eyes
– brown vs. blonde hair
– Alleles = different forms of a gene
Homozygous dominant = AA
Homozygous recessive = aa
Heterozygous = Aa
rr
Ww
bb
Tt
aa
Ss
XY
Aa
Yy
BB
RR
Ee
AB
Bb
Genes affect how you look…
X
bb
Bb
BB
Bb
Bb
Where did the blue eyes go??
Bb
X
bb
Bb
Bb
Bb
bb
Why did the blue eyes stay??
bb
X
Bb
BB or Bb BB or Bb BB or Bb
Bb
bb
Where did the blue eyes come from??
• Genes come in “versions”
– brown vs. blue eye color
– Alleles (different forms of a gene)
• Alleles are inherited separately from each
parent
– brown & blue eye colors are separate & do
not blend
• either have brown or blue eyes, not a blend
• Some alleles mask others
– brown eye color masked blue
How does this work?
• Paired chromosomes have same kind of
genes
– but may be different alleles
allele
gene
eye
color
(blue?)
hair
color
eye
color
(brown?)
hair
color
Traits are inherited as separate units
• For each trait, an organism inherits
2 copies of a gene, 1 from each parent
– a diploid organism inherits
1 set of chromosomes from each parent
• diploid = 2 sets (copies) of chromosomes
1 from Mom
homologous chromosomes
1 from Dad
Making gametes
BB = brown eyes
bb = blues eyes
Bb = brown eyes
B
BB
B
b
Dominant = can mask others
bb
b
 brown is dominant over blue
 blue is recessive to brown
Recessive = can be hidden
by others
Remember meiosis!
B
Bb
b
How do we say it?
2 of the same alleles
Homozygous
B
BB
B
BB = brown eyes
bb = blues eyes
homozygous dominant
homozygous recessive
2 different
Heterozygous
Bb = brown eyes
b
bb
b
B
Bb
b
Punnett squares
Bb x Bb
male / sperm
female / eggs
X
B
b
BB
Bb
Bb
bb
B
b
Punnett square practice.
Genetics vs. appearance
• There can be a difference between how
an organism looks & its genetics
– appearance or trait = phenotype
• brown eyes vs. blue eyes
– genetic makeup = genotype
• BB, Bb, bb
2 people can have the same appearance but
have different genetics: BB vs Bb
Genetics vs. appearance
How were these
brown eyes made?
eye
color
(brown)
eye
color
(brown)
eye
color
(brown)
eye
color
(blue)
vs.
B
BB
B
Bb
B
b
Making crosses
• Can represent alleles as letters
– flower color alleles  P or p
– true-breeding purple-flower peas  PP
– true-breeding white-flower peas  pp
PP x pp
X
P
purple
white
F1
all purple
Pp
Punnett squares
Pp x Pp
1st
Aaaaah,
phenotype & genotype
can have different
ratios
generation
(hybrids)
%
genotype
male / sperm
female / eggs
P
p
PP
25%
75%
Pp
P
PP
%
phenotype
50%
Pp
Pp
p
Pp
pp
pp
25% 25%
1:2:1
3:1
Any Questions??
Assignment:
Punnett Square Practice Worksheet
www.publispain.com
Beyond Mendel’s Laws
of Inheritance
2007-2008
Extending Mendelian genetics
• Mendel worked with a simple system
– peas are genetically simple
– most traits are controlled by single gene
– each gene has only 2 version
• 1 completely dominant (A)
• 1 recessive (a)
• But its usually not that simple!
Incomplete dominance
• Hybrids have “in-between” appearance
– RR = red flowers
– rr = white flowers
– Rr = pink flowers
• make 50% less color
RR
RR
WW or R’R’
RW or RR’
Rr
rr
Incomplete dominance
P
X
true-breeding
red flowers
true-breeding
white flowers
100% pink flowers
1st
100%
generation
(hybrids)
self-pollinate
25%
red
2nd
generation
50%
pink
25%
white
1:2:1
Incomplete dominance
RW x RW
male / sperm
female / eggs
R
R
W
W
%
genotype
RR
RW
%
phenotype
25% 25%
50% 50%
RW
WW
25% 25%
1:2:1
1:2:1
Codominance
• Equal dominance
– Chickens
• A black-feathered chicken is crossed with a whitefeathered chicken.
• All of the babies are white with black speckling.
• Both white and black show up equally.
x
=
More Codominance…
x
Multiple Alleles
• More than one allele to select from.
– Blood “types” can be A, B, AB, or O.
– The alleles to make these types include A, B and i.
– “i” is the recessive allele and A and B are both
dominant.
– So to get…
• Type A you must have AA or Ai
• Type B you must have BB or Bi
• Type AB you must have AB
• Type O you must have ii
BLOOD
Blood cells
have
antigens
and
antibodies.
Antibodies are
what the cell
doesn’t like
(which is
anything different
from the “type.”)
Antigens
are tiny
receptors
on the
outside of
the blood
cell that
matches
the “type.”
Blood Types
A
B
Type A
Type B
A
Type AB
Antigens
(none)
Type O
Genetics of Blood type
phenogenotype
type
A
B
AB
O
antigen
on RBC
antibodies
in blood
donation
status
AA Ai
type A antigens
on surface
of RBC
anti-B antibodies
Receive
A or O
or
BB B i
type B antigens
on surface
of RBC
anti-A antibodies
Receive
B or O
AB
both type A &
type B antigens
on surface
of RBC
no antibodies
universal
recipient
ii
no antigens
on surface
of RBC
anti-A & anti-B
antibodies
universal
donor
or
One gene : Many effects?
• The genes that we have covered so far
affect only one trait
• But most genes are affect many traits
– 1 gene affects more than 1 trait
• dwarfism (achondroplasia)
• gigantism (acromegaly)
Acromegaly: André the Giant
Inheritance pattern of Achondroplasia
Aa
x aa
A
a
a
Aa
aa
a
Aa
aa
50% dwarf:50% normal or 1:1
Aa
x Aa
A
a
A
AA
Aa
a
Aa
aa
67% dwarf:33% normal or 2:1
Many genes : One trait
• Polygenic inheritance
– additive effects of many genes
– humans
•
•
•
•
•
•
skin color
height
weight
eye color
intelligence
behaviors
Human skin color
• AaBbCc x AaBbCc
– range of shades
– most children =
intermediate
skin color
– some can be
very light & very
dark
Albinism
melanin = universal brown color
albino
Africans
Johnny & Edgar Winter
OCA1 albino
Bianca Knowlton
Coat color in other animals
• 2 genes: E,e and B,b
– color (E) or no color (e)
– how dark color will be: black (B) or brown (b)
eebb
eeB–
E–bb
E–B–
SEX and GENES
• Women & men are very different, but just a few
genes create that difference
• In mammals = 2 sex chromosomes
–X & Y
– 2 X chromosomes = female: XX
X
X
X
Y
– X & Y chromosome = male: XY
– X only = XO (Turner’s Syndrome)
Sex-linked traits
• Sex chromosomes have other genes on
them, too
– especially the X chromosome
– hemophilia in humans
• blood doesn’t clot
– Duchenne muscular dystrophy in humans
X
X
X
Y
• loss of muscle control
– red-green color blindness
• see green & red as shades of gray
HY
XHH
x
sex-linked recessive
H Xh
XHh
2 normal parents,
but mother is carrier
XH
male / sperm
XH Y
XH
Y
XH
XH XH
XH Y
Xh
XH Xh
XhY
XH
XH Xh
Xh
female / eggs
Y
Most Common Allele
Dominant Either
or One! Recessive
• Because an allele is dominant
does not mean…
– it is better, or
– it is more common
Polydactyly
dominant allele
Polydactyly
individuals are born with
extra fingers or toes
the allele for >5 fingers/toes
is DOMINANT & the allele for
5 digits is recessive
Recessive allele far more
common than dominant
 only 1 individual out of 500
has more than 5 fingers/toes
 so 499 out of 500 people are
homozygous recessive (aa)
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Any Questions?
Assignment:
Coach Book L17
Textbook pg 180-181 #1-6