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Ch.14 The Human Genome
Sec. 2 Human Chromosomes
12
Biology
9th Grade
04/20/2010

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Term
sex-linked gene
Definition
gene located on the X or chromosome
Term
nondisjunction
Definition
error in meiosis in which homologous chromosomes fail to seperate
Term
*
Definition
Males have just one X chromosome. Thus, all X-linked alleles are expressed in males, even if they are ressecive
Term
**
Definition
If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result
Term
A Human diploid cell contains
Definition
more than 6 billion base pairs of DNA
Term
Smallest Human Autosomes?
Definition
21 and 22
Chromosome 21:43 million DNA base pairs
Chromosome 22:32 million DNA base pairs
Term
Many sex-linked genes are found on the
Definition
X chromosome
(more then 100 sex-linked disorders)
Term
Colorblindness
Definition
an inability to distinguish certain colors

Most common form: red-green colorblindness
Males
Term
Hemophilia
Definition
Two important genes carried on the X chromosome help control blood clotting
-occurs when a protein nessecary for blood clotting is missing.
Term
Duchenne Muscular Dystrophy
Definition
results in the progressive weakening and loss of skeletal muscle
--1/3000 males
Term
X-Chromosome Inactivation
Definition
In females one X chromosome is randomly switched off; The turned-off chromosome forms a dense region in the nucleus known as a Barr body.
Term
Barr body
Definition
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