Studied by 0 peoplewho are genetic counselors
people that help individuals understand modes of inheritance and medical consequences of genetic disorders
what is karyotyping
a visual display of someone’s chromosomes
what is amniocentesis
a prenatal test
what occurs in amniocentesis?
a sample of amniotic fluid is collected so fetal cells can be isolated and analyzed
what is the chance of spontaneous abortion in amniocentesis
0.25 - 0.5%
how does chromosome numbers change
nondisjunction
what is a trisomy
an extra chromosome is carried by an egg or sperm
what is a monosomy
an egg or sperm that lacks a chromosome
what does an extra copy of chromosome 21 account for
down syndrome
extra copies of gart genes = ?
more purines in the body
what are characteristics of down syndrome
short stature, enlarged tongue, distinct palm crease
what can cause chromosomes to break apart
radiation, certain chemicals, and some viruses
what is williams syndrome
a chromosome deletion where chromosome 7 loses an end piece
what are the symptoms of williams syndrome
individuals have a turned up nose and a wide mouth with small chin with poor academic skills but amazing verbal and musical skills
what is cri du chat syndrome
a chromosome deletion where chromosome 5 loses an end piece
what are the symptoms of cri du chat syndrome
small head, mental disabilites, cat-like cry
what is chromosomal duplication
when chromosome segment is repeated in same or nonhomologous chromosome
what can also occur to a duplicated chromosome
it can be in an inverted direction - inversion
what is inversion
segment is turned 180 degrees
what does inversion lead to
altered gene activity in crossing-over
what can inversion result in
duplication and deletion when inverted segments loop in crossing-over
what is chromosomal translocation
the exchange of chromosomal segments between two nonhomologous segments
what is alagille syndrome
translocation between chromosomes 2 and 20
what are family pedigrees
chart of family’s history
what are males indicated on pedigrees
squares
what are females indicated on pedigrees
circles
what does shaded shapes mean in pedigrees
individual is affected by disorder
how can we tell if a pedigree is autosomal recessive?
most affected children have unaffected parents
heterozygotes (Aa) have an unaffected phenotype
two affected parents will always have affected children
affected individuals with homozygous unaffected mates will have unaffected children
close relatives who reproduce are more likely to have affected children
both males and females affected with equal frequency
how can we tell if a pedigree is autosomal dominant
affected children will usually have an affected parent
heterozygotes (Aa) are usually affected
two affected parents can produce an unaffected child
two unaffected parents will not have affected children
both males and females affected with same frequency
in pedigrees for x-linked disorders, how can a daughter be affected?
must inherit it from both parents
in pedigrees for x-linked disorders, how can sons be affected?
only inherit it from mother, therefore more males affected than females
in y-linked disorders, how can sons be affected
fathers pass trait to all sons (present in only males)
how can we tell if a x-linked pedigree is recessive
more males than females affected
affected son can have parents who have normal phenotype
for a female to have the characteristic, father must have it and mother must have it or carrier
the characteristic often skips a generation from the grandfather to the grandson
if a woman has characteristic, all sons will have it
what are 4 autosomal recessive disorders
tay-sachs disease
cystic fibrosis
phenylketonuria
sickle-cell disease
what is tay-sachs disease
lack of hex A enzyme and symptoms appear in the first year of life
what does tay-sachs disease cause
defective lysosomes (especially in the brain)
what is cystic fibrosis
defect in chloride channel proteins in cells (most common genetic disorder for caucasian males in the us)
what does cystic fibrosis cause
thick, abnormal mucus production in lungs, bronchial tubes, and pancreatic ducts
what is phenylketonuria
lack enzymes for phenylanine (1 of 20 amino acids) metabolism
what does phenylketonuria affect
nervous system development (can be controlled with diet)
what is sickle-cell anemia
irregular red blood cells caused by abnormal hemoglobin
what does sickle-cell anemia cause/do
clog vessels - poor circulation and internal hemorrhaging
heterozygous individuals are normal until?
dehydrated or experience mild oxygen deprivation
what are 2 autosomal dominant disorders
marfan syndrome and huntington disease
what is marfan syndrome
a defect in fibrillin-protein in elastic connective tisuse
what does marfan syndrome
long limbs and fingers, weakened arteries, dislocated lenses in the eyes
what is huntington syndrome
progressive degeneration of brain cells
gene for defective protein called huntington
what does huntington syndrome
too many copies of the amino acid glutamine in the protein causes it to change shape and clump in neurons
encourages other proteins to clump
what is familial hypercholesterolemia
incompletely dominant disorder that affects the number of LDL (low-density lipoproteins)-cholesterol receptors on cells
what does familial hypercholesterolemia lead to
high cholesterol and cardiovascular
what would being homozygous for defective gene mean (familial hypercholesterolemia)
have no LDL-cholesterol receptors and develops cardiovascular disease and die as a child or in teenage years
what would being heterozygous for defective gene mean (familial hypercholesterolemia)
would have half the normal amount of LDL-cholesterol receptors and live longer
what would being homozygous for normal gene mean (familial hypercholesterolemia)
normal number of receptors
what percentage of caucasian males have red-green colourblindness
8%
what is duchene’s muscular dystrophy
x-linked recessive disorder that has the absence of a protein called dystrophin
what does duchene’s muscular dystrophy cause
causes calcium to leak into muscle cells which activates enzymes that break down the cells
what is hemophilia A
a lack of clotting factor VIII
what is hemophilia B
a lack of clotting factor IX
what does hemophilia cause
blood clotting to go slow or not at all - can bleed externally or internally leading to hemorrhaging or death (clotting factors are now available)
how do mutations lead to disorders
caused by a missing enzymes
what does tay-sachs disease test for
quantity of hex A enzyme present in a sample of cells
what can a tay-sachs disease test determine
if individual is homozygous normal, a carrier, or has Tay-sachs
what is the PKU test
test done on newborns to determine the presence of phenyalanine
what are 3 ways to test DNA for genetic disorders
genetic markers, dna probes, dna chip
how do we test DNA with genetic markers
in genetic markers, restriction enzymes cleave DNA
what disorder does genetic markers test for
huntington disease
how do we test DNA with dna probes
a DNA probe (single stranded piece of DNA) binds to complementary DNA
in genetic testing, what do dna probes typically have
mutation of interest
how do we test DNA with dna chip
tagging person’s DNA with fluorescent dye and convrted to single stranded DNA before being applied to the chip
what occurs on the dna chip during testing
mutated genes bind if present and are detected by laser scanner
how do we test a fetus
ultrasound
what is an ultrasound
high frequency sound waves used to produce an image
when are fetal cells tested for in amniocentesis
15 weeks of gestation (process or period of development inside womb between contraception and birth)
what can amniocentesis also test for
alpha fetoprotein which can indicate neural tube defects
when can fetal cells be tested during chorionic villi sampling
earlier than amniocentesis (no amniotic fluid taken so cannot test for afp
how can fetal cells in mothers blood be tested
when a small number of fetal cells enters the mother’s blood
how can an embryo be tested
at the 8-cell stage following in vitro fertilization
only “normal” embryos are tested
how are eggs tested
by testing the polar bodies of women who are heterozygous prior to in vitro fertilization
if a polar body is defected, what occurs to the ovum
ovum is normal
what is genomics
study of genomes
what is a genome
complete set of DNA in an organism
how many genomes do humans have
20,000 - 25,000
what is the human genome project
a project that wanted to sequence all of the base pairs in all of the DNA of human chromosomes
also revealed that humans probably have 20,000 - 25,000 genomes
what was the objective of the hapmap project
to catalog common sequence differences that occur in humans so scientists can link haplotypes to the risk of specific illnesses
what are haplotypes
patterns of sequence differences
what are proteomics
study of structure, function, and interaction of cellular proteins
what is a proteome
translation of all human genes resulting in a collection of proteins
how does the info computer modeling provide about the shape of proteins help
allows for greater understanding of how they work and increased efficiency of drugs
what is bioinformatics
application of computer technologies to the study of genome
what occurs in bioinformatics
an analysis of data produced by genomics and proteomics
what is the human genome described as
three-dimensional
what is the first dimension of the human genome
the sections of DNA that codes for proteins (accounts for less than 2% of DNA)
what is the second dimension of the human genome
“junk DNA” that may code for RNA
what is the third dimension of the human genome
outside layer that surrounds DNA and consists of proteins and other chemicals
what is gene therapy
insertion of genetic material into human cells for treatment of a disorder
what is vivo gene therapy
when cells are removed from the patient and those cells are treated outside the body then returned back
what is an example of vivo gene therapy
SCID (severe combined immunodeficiency) and cystic fibrosis
what occurs in vivo gene therapy
patient is given a foreign gene directly through viruses or lipoprotein vesicles
where is the foreign gene of vivo gene therapy incorporated within
the genome within the body
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