Transcript Chapter 11

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SKIM READ SECTION 11-1 ON PG._________
GOAL: To understand the relationship
between the genes we inherit and human
genetic disorders.
 If
someone looks more
like one parent than the
other, did that person
inherit more genes from
that parent?
 No.
You inherit the same
number of genes from
each parent
 23 from Mom 23 from
Dad
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You look the way you do based on the pattern
of inheritance:
Dominant/ Recessive
But it is not always so straight forward.
If you inherit a recessive gene from
both parents you will have that
recessive phenotype.
Eye color Brown- dominant
Bb X Bb
Blue- recessive
bb
If you have blue eyes you inherited a recessive
gene from BOTH parents
Some genetic disorders are passed on
through a recessive allele.
 The parent may or may not have the
genetic disorder.
 If the parent has the dominant trait
they will NOT have the genetic
disorder. EX. Gg
 Since they are heterozygous- they
have the recessive allele and are called
CARRIERS
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 1.
Cystic Fibrosis
 2. Albinism
 3. Tay-Sachs disease
 4. Galactosemia
Who has heard
of any of these
genetic
disorders?
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Effects: One of the most common recessive
genetic disorders among Caucasians.
(Cystic fibrosis is less common in other ethnic groups,
affecting about 1 in 17,000 African Americans and 1 in
31,000 Asian Americans.)
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It affects the mucus producing glands, sweat
glands and the digestive enzymes
Mucus and fluid build up in the lungs
Treatment: physical therapy, special diets,
and replacement digestive enzymes
Pre-natal Genetic testing is available to see if
you are a carrier
PG. 297
Caused: By an altered genes the
result in the absence of the skin
pigment melanin in hair and eyes
 A person with albinism has pale skin,
white hair and pink pupils
 Causes vision problems and the
person has to be very careful in the
sun
 No treatment- Occurs in other
animals
 PG. 297
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Caused: By a recessive gene found on
Chromsome 15
More prevalent in Jewish people of eastern
European descent
Causes an absence of an enzyme that breaks
down a fatty acid (gangliodsides)
The fatty acid they builds up in the brain
Most die before their 5th birthday
Treatment: No cure
Genetic testing is available for perspective
parents
PG. 297
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Effect: This person has the inability to digest
galatose
During digestion, lactose from milk is broken
down into galactose and glucose.
The glucose goes to the cells for energy, but
the galactose must be broken down further.
People with galactosemia can not break it
down further
Treatment: Avoid milk. No cure
PG. 298
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1. Huntington’s Disease
2. Achondroplasia
Only have to inherit the genetic disorder from
one parent.
BB and Bb would have the genetic disorder
bb would not have the genetic disorder
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Effects the person’s nervous system.
Between the ages of 30- 50 years old the 1st
symptoms appear
Symptoms include: loss of brain function,
uncontrollable movements, and emotional
disturbances
Treatment: None
Genetic testing is available for this disease
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HD is a familial disease, passed from parent
to child through a mutation in a dominant
gene.
Each child of an HD parent has a 50-50
chance of inheriting the HD gene.
If a child does not inherit the HD gene, he or
she will not develop the disease and cannot
pass it to subsequent generations.
A person who inherits the HD gene will
sooner or later develop the disease. They
could also pass it on to their children
PG 298
Most common form of dwarfism
 Small body size and comparatively small limb
 Adult height of 4 feet.
 Average life expectancy
 75% of people with this are born
to average sized people- this means
that this disorder is most often
caused By a mutation on a gene
PG. 298
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Are used to study a family history.
The diagram traces a ONE specific trait
through several generations of a family
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Knowing physical traits can determine what
genes an individual is most likely to have.
Pedigrees look at physical traits(phenotypes)
to infer what the persons genotype is.
Keeping track of family history can be used
for predicting the pattern of inheritance of
different traits/ disorders
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Skim read section 11.2 pg. _________.
GOAL: To understand to complex patterns of
inheritance that lead to variation of
phenotypes in populations. To understand
the importance of variation in genes.
Hmmm…When we say someone has BROWN
eyes can you picture EXACTLY what there eye
color looks like?
 In
the real world many traits
follow a complex pattern of
inheritance
 …..which basically means that
the Dominate / Recessive
inheritance pattern does not
explain how some traits are
expressed in offspring
1. Incomplete Dominance: When the
offspring’s phenotype is a blend of
both of the parents. (In the book it is
referred to as an “intermediate
type.”)
 2. Codominance: When both are
dominate and are expressed in the
offspring’s phenotype.
 3. Multiple Alleles: when more than
one set of alleles controls the
phenotype
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Incomplete dominance
OR
Co dominance
So a heterozygous genotype
Gives you a phenotype that is a
Blend of the parents ……in this
example Pink
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When both are
dominate and are
expressed in the
offspring’s
phenotype
Example: Sickle- cell
disease
 Sickle Cell
 Normal Red
Blood Cell
More common in people
with African American descent.
9% of African Americans have one form of the
trait.
Affects red blood cells ability to transport
oxygen. The sickle cells get stuck in small
blood vessels
SS- Normal person
SSs- have normal & sickle cells but lead a
normal life
SsSs – have sickle cell disease
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Sickle cell disease (SsSs ) causes many
symptoms such as pain, fever, respiratory
failure, and neurological problems.
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someone that is
Heterozygous for Sickle- Cell (SSs)
has a higher resistance to Malaria
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Every 30 seconds a child dies of Malaria- the
vast majority (90%) from Africa
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traits have two versions
of alleles
 BUT multiple allele traits have
3 or more alleles that control
the phenotype
 Examples: Blood type & Fur
color of rabbits
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There are 4 blood types: A, B, AB, and O
There are 3 alleles that control the blood
type:
◦IA
Codominant
◦IB
◦(i)
Codominant
Recessive
Blood Group
Alleles
Safe to transfuse
to:
From:
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A
IA IA or IA i
A or AB
A, O
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B
IB IB or IB i
B or AB
B, O
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AB
IA IB
AB
A, B, AB,O
Universal
Receiver
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O
Universal Donor
ii
A, B, AB, O
O
 This
is another part of our blood
type.
 Rh factor follows a dominant /
recessive pattern of inheritance.
 Rh
(+) is dominant
 Rh (-) is recessive
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Has a hierarchy of dominance: C,cch, ch, and
c.
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Variety is the result of one allele hiding the
effects of another allele.
Lab’s fur color is controlled by 2 sets of
alleles
One controls if pigment is present and the
other controls how dark the pigment will be
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Everyone has 23 pairs of chromosomes
The first 22 pairs of chromosomes are
called autosomes
The last pair is called the sex chromosomes
and carries the information the determines
the sex of an individual
Female has two X chromosomes = XX
Male has one X and one Y= XY
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Sex Linked traits are inherited through the
sex chromosomes .
Most information is on the X chromosome. It
is larger than the Y chromosome.
The Y chromosome only provides information
to make a male.
Two Recessive Sex- linked traits are:
1. Red- green color blindness
2. Hemophilia
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Carried on the X chromosome.
More common in males because they only
have one X chromosome and if they get a
defective X chromosome……. they will be
color blind
Females would have to inherit 2 defective X
chromosomes…….much less likely
So most people with color blindness are male
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This is disease causes a delay in the person’s
ability to clot their blood.
Again, this is much more common in males
because they only have to inherit 1 defective
gene (females would have to inherit 2 genes).
A person with hemophilia have to be very
careful not to injure themselves because they
could cause a blood vessel to break and they
could bleed to death
Before current treatments people with this
disease died at an early age
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traits arrise from the
interaction of multiple pairs of
genes.
 Examples:
◦ Skin color
◦ Eye color
◦ Height
◦ Fingerprint pattern
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The environment has an effect on phenotype
Epigenetics literally means "above" or "on top
of" genetics. It is what control the DNA and
what genes are turned "on" or "off."
Environmental influences, such as a person’s
diet and exposure to pollutants, can impact
the epigenome.
The epigenome can remain as cells divide and
in some cases can be inherited through the
generations.
Twin studies have helped us discover what
role heredity and the environment play in
disease
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Environmental Effects on Gene Expression
 Gene expression can be affected by both the external
environment and the internal environment inside an
organism. Phenotype is generally a combination of
genetic and environmental influences.
Example: Japanese goby fish (social environment)
 1. The goby fish can change its sex back and forth
 in response to changes in its social environment.
 2. Goby fish exist in schools of many females and only a
 few males.
 3. If a large male goby leaves a population, a female goby
 will become male.
 4. If another large male enters that goby population, this
 new male turns back into a female.
Example: Human height (internal environment)
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While human height is a polygenic trait, it is also
affected by the nutrients in your diet
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Skim Read Section 11.3 pg____________
GOAL: To understand the effects mistakes
made during gamete formation can create
such as, chromosome number disorders.
 Karyotypes- are used to study
chromosomes pg. 311
 Images (a picture) are taken of the
chromosomes when the cell is in metaphase.
 The chromosomes images are then arranged
in decreasing size
 Chromosome #1 is the largest and
chromosome #22 is the smallest & the sex
chromosomes are paired together.
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Can occur during Meiosis I and II.
Nondisjuction is when the sister chromatids
do not fully separate resulting in one gamete
getting too many chromosomes (Trisomy)
and another too few chromosomes
(monosomy)
Alterations in the number of chromosomes
someone has causes serious genetic defects
and are often fatal (the fertilized egg would
die)
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Down’s Syndrome is a nondisjunction
disorder called trisomy 21
There is an extra copy of the 21st
chromosome
Frequency of down’s syndrome is 1 in every
800 births
Causes: mental disabilities, heart defects,
distinctive facial feature
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XO- Turner’s syndrome The female only has
1 X chromosome. She is not fertile
XXY- Klinefelter’s syndrome This male has an
extra X chromosome. He is sterile. Five to 10
boys with 47,XYY syndrome are born in the
United States each day.
XXX- Triple X syndrome Nearly normal
female. Most are never know they are triple X
XYY- XYY syndrome Nearly normal male. Is
fertile
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Aminocentesis
Choronic villus sampling
Fetal Blood sampling
Are tests available to determine if the fetus
has a genetic disorder or abnormality