Name ______Test Date______
UNIT VIII - HUMAN INHERITANCE & GENETIC ENGINEERING
I. HUMAN GENETICS (pp. 270 - 271, 299 – 301)
A. Human Somatic Cells
Human somatic cells (______cells) are ______or 2n. Each human somatic cell has ______
chromosomes, or 23 pairs of chromosomes. Of these 23 pairs, 22 pairs are called ______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 XX; in a male’s somatic cells, the sex chromosomes are XY. All human
somatic cells contain 44 autosomes and 2 sex chromosomes.
B. Human Gametes
Gametes are ______or n, and contain ______chromosomes. Female gametes are ______cells, and male
gametes are ______cells. Gametes are produced through the process of ______in the ovaries or testes,
respectively. In meiosis, when the tetrad, or homologous pairs of chromosomes separate in ______,
the sex chromosomes separate also. The resulting egg cell can ONLY contain an X chromosome, while the sperm cell
produced has a 50% chance of containing an X, and a 50% chance of containing a Y. Therefore, the ______determines
the sex of the offspring.
C. Analyzing Human Inheritance
A pedigree is a diagram that follows the inheritance of a single gene through several generations of a family. In a pedigree,
males are represented by squares, and females are represented by circles. Individuals who are affected by the trait are
represented with shaded figures. Individuals that are not affected by the trait are shown by non-shaded figures. Vertical lines
connect parents and children. Horizontal lines connect siblings or spouses. Children are placed in birth order, from left to right.
The following pedigree shows the inheritance of a recessive trait.
1. How many generations are shown in this pedigree? ______
2. How many children did Parents I-I and I-II have? ______How many were boys? ______Girls?______
3. How many children did Parents II-I and II-II have? ______How many were boys? ______Girls?______
4. Key: R = non-affected; r = affected
5. Determine the genotypes of each person in this pedigree. Hint: label all homozygous recessives first!!!
II. NUMBER DISORDERS (pp. 311 - 315)
Number disorders occur because of a failure of a chromosome pair to separate correctly in ______
of meiosis. The most common type of failure is ______, which means chromosomes fail to separate.
Nondisjunction can occur during meiosis I, in which ______fail to separate or in meiosis II, in which
______fail to separate. In both cases, the gametes produced have an abnormal number of chromosomes.
**Number disorders are NOT inherited; therefore, they CANNOT be predicted with ______**
A. Karyotypes
A karyotype is a photograph of chromosome pairs. Cells from the developing embryo or individual being tested are cultured in a
nutrient growth medium. Then chemically treated to stop ______at ______. 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 sex chromosomes making up the 23rd pair. Karyotypes can only be
used to detect ______disorders and to determine ______of an unborn child. They do not
detect any other type of genetic abnormality; therefore, a normal karyotype does NOT guarantee a normal child!
B. Autosomal Number Disorders
Most autosomal number disorders are ______. The ONLY autosomal number disorder that allows survival into adulthood
is Down syndrome. Down syndrome is also known as Trisomy 21 because there are 3 chromosomes at the 21st position,
instead of 2. Individuals have characteristic facial features; growth, behavior, and mental development are all retarded. There is
also a higher risk of congenital heart defects. The incidence of babies with Down syndrome is much higher in older mothers.
C. Sex Chromosome Number Disorders
1. Turner Syndrome – Also called 45 XO because individuals lack a 2nd ______. Patients are females,
typically short in stature, underdeveloped sexually, sterile, with a normal life expectancy.
2. Klinefelter Syndrome – Also called 47XXY, because individuals inherit an extra sex chromosome. Symptoms do not
appear until puberty at which time affected males show poor sexual development and infertility. Treated with hormone
therapy. Normal life expectancy.
III. SEX-LINKED INHERITANCE (pp. 305 - 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 sexual development. Females have 2 X chromosomes; males have 1 X. Females will only show recessive traits
located on the X chromosome if they are homozygous recessive. But a male will always show a recessive trait located on the X
chromosome because he only has 1 X. This results in ______having a much higher incidence of sex-linked disorders.
Genotypes for sex-linked traits are written using the X and Y chromosomes to show path of inheritance. For example, red-green
color blindness is a sex-linked recessive trait. If C = normal vision and c = colorblindness, then a colorblind male = ______;
colorblind female = ______. Females can be ______for sex-linked recessive disorders. A carrier someone
who has the defective allele, but doesn’t ______. The genotype of a female carrier is ______.
Males CANNOT be carriers for a sex-linked trait because they only have one X chromosome.
A. Sex-linked Disorders – All of these disorders are sex-linked RECESSIVE.
1. Color Blindness – Inability to differentiate and distinguish colors; for example, red-green colorblindness
2. Hemophilia – Missing an enzyme required for normal blood clotting. Have uncontrolled bleeding episodes. Treated with
blood transfusions or Factor VIII injections.
3. Duchenne’s Muscular Dystrophy – Symptoms develop at 3-6 years of age. Causes muscle weakening and the breakdown
Of muscle fibers, leading to eventual death. There is no available treatment or cure. Death usually occurs before adulthood.
B. Sex-Linked Punnett Squares – In sex-linked traits, probabilities for male and female offspring must be calculated separately
because traits are inherited differently.
1. A colorblind female marries a man with normal vision. What is the probability of them having colorblind children?
Key: ______
Cross: ______
Probability of having a colorblind daughter = ______son=______
2. A genetics counselor interviews a couple with a family history of hemophilia to evaluate the possibility of having 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 having a daughter with hemophilia = ______
Probability of having a son with hemophilia = ______
IV. AUTOSOMAL DISORDERS (pp. 296 – 304)
Most genes are carried on the ______, 44 chromosomes other than the sex chromosomes. So it follows
that most genetic disorders are autosomal disorders. These disorders affect males and females equally. 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 the pigment, ______. Affected individuals lack coloration in skin,
hair, and eyes. Very susceptible to skin cancer. Symptoms appear at birth; they have a normal life expectancy.
2. Tay-Sachs Disease – Characterized by the inability of nerve cells to break down a specific type of lipid. Symptoms appear
between the ages of 3-6 months. Lipid build-up causes seizures, blindness, degeneration of mental & motor skills, and death
at or before age 5. Historically associated with Jewish population, although genetic testing has decreased its incidence.
3. Cystic Fibrosis – Characterized by excess mucus production in lungs & respiratory system. Symptoms appear just after
birth and include frequent respiratory infections, poor nutrition. With treatment, patients can survive to their 20’s & 30’s.
Cystic fibrosis is the most common ______genetic disorder in the US among Caucasians.
4. Phenylketonuria or PKU – Characterized by an inability to breakdown the amino acid, phenylalanine. Build-up results in
severe brain damage & mental retardation. All babies born in US hospitals are tested for PKU because it is easily treated
with a diet low in phenylalanine.
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. Individuals that are AA produce normal hemoglobin.
1. 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 RBC’s are more fragile, easily destroyed –
results in lack of energy due to decreased ______production in cells, blockage of blood vessels, and severe brain
damage. Shortened life expectancy (40’s). Most common inherited disease among African Americans.
2. 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 ______because they are resistant to ______. Malaria is a serious,
sometimes fatal disease spread by mosquitos that affects millions of people each year in Africa. 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 connective tissue of the skeletal system, eyes, and circulatory system.
Affected individuals have very long limbs, vision problems, and are susceptible to aortic rupture.
2. Huntington’s Disease – Fatal genetic disorder in which symptoms do not show until ______. Characterized by
deterioration of nervous system. Once symptoms begin, they are irreversible and ______- death usually results
within 10 – 25 years of onset of symptoms. Genetic testing is available, but controversial because of knowing that you have a
predetermined fatal condition. Individual that has the Huntington allele has at least a ______chance of passing it on to
the children and giving them the disorder.
3. Achondroplasia – dominant disorder that causes a mutation in growth, causes an abnormality in cartilage formation, severely
shortened bones. The disorder is fatal IF Individuals inherit ___ dominant alleles. Individuals with one dominant allele have little
treatment available. Ex of treatments include – hormone therapy, limb lengthening.
VI. The Human Genome Project
A ______ is an organism’s entire set of DNA.
Project began in1990; Completed in 2003; Coordinated by National Institutes of Health (NIH) & U.S. Department of Energy (DOE)
A. Goals of Human Genome Project (HGP)
1. ______and determining the sequence of the 3 billion base pairs in the human genome.
2. ______and identifying all genes in the human genome which there is about 30,000
3. ______information into databases that is accessible to the public
4. ______and addressing ethical, legal, & social issues involved in using this information
B. Benefits of the Human Genome Project
1. We have located many diseased ______and genetic tests have been created.
2. Researching bacteria genomes furthered research for ______and environmental clean-up.
3. Improved technology for ______forensic science
4. Other sequences completed for E. coli, yeast, simple round worm, fruit fly, rat & chimpanzee (model organisms for studying how
similar genes work in ______.)
C. DNA fingerprinting/Electrophoresis
Tool used by forensics scientists to identify a person using
______.
How it Works:
1. A sample of the person’s DNA is taken from blood, semen,
bone, or hair.
2. DNA fragments are cut - ______
enzymes cut DNA at specific sequences. Useful to divide DNA
into manageable fragments.
3. DNA fragments are separated based on______
and ______.
4. ______groups are negatively
charged.
5. DNA is placed into a gel & connected to an electric current
6. DNA (neg charged) moves through the gel toward + pole;
shortest lengths move the fastest & longest lengths move the
slowest.
7. A characteristic banding pattern is produced and a photograph is taken.
8. The banding pattern is ______for each
person, thus called a DNA ______.
D. How Cloning Occurs in Nature
1. Clone: an organism that is genetically
______to another organism.
a. All of the genes are the same (identical)
2. Examples of cloning that occur in nature:
a. Reproduction in bacteria & sponges (asexual)
b. Identical ______are natural clones.
E. What are Stem Cells? & Why Do Scientists Want Them?
Stem Cells are ______cells that
reproduce continuously and can develop into any type of
______or tissue.
The hope is to be able to produce ______
and ______for transplants.
Two types of stem cells:
a. ______Stem cells are most easily obtained
from embryos and umbilical cords. They are pluripotent.
b. ______Stem cells are found in bone marrow
and skin.
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