Genetics II PowerPoint, non-Mendelian genetics. Blood types, sex-linked, linked, genetic disorders.

1. 1
Genetics Part II
The Genetics of Blood, Sex-linked Traits & Human Genetic Disorders

2. Multiple Alleles
• 3 or more alleles of the
same gene that code for
a single trait
• In humans, blood type is
determined by 3 alleles –
A, B, and
• BUT each human can
only inherit 2 alleles

3. Multiple Alleles
1. Dominant – A and B
(codominance)
Recessive – O
2. Blood type
A = AA or AO
B = BB or BO
AB = AB
O = OO

4. Multiple Alleles
1. Dominant – A and B
(codominance)
Recessive – O
2. Blood type
A = AA or AO
B = BB or BO
AB = AB
O = OO

5. A B
What would be the
possible blood types of
children born to a female
with type AB blood and
a male with type O blood?
AB X OO
AO BO
AO BO
O
O
Children would be type A or B only
Example:

6. Sex Chromosomes:
Sex Symbol Chromosome
Pair
Human
Size
Male Y XY smaller
Female X XX larger
6

7. Sex Chromosomes:
7

8. Other chromosomes:
 Other chromosomes are called autosomes.
8

9. Sex – linked Traits
•Genes for these traits are
located only on the X
chromosome (NOT on the Y
chromosome)
•X linked alleles always show
up in males whether
dominant or recessive
because males have only one
X chromosome

10. Example of Humans
 Females: 23 homologous pairs
 Males: 22 homologous pairs + 1
pair different
#
Chromosomes Type
46 chromosomes
— 2 sex chromosomes
44 autosomes
Example of Fruit Flies
 Females: 4 homologous pairs
 Males: 3 homologous
pairs + 1 pair different
#
Chromosomes Type
8 chromosomes
— 2 sex chromosomes
6 autosomes
10

11. Sex Linked
 Some alleles are carried only
on one of the sex
chromosomes.
 Thomas Hunt Morgan (1866-
1945) discovered Drosophila's
(fruit flies) eye color are carried
only on the female
chromosome.
 This is called a sex-linked
characteristic.
 As with other genetic traits the
outcome of breeding can be
predicted.
Thomas Hunt Morgan
1866-1945
11

12. Sex-linked
These traits for fruit fly eye color are written : R stands for red
while r stands for white.
XR XR Red-eyed
XR Xr Red-eyed
Xr Xr White Eyed
Female
XR Y Red-eyed
Xr Y White Eyed
Male
Possible Genotypes & Phenotypes
12

13. Sex-linked Parental Cross
Red-eyed female
&
White-eyed male
13

14. Sex-linked Parental Cross
Red-eyed female
&
White-eyed male
XR
XR
Xr Y
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15. Sex-linked Parental Cross
Red-eyed female
&
White-eyed male
XR Xr XR Y
XR Xr XR Y
XR
XR
Xr Y
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16. Sex-linked ƒ1 Cross
Red-eyed female
&
Red-eyed male
From Parental Cross
16

17. Sex-linked ƒ1 Cross
Red-eyed female
&
Red-eyed male
XR Y
XR
Xr
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18. Sex-linked ƒ1 Cross
Red-eyed female
&
Red-eyed male
XR XR XR Y
XR Xr XR Y
XR
Xr
XR Y
18

19. Results: ƒ1 cross: ƒ2 generation
XR XR Red-eyed
XR Xr Red-eyed
Female
XR Y Red-eyed
Xr Y White Eyed
Male
Possible Genotypes & Phenotypes
Note: There are not any white-eyed females
19

20. Human Colorblindness
An inability to distinguish
between certain colors.
Examples of recessive sex-linked disorders:

21. Examples of recessive sex-linked disorders:
You should see
58 18
E 17
The most
common type
is red-green
color
blindness,
where red
and green are
seen as the
same color.
21

22. Hemophilia
Blood doesn’t clot properly.
The ability of the blood to
clot is severely reduced,
causing the sufferer to
bleed severely from even a
slight injury. The condition
is typically caused by a
hereditary lack of a
coagulation factor, most
often factor VIII.
Examples of recessive sex-linked disorders:

23. Nondisjunction
 Remember: genes are located on chromosomes.
When homologous chromosomes fail to segregate
during meiosis it is called nondisjunction.
 Calvin Bridge's (1889-1938) work with Drosophila (
fruit flies ) determined that to be a female Drosophila
there must be two X chromosomes present.
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24. Sexing Drosophila
What sex would each of the following be?
XXY
X
Female
Male
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25. Sexing Homo sapiens
For humans it has been found that the Y
chromosome determines sex.
What sex would each of the following be?
XX
XXX
Female Male•XXY
•XXXYFemale Male
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26. Linked Genes:
 When two genes are on the same chromosomes they
are called linked
 Linked genes reduces chances for genetic variation
and variety.
 Normally: GgRr
 GR, Gr, gR, gr (gametes)
 Linked Genes: GgRr (where green and round are linked)
 GR and gr (gametes)
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27. Crossing Over
• Crossing over occurs when
homologous chromatids fail to
correctly separate during
prophase I of meiosis.
• This results in offspring that may
have a different genetic make-up
than their parents.
• Gametes that have undergone
this process are called crossing
over.

28. Maps & Genomes
• Scientist are developing
genetic map (or genome)
which shows the
relationship among different
genes along a chromosome.
• These are used to pin-point
errors in genetic make-up
and help scientists
understand other problems.
Human Genome Karyotype

29. Karyotype
• A picture of a person's
chromosomes.
• Chromosomes are isolated, stained
and examined under the
microscope.
• Uses the chromosomes in the white
blood cells.
• A picture of the chromosomes is
taken through the microscope.

30. Comparing Chromosome Numbers
30
 Looking at Different
Genomes
Chromosomal
Numbers

31. Karyotypes of other organisms
31
Mus sp. (mouse)
Drosophlia sp. (fruit fly)

32. Mutations
• Mutation – sudden genetic change (change
in base pair sequence of DNA)
• Can be :
Harmful mutations – organism less able to
survive: genetic disorders, cancer, death
Beneficial mutations – allows organism to
better survive: provides genetic variation
Neutral mutations – neither harmful nor
helpful to organism
• Mutations can occur in 2 ways:
chromosomal mutation or gene/point
mutation

33. Genetic Disorders:
Lethal genes
Sickle-Cell Anemia
Galactosemia
PKU
Tay-Sachs Disease
Diabetes Mellitus
Sex-linked Diseases
Hemophilia
Colorblindness
Chromosomal Disorders
Down Syndrome
Turner Syndrome
Klinefelter Syndrome
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34. Sickle-Cell Anemia
 Mostly affecting
those of African
ancestry, but also
occurs in other
ethnic groups,
including people
who are of
Mediterranean and
Middle Eastern
descent.
 More than 70,000
Americans have
sickle cell anemia.
And about 2 million
Americans — 1 in 12
African Americans —
have sickle cell trait.
The sickle hemoglobin (HbS) mutation confers a
genetic advantage against malaria so carrier
frequency is highest in areas where malaria is (or
was) endemic (regularly found among particular
people or in a certain area )
34

35. Sickle cell anemia is a blood disorder
affecting hemoglobin, the protein found
in red blood cells (RBCs), which carries
oxygen throughout the body.
Sickle cell anemia occurs when a person
inherits two abnormal genes (one from
each parent) that cause their RBCs to
change shape.
Instead of being flexible and disc-
shaped, these cells are more stiff and
curved in the shape of the old farm tool
known as a sickle — that's where the
disease gets its name.
The shape is similar to a crescent moon.
Sickle-Cell Anemia
35

36. Sickle-Cell Anemia
How the trait
is passed to
offspring
36

37. Galactosemia
 Is a rare genetic
metabolic disorder is
a disorder that
affects how the body
processes a simple
sugar called
galactose.
 Galactosemia is not
related to and
should not be
confused with
lactose intolerance.
 Without treatment,
mortality in infants
with galactosemia is
about 75%.
37

38. PKU — Phenylketonuria
PKU is short for "phenylketonuria." People with
PKU can't process one of the amino acids found in
many foods.
The amino acid, called phenylalanine or "Phe" for
short, builds up in the body.
Too much Phe is toxic to the brain and can cause
many problems.
In infants and children, if PKU is not treated, the
resulting high Phe can cause severe mental
retardation.
 Even if PKU is treated problems like brain changes,
lower IQ, and behavior problems may still occur.
In adults and teens, high Phe can cause lower
intelligence (IQ), poor focus, mood swings, being
irritable, depression, slow reaction time, and other
problems.
One of the first tests a baby receives
38
Anamino acid common in milk
cannot be broken down and as it
builds up it causes mental
retardation – newborns are tested
for this

39. Tay-Sachs disease
A metabolic disorder commonly associated with
Ashkenazi Jews, has also been found in the
French Canadians of Southeastern Quebec, the
Cajuns of Southwest Louisiana, and other
populations throughout the world.
The severity of expression and the age at onset
of Tay-Sachs varies from infantile and juvenile
forms that exhibit paralysis, dementia, blindness
and early death to a chronic adult form that
exhibits neuron dysfunction and psychosis.
Tay-Sachs is an autosomal recessive disease
caused by mutations in both alleles of a gene
(HEXA) on chromosome 15. HEXA codes for an
enzyme found in lysosomes, organelles that
break down large molecules for recycling by the
cell.
In Tay-Sachs individuals, the enzyme is absent or
present only in very reduced amounts, allowing
excessive accumulation of the GM2 ganglioside
in neurons.
39
Deterioration of the nervous system –
early death

40. Type 1 • Diabetes Mellitus
Previously called insulin-
dependent diabetes
mellitus (IDDM) or
juvenile-onset diabetes.
It develops when the
body’s immune system
destroys pancreatic beta
cells, the only cells in the
body that make the
hormone insulin that
regulates blood glucose.
40

41. Type 2 • Diabetes Mellitus
Previously called non-insulin-dependent
diabetes mellitus (NIDDM) or adult-onset
diabetes.
 In adults, type 2 diabetes accounts for
about 90% to 95% of all diagnosed cases
of diabetes. It usually begins as insulin
resistance, a disorder in which the cells
do not use insulin properly.
As the need for insulin rises, the pancreas
gradually loses its ability to produce it.
 It is associated with older age, obesity,
family history of diabetes, history of
gestational diabetes, impaired glucose
metabolism, physical inactivity, and
race/ethnicity.
African Americans, Hispanic/Latino
Americans, American Indians, and some
Asian Americans and Native Hawaiians or
other Pacific Islanders are at particularly high
risk for type 2 diabetes and its complications.
41

42. Colorblindness
Color blindness or color
vision deficiency is the
inability to perceive
differences between some
of the colors that others
can distinguish.
It is most often of genetic
nature, but may also occur
because of eye, nerve, or
brain damage, or exposure
to certain chemicals.
42

43. Colorblindness Tests
25 6 56 45
43

44. Down Syndrome • Trisomy 21
But a baby with Down syndrome has an extra
chromosome #21 (47 instead of 46) or one
chromosome has an extra part.
About half of babies with Down syndrome are born
with heart defects. Usually, these problems can be
corrected by surgery. Some babies may have
intestinal problems that also require surgery to fix.
Kids with Down syndrome are more likely to get
infections affecting their lungs and breathing.
These infections often last longer. They may have
eye or ear problems or digestion problems like
constipation. Some may develop leukemia, a type
of cancer.
Kids with Down syndrome tend to grow and
develop more slowly than other children do. They
may start walking or talking later than other
babies.
About 1 out of every 800 babies born has Down
syndrome, no matter what race or nationality the
parents are.
44

45. Down Syndrome • Trisomy 21
45

46. Turner Syndrome • OX
A female does not have the
usual pair of two X
chromosomes.
Other Names: Bonnevie-Ullrich
syndrome; Gonadal dysgenesis;
Monosomy X
Occurring in 1 of 2,500 girls.
Characteristic physical
abnormalities, short stature,
swelling, broad chest, low
hairline, low-set ears, and
webbed necks.
46

47. Turner Syndrome • OX
47

48. Klinefelter Syndrome • XXY
 47, XXY, or XXY syndrome is a condition in which males
have an extra X sex chromosome.
 While females have an XX chromosomal makeup, and
males an XY, affected individuals have at least two X
chromosomes and at least one Y chromosome.
 1 out of every 1,000 males.
 One in every 500 males have an extra X chromosome
but do not have the syndrome.
 The syndrome can affect different stages of physical,
language and social development. The most common
symptom is infertility. Because they often don't make as
much of the male hormone testosterone as other boys,
teenagers with Klinefelter's syndrome may have less
facial and body hair and may be less muscular than
other boys.
 They may have trouble using language to express
themselves. They may be shy and have trouble fitting
in.
48

49. Klinefelter Syndrome • XXY
49

50. Detecting Human Genetic Disease
 Amniocentesis
 Ultrasonography
 Fetoscopy
 DNA tests
50

51. Detecting Human Genetic Disease
 Is a medical procedure used in prenatal
diagnosis of chromosomal abnormalities
and fetal infections
 A small amount of amniotic fluid, which
contains fetal tissues, is extracted from the
amnion or amniotic sac surrounding a
developing fetus
 The fetal DNA is examined for genetic
abnormalities.
Amniocentesis (amniotic fluid test or AFT)
51

52. Detecting Human Genetic Disease
 Sonography is used to visualize the
embryo or foetus in its mother's uterus
(womb).
 The procedure is often a standard part
of prenatal care, as it yields a variety of
information regarding the health of the
mother and of the fetus, as well as
regarding the progress of the
pregnancy.
Ultrasonography
52

53. Detecting Human Genetic Disease
 Is an endoscopic procedure during pregnancy to allow access
to the fetus, the amniotic cavity, the umbilical cord, and the
fetal side of the placenta.
 A small (3-4 mm) incision is made in the abdomen, and an
endoscope is inserted through the abdominal wall and uterus
into the amniotic cavity.
 Fetoscopy allows medical interventions such as a biopsy or a
laser occlusion of abnormal blood vessels.
 Evaluate the fetus for birth defects, such as spina bifida as
well as other defects.
 Collect samples of embryo, These samples can then be tested
further for diseases such as hemophilia or sickle cell anemia.
Fetoscopy
53

54. Detecting Human Genetic Disease
Examines the nucleotides at specific
locations on a person's DNA for genetic
purposes.
Carrier testing is used to identify people
who carry one copy of a gene mutation
that, when present in two copies, can
cause a genetic disorder.
This type of testing is for individuals who
have a family history of a genetic disorder
and to people in ethnic groups with an
increased risk of specific genetic
conditions.
Having both parents tested can provide
information about a couple's risk of having
a child with a genetic condition.
Immune System
 Lupus
 Graves' disease
 Celiac disease
 Multiple sclerosis
Psoriasis
Cardiovascular Conditions
 Aneurysm
 Atrial fibrillation
 Heart disease
 Peripheral arterial disease
Venous thromboembolism
Aging
 Macular degeneration
 Alzheimer's disease
 Osteoarthritis
 Rheumatoid arthritis
General Health
 Obesity
 Migraine
 Type 1 diabetes
Type 2 diabetes
Cancers
 Bladder cancer
 Breast cancer
 Colorectal cancer
 Gastric cancer
 Lung cancer
 Prostate cancer
 Skin cancer
DNA testing
54

55. Pedigrees
• Graphic representation of how a trait is passed
from parents to offspring
• Tips for making a pedigree
1. Circles are for females
2. Squares are for males
3. Horizontal lines connecting a male and a
female represent a marriage
4. Vertical line and brackets connect parent
to offspring
5. A shaded circle or square indicates a
person has the trait
6. A circle or square NOT shaded represents
an individual who does NOT have the trait
7. Partial shade indicates a carrier – someone
who is heterozygous for the trait

56. Example: Make a
pedigree chart for the
following couple.
• Dana is color blind; her
husband Jeff is not.
They have two boys
and two girls.
• HINT: Colorblindness is
a recessive sex-linked
trait.
XNY
Has trait Can pass trait to
offspring
XnXn
Pedigrees