Dragonfly Chapter 14

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Dragonfly Chapter 14

• The Human Genome

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Section 14-1 Human Heredity
Key Concepts How is sex determined? How do
small changes in DNA Cause genetic disorders?

• Human Chromosomes
• A. Karyotype A picture of chromosomes taken
  during mitosis and cut out and arranged into
  homologous pairs.

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Diploid Cell ________ of homologous
chromosomes Human diploid cell has ____
chromosomes arranged in ____ pairs The 46
chromosomes contain
Two sets
46
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6 billion nucleotide pairs
Mendelian genetics requires that organisms of
gene from each parent
inherit a single copy
In humans, _______________ (reproductive cells of
egg and sperm) contain a single copy of each gene
(one set of genetic information).
the gametes
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testes
Gametes are formed in the __________ (sperm) and
__________(egg) by meiosis.   Each gamete
contains 23 chromosomes (one set) or
__________________ (N) of chromosomes.   _________
_______ requires the egg and the sperm to join
and produce a ______________ (fertilized egg)
that contains 46 chromosomes (two sets) or
_____________________ (2N).  
ovaries
haploid number
Fertilization
zygote
diploid number
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Humans have 46 total chromosomes 44
_____________ follow regular Mendelian
genetics 2 _________________ (X and Y) are
sex-linked
autosomes
sex chromosomes

• Pedigree Chart A pedigree chart shows the
  _________________ within a family and can be
  useful to help with __________________________
  within families. It is another __________________
• _________ of a particular cross and the genotype
  of the family members.

relationship
genetic inheritance problems
way to predict the
outcome
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Pedigree
Figure 14-3 A Pedigree
Section 14-1
A circle represents a female.
A square represents a male.
A horizontal line connecting a male and female
represents a marriage.
A vertical line and a bracket connect the parents
to their children.
A half-shaded circle or square indicates that a
person is a carrier of the trait.
A circle or square that is not shaded indicates
that a person neither expresses the trait nor is
a carrier of the trait.
A completely shaded circle or square indicates
that a person expresses the trait.
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Human Traits Phenotypes are determined by
genotype as well as ______________________________
__.   ________________________________ on gene
expression are not inherited, but genes are.
environmentally influenced
Environmental influences
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III. Human Genes The __________________
Complete set of genetic information Composed
of about 30,000 genes
human genome
Blood Group Genes Human Blood comes in a variety
of genetically determined blood groups   There
are many different types of blood groups but the
ones associated with the ABO blood group and the
Rh blood groups are best known.   .
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Rh blood groups is controlled by single gene with
________________. It is another antigen in blood,
first discovered in Rhesus monkeys. The
arrangement of the alleles determines only
_______ possible types _____________ () contains
the antigen, or ___________ (-) doesnt contain
the antigen. Positive is ______________ over
negative. Rh-positive is identified with two
genotypes Rh/Rh or Rh/Rh- Rh-negative is
identified with one genotype Rh-/Rh-  
Two alleles
two
positive
negative
dominant
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ABO Blood Groups Discovered in 1900 by Karl
Landsteiner. He realized that all blood is
classified into four types ____, ____, ____, and
_____ due to the presence of or absence of
specific __________ in the blood.   Alleles IA
and IB are __________________ and io is
________________ to both IA and IB
A
O
AB
B
antigens
codominant
recessive
Antigens are ______________________ used by the
immune system. When an unrecognized antigen is
present an immune response takes place and the
cells ____________________________.
chemical markers
_
clump or agglutinate
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Blood Type and Antigen Interactions
Figure 14-4 Blood Groups
Section 14-1
Safe Transfusions
Antigen on Red Blood Cell
Phenotype (Blood Type
Genotype
From
To
Go to Section
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• B. Recessive Alleles Trait controlled by a
  recessive allele. This results in the disorder
  being present ___________________________.
• Examples include PKU (Phenylketonuria), Tay
  Sachs disease and Cystic Fibrosis, Albinism, and
  Galactosemia (See chart on page 345)

only if both alleles are recessive
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• C. Dominant Alleles Traits controlled by a
  dominant allele. This results in the disorder
  being present when __________________________.
• Examples include Achondroplasia (dwarfism),
  Hypercholesterolemia, and Huntingtons Disease

only one allele is present
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Autosomal Disorders
Section 14-1
Autosomol Disorders
caused by
include
include
include
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Huntington Disease It is controlled by a
_________________________. The gene is located
on Chromosome 4.
single dominant allele
Genetic degenerative disease that shows no
symptoms until a person is in their
____________________. It progresses with gradual
degeneration of their nervous system leading to
loss of muscle control and mental function until
death occurs.
thirties or forties
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Question? Would you want to know now if you
could potentially get Huntingtons disease when
you are older? Would you want to know if you
could pass the gene on to your offspring before
you have children? A. Codominant Alleles
controlled by ____________________________________
___. Sickle Cell Anemia is such a disorder. (This
will be discussed in detail later)
two alleles that share dominance
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• IV. From Gene to Molecule
• The link between ______________________
• is not easily determined but for several diseases
  we
• have been able to make the connection.
•  
• For both _____________ and ________________
• a small change in the DNA of a _____________
• affects the ______________________, causing a
• serious genetic disorder.

genetics and phenotype
Cystic fibrosis
Sickle cell disease
single gene
structure of a protein
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• A.     Cystic Fibrosis (See figure 14-8 p. 347)
• Cystic Fibrosis a.k.a. CF is a common genetic
  disease. It is most common in people of Northern
  European decent.
•  
• It is a _______________________ of a gene found
  on the 7 chromosome and affects
  the______________________________

Recessive disease
digestive and respiratory systems
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• It is caused by the____________________ in
• the middle of a sequence for a protein and
• causes the protein to be ______________ and
• doesnt allow Chloride ions to transport across
• the membrane, as they should. This causes
• the cells in a persons airways to be unable to
• transport chloride ions and become
• __________________.

deletion of 3 bases
abnormal
clogged with mucus
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Figure 14-8 The Cause of Cystic Fibrosis
Section 14-1
Chromosome 7
CFTR gene
The most common allele that causes cystic
fibrosis is missing 3 DNA bases. As a result,
the amino acid phenylalanine is missing from the
CFTR protein.
Normal CFTR is a chloride ion channel in cell
membranes. Abnormal CFTR cannot be transported
to the cell membrane.
The cells in the persons airways are unable to
transport chloride ions. As a result, the airways
become clogged with a thick mucus.
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• B. Sickle Cell Anemia
• The patients blood cells were found to be
• irregularly shaped, ____________________,
• and this is how the disease got its name.
• In normal red blood cells the
• ____________________ carries ___________
• and distributes it around the body. In sickle
  cell
• disease, the red blood cells are sickleshaped,
• causing the blood hemoglobin to no longer carry
• oxygen as well and _____________________

like a sickle
oxygen
hemoglobin molecule
disrupts the normal functioning of the
bodies cells, tissues and organs
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• This person is deprived of oxygen and the result
  is physical weakness, and damage to the brain,
  heart, spleen. It may be fatal.
•  
• The cause A _________________ in the DNA that
  codes for Hemoglobin polypeptides is changed.
  This substitutes Valine for glutamic acid.
•  
• This change makes the hemoglobin less soluble in
  blood. This will cause the hemoglobin to come
  out of the blood and _______________. This
  crystallization causes the ________________ of
  the blood cells and the medical consequences.
•  

single base
crystallize
sickle shape
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The genetics The allele for sickle cell (HS) is
___________ with the allele for normal hemoglobin
(HA).
codominant
Heterozygotes (HS HA) are said to be ____ ____
__________ and have some effects of the disorder
because they have both normal and sickle cell
blood hemoglobin.
Sickle cell
carriers
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DNA normal hemoglobin CAC GTG GAC TGA GGA CTC
CTC Messenger RNA sequence
GUG CAC CUG ACU CCU GAG GAG Normal hemoglobin
amino acid sequence Val His Leu Thr Pro
Glu Glu 1 2 3 4
5 6 7 146  
DNA Sickle Cell Anemia CAC GTG GAC TGA GGA CAC
CTC Messenger RNA sequence GUG CAC CUG ACU CCU
GAG Val His Leu Thr Pro
Glu 1 2 3 4 5
6 7 146  
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The distribution Sickle Cell anemia is most
prevalent in people of __________________.
  10 of African Americans and 40 of
populations in Africa and Asia carry the gene for
Sickle cell anemia.   Why? The carriers for
the disease have a ___________________, a
dangerous disease caused by a blood parasite
found in tropical areas of the world.
African descent
resistance to Malaria
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Sickle Cell Anemia is a __________ that has
provided an ____________ in Malaria prone areas
and in these areas it is _______________________
and therefore Sickle Cell Anemia persists.
mutation
advantage
favored by natural selection
HS HA
HS HS
HS HA
HS HA
HS HA
HA HA
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• Section 14-2 Human Chromosomes
• Key concepts Why are sex-linked disorders more
• common in males than in females?
• What is nondisjunction, and what problems does it
• cause?

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• I. Human Genes and Chromosomes
• Human diploid cell contains ______________________
  of DNA. All neatly packed into the 46
  chromosomes.
• __________________ of the DNA actually functions
  as genes.
• Genes are located on the chromosomes and each
  gene occupies a ______________________ on a
  chromosome.
• Genes may exist in ____________________ (alleles)
• Each chromosome contains ______ of the alleles
  for each of its genes
• Chromosome 21 and 22 are the ____________ of the
  human autosomes. These were the first two
  chromosomes whose sequences had been determined.

6 billion base pairs
Small part
specific place
several forms
one
smallest
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• Both also contain genes for some genetic
• disorders like ________________________
• ___________________________
• We also discovered that there are many
• _________________________ segments of DNA
• Human chromosomes also have
• ________________ that can cross over just as we
• saw in the fruit fly.

Leukemia and
Amyotrophic Lateral Sclerosis (ALS)
non-coding, repeating
Linked genes
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• II. Sex-linked Genes
• 1. _______________________ are the ones that
• __________ in males and females
• 2. Chromosomes that are the ________ in male and
  females _______________
• 3. In humans females ____ and Males ____
• 4. The Y chromosome is smaller than the X

Sex Chromosomes
differ
same
autosomes
XY
XX
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• A. Sex Determination
• 1. Female _________ carry an X chromosome
• 2. _________ gametes can carry either an X or Y
  (meiosis segregates the chromosomes _______ of
  the sperm carry X and ______ of the sperm carry
  Y)
• 3. In humans, _____________________________ of an
  offspring
• Female XX
• male XY

gametes
Male
50
50
males determine the sex
X
Y


X
XX
XY
X
XX
XY
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• In some animals such as birds, butterflies, and
• some fish, the female determines the sex
• because she has the __________ chromosomes.
• Sex-linked Genes
• 1. In addition to determining the sex of an
  individual, the sex chromosomes carry genes
• that ____________________

differing
affect other traits.
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Sex-linked Genetic Disorders May be on the X or Y
chromosome, but    Most often expressed in
____________because they only have one X
chromosome and thus all the alleles are expressed
even if they are recessive.
usually on the X because the Y has very few genes.
males
Colorblindness is a recessive disorder in which
people cant distinguish between certain colors.
____________________ colorblindness is most
common.   XC and Xc are ________________ for
normal and colorblind vision.
Red-green
the alleles
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XC XC and XC Xc are XC Xc is a
_______________________ and can pass the gene on
to her sons. Xc Xc is a XC Y is a Xc Y
is a
both normal vision females.
carrier for colorblindness
colorblind female.
normal male and
colorblind male.
http//www.toledo-bend.com/colorblind/Ishihara.htm
l
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Colorblindness
Figure 14-13 Colorblindness
Section 14-2
Father (normal vision)
Normal vision
Colorblind
Male Female
Daughter (normal vision)
Son (normal vision)
Mother (carrier)
Daughter (carrier)
Son (colorblind)
Go to Section
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Colorblindness
Figure 14-13 Colorblindness
Section 14-2
Father (normal vision)
Normal vision
Colorblind
Male Female
Daughter (normal vision)
Son (normal vision)
Mother (carrier)
Daughter (carrier)
Son (colorblind)
Go to Section
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Hemophilia is a __________________________ in
which one is unable to clot their blood.   Also
known as   Hemophilia is caused by a defect in a
gene and the protein for normal blood clotting is
missing.  
recessive sex-linked disorder
bleeders disease.
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Royal Family and Hemophilia

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Muscular Dystrophy is another     Here the
affected individual inherits a degenerative
__________disorder.   The gene that codes for a
_____________ is defective. They rarely live
past early adulthood.   Treatments are being
explored that ___________ the defective gene.  
sex-linked recessive disease.
muscle
muscle protein
replace
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• III. X-Chromosomes Inactivation
• Males survive with only one X chromosome so, what
  do females do with 2? They ___________
• it becomes inactive. This creates a dense
  region in the nucleus known as a ______________.
• This is seen in coat color in cats. The cells
  will randomly shut off the coat color allele in
  one X chromosome and turn them off in the other X
  chromosome in other cells and this leads to some
  areas that are spotted orange and some spotted
  black, creating a tricolor cat, ________. This
  only happens in __________ because males only
  have one X chromosome.

shut one off
Barr body
calico
females
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• IV. Chromosomal Disorders
• Whole/sets of chromosome mutations
• _______________ failure of homologous
  chromosomes to separate normally during meiosis
• This results in a disorder of __________________
• 2. Examples of disorders include Downs Syndrome,
  Klinefelters, and Turners Syndrome

Nondisjunction
chromosome number
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Nondisjunction
Section 14-2
Homologous chromosomes fail to separate
Meiosis I Nondisjunction
Meiosis II
Go to Section
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Nondisjunction
Section 14-2
Homologous chromosomes fail to separate
Meiosis I Nondisjunction
Meiosis II
Go to Section
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Nondisjunction
Section 14-2
Go to Section
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Nondisjunction

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• 2. Examples of disorders include Downs Syndrome,
  Klinefelters, and Turners Syndrome
•  
• Nondisjunction disorders Disorders in which the
  failure of _____________________ during one of
  the stages of meiosis causes a gamete to have
  _______________________________.
•  
• Nondisjunction can occur in ______________________
  _____.

chromosome separation
too few or too many chromosomes
autosomes or sex chromosomes
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Downs Syndrome Downs syndrome is an example of
____________________________, specifically
chromosome 21. In Downs syndrome there is an
___________ of chromosome 21 (trisomy 21).
Doing a _____________ (display of all the
chromosomes in a cell nucleus) and looking at the
chromosomes under a microscope detect the extra
chromosome. Characteristics of Downs syndrome
include _________________, physically challenged,
facial irregularities, and often heart defects.
nondisjunction of an autosome
extra copy
karyotype
mental retardation
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Incidence of Downs Syndrome and mothers age

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Turners Syndrome Nondisjunction of the sex
chromosomes in which   They have the
chromosome makeup of _________ where O
represents the missing chromosome.
a chromosome is missing.
45 XO
This individual is female in appearance but does
not develop the female sex organs during puberty
and is ________.
sterile.
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Klinefelters Syndrome Nondisjunction of the
sex chromosomes in which an _____________________
is present.   They have the chromosome makeup
of ________. They are ___________ in appearance
and are also sterile. May also be 48 XXXY or 49
XXXXY
extra X chromosome
47XXY
male
No nondisjunctions of the sex chromosomes have
ever produced and survived without an
______________. This is because the X chromosome
carries many genes
X chromosome
essential for life.
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• XXY condition
• Results mainly from nondisjunction in mother
  (67)
• Phenotype is tall males
• Sterile or nearly so
• Feminized traits (sparse facial hair, somewhat
  enlarged breasts)
• Treated with testosterone injections

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Nondisjunction of Sex Chromosomes

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• The impact of the sex chromosome nondisjunction
  has led us to understand the importance of the
  _____________________ in determination of sex of
  an individual.
•  
• This has recently been determined to be true
  because the Y chromosome has been found to have a
  gene that turns on ______________________ in the
  embryo even if many X chromosomes are present. 

Y chromosome
male sexual development