Download Human Genes

Human Genetics Notes:
Human Chromosomes
Cell biologists analyze chromosomes by looking at ________________.
Cells are ___________________ during mitosis. Scientists then cut out the
chromosomes from the _________________ and group them together in
pairs.
A picture of chromosomes arranged in this way is known as a _____________.
Two of the 46 human chromosomes are known as ______________________,
because they determine an individual's _________.
 Females have _______ copies of an ________ chromosome.

Males have _______ _____ chromosome and _____ ____ chromosome.
The remaining __________chromosomes are known as autosomal
chromosomes, or _________________.
All human egg cells carry a single ______chromosome (____,___).
________of all sperm cells carry an X chromosome (____,___) and _______
carry a Y chromosome (____,___).
About _________of the ___________ will be 46,XX (__________) and half
will be 46,XY (_____________).
Males and females are born in a roughly _____:_____ ratio because of the way
in which sex chromosomes _______________during ______________.
Make a Sex Chromosome Punnett Square:
Human Traits
They have to study how the trait is passed from one generation to the next.
________________Charts
A ________________ chart shows the relationships within a ______________.
Label the pedigree to the
right. Show: male, female,
infected, marriage line,
childe line, and all genotypes
Genes
Some obvious human traits are almost impossible to associate with
_____________ genes.
Traits, such as the shape of your eyes or ears, are ______________, meaning
they are controlled by many genes.
Human Genes
The human genome includes tens of __________________ of genes.
In 2003, the DNA sequence of the ________________________ was published.
In a few cases, biologists were able to identify __________ that directly control a
_______________ human trait such as __________________.
Blood Group Genes
A ________________ of genes are responsible for human blood groups.
The best known are the _________blood groups and the ______ blood groups.
The ___________ blood group is determined by a single gene with two alleles—
____________ and _____________.
The positive (______) allele is ___________, so individuals who are __________
or ____________ are said to be Rh-positive.
Individuals with two _________ alleles are said to be Rh-negative.
ABO blood group
There are three alleles for this gene, ____, _____, and _____
Alleles IA and IB are _____________
Individuals with alleles IA and IB produce both A and B ____________, making
them blood type __________.
The i allele is ______________.
Individuals with alleles ______ or _______ produce only the A antigen, making
them blood type A.
Individuals with _________ or __________ alleles are type B.
Individuals who are __________________ for the i allele (____) produce no
____________ and are said to have blood type __________.
Fill in the table below:
Blood type
Genotype
Antigen
Present
Donate Blood
to
Receive Blood
from
A
B
AB
O
Recessive Alleles
The presence of a normal, functioning gene is _______________ only when an
abnormal or nonfunctioning allele affects the ________________.
Many disorders are caused by ___________________ alleles.
Examples:
Dominant Alleles
The effects of a dominant allele are ______________ even when the recessive
allele is present.
Examples of Autosomal Dominant Disorders:
Codominant Alleles
Sickle cell disease is a serious disorder caused by a _______________ allele.
Sickle cell is found in about _______ out of _______ African Americans.
In both cystic fibrosis and sickle cell disease, a ____________change in the
DNA of a _____________ affects the structure of a protein, causing a
serious genetic disorder.
Cystic Fibrosis
Cystic fibrosis is caused by a ________________ allele.
Sufferers of cystic fibrosis produce a thick, heavy mucus that clogs their
_________ and ____________ passageways.
Sickle Cell Disease
Sickle cell disease is a common genetic disorder found in _________________.
It is characterized by the _________ and __________ shape of the _______
blood cells.
___________________ is the protein in red blood cells that carries __________.
In the sickle cell allele, just __________________ is changed.
As a result, the _________________ hemoglobin is less soluble than normal
hemoglobin.
Low __________________ levels cause some red blood cells to become sickle
shaped.
People who are __________________for the sickle cell allele are generally
healthy and they are resistant to ________________.
Sex-Linked Genes
The X chromosome and the Y chromosomes determine ________.
Genes located on these chromosomes are called ______________________.
The Y chromosome is much ______________ than the X chromosome and
appears to contain only a few genes.
Why are sex linked disorders more common in males?
For a _________________ allele to be expressed in females, there must be
____ copies of the allele, one on each of the two X chromosomes.
Males have just ______ X chromosome. Thus, all X-linked alleles are
expressed in males, even if they are ______________.
Colorblindness
Three human genes associated with color vision are located on the ____-
chromosome.
In males, a defective version of any one of these genes produces colorblindness.
Make a Punnett square of a sex-linked cross: Normal male, heterozygous
mother.
Hemophilia
The X chromosome also carries genes that help control ________________. A
________________ allele in either of these two genes may produce hemophilia.
In hemophilia, a ________ necessary for normal __________________ is
missing.
Hemophiliacs can bleed to __________ from cuts and may suffer internal
bleeding if ____________.
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy is a _________________ disorder that results in
the weakening and loss of _______________ muscle.
It is caused by a defective version of the gene that codes for a ___________
____________.
X-Chromosome Inactivation
British geneticist Mary Lyon discovered that in female cells, ________________
is randomly switched _______.
This chromosome forms a dense region in the ____________ known as a
_________ body.
_________________ are generally not found in males because their single ____
chromosome is still active.
Other Chromosomal Errors:
The most common error in _____________ occurs when homologous
chromosomes fail to _________________.
This is known as ______________________, which means, “not coming apart.”
If ___________________occurs, abnormal ______________ of
chromosomes may find their way into gametes, and a disorder of
chromosome numbers may result.
Draw nondisjunction:
Down Syndrome
If _______copies of an __________________ chromosome fail to separate
during _______________, an individual may be born with ___________ copies
of a chromosome.
Down syndrome involves three copies of chromosome ________.
Down syndrome produces mild to severe _______________________.
It is characterized by:
• increased susceptibility to many _______________
• higher frequency of some _______________________
Sex Chromosome Disorders
In females, nondisjunction can lead to _________________ syndrome.
A female with Turner’s syndrome usually inherits only _________ chromosome
(karyotype ____,____).
Women with Turner’s syndrome are ______________.
In males, nondisjunction causes ______________ syndrome (karyotype
____,_______).
The extra _____ chromosome interferes with meiosis and usually prevents these
individuals from _____________.
Human DNA Analysis
There are roughly ____________________base pairs in your DNA.
Biologists search the human genome using sequences of DNA bases.
Genetic tests are available for hundreds of _________________.
DNA Fingerprinting
DNA fingerprinting analyzes sections of ____________ that have little or no
known ________________ but vary widely from one individual to another.
Only ________________________ are genetically identical.
DNA samples can be obtained from __________, _________, and _________
___________ with tissue at the base.
Chromosomes contain large amounts of DNA called ______________ that do
not code for _______________.
This DNA pattern ____________ from person to person.
_________________________ are used to cut the DNA into fragments
containing genes and repeats.
DNA fragments are separated using _____________________________.
Fragments containing repeats are labeled.
This produces a series of bands—the ________________________.