Goal 3.03 Interpret and predict patterns of inheritance.
description
Transcript of Goal 3.03 Interpret and predict patterns of inheritance.
Goal 3.03 Interpret and predict patterns of inheritance.
Let there be PEAS ON EARTH!
Let there be PEAS ON EARTH!
And let it begin with me!
math.uit.no
• 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
Gregor Mendel
Pollen transferred from white flower to stigma of purple flower
anthersremoved
all purple flowers result
• Bred pea plants– cross-pollinate
true breeding parents– raised seed & then
observed traits– allowed offspring
to self-pollinate & observed next generation
?
self-pollinate
When bred to themselves will always produce
organisms with same phenotype.
EX. White bred to white always produces white; purple bred to purple
always produces purple.
When a flower pollinates itself. No new genes are
introduced.
Mendel’s workMendel’s work
Mendel collected data for 7 pea traitsMendel collected data for 7 pea traits
Each of these traits is represented by a specific allele on a specific chromosome.
Allele = genes that determine a specific trait.
Flower colorFlower color
Seed colorSeed color
Seed shapeSeed shape
Pod colorPod color
Pod shapePod shape
Flower locationFlower location
Plant sizePlant size
2nd
generation
3:175%purple-flower peas
75%purple-flower peas
25%white-flower peas
Parents
100%1st
generation(hybrids)
100%purple-flower peas
100%purple-flower peas
Xtrue-breedingpurple-flower peas
true-breedingpurple-flower peas
true-breeding white-flower peas
self-pollinate
• Some traits mask others – purple & white flower colors are separate
traits that do not blend • purple x white = light purple• purple masked white
– Dominant allele • functional protein
– affects characteristic• masks other alleles
– recessive allele • no noticeable effect• allele makes a
non-functioning protein
homologouschromosomeshomologous
chromosomes
allele producingfunctional protein
mutant allele malfunctioning
protein
What did Mendel’s findings mean?
• 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
Explain Mendel’s results using…dominant & recessive …phenotype & genotype F1
P X
purple white
all purple
Genotype vs. phenotype
Environment effect on genes• Phenotype is controlled by
both environment & genes
Color of Hydrangea flowers is influenced by soil pH
Human skin color is influenced by both genetics & environmental conditions
Coat color in arctic fox influenced by heat sensitive alleles
Phenotype is a result of both genetics and environment.Phenotype is a result of both genetics and environment.
www.safeandsoundlostandfound.org
www.cats-central.com
Cold Environment
Warm Environment
Siamese cats that grow up in a cold environment are
darker…
…than those that grow up in a
warmer 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 = same
Heterozygous = different
Homozygous = same
Heterozygous = differentHomozygous dominant = AAHomozygous recessive = aaHeterozygous = Aa
TtTt
BbBb
WwWwYyYy
rrrr
RRRR
AaAa
ABAB
SsSs
bbbb EeEeBBBB
aaaaXYXY
Genes affect how you look…
XBBbb
Bb Bb Bb Bb
Where did the blue eyes go??
XBbbb
Bb Bb bb bb
Why did the blue eyes stay??Why did the blue eyes stay??
XBbBb
BB or Bb BB or Bb BB or 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?
eye color(brown?)
hair color
hair color
eye color
(blue?)
• Paired chromosomes have same kind of genes– but may be different alleles
gene
allele
Traits are inherited as separate units
1 from Mom
1 from Dad
• 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
homologous chromosomes
Making gametesBB = brown eyesbb = blues eyesBb = brown eyes
BB
bb
Bb
brown is dominant over blue
blue is recessive to brown
Remember meiosis!
B
B
b
b
B
b
Dominant = can mask others
Recessive = can be hidden by others
How do we say it?
BB = brown eyesbb = blues eyes
Bb = brown eyes
2 of the same allelesHomozygous
2 differentHeterozygous
BB
B
B
bb
b
b
Bb
B
b
homozygous dominanthomozygous recessive
Punnett squaresBb x Bb
male / sperm
fem
ale
/ eg
gs
X
BB
Bb bb
BbB
b
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
eye color(brown)
eye color
(brown)
eye color(blue)
eye color
(brown)
vs.
BB
B
BBb
B
b
How were these brown eyes made?How were these brown eyes made?
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
PpF1
P X
purple white
all purple
Punnett squaresPp x Pp
P pmale / sperm
P
p
fem
ale
/ eg
gs
PP
75%
25%
3:1
25%
50%
25%
1:2:1
%genotype
%phenotype
PP Pp
Pp pp pp
Pp
Pp
1st
generation(hybrids)
Aaaaah,phenotype & genotype
can have different ratios
Any Questions??Any Questions??
www.publispain.com
Assignment:Punnett Square Practice Worksheet
2007-2008
Beyond Mendel’s Lawsof Inheritance
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 rr
RR
WW or R’R’
RW or RR’
Incomplete dominance
true-breedingred flowers
true-breeding white flowers
XP
100%
100% pink flowers1st
generation(hybrids)
self-pollinate
25%white
2nd
generation
25%red 1:2:1
50%pink
Incomplete dominance
RW x RW
R Wmale / sperm
R
Wfem
ale
/ eg
gs
25%
1:2:1
25%
50%
25%
1:2:1
%genotype
%phenotype
RR
RW
RW
WW
25%
50%
Codominance• Equal dominance
– Chickens• A black-feathered chicken is crossed with a white-
feathered 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
BLOODBlood cells have antigens and antibodies.
Antigens are tiny receptors on the outside of the blood cell that matches the “type.”
Antibodies are what the cell doesn’t like (which is anything different from the “type.”)
Multiple Alleles
Multiple Alleles
Blood Types
A
A
A
Type A
B
BB
Type B
Type O
A
B
A
Type ABB
Antigens(none)
Anti-B Anti-
A
noneAnti-A and B
Multiple Alleles
Multiple Alleles
Genetics of Blood type
pheno-type
genotypeantigenon RBC
antibodiesin blood
donationstatus
A A A or A itype A antigens
on surface of RBC
anti-B antibodiesReceive A or O
B BB or B itype B antigens
on surface of RBC
anti-A antibodiesReceive B or O
AB ABboth type A &
type B antigens on surface
of RBC
no antibodiesuniversal recipient
O i ino antigens on surface
of RBC
anti-A & anti-B antibodies
universal donor
Multiple Alleles
Multiple Alleles
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
AA
Aa x aa
Inheritance pattern of Achondroplasia
A a
a
a
A a
A
a
Aa x Aa
Aa
Aa aa
aa
50% dwarf:50% normal or 1:1
aa
Aa
67% dwarf:33% normal or 2:1
Aa
Many genes : One trait
• Polygenic inheritance– additive effects of many genes– humans
• skin color• height• weight• eye color• intelligence• behaviors
Polygenic =
“many genes”Polygenic =
“many genes”
Human skin color• AaBbCc x AaBbCc
– range of shades– most children =
intermediate skin color
– some can be very light & very dark
Polygenic =
“many genes”Polygenic =
“many genes”
Albinism Johnny & Edgar Winter
albinoAfricans
melanin = universal brown color
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)
E–B–E–bbeeB–eebb
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 & Y chromosome = male: XY– X only = XO (Turner’s Syndrome)
X Y
X X
Who you are…Who you are…
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• loss of muscle control
– red-green color blindness• see green & red as shades of gray
X Y
X X
XH Ymale / sperm
XH
Xhfe
mal
e / e
gg
s XHXH
XHXh
XHY
XhY
XHXh
XH
Xh
XHY
Y
XH
XHXH XHY
XHXh XhY
sex-linked recessive
2 normal parents,but mother is carrier
HH HhxXHY XHXh
Most Common AlleleDominant or Recessive
• Because an allele is dominant does not mean…– it is better, or– it is more common
Polydactylydominant allele
Either One!
Polydactyly
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)
the allele for >5 fingers/toes is DOMINANT & the allele for 5 digits is recessive
individuals are born with extra fingers or toes
Hound Dog Taylorhttp://www.last.fm/music/Hound%2BDog%2BTaylor%2B%2526%2Bthe%2BHouse%2BRockers
Any Questions?
Assignment:Coach Book L17Textbook pg 180-181 #1-6