Unformatted text preview: te Americans Tay Sachs (Chr. 15, rec.) Missing enzyme resulting in build up of
Missing
fatty deposits in the brain, MR
fatty 1/3300 E. Eur. Jews Phenylketonuria (PKU) (Chr. 12, rec.) Defective phenylalanine hydroxylase,
Defective
blocks conversion of phenylalanine to
tyrosine, MR
tyrosine, 1/10,000 White Americans Galactosemia (Chr.9, rec.) Deficiency in galactose-1-phosphate
Deficiency
uridyltransferase (GALT) leading to
galactose build-up, MR
galactose 1/80,000 Albinism (Chr. 11, rec.) Defective tyrosinase blocks conversion of
Defective
tyrosine to DOPA in the pathway to melanin
in eyes, hair and skin
in 1/10,000 in Northern Ireland Hypercholesterolemia (Chr. 19, dom.) Missing protein that causes cholesterol
Missing
buildup, early heart attacks
buildup, 1/122 French Canadians Huntington disease (Chr. 4, dom.) Progress mental and neurological
Damage and disorders by 40 1/25,000 White Americans BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 22 The X-Chromosome X chromosome sequenced
chromosome
and reported in Nature on
March 17, 2005. 1098
genes.
genes. Y chromosome sequenced
chromosome
and reported in Nature on
June 19, 2003. 78 genes.
June BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 23 X-Linked Inheritance Examples of X-Linked Disease in Humans
Disease
Anhidrotic ectodermal
dysplasia (recessive)
Duchenne muscular
distrophy (recessive)
Fragile-X Syndrome
(recessive)
Familial Hypophosatemia
(dominant)
Hemophilia A and B
(recessive)
Testicular Feminization
(recessive) Frequency Symptom 7 in 10,000 No sweat glands 1 in 3000 or 4000 Muscular wastage in
teenage years 1 in 1000 Mental retardation 1 in 20,000 vitamin D resistant rickets 1 in 10,000
1 in 65,000 male births Lack of blood clotting
after trauma
Lack of androgen
receptors in males BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 24 Y-Linked Inheritance There seem to be few genes that have been linked
There
to the human Y chromosome. Testis determining
factor “TDF” and “Hairy ear” are two examples.
“TDF” BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 25 Pedigree Analysis Because humans can not be bred like fruit flies,
Because
mice and flowers, geneticists must resort to
analyzing the descendants of the affected individual
to determine the genetic basis of certain traits and
diseases.
Over the years, geneticists and genetic counselors
Over
have developed symbols and a list of common
characteristics of X-linked traits used for pedigree
analysis. These symbols are shown on page 51 of
your text and on handout accompanying this lecture.
your BIS101001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BI...
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