Transcript Human Heredity and Disorders

Human Heredity
• Humans have 46
chromosomes
– 22 pairs of Autosomes
(body cells)
– 1 pair of Sex chromosomes
(XX or XY)
• Chromosomes can be cut up
and arranged in a Karyotype.
– Females are XX
– Males are XY
• There is a 50% chance of
having a boy or 50% chance of
having a girl.
• Humans with more or less
than 46 chromosomes tend to
have serious disorders.
– Called chromosomal disorders
What is a Karyotype?
• A cell is
photographed in
mitosis when
chromosomes are
fully condensed and
easier to see.
• They are cut from
photographs and
arranged into pairs.
• This is called a
karyotype.
Chromosomal Disorders
http://www.mtholyoke.edu/courses/rfink/Video
pages/video8.htm
http://www.biostudio.com/d_%20Meiotic%20N
ondisjunction%20Meiosis%20I.htm
• Due to a failure in
meiosis,
homologous
chromosomes will
fail to separate
properly.
• Called
Nondisjunction.
• Therefore,
abnormal (+ or -)
numbers of
chromosomes will
end up in the
gametes.
•
Chromosomal
Disorders
http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html
• Disorders can be within the chromosome as well:
– Deletion - a portion of one chromosome is
lost during cell division.
• Example: Cri Du Chat
– Duplication – if the fragment joins the
homologous chromosome, then that region is
repeated.
• Example: Fragile X
– Inversion – if part of a fragment flips 180
degrees on the same chromosome.
• Example: Hemophilia A
– Translocation –a fragment of a chromosome
is moved ("trans-located") from one
chromosome to another and joins a nonhomologous chromosome.
• Example: Acute Myelogenous Leukemia
Diseases/Disorders you should
know!
• Chromosomal Disorders
– Down Syndrome or Trisomy 21 (47,+21) –birth
defects, mild to severe mental retardation,
deformed facial features (1:800 babies)
– Turner’s Syndrome (45,X0) – Sterile, sex organs
do not develop at puberty (1:2500 females)
– Klinefelter’s Syndrome (47,XXY) – sterile, subject
tends to have both stunted male yet feminine
features (1:750 males)
• Note: A single Y will cause male development
Down Syndrome (Trisomy 21)
http://www.ndss.org/index.php?option=com_conte
nt&view=article&id=59&Itemid=76
Turner’s Syndrome
http://vodpod.com/watch/
74840-turners-syndrome
Klinefelter’s Syndrome
http://www.nichd.nih.gov/health/topic
s/klinefelter_syndrome.cfm
Diseases/Disorders you should
know!
• Recessive Disorders: Autosomal
– Cystic Fibrosis –Mucus clogs airways and ducts in lungs,
and other organs. Life expectancy is 30 years. (1:3500)
– Albinism –lack of pigment (melanin) in skin, hair, eyes,
extremes case deafness. (1:17000)
– Phenylketonuria (PKU) –missing the enzyme to process
the amino acid phenylalanine, builds in the body and causes
mental retardation. (1:15000)
• Very easily treatable with dietary restrictions.
– Tay-Sachs disease –Lipid accumulation in the brain due to
abnormal lysosomes. Causes mental retardation, blindness,
early death before age 5. (1:5000) where (1:300 carrier)
• Occurs mainly in eastern European Jews (1:27 carrier)
Cystic Fibrosis
http://www.ygyh.org/cf/whatisit.htm
Albinism
PKU
Tay-Sachs
Diseases/Disorders you should
know!
• Recessive Disorders: Sex-linked
– Colorblindness – the disability to perceive colors in the
cones of the eyes. red/green (1:10 males) & (1:100
females)
– Hemophilia – blood fails to clot after injury (1:10000 males)
• Hemophilia figured prominently in the history of European royalty in the 19th
and 20th centuries. Queen Victoria, through two of her five daughters passed
the mutation to various royal houses across the continent, including the royal
families of Spain, Germany and Russia. Victoria's son Leopold suffered from
the disease. For this reason, hemophilia was once popularly called "the royal
disease".
– Duchenne Muscular Dystrophy –weakening and loss of
skeletal tissue (1:3500 boys)
Colorblindness
Interactive Colorblindness Test:
http://micro.magnet.fsu.edu/primer/java/humanvi
sion/colorblindness/index.html
Hemophilia
Duchenne Muscular Dystrophy
Muscles are made up of bundles of
fibers (cells). A group of
interdependent proteins along the
membrane surrounding each fiber
helps to keep muscle cells working
properly. When one of these proteins,
dystrophin, is absent, the result is
Duchenne muscular dystrophy; poor
or inadequate dystrophin results in
Becker muscular dystrophy.
Diseases/Disorders you should
know!
• Dominant Disorders: Autosomal
– Achondroplasia – A genetic form of Dwarfism (1:30000)
– Huntington’s Disease –A wasting away of brain tissue,
causes uncontrolled movements, emotional disturbances
and mental deterioration. Is fatal (8:100000)
• Huge problem in passing to children without even knowing! Tested
for often.
• CoDominant Disorders: Autosomal
– Sickle Cell Anemia – Misshapen red blood cells due to a
mutation in hemoglobin, the protein that carries oxygen in
the blood. Causes pain and damage to tissues (72,000 US,
1:500 African-American births, 1:1200 Hispanic births)
• Heterozygous condition: malaria immunity
Achrondroplasia
Huntington’s
Disease
Sickle Cell
Anemia