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UNIT 11 – THE HUMAN GENOME
I. HUMAN GENETICS
(pp. 341-343)
A. Human Somatic Cells
Human somatic cells (_______ cells) are ________________ or ______. Each cell contains ______ chromosomes,
or ______ pairs of chromosomes. Of these pairs of chromosomes, _____ pairs are ___________________ pairs,
meaning they contain the same genes in the same order. The 44 chromosomes that make up the 22 homologous
pairs in each cell are called ____________________. The 23rd pair of chromosomes are the ________
chromosomes. In female somatic cells, the sex chromosomes are _____; in a male’s cells, the sex chromosomes
are ______.
B. Human Gametes
Gametes are ______________, or _______, and contain ________ chromosomes. Female gametes are _______
cells and male gametes are _____________cells. Gametes are produced through the process of _____________
in the _______________ or ______________, respectively. In meiosis, when the _________________ pairs of
chromosomes separate in __________________, the sex chromosomes separate also. The resulting egg cell can
only contain an _______ chromosome, while the sperm cell produced has a ______% chance of containing a
_______ and a ______% chance of containing an _______. Therefore, the __________ determines the sex of the
offspring.
C. Analyzing Human Chromosome Numbers
1. Nondisjunction - Abnormal numbers of chromosomes in ________________________ result in genetic
disorders called ____________________________________. This must often is a result of
___________________________, which means __________________________________________.
In nondisjunction, a chromosome pair fails to separate correctly in __________________ so the
gametes produced have an abnormal __________________________. Number disorders are not
inherited; therefore, they cannot be predicted with ___________________________.
2. Karyotypes - A karyotype is a photograph of ______________________________________.
Cells from the developing embryo or individual being tested are cultured in a nutrient growth medium, then
chemically treated to stop ____________________. The cells are stained, the chromosomes photographed, and
the photograph is enlarged. The chromosomes are cut out and arranged in _______________ pairs in size order,
with the _______ chromosomes making up the 23rd pair. Karyotypes can only be used to detect _____________
disorders and to determine the _________________ of an unborn child. They do not detect abnormal
__________; therefore, a normal karyotype does not guarantee a ______________ child!
II. HUMAN GENETIC DISORDERS – NUMBER DISORDERS
(pp. 352, 353)
A. Autosomal Number Disorders
Most autosomal number disorders are ____________. The only autosomal number disorder that allows
survival into adulthood is ___________________________.
Down syndrome is also known as _______________________ because there are _________ chromosomes at
the ____________ position, instead of _______. Individuals have characteristic facial features; growth, behavior,
and mental development are all affected. There is also a higher risk of ___________________ heart defects. The
incidence of babies with Down syndrome is much higher in ____________ mothers.
B. Sex Chromosome Number Disorders
1. Turner Syndrome
Also called ___________ because individuals lack _______________________________. Patients are
________________, typically __________ in stature, underdeveloped sexually, ______________, with a
normal life expectancy.
2. Klinefelter Syndrome
Also called _____________. Symptoms do not appear until ______________ at which time affected _________
show poor sexual development and infertility. Treated with __________________. Normal life expectancy.
III. ANALYSIS OF HUMAN INHERITANCE
A. Punnett Squares & Multiple Alleles (pp. 345-346)
Most genes follow Mendel’s basic principles of 2 alleles in which one is dominant and the other, recessive.
There are some genes that have multiple alleles; that is, _____________________ alleles. An example
of this is ABO blood groups. There are _________ alleles for this gene. Two of the alleles, ________
and ________ are co-dominant, meaning ______________________________________________ if
present. The third allele, ________, is recessive, meaning it will only show if the genotype is _______.
Each individual inherits ________ alleles for this gene, one from _________ and one from _________.
The possibilities for blood group genotypes and phenotypes are:
Phenotype
Type A blood
Genotype
Type B blood
Type AB blood
Type O blood
1. A couple preparing for marriage have their blood typed. Both are AB. They ask you what types of
blood their children may have. What would you tell them?
Cross: __________________________________
Phenotype Ratio: ________________________________________
2. An old, rich couple die in an accident. Soon a man shows up to claim their fortune, saying he is the
long-lost son who ran away with a circus as a boy. Other relatives say he is lying. Hospital records
show the couple'’ blood types were AB and O. The claimant is O.
Cross: __________________________________
Is he an imposter? _______________
B. Pedigrees
A pedigree is a diagram that follows the inheritance of a single _________ through several ___________________
of a family. In a pedigree, males are represented by ______________ and females, by __________________.
Individuals with the trait are represented with ___________ figures. Individuals shown with unshaded figures
_________________________________. Vertical lines connect ____________ and ___________. Horizontal
lines connect ____________ or ___________________. Children are placed in ________________________,
from _____________ to _______________.
1. The following pedigree shows the inheritance of a recessive trait.
a.
b.
c.
d.
e.
How many generations are shown in this pedigree? _______________
How many children did Parents I1 and I2 have? ________ How many boys? _______ Girls? ________
How many children did Parents II1 and II2 have? ________ How many boys? _______ Girls? ________
Key: _______________________________________________________________________
To solve a pedigree: Label all ________________________________________________ first!
2. Determine the genotype of all individuals in this pedigree showing the inheritance of red hair, a recessive
trait.
Key: ___________________________________________________________________
3. Determine the genotype of all individuals in the following pedigree showing the inheritance of a dominant
trait.
Key: __________________________________________________________________
IV. INHERITED HUMAN GENETIC DISORDERS
A. Gene Mutations
Inherited human genetic disorders are the result of gene mutations; that is, _______________________________
____________________________________________________.
B. Types of Inherited Genetic Disorders
1. Sex-Linked Disorders – Mutated gene is on the _______ chromosome.
2. Autosomal Genetic Disorders – Gene mutation is on any chromosome other than ______________________
V. GENETIC DISORDERS - SEX-LINKED DISORDERS
A. Sex-Linked Inheritance (pp.350, 351)
A gene is referred to as “sex-linked” if it is located on a sex chromosome (_____ or _____). In humans,
sex-linked genes are almost always located on the larger ________ chromosome. The _____ chromosome is
much smaller and carries only a few genes related to ____________________________. Females have ______ X
chromosomes; males have __________. Females will only show recessive traits located on the X chromosome if
they are __________________________________. But a male will always show a recessive trait located on the
X chromosome because he only has _____ X chromosome, so all _________ on the X chromosome will show.
This results in _______________ having a much higher incidence of sex-linked disorders.
1. Genotypes for sex-linked traits are written using the X and Y chromosomes to show path of inheritance. For
example, male-pattern baldness is a sex-linked recessive trait. If H = normal head of hair and h = baldness,
bald male = ___________; bald female = __________. Females can be __________________ for sex-linked
recessive disorders. A carrier has the defective allele, but ____________________________________. The
genotype of a female carrier is _________________. Males __________________ be carriers for sex-linked
traits because their 2nd sex chromosome is the __________________________!
2. Sex-Linked Punnett Squares – In sex-linked traits, probabilities for male and female offspring must be
calculated separately because traits are ___________________________.
If a man with a full head of hair marries a woman who is heterozygous, what is the probability they would have a
son who would go bald? A daughter?
Key: ______________________________________
Cross: _____________________________________
Probability of bald daughter = ________________
Probability of bald son = ____________________
B. Sex-Linked Disorders – All of these disorders are sex-linked ___________________.
1. Color Blindness – Inability to differentiate and distinguish ___________________.
2. Hemophilia – Missing an enzyme required for normal __________________________ - results in
_______________________________. Treated with blood transfusions, injections of missing factor.
3. Duchenne’s Muscular Dystrophy – Symptoms develop at ____________________. Muscles
_____________________________________________, leading to eventual death. No available
_______________________ or _____________. Death usually occurs before adulthood.
C. Examples
1. A colorblind female marries a man with normal vision. What is the probability of colorblind children?
Key: ______________________________________
Cross: _____________________________________
Probability of colorblind daughter = ____________ Probability of colorblind son = ____________
2. A genetics counselor interviews a couple with a family history of hemophilia to evaluate the possibility
of offspring with the disorder. The woman does not have hemophilia, but states that her father had
the disorder. The man is normal.
Key: ___________________________________________
Cross: ___________________________________
Probability of daughter with hemophilia = ___________
Probability of son with hemophilia = __________
3. The following pedigree shows the path of inheritance of hemophilia through several generations. Identify the
genotypes of each individual.
Key: ________________________________________________________________
VI. GENETIC DISORDERS - AUTOSOMAL DISORDERS
(pp. 345-348)
Most genes are carried on the _________________________, ______ chromosomes other than the sex
chromosomes. So it follows that most genetic disorders are ________________ disorders. These disorders
affect males and females _________________ and are due to _________ mutations. Autosomal disorders
can be divided into three groups based on the pattern of inheritance.
A. Autosomal Recessive Disorders
1. Albinism – Characterized by failure to produce pigment, _______________. Affected individuals lack
coloration in _________, ___________, and ______________. Very susceptible to ______________.
Symptoms appear ________________________; _________________ life expectancy.
2. Tay-Sachs Disease – Characterized by inability of _________ cells to break down a specific type of
__________. Symptoms appear __________________________. Lipid build-up causes seizures,
blindness, degeneration of mental & motor skills, and death at __________. Historically associated
with _______________ population, although genetic ____________ has decreased its incidence.
3. Cystic Fibrosis – Characterized by excess _______________________________ in _________,
_________________ system. Symptoms appear just after birth and include frequent respiratory
infections, poor nutrition. With treatment, patients can survive to young adulthood. Cystic fibrosis is
the most common ___________ genetic disorder in the __________________________ among
Caucasians.
4. Phenylketonuria or ________ - Characterized by an inability to breakdown the amino acid,
________________________. Build-up results in severe mental retardation. All babies born in US
hospitals are tested for PKU because it is easily treated with a diet low in _________________.
B. Autosomal Co-Dominant Disorders
Sickle cell anemia is an autosomal co-dominant disorder that affects _________________ production.
Hemoglobin is the protein that binds _____________________ to red blood cells.
1. Individuals with the normal genotype, AA, do not have the sickle cell allele and produce only normal
hemoglobin.
2. Individuals that are SS produce abnormal hemoglobin that causes the red blood cells to “sickle” when
oxygen availability is decreased; for example, in high altitudes or during periods of stress. Sickled
RBCs are more fragile, easily destroyed – results in lack of ______________ due to decreased
__________ production in cells, blockage of blood vessels, and severe pain. Shortened life
expectancy. Most common inherited disease in individuals of _____________ ancestry.
3. Heterozygotes (AS) produce both normal and abnormal hemoglobin and are said to have
__________________________________. They do not show symptoms of the disorder. In certain
areas, individuals with sickle cell trait have a benefit over individuals that lack the sickle cell allele
because they are resistant to __________________. Malaria is a serious, sometimes fatal disease
spread by ______________ that affects millions of people each year in _____________. This
increased malarial resistance has resulted in a very high incidence of AS individuals. If two
heterozygotes marry and have children, they have a _________% chance of having a child with sickle
cell anemia.
C. Autosomal Dominant Disorders
1. Marfan Syndrome – Dominant disorder that affects the ___________________ tissue of the
_____________ system, eyes, and _________________ system. Affected individuals have very long
limbs, vision problems, and are susceptible to ______________ rupture.
2. Huntington’s Disease – Fatal genetic disorder in which symptoms do not show until _____________.
Characterized by deterioration of _______________________.
3. Achondroplasia - ______________________