1. Goal 3.03 Interpret and predict patterns of inheritance.
Let there be
PEAS ON EARTH!
And let it begin with me!
math.uit.no

2. 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
He studied at the University of Vienna from 1851 to 1853 where he was influenced by a physicist who encouraged experimentation and the application of mathematics to science and a botanist who aroused Mendel’s interest in the causes of variation in plants. After the university, Mendel taught at the Brunn Modern School and lived in the local monastery.
The monks at this monastery had a long tradition of interest in the breeding of plants, including peas. Around 1857, Mendel began breeding garden peas to study inheritance.

3. When a flower pollinates itself. No new genes are introduced.
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 phenotype.
EX. White bred to white always produces white; purple bred to purple always produces purple.
anthers
removed
all purple flowers result
P = parents
F = filial generation
When a flower pollinates itself. No new genes are introduced.
self-pollinate ?

4. Mendel 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 color
Seed color
Seed shape
Pod color
Pod shape
Flower location
Plant size

5. 1st 100% 3:1 2nd X self-pollinate
true-breeding
purple-flower peas
true-breeding
white-flower peas X
Parents
100%
1st
generation
(hybrids)
purple-flower peas
self-pollinate
2nd
generation
3:1
75%
purple-flower peas
25%
white-flower peas
In a typical breeding experiment, Mendel would cross-pollinate (hybridize) two contrasting, true-breeding pea varieties.
The true-breeding parents are the P generation and their hybrid offspring are the F1 generation.
Mendel would then allow the F1 hybrids to self-pollinate to produce an F2 generation.

6. Some traits mask others
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
Dominant allele
functional protein
affects characteristic
masks other alleles
recessive allele
no noticeable effect
allele makes a non-functioning protein
mutant allele malfunctioning protein
allele producing functional protein
homologous chromosomes

7. Difference between how an organism “looks” & its genetics
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 F1 P X
purple
white
all purple
Explain Mendel’s results using
…dominant & recessive
…phenotype & genotype

8. Environment effect on genes
Phenotype is controlled by both environment & genes
Coat color in arctic fox influenced by heat sensitive alleles
Human skin color is influenced by both genetics & environmental conditions
The relative importance of genes & the environment in influencing human characteristics is a very old & hotly contested debate
a single tree has leaves that vary in size, shape & color, depending on exposure to wind & sun
for humans, nutrition influences height, exercise alters build, sun-tanning darkens the skin, and experience improves performance on intelligence tests
even identical twins — genetic equals — accumulate phenotypic differences as a result of their unique experiences
Color of Hydrangea flowers is influenced by soil pH

9. Phenotype is a result of both genetics and environment.
Cold Environment
Siamese cats that grow up in a cold environment are darker…
…than those that grow up in a warmer environment.
Warm Environment

10. 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?)

11. This separation is called the Law of Segregation.
Remember how Meiosis separates the alleles into sex cells?
This separation is called the Law of Segregation.

12. Effect of genes Genes come in different versions - alleles
brown vs. blue eyes
brown vs. blonde hair
Alleles = different forms of a gene

13. Heterozygous = different
Homozygous dominant = AA
Homozygous recessive = aa
Heterozygous = Aa
Homozygous = same
Heterozygous = different aa rr XY Ss Ww Tt Aa Yy BB RR bb Ee AB Bb

14. Genes affect how you look… Where did the blue eyes go??X bb BB Bb Bb Bb Bb
Where did the blue eyes go??

15. Why did the blue eyes stay??X bb Bb Bb Bb bb bb
Why did the blue eyes stay??

16. Where did the blue eyes come from??X Bb Bb
BB or Bb
BB or Bb
BB or Bb bb
Where did the blue eyes come from??

17. 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

18. How does this work? Paired chromosomes have same kind of genes
but may be different alleles
gene
eye color
(blue?)
eye color
(brown?)
allele
hair color

19. 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

20. Making gametes Remember meiosis! B BB BB = brown eyes bb = blues eyes
Dominant = can mask others bb
 brown is dominant over blue
 blue is recessive to brown B b
Recessive = can be hidden by others Bb
Remember meiosis!

21. How do we say it? B 2 of the same alleles Homozygous BB
BB = brown eyes
bb = blues eyes bb b
homozygous dominant
homozygous recessive
2 different
Heterozygous Bb B b
Bb = brown eyes

22. Punnett square practice.
Punnett squares
Bb x Bb
male / sperm B b X BB Bb B b
female / eggs Bb bb
Punnett square practice.

23. 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

24. Genetics vs. appearance
How were these brown eyes made?
eye color
(brown)
eye color
(brown)
eye color
(brown)
eye color
(blue)
vs. BB B Bb B b

25. PP pp Pp Making crosses x Can represent alleles as letters
flower color alleles  P or p
true-breeding purple-flower peas  PP
true-breeding white-flower peas  pp F1 P X
purple
white
all purple PP x pp Pp

26. phenotype & genotype can have different ratios
Punnett squares
Aaaaah,
phenotype & genotype can have different ratios
Pp x Pp
1st
generation
(hybrids) %
genotype %
phenotype P p
male / sperm PP
25%
75% Pp
50% P p
female / eggs PP Pp Pp Pp pp
25%
25% pp
1:2:1
3:1

27. Any Questions?? Assignment: Punnett Square Practice Worksheet

28. Beyond Mendel’s Laws of Inheritance

29. 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!

30. Incomplete dominance Hybrids have “in-between” appearance RR
RR = red flowers
rr = white flowers
Rr = pink flowers
make 50% less color
RR
WW or R’R’
RW or RR’ RR Rr rr

31. Incomplete dominance P 1st 100% 1:2:1 2nd X true-breeding red flowers
white flowers
100%
100% pink flowers
1st
generation
(hybrids)
self-pollinate
25%
white
2nd
generation
25%
red
1:2:1
50%
pink

32. Incomplete dominance RW x RW RR R W RW R W RW WW 25% 25% 50% 50% 25%
genotype %
phenotype RR
25%
25% R W
male / sperm
50%
50% RW R W
female / eggs RW WW
25%
25%
1:2:1
1:2:1

33. Codominance x = 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 =

34. More Codominance… x

35. 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

36. BLOOD
Antigens are tiny receptors on the outside of the blood cell that matches the “type.”
Multiple Alleles
Blood cells have antigens and antibodies.
Antibodies are what the cell doesn’t like (which is anything different from the “type.”)

37. Blood Types Multiple Alleles Anti-B Anti-A Type B Type A B A Antigens
(none)
Type O
Anti-A and B
none

38. Genetics of Blood type A A A or A i B BB or B i AB O i i pheno-type
Multiple Alleles
pheno-type
genotype
antigen on RBC
antibodies in blood
donation status A
A A or A i
type A antigens on surface of RBC
anti-B antibodies
Receive A or O B
BB or 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 O
i i
no antigens on surface of RBC
anti-A & anti-B antibodies
universal donor

39. 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)
The genes that we have covered so far affect only one phenotypic character, but most genes are pleiotropic

40. Acromegaly: André the Giant

41. Inheritance pattern of Achondroplasia
Aa x aa
Aa x Aa A a A a a Aa aa A AA Aa a Aa aa a Aa aa
50% dwarf:50% normal or 1:1
67% dwarf:33% normal or 2:1

42. Polygenic = “many genes”
Many genes : One trait
Polygenic = “many genes”
Polygenic inheritance
additive effects of many genes
humans
skin color
height
weight
eye color
intelligence
behaviors

43. Polygenic = “many genes”
Human skin color
AaBbCc x AaBbCc
range of shades
most children = intermediate skin color
some can be very light & very dark

44. Albinism melanin = universal brown color Johnny & Edgar Winter
albino Africans

45. OCA1 albino
Bianca Knowlton

46. 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–

47. SEX and GENES X & Y 2 X chromosomes = female: XX
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 X X Y

48. Who you are…
Autosomes
Sex Chromosomes

49. Sex-linked traits Sex chromosomes have other genes on them, too X X X
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 X
Duchenne muscular dystrophy affects one in 3,500 males born in the United States.
Affected individuals rarely live past their early 20s.
This disorder is due to the absence of an X-linked gene for a key muscle protein, called dystrophin.
The disease is characterized by a progressive weakening of the muscles and loss of coordination. X Y

50. XHY HH XHXh Hh x XHY Y XH XH Y XHXH XHXH XHY XHY XH Xh XHXh XH Xh XHXh
sex-linked recessive x
2 normal parents,
but mother is carrier
XHY Y XH XH Y
male / sperm
XHXH
XHXH
XHY
XHY XH Xh
female / eggs
XHXh XH Xh
XHXh
XHXh
XhY
XhY

52. Most Common Allele Dominant or Recessive
Either One!
Because an allele is dominant does not mean…
it is better, or
it is more common
Polydactyly
dominant allele

53. Polydactyly Recessive allele far more common than dominant
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)

54. Hound Dog Taylor Any Questions? Assignment: Coach Book L17
Any Questions?
Assignment:
Coach Book L17
Textbook pg #1-6