Download Report

Transcript Presentation

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)
Tay Sachs
Xeroderma Pigmentosum (XP)
Primordial Dwarfism
Phenylketonuria (PKU)
Cystic Fibrosis (CF)
– affects the mucus producing glands, digestive enzymes and sweat glands
• recessive allele that is defective
• excessive mucus production
• respiratory system is compromised; high risk of infection
• digestive and respiratory system failure
• life expectancy 36.8 years
• no cure
• daily breathing treatments
• mucus-thinning drugs
• pancreatic enzyme supplements
Cystic Fibrosis -
– partial or total lack of pigment (melanin)
in hair, skin and eyes
• 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
• no cure
• protect eyes and skin from sun
– an inability to digest galactose (milk sugar)
• 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
• 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
• recessive allele that is defective
• lack of enzyme
that breaks down fatty substances
• inability to break down fatty acids
• fatty deposits build up in the brain
• brain cells deteriorate
• mental capacity is diminished
• death by age 5
• 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
• 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
• recessive genetic disorder
• 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)
• recessive genetic disorder
• 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
Tetra-Amelia Syndrome
• recessive genetic disorder
• rare disorder characterized by the absence of all four limbs
• severe malformations of various parts of the body, including the
face and head, heart, nervous system, skeleton, and genitalia
• most are stillborn or die shortly after birth
• Nick Vujicic – Australian Motivational Speaker
DOMINANT Genetic Disorders
• only need 1dominant allele (AA or Aa) to inherit the disorder
• either you have the disorder or you don’t
Huntington’s Disease
Treacher Collins
Marfan Syndrome
Huntington’s Disease
- the genetically programmed degeneration of brain cells
• dominant allele that affects neurological function
• symptoms appear between age 30 - 50
• degeneration of brain cells (neurons)
• loss of intellectual faculties
• uncontrollable movements
• emotional disturbances
woman with Huntington’s
• none
Disease at age 48
Huntington’s -
- a common form of dwarfism
• dominant allele that affects bone growth
• 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
• none; normal life expectancy
Achondroplasia -
• 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 -
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.
• No cure - only affects physical features
• physical features can be made less obvious by plastic surgery
Treacher Collins -
Marfan Syndrome
• disoder of connective tissue
• 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
• no cure
• medications to slow progression of disease
• new treatments being developed
• life expectancy today - similar to that of the average person
Sickle Cell Anemia
• CODOMINANT ALLELE that is defective
• DD = disc shaped; CD = some disc + some crescent; CC = crescent shaped
• both mom and dad must be “carriers” of a defective allele
• causes Red Blood Cells to be misshapen – sickle/C/crescent shaped
• defective RBCs don’t live long; don’t effectively transport oxygen;
are stiff and sticky; block blood flow
• cause pain, organ damage, increased risk of infection
• 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 -
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?
Queen Victoria…
• born 1819…..became Queen of England in 1837
• married her 1st cousin Prince Albert (of Germany) in 1840
• this was the custom – royalty would not marry a commoner
• 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
Granddaughter Of Queen Victoria …
Princess Alexandria Victoria… born in 1872
o in 1890 she married her 2nd cousin,
Nicholas Romanov II, the Tsar of Russia
Tsar (Nicholas) and Tsarina (Alexandria) of Russia
had 5 children…
4 GIRLS - Olga, Tatiana, Maria, Anastasia
1 BOY - Alexei - heir to the Russian throne
1918 - Russian Civil War
• Tzar Nicholas II, his wife and the 5 children disappeared
• there were many theories surrounding their disappearance
Nat Geo – Mystery of the Romanovos – 4 min
• 1991 - the remains of Tzar Nicholas, his wife, and
3 of the children were found and exhumed for DNA testing
• the bodies of Alexi and 1 of his sisters was missing….
Human somatic cells contain….
46 individual chromosomes
or 23 chromosome pairs
Of these 23 pairs…
• determine the sex
of an individual
AUTOSOMES (22 pairs)
• do not determine the sex
of an individual
photomicrograph of the chromosomes in a dividing cell
chromosomes are grouped and placed into (23)pairs
female - 46 XX
male - 46 XY
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
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
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
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
– A piece of a chromosome is LOST
– A piece of a chromosome breaks off, FLIPS OVER + REATTACHES
– A piece of a chromosome breaks off and attaches
to ANOTHER chromosome
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
“not coming apart”
Nondisjunction in Meiosis… leads 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
Down’s Syndrome
Turner’s Syndrome
Klinefelter’s Syndrome
Jacob’s Syndrome
Down Syndrome (monosomy)
male or female having an extra chromosome in pair #21
• (3 chromosomes instead of 2) - 47 XX or 47 XY
• nondisjunction on #21 = Trisomy 21
Down Syndrome
male or female having an extra chromosome in pair #21
(3 chromosomes instead of 2) - 47 XX or 47 XY
• almond shaped eyes; flat nose bridge; large tongue
• ears are set lower on the head
• shorter in stature
• simean crease on the palm of the hand
• possible congenital heart defects
• flat feet, sandal toe (large gap between big toe and the next)
• lower IQ and 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
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