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Dragonfly Chapter 14The Human Genome
Section 14-1: Human Heredity
Key Concepts: How is sex determined?
How do small changes in DNA Cause genetic disorders?
I. Human Chromosomes
A. Karyotype: A picture of chromosomes taken during mitosis, cut out and _______________
________________________.
B. Diploid cell: _____________ of homologous chromosomes
Human diploid cell has _____chromosomes arranged in _____ pairs
The 46 chromosomes contain __________________________________ of DNA
Mendelian genetics requires that organisms ____________________________ of a gene from
each parent.
In humans, __________________ (reproductive cells of egg and sperm) contain a single copy
of each gene (one set of genetic information).
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).
Humans have 46 total chromosomes
44 _________________
2 ____________________ (X and Y)
II. Human Traits
A. 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.
B. Genes and the Environment
Phenotypes are determined by _______________ as well as _________________ influenced.
Environmental influences on gene expression are ______________________ but genes are.
III. Human Genes
The __________________: Complete set of genetic information
Composed of about 30,000 genes
A. 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.
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 ___________ (-) doesn’t
contain the antigen. Positive is ______________ over negative.
Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/RhRh-negative is identified with one genotype: Rh-/RhABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is
classified into four types: _____________ due to the presence or absence of specific
_______________ in the blood.
Alleles IA and IB are codominant and io is recessive to both IA and IB
Antigens are ________________ used by the immune system. When an unrecognized
antigen is present an immune response takes place and the cells
____________________________.
Phenotype
(Blood Type)
Genotype
Antigen on
Red Blood
Cell
Safe Transfusions
To
From
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)
C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder
being present when __________________________.
Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s
Disease
Huntington Disease:
It is controlled by a _______________________. The gene is located on Chromosome #4
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.
Question? Would you want to know now if you could potentially get Huntington’s disease
when you are older? Would you want to know if you could pass the gene on to your
offspring before you have children?
D. Codominant Alleles: controlled by _______________________________________.
Sickle Cell Anemia is such a disorder.
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.
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
____________________________ ____________________.
It is caused by the _______________________ in the middle of a sequence for a protein
and causes the protein to be ______________ and doesn’t allow Chloride ions to transport
across the membrane, as they should. This causes the cells in a person’s airways to be
unable to transport chloride ions and become ______________________________.
B. Sickle Cell Anemia
The patient’s blood cells are 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 sickle–
shaped, causing the blood hemoglobin to no longer carry oxygen as well and
_____________________
___________________________. 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.
The genetics: The allele for sickle cell (HS) is codominant with the allele for normal
hemoglobin (HA).
Heterozygotes (HS HA) are said to be ________________________ and have some
effects of the disorder because they have both normal and sickle cell blood hemoglobin.
The distribution: Sickle Cell anemia is most prevalent in people of __________descent.
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.
(See figure 14-10 p. 348)
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.
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?
I. Human Genes and Chromosomes
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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.
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.
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
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
4. In some animals such as birds, butterflies, and some fish, the female determines
the sex because she has the ______________ chromosomes.
B. Sex-linked Genes
1. In addition to determining the sex of an individual, the sex
chromosomes carry genes that __________________________.
May be on the X or Y chromosome, ________________________________________
_____________________________________________________
Most often seen in _____________ because they only have one X chromosome and
thus all alleles are expressed even if they are recessive.
Colorblindness is a recessive disorder in which people can’t distinguish between
certain colors. _________________ colorblindness is most common.
XC and Xc are ________________ for normal and colorblind vision.
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 __________________ and
Xc Y is a _________________.
Hemophilia is a _________________________ in which one is unable to clot their
blood.
Also known as ____________________. Individuals with hemophilia can bleed to
death from minor cuts and may suffer internal bleeding from a bruise.
Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is
missing.
Muscular Dystrophy is another ____________________________.
Here the affected individual inherits a degenerative _________________disorder. In
which there is a progressive weakening and loss of skeletal muscle.
The gene that codes for a _________________ is defective. They rarely live past early
adulthood.
Treatments are being explored that _________the defective gene.
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.
IV. Chromosomal Disorders
Whole/sets of chromosomes mutations
1. _________________ = failure of homologous chromosomes to separate normally during
meiosis.
This results in a disorder of chromosome numbers.
Homologous
chromosomes fail
to separate
Meiosis I:
Nondisjunction
Meiosis II
2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s 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 _________________________________.
Down’s Syndrome: Down’s syndrome is an example of _____________________________,
specifically chromosome 21.
In Down’s 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 Down’s syndrome include _________________, physically challenged,
facial irregularities, and often heart defects.
Turners Syndrome: Nondisjunction of the sex chromosomes in which __________________
______________.
They have the chromosome makeup of ________ where O represents the missing
chromosome.
This individual is female in appearance but does not develop the female sex organs during
puberty and is ____________.
Klinefelter’s Syndrome: Nondisjunction of the sex chromosomes in which an extra ____
____________________ is present.
They have the chromosome makeup of ___________. They are _________ in appearance
and are also sterile. May also be 48 XXXY or 49 XXXXY
No nondisjunctions of the sex chromosomes have ever produced and survived without an ___
________________. This is because the X chromosome carries many genes _____________
____________
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.