This document provides information about Gregor Mendel and his experiments with pea plants that formed the basis of classical genetics and heredity. It discusses Mendel's work with traits controlled by single genes, including his discovery of dominant and recessive alleles and his laws of segregation and independent assortment. It also describes more complex patterns of inheritance beyond simple Mendelian genetics, including incomplete dominance, codominance, multiple alleles, epistasis, pleiotropy, and polygenic and sex-linked traits. The document uses examples like coat color in cats and human genetic disorders to illustrate these concepts.
Removal Strategy _ FEFO _ Working with Perishable Products in Odoo 17
AP Biology Inheritance and chromosomal mutations
1. War m up
Match the items on the left with one item on
the right
1. HH A. heterozygous
2. Curly hair B. homozygous
3. Hh C. phenotype
4. Genotype D. tt
2. Hel pf ul
Crash Course Biology
Hank Green
Bozeman Biology
Paul Anderson
4. Main Topics
Gregor Mendel’s work
Mendel’s Laws
Dominant/recessive
Heterozygous/homozygous
Alleles
Codominance and incomplete dominance
Epistasis, Pleiotropy, Multifactorial Inheritance,
Polygenic Traits
5. The father of genetics
Gregor Mendel is
considered the Father of
Genetics
Born in 1822
Studied math & physics
at an Austrian university
He was the first person to
study how traits are
passed along from one
generation to the next.
He did his work with the
pea plant
Who’s your
daddy?
7. Mendel’s Garden
Eight years & 20
volumes of data
and analysis on 7
distinctive traits
Published in 1865
8. Why peas?
The garden pea was a good choice for a
variety of reasons. The garden pea:
is easy to raise
produces large numbers of offspring
reproduces quickly
has flowers which are self fertilizing but can be
easily crossed to other varieties
12. Allele for purple flowers
Homologous
pair of
chromosomes
Allele for white flowers
Locus for flower-color gene
13. Mendel's
Theory of Segregation
Diploid organisms inherit two genes
per trait
Each gene segregates from the other
during meiosis so that each gamete
will receive only one gene per trait
14. How can the Chances of an Offspring’s Traits
be Determined?
The chance of an offspring showing a certain trait can
be determined by using the Punnett square.
The table contains spaces for the parent’s gametes
and the possible offspring from that mating.
The alleles are represented by their letters.
Genes come in pairs and must be separated during
gamete formation.
These gametes (letter) of each pair are placed in each
of the outside spaces.
They are then combined to form the possible
offspring.
16. Monohybrid Crosses
Mendel's first
experiments
One trait
Monohybrid crosses
have two parents that
are true-breeding for
contrasting forms of a
trait.
17. All the offspring from the
first cross showed only 1
form of the trait
This trait seemed
“stronger” so he called it
DOMINANT
When he crossed the
offspring from the first
cross, the other form of
the trait reappeared, but
only 1/4 of the time
This trait seemed
“weaker” so he called it
recessive
18. Predicting the Outcome
Why does one form of the trait disappear
in the
first generation (F1),
only to show up in the
second generation (F2)??
19. Artificial selection: populations could evolve (i.e.
change) if members show variation in heritable traits
Variations that improved survival chances in the wild
would be more common in each generation
This idea is known as natural selection
Prevailing Theories
20. Mendel’s Experiments
Natural selection did not fit with prevailing view
of inheritance-blending
Blending would produce uniform populations;
such populations could not evolve
21. Mendel’s Experiments
Many observations did not fit blending
A white horse and a black horse did not
produce only gray horses
22. Test (Back) Crosses
To support his concept of segregation,
Mendel crossed F1 plants (Pp) BACK with
homozygous recessives (pp)
What ratio would
Mendel have gotten?
He didn’t know the letter
combination of the F1
plants. The test (back)
cross allowed him to
figure it out
23. Dominant phenotype,
unknown genotype:
PP or Pp?
If PP,
then all offspring
purple:
p p
P
P
Pp Pp
Pp Pp
If Pp,
then 1
2 offspring purple
and 1
2 offspring white:
p p
P
P
pp pp
Pp Pp
Recessive phenotype,
known genotype:
pp
His back
crossed
supported
his idea of 2
“factors” for
each
individual,
and the idea
that those
“factors” are
segregated
25. Predicting the Outcome
What is the predicted PHENOTYPIC
ratio
and the predicted
GENOTYPIC ratio
that Mendel saw?
26. Predicting the Outcome
The F2 results showed 9/16
were tall and purple-
flowered and 1/16 were
dwarf and white-
flowered-as were the
original parents;
however, there were 3/16
each of two new
combinations: dwarf
purple-flowered and tall
white-flowered.
28. Theory of Independent Assortment
Each gene of a pair tends to assort into
gametes independently of other gene pairs
on non-homologous chromosomes
29. Theory in
Modern Form
Genes located
on non-
homologous
chromosomes
segregate
independently
of each other
30. Practice with your neighbor
For the following questions
Work with your neighbor to answer
the question.
Answer the multiple choice question
then,
Use your notes to determine which one
of Mendel’s principles it demonstrates
31. 1. A father carries 2 alleles for the gene
for widow’s peak. He carries one
dominant allele and one recessive
allele. His gametes will
a. All contain the dominant allele
b. All contain the recessive allele
c. ½ will get the dominant allele and ½ will get the
recessive allele
d. Each gamete will get both the dominant and the
recessive allele
32. Which principle does question
number one best demonstrate?
Principle of Segregation
The dominant allele goes to one gamete and
the recessive allele goes to another
gamete
33. 2. A mother that is homozygous dominant
for bushy eyebrows (BB) and
heterozygous for round ears (Rr). The
gametes she can make will
a. All have a B and a R in them
b. ½ will have a B and ½ will have a R or a r in
them
c. ½ will have a B and a R and ½ will have b and
r
d. ½ will have B and R and ½ will have B and r
34. What principle does number 2
demonstrate?
The Principle of Independent Assortment
All gametes will have a B, since mom only has B.
The big B can be with the big R or the big B can
be with the little r.
35. 3. In meiosis, a diploid cell divides
twice to form 4 haploid gametes.
Each gamete contains:
a. A complete set of DNA identical to the parents
b. A ½ set of DNA, with just one copy of each
chromosome
c. Homologous pairs of chromosomes
d. Multiple copies of chromosomes, depending on
which ones moved during meiosis
36. Which one of Mendel’s Principles
does number 3 demonstrate?
Principle of Segregation
All the homologous pairs of chromosomes
separate so that there is just one of each
pair in each gamete.
37. 4. When Mendel crossed a true
breeding green pea plant (GG) with a
true breeding yellow pea plant (gg),
the offspring plants were
a. All green
b. All yellow
c. ½ green and ½ yellow
d. Green and yellow mixed
38. Which one of Mendel’s principles
does number 4 demonstrate?
Principle of Complete Dominance
All offspring were Gg, and the dominant
allele (G) masked the recessive allele (g)
39. 5. Mendel wanted to know if the color for
pea seeds was linked to the shape of the
pea seeds. He crossed a green, wrinkled
seed plant (Ggrr) with a yellow, smooth
seed (ggRr) plant. The offspring produced
were:
a. All green and wrinkled
b. All yellow and wrinkled
c. All green and smooth
d. All yellow and smooth
e. Some of each of the above
40. Which one of Mendel’s Principles
does number 5 demonstrate?
Principle of Independent Assortment
The green trait can go with the smooth or
the wrinkled trait
The yellow trait can go with the smooth or
the wrinkled trait
41. Mendel’s Work
The work that Mendel did
helped explain patterns of
inheritance in eukaryotes.
But Mendel worked with
traits that had a clear
dominant/recessive
pattern.
Also, the traits he worked
with were all controlled by
a single gene.
42. Different Patterns of Inheritance
As we now know,
many traits do not
follow Mendelian
Inheritance patterns.
43. Degr ees of Domi nance
Complete Dominance - BB and Bb =
same phenotype
Incomplete Dominance - Bb has in-
between phenotype
Codominance - Bb has both B and b
phenotype
44. Co-dominance
When both
alleles are
expressed
equally in the
heterozygous
individual.
A and B blood type alleles are
co-dominant, because a person
with AB genotype will have
both A and B blood proteins.
Black and orange color in cats
are co-dominant, because a
heterozygous female will have
both orange and black hair.
45. Incomplete Dominance
Both alleles are blended
together in the
heterozygous individual.
Dominant allele cannot
completely mask the
expression of another
46. Multiple Alleles
More than 2 versions
(alleles) for a single trait
can be completely
dominant or
codominant
47. Bl ood Types
Genotype of
offspring
Phenotype of
offspring
A
iA
iB
AB
iA
i A
iA
iA
iB
iB
B
iB
i B
ii o
48. Rh f act or
Rh factor Possible genotypes
Rh+
Rh-
+/+ or +/-
-/-
49. So far we’ve only looked at how a
single gene pair affects phenotype
More often - multiple genes involved
2 primary cases:
1. 2 or more genes affect a single trait
2. 1 gene affects the phenotype of
another gene
50. Epi st asi s ( s t a nd i ng up o n)
- 2 or mor e genes af f ect a
si ngl e t r ai t
Labs can be black, yellow, or chocolate
51. Black is dominant to chocolate
BB and Bb = black
bb = chocolate
52. AND - another gene P codes for
whether or not any pigment is put into
the hair
PP and Pp = hair has pigment and dog
will be black (BB or Bb) or brown (bb)
pp = no hair pigment and dog will be
yellow, regardless of the “b” alleles
53. So in this case, the P gene “stands upon” the
B gene
P is epistatic to B
We don’t get the classic 9:3:3:1 but some
other version of it
54.
55. Pl ei ot ropy
A single gene can
have multiple effects
on phenotype
e.g. pleiotropic alleles
--> multiple symptoms
of sickle cell anemia
(pain, jaundice,
infections, fatigue, etc)
56. Pol ygeni c Inheri t ance
2 or more genes affect a single
phenotypic trait
Eye color, skin color, height
57. Skin color is controlled by at least 3
separate gene pairs
Genotype AABBCC would be very dark
skin
Genotype aabbcc would be very light skin
Any other combination would be
intermediate
58. And, of course, skin color is also
influenced by your environment -
multifactorial inheritance
59. X-linked traits
genes found on the X
chromosome.
show different inheritance
patterns in men than in
women.
X-linked traits may show
dominant/recessive or
codominant patterns.
60. Sex- l i nked
genes
• An organism’s sex is
an inherited
phenotypic character
determined by the
presence or absence
of certain
chromosomes
• Mammals like
humans have an XX
or XY system of
inheritance
• Other organisms
have other systems
61. Genes on t he sex
chr omosomes ar e
cal l ed sex- l i nked
genes
• Some diseases on the X
chromosome:
• Color blindness
• Rare in females, mild disease
• Duchenne muscular dystrophy
• 1 in 3500 males in US gets it
• Lack the gene for the muscle protein
dystrophin
• Muscles get weaker and lose
coordination
• Usually don’t live past 20s
• Hemophilia
• Lack the protein to cause clotting
• Don’t clot normally
62. Bar r
bodi es
• In mammalian females, 1 of the 2 X
chromosomes is inactivated during embryonic
development
• The inactive X condenses into what is called a
Barr body (we can see it under the
microscope)
• If she is heterozygous for a sex-linked trait,
she will be a mosaic for that trait
63. • Some cells have
the maternal X
inactivated
• These cells have
the orange color
• Some cells have
the paternal X
inactivated
• These cells have
the black color
• All cells in the
ovaries have active
X chromosomes
64. Y- l i nked t r ai t s
Y-linked traits called holandric
inheritance.
Y-chromosome is small and does not
contain many genes
Deletions on y chromosome male
infertility
SRY gene sex determining region
65. The cur i ous case of
t he guevedoces
Deficient in an enzyme that converts
testosterone to dihydrogen testosterone, so
don’t develop male genitalia as embryos.
66. 20.
Orange and black coat color are on the X
chromosome in cats and they are codominant
to each other. Tortoise shell is the codominant
phenotype.
A black female (XB
XB
) mated with an unknown
male. The kittens were:
2 tortoise shell females and 2 black males.
What is the father’s genotype and phenotype?
XO
Y- orange
67. 21.
• Ricket’s is a dominant disorder on the X
chromosome in humans.
• X = normal XR
= affected by rickets
A couple wants to know their chances of having
a child born with Rickets.
The wife is normal, the husband has the
disease.
What are the chances of having an affected
son? An affected daughter?
0% affected son, 100%
affected daughter
68. 22.
• Another couple, same disease. This
time, the wife is affected. Her father was
normal. The husband is not affected.
Same question: chances of an affected
son? Affected daughter?
50% son, 50% daughter
69. 23.
• A tortoise shell female mated with an
unknown male. The kittens were 2
orange females, 1 tortoise shell
females, 1 black male, 2 orange males.
• What is the genotype and phenotype of
the father?
XO
Y- orange
70. Chr omosomal mut at i ons
• In nondisjunction,
pairs of homologous
chromosomes do
not separate
normally during
meiosis
• As a result, one
gamete receives two
of the same type of
chromosome, and
another gamete
receives no copy
71. What r esul t s…
• Aneuploidy - a zygote
produced from a normal
gamete and a gamete
produced by
nondisjunction
• Offspring with this
condition have an
abnormal number of a
particular chromosome
72. What
r esul t s…
• Trisomy - having 3 copies of a particular chromosome
• Monosomy - having just one copy of a particular
chromosome
• Polyploidy - a condition in which an organism has more
than two complete sets of chromosomes
Recent research
has shown that
this Chilean
rodent is a
tetraploid
Very rare among
animals
Common in plants,
some fish, some
amphibians
73. Chr omosomal br eakage
• Breakage of a chromosome can lead to
four types of changes in chromosome
structure:
• Deletion removes a chromosomal
segment
74. Del et i on mut at i on
• Example: retinoblastoma (eye
tumors)
76. Dupl i cat i on mut at i on –
f r agi l e X syndr ome
77. Chr omosomal br eakage
• Inversion reverses a segment within a
chromosome
78. Hemophi l i a A – i nver si on
mut at i on pat i ent was gi ven
i nj ect i on i n but t ocks
79. Chr omosomal br eakage
• Translocation moves a segment from
one chromosome to another
80. Tr ansl ocat i on mut at i on
causes Bur ki t t ’ s l ymphoma
Tumor s on hand f r om cancer
81. Why does t hi s happen?
When would you predict these kinds of
chromosomal errors would occur?
Why?
82. Down syndr ome
• Trisomy 21 - 3 number 21
chromosomes
• 1 in 700 children in US
• Frequency increases with
age of mother
83. Tr i somy 18 – Edwar d’ s
syndr ome l ow bi r t h wei ght ,
ment al r et ar dat i on, ext r a
f i nger s and t oes
84. Tr i somy of sex
chr omosomes
• Klinefelter
syndrome is the
result of an extra
chromosome in a
male, producing
XXY individuals
• Monosomy X, called
Turner syndrome,
produces X0 females,
who are sterile; it is the
only known viable
monosomy in humans
85. DNA is also found in
mitochondria and
chloroplasts.
Mitochondrial DNA is
only passed from
Mother to child.
86. How ar e t r ai t s
i nher i t ed?
What mode(s) of inheritance would you
predict for the trait of skin color? Why?
Make a list of all the possible modes of
inheritance we’ve learned about
Next to each one give a short definition and
an example