Transcript Cure/Treatment

Human
Heredity
Chapter 11.1 & 11.3
RECESSIVE GENETIC DISORDERS
• may be passed on to children without “knowing”
• both parents are CARRIERS of recessive alleles – Aa x Aa
• passed like any recessive trait – offspring must get
recessive allele from mother + father – aa
Cystic Fibrosis (CF)
Albinism
Galactosemia
Tay Sachs
Primordial Dwarfism
Phenylketonuria (PKU)
Xeroderma Pigmentosum (XP)
CYSTIC FIBROSIS (CF)
– affects the mucus producing glands, digestive enzymes and sweat glands
Cause:
• recessive allele that is defective
Effects:
• excessive mucus production
• respiratory system is compromised; high risk of infection
• digestive and respiratory system failure
• life expectancy 36.8 years
Cure/Treatement:
• no cure
• daily breathing treatments
• mucus-thinning drugs
• pancreatic enzyme supplements
Cystic Fibrosis - http://www.youtube.com/watch?v=PjoE-yzyDNk
ALBINISM
– partial or total lack of pigment (melanin)
in hair, skin and eyes
Cause:
• recessive allele that is defective
Effects :
• do not produce normal amounts of melanin
• skin susceptible to UV damage
• higher risk of skin cancer and eye damage
• occurs in humans and other mammals
Cure/Treatment:
• no cure
• protect eyes and skin from sun
GALACTOSEMIA
– an inability to digest galactose (milk sugar)
Cause:
• recessive allele that is defective
• lack of enzyme that breaks down galactose
Effects :
• enlarged liver and kidney failure
• galactose builds up in the cells and becomes toxic
• usually causes no symptoms at birth
• if not detected immediately results in liver disease, mental retardation and
death
Cure/Treatment:
• no cure
• children diagnosed early can have a normal, healthy life
• treatment is the restriction of galactose and lactose from the diet
TAY-SACHS DISEASE
– an inability to break down fatty acids:
only affects people of Jewish descent
Cause:
• recessive allele that is defective
• lack of enzyme
that breaks down fatty substances
Effects
• inability to break down fatty acids
• fatty deposits build up in the brain
• brain cells deteriorate
• mental capacity is diminished
• death by age 5
Cure/Treatment
• no cure or treatment
Xeroderma Pigmentosum (XP)
• recessive genetic disorder
• inability to repair damage caused by UV light
• in extreme cases, all exposure to sunlight must be forbidden, no matter how
small
• individuals with the disease are often referred to as Children of the Night
• suffer from basal cell carcinomas and other skin malignancies (such as
malignant melanoma and squamous cell carcinoma)
Primordial Dwarfism
• form of dwarfism that results in a smaller body size in all
stages of life beginning from before birth
• proportionate dwarfism, in which individuals are
extremely small for their age, even as a fetus
• caused by inheriting a mutant gene from each parent
Kenadie - born February 13, 2003
2 lbs 8oz and 11 inches long
Phenylketonuria (PKU)
• Caused by a mutation in the gene for a liver enzyme called PAH
• this enzyme is necessary to metabolize the amino acid phenylalanine
Effects of untreated PKU…
• children normal at birth but fail to attain early developmental milestones
• microcephaly, progressive impairment of mental function seizures, learning
disabilities nd other serious medical problems,
Cure/Treatment of PKU…
• there is no cure
• treatment with restricted diet supplemented by amino acids and other nutrients
• PKU is commonly included in newborn screenings performed just after birth
Dominant Genetic Disorders
• one dominant allele (AA or Aa) to inherit the disorder
• NO CARRIERS
• either you have the disorder or you don’t
Huntington’s Disease
Achondroplasia
Progeria
Treacher Collins
Marfan Syndrome
HUNTINGTON’S DISEASE
- the genetically programmed degeneration of brain cells
Cause:
• dominant allele that affects neurological function
Effects:
• symptoms appear between age 30 - 50
• degeneration of brain cells (neurons)
• loss of intellectual faculties
• uncontrollable movements
• emotional disturbances
Cure/Treatment:
woman with Huntington’s
• none
Disease at age 48
Huntington’s - http://www.youtube.com/watch?v=xguyxdmeUK8
ACHONDROPLASIA
- a common form of dwarfism
Cause:
• dominant allele that affects bone growth
Effects:
• short arms and legs
• 75 % of individuals with achondroplasia
are born to parents of average size…
• this means that most cases of achondroplasia
occur “out of the blue” and are the
result of a new mutation in the gene
Cure/Treatment:
• none; normal life expectancy
Achondroplasia - http://www.youtube.com/watch?v=d8B-rdUrO9U
Progeria
• extremely rare genetic disease wherein symptoms
resembling aspects of aging are manifested at an early age
• typically live to their mid teens and early twenties
• occurs as a result of a dominant, new mutation
• rarely inherited
Progeria - http://www.youtube.com/watch?v=T8eaD6FdFJw
Treacher Collins
• rare, congenital disorder characterized by craniofacial deformities
• caused by a defective protein called treacle
Physical Features Include ….
• downward slanting eyes
• micrognathia (a small lower jaw)
• conductive hearing loss
• absent cheekbones
• malformed or absent ears.
Cure/Treatment…
• No cure - only affects physical features
• physical features can be made less obvious by plastic surgery
Treacher Collins - http://www.youtube.com/watch?v=tYYMRd39wcE
Marfan Syndrome
• disoder of connective tissue
Effects…
• unusually tall, long limbs and long, thin fingers
• range of expressions - from mild to severe
• defects of the heart valves and aorta, lungs, skeleton, hard palate
Cure/Treatment….
• no cure
• medications to slow progression of disease
• new treatments being developed
• life expectancy today - similar to that of the average person
Codominance and Red Blood Cells
Codominance occurs when…
• both alleles are dominant
• both alleles are fully expressed – NO BLENDING
Red Blood Cells (RBCs) can be….
• disc shaped (D) NORMAL –
easily flow through blood vessels
• crescent shaped (C) ABNORMAL
clump and block blood flow
DD = all RBC’s normal shaped
DC or CD = some RBC’s normal + some abnormal
CC = all RBC’s abnormal – causes SICKLE CELL ANEMIA
SICKLE CELL ANEMIA
- results from misshapen RBC’s
Cause:
• recessive allele that is defective
• both mom and dad are “carriers”
Effects:
• causes RBCs to be misshapen – “sickle” or “C” or “crecsent” shaped
• misshapen RBCs break down prematurely, cannot effectively transport
oxygen, are stiff and sticky and block blood flow
• pain, organ damage, increased risk of infection
Cure/Treatment:
• bone marrow transplant – finding matching donor is difficult and
procedure has risks – may work for some
• regular medical care, pain medicine, fluids, oxygen therapy
Sickle Cell Anemia - http://www.youtube.com/watch?v=LlF_8oRs6Bw
Videos – Genetic Disorders
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Cockayne - http://www.youtube.com/watch?v=6QeXF3d9jY8
Brittle Bone - http://www.youtube.com/watch?v=6b7cWvMlw8Y
Ectodermal Dysplasia - http://www.youtube.com/watch?v=cAl6ZoQ7Mes
Duchenne MD - http://www.youtube.com/watch?v=CT3CsVoxWs0
Tetra-Amelia Syndrome
Nick Vujicic
• rare disorder characterized by the absence of all four limbs
LOOK AT YOURSELF http://www.youtube.com/watch?v=Gc4HGQHgeFE
PEDIGREE
chart which shows the
inheritance of a trait
from one generation
to the next
Allows geneticists to trace
the transmission of a trait
through a family.
square = male
circle = female
colored shape = has trait
half colored shape = carrier
slash = deceased
How many generations are represented?
How many males? afflicted males? normal males?
How many females? afflicted females? normal females?
Any carriers?
Sex-linked or autosomal trait?
Dominant or recessive trait?
Any twins? deceased individuals?
Victoria…(born into the British Monarchy in 1819)
• 1837 - became Queen of England
• 1840 - married her 1st cousin Prince Albert – which was the custom
• she was a carrier of HEMOPHILIA
• had 9 children and PASSED HEMOPHILIA ON TO SEVERAL OF THEM
• ALL OF HER CHILDREN MARRIED INTO THE ROYAL FAMILIES OF EUROPE
• HEMOPHILIA BECAME KNOWN AS THE ROYAL DISEASE
Princess Alexandrina Victoria…
o the granddaughter of Queen Victoria
o was born into the British Monarchy in 1872
She was also a CARRIER OF HEMOPHILIA
o hemophilia is an X-linked recessive trait
o results in an inability to clot the blood
Princess Alexandrina Victoria…
• married her 2nd cousin, Nicholas Romanov II, Tsar of Russia
• they had 5 children …
– 4 girls - Olga, Tatiana, Maria, Anastasia
– 1 boy - Alexei - heir to the throne - had HEMOPHILIA
• 1918 - Russian Civil War
• Tzar Nicholas II, his wife and their 5 children disappeared
• 1991 - the remains of Tzar Nicholas, his wife, and
3 of the children were found and exhumed for DNA testing
HUMAN CHROMOSOMES
Human somatic cells contain….
46 individual chromosomes
or 23 chromosome pairs
Of these 23 pairs…
SEX CHROMOSOMES (1 pair)
• determine the sex
of an individual
AUTOSOMES (22 pairs)
• do not determine the sex
of an individual
KARYOTYPE
photomicrograph of the chromosomes in a dividing cell
chromosomes are grouped and placed into (23)pairs
female - 46 XX
male - 46 XY
nonhomologous
Telomeres
protective caps on ends on chromosomes
made of protein and DNA
may play a role in cancer and aging
telomeres are
like… aglets
on the ends
of a shoe string
Mutations
What is a mutation?
a change in the DNA
it is interesting that mutations
can be helpful, harmful or
may have no effect
mutations – are a source of
genetic variation in LT
Mutations
What causes a mutation? a mutagen
….anything that can cause
a change in the DNA
Some mutagens are….
viruses, chemicals, toxins, UV light,….
Mutations can also happen as a result of …
DNA being copied incorrectly
Types of
Mutations
SOMATIC cell mutations - affect body (somatic) cells
will affect individual, but not offspring
GERM cell mutations - affect germ (sex) cells
will affect offspring, but not the individual
LETHAL mutations
will cause death either before or shortly after birth
Types of
Chromosome
Mutations
Deletion
– A piece of a chromosome is LOST
Inversion
– A piece of a chromosome breaks off, FLIPS OVER + REATTACHES
Translocation
– A piece of a chromosome breaks off and attaches
to ANOTHER chromosome
Nondisjunction
– Homologues DO NOT SEPARATE PROPERLY DURING CELL
DIVISION - results in too many or too few chromosomes
loss of a portion of a chromosome
Williams Syndrome
• caused by spontaneous deletion of genes on chromosome 7
• rare, neurodevelopmental disorder
• characterized by, "elfin" facial appearance, low nasal bridge,
cheerful demeanor and ease with strangers
• developmental delays and cardiovascular problems
Inversion – a section of a chromosome breaks off,
flips over and reattaches
Translocation – a portion of a chromosome detaches and
reattaches to a nonhomologous chromosome
Let’s Practice – What type of mutation?
NONDISJUNCTION - when chromosomes don’t
separate properly during CELL DIVISION
(CAN OCCUR IN mitosis or meiosis)
nondisjunction
means
“not coming apart”
Nondisjunction in Meiosis…can lead to …
monosomy (45) – missing a chromosome of a pair
(having only 1 chromosome of the pair)
trisomy (47) – having an extra chromosome in a pair
(having 3 chromosomes in the pair)
Conditions resulting from
Nondisjunction
• Down’s Syndrome
• Turner’s Syndrome
• Klinefelter’s Syndrome
DOWN SYNDROME
male or female having an extra chromosome in pair #21
(3 chromosomes instead of 2) - 47 XX or 47 XY
Down Syndrome (onosomy)
nondisjunction on #21 = Trisomy 21
Characteristics of Down Syndrome
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almond shaped eyes
flat nose bridge
large tongue
ears are set a bit lower on the head
shorter in stature
simean crease on the palm of the hand
possible congenital heart defects
lat feet, sandal toe (large gap between big toe and the next)
lower IQ
developmental delays
Turner Syndrome (Monosomy)
• female missing a sex chromosome; 45 XO
• nondisjunction on #23; monosomy
Klinefelter Syndrome (Trisomy)
• male having an extra sex chromosome
• 47 XXY or 48 XXXY; nondisjunction on #23; trisomy
Jacob’s or XYY Syndrome (Trisomy)
• male having an extra Y (sex) chromosome
• 47 XYY; nondisjunction on #23; trisomy
• clinical phenotype is normal
Fetal (genetic)Testing
– pre-pregnancy: DNA testing & genetic counseling
– post-pregnancy: PKU testing
– during pregnancy:
• Amniocentesis
• Chorionic Villi Sampling (CVS)
• Fetal Blood Sampling
Amniocentesis - a small amount of amniotic fluid (containing
fetal tissues and cells) is extracted from the amniotic sac
surrounding the developing fetus - the DNA is examined
for genetic abnormalities
Chorionic Villi Sampling (CVS) - the removal of a small
piece of the placenta (chorionic villi) during early
pregnancy to screen for genetic defects – the placenta has
the same genetic makeup as the fetus
Fetal Blood Sampling (FBS) - the collection of fetal blood
from the umbilical cord or fetus – the blood is tested
genetic defects or other abnormalities