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UNIT 8 – THE HUMAN GENOME
I. HUMAN GENETICS
(pp. 311-315)
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
__________________________________________. Nondisjunction may occur in:
 ___________________________ if ____________________________________________ do not separate correctly
 ___________________________ if _____________________________________ do not separate correctly
In either case, ______________________ are produced with an abnormal number of chromosomes.
2. Karyotypes - A karyotype is a photograph of ______________________________________.
Cells from the developing embryo or individual being tested are cultured, and treated to stop ___________________ in
__________________. 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 normal child!
II. HUMAN GENETIC DISORDERS – NUMBER DISORDERS
A. Autosomal Number Disorders
Most autosomal number disorders are ____________. The only autosomal number disorder that allows survival into adulthood 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. Higher risk of
___________________ heart defects.
 Incidence of babies with Down syndrome is much higher in ____________ mothers.
B. Sex Chromosome Number Disorders
1. Turner Syndrome
 Also called ___________ because individuals lack __________________________.
 Affected individuals are ________________, typically short 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. 304)
A multiple alleles gene has _____________________ possible alleles. An example of this is ABO blood groups. There are
_________ alleles for this gene.
 _______ and _______ are co-dominant, meaning _________________________________ if present.
 ________ is recessive, meaning it will only show if the genotype is _______.
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 (299-301)
A pedigree is a diagram that follows the inheritance of a single _________ through several ___________________ of a family.
 Males are represented by ______________ and females, by __________________.
 Individuals with the trait are represented with ___________ 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.307-308)
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.
 Male-pattern baldness is a sex-linked recessive trait. If H = normal head of hair and h = baldness,
o Bald male = ___________
o Bald female = __________
 Females can be __________________ for sex-linked recessive disorders. A carrier has the defective allele, but
____________________________________.
o The genotype of a female carrier is _________________.
o Males __________________ be carriers for sex-linked traits because their 2nd sex chromosome is the
__________________________!
2. Sex-Linked Punnett Squares
A man with a full head of hair marries a woman who is heterozygous. If they have a son, 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
 Muscles gradually weaken leading to eventual death.
 No available treatment or cure; 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
More common that sex-linked disorders because ___________________________________________. These disorders
affect males and females _________________ . Autosomal disorders can be divided into three groups based on the pattern of
inheritance.
A. Autosomal Recessive Disorders (296-298)
1. Albinism
 Characterized by failure to produce pigment, _______________.
 Very susceptible to ______________.
2. Cystic Fibrosis
 Characterized by excess _______________________________ in _________, _________________ system.
 Symptoms appear just after birth and include frequent respiratory infections, poor nutrition.
 With treatment, patients can survive into adulthood.
 Most common ___________ genetic disorder in the __________________________ among Caucasians.
3. Phenylketonuria or ________
 Characterized by an inability to breakdown the amino acid, ________________________.
 If untreated, 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 (303)
Sickle cell anemia is an autosomal co-dominant disorder that affects _________________ production. Hemoglobin is the protein
that binds _____________________ to red blood cells.
1. AA
 Individuals with the normal genotype do not have the sickle cell allele and produce only normal hemoglobin.
2. SS
 Sickle Cell Anemia
 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. AS
 Described as _______________________________
 Produce both normal and abnormal hemoglobin
 Do not typically show symptoms of the disorder.
 Heterozygote Advantage – Provides resistance to ___________________.
C. Autosomal Dominant Disorders (298)
1. Huntington’s Disease
 Fatal genetic disorder in which symptoms do not show until _____________.
 Characterized by deterioration of _______________________.
2. Achondroplasia - ______________________