GENETIC DISORDERS

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GENETIC DISORDERS
SENIOR LEVEL BIOLOGY SBI OA
2
2N
Diploid
4N
Double diploid
MITOSIS
Diploid
2N
2N
4N
4N
Double diploid
2N
2N
2N
2N
Diploid cells repeat the cell cycle.
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46 Single stranded
2N
Interphase (S) -Double diploid
4N
46 Double stranded
MEIOSIS
Meiosis I Reductive Division
2N
2N
23 Single stranded
Meiosis II
Meiosis II
1N
1N
1N
1N
23 Single stranded - Haploid gametes
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The genetic past...
The embryo(s) was contained within the male
gamete Umbilical cord was part of the
flagellum The womans role was one of incubator,
and her traits could be passed to the embryo
through her blood.
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HEREDITARY DISORDERS (nature) - genetic
abnormalities caused by recombination
aneuploidy, sex-linked, nondisjunction
CONGENITAL DEFECTS (nurture) - abnormalities
caused by embryonic and/or developmental
anomalies cleft lip/palate, conjoined, fetal
alcohol syndrome
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ALBINISM
Autosomal recessive
Lack of melanin pigment
Panamanian tribe Moon children
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CHROMOSOME DELETION Chromosome 2 - short arm
Physical challenges Limited mental
development Decreased vision acuity Most
chromosome deletions result in spontaneously
aborted pregnancies
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DERMATISIS IMPERFECTA
Autosomal recessive Reduced enamel - tooth and
gum disease
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SEX CHROMOSOME ABNORMALITIES
XY Genotypic male XX Genotypic female XO Turners
Syndrome - nondisjunction XXY Klinefelters
Syndrome - nondisjunction XYY Super male -
nondisjunction
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TURNERS SYNDROME XO
Two sets of autosomes but only one sex
chromosome 97 spontaneous abortions Female -
short and sexually undeveloped (infertile) Webbing
of the neck Wide chest with broadly spaced
nipples Narrowing of the aorta
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KLINEFELTERS SYNDROME XXY
Phenotype is not strikingly different form XY and
not apparent until after puberty Extremities are
longer 50 develop breasts Body hair is sparse
(female pattern) Somewhat mentally
disadvantaged Nondisjunction oogenesis (XX Y)
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XXXXY - A rare form of Klinefelters Pentasomy 2N
3 (autosomal lethal)
Polyploidy Mental deficiency Facial
abnormalities Genital abnormalities
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POLYPLOIDY - Semilethal Mosaic of two cell types
- tetraploid (XXYY) and diploid (XY)
The child died at nine months.
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TETRAPLOID Cranial bone abnormalities, ocular
anomalies facial clefts Enlarged
placenta Spleen, heart, kidneys, adrenal glands,
brain anamolies
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Aneuploidy One to a few chromosomes are lost or
added to a normal set or nondisjunction
(irregular distribution of sister chromatids
(mitosis) or homologues (meiosis)
Nullisomy - loss of one homologous pair 2N - 2
Monosomy - loss of a single chromosome 2N - 1
Trisomy - single extra chromosome three copies
of one chromosome type 2N 1
Tetrasomy - an extra pair four copies of
one chromosome pair 2N 2
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Trisomy 21 Downs Syndrome
Trisomy - single extra chromosome three copies
of one chromosome type 2N 1
Low IQ (variable) Epicanthal folds over
eyes Short - broad hands with the simian line
across the palms Below-average height
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HAIRY PINNA
Abnormal amounts of hair grow out from the ear
canal
Y - linked gene (uncertain)
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ICHTHYOSIS CONGENITA
Brittle, leathery skin with deep bleeding
fissures A recessive lethal allele with no
obvious heterozygous phenotype. Similar in
transmission to Tay-Sachs and Cystic fibrosis
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Elephant Man - John Merrick - London Hospital
1886
NEUROFIBROMYLEYIS - von Recklinghausen
disease Tumours in the central and peripheral
nevous system Variable expressivity - degree of
phenotype varies
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MARFAN SYNDROME A dominant collagen
disorder Affects eyes, CV system, and the
musculoskeletal system The silent killer
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SEX - LINKED DISORDERS HEMOPHILIA The Royal
Disease
Colour blindness
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BI-LATERAL CLEFT LIP AND CLEFT PALATE
Perhaps environmental...??? Studies continue
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CONJOINED TWINS An improper division of cells
thought to occur embryonically somewhere between
morula to blastula stage
An environmental component?
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Science rules!
In a biological context, it is often asked Why
do things go wrong? After reviewing genetics and
some of the anamolies associted with genetics,
perhaps a better question to pose is How does
anything possibly go right? But it does. Every
day, the planet bears witness to millions of
successful recombinations and nature continues to
defy the odds.
P.S. I love my dad.
THE END... cs