genetic influence on patient outcomes, note taking guide Flashcards
aneuploidy
not having 23 chromosomes in each cell
trisomy
3 copies of one chromosome instead of two copies
monosomy
1 copy of one chromosome, missing one chromosome from a pair, results in 45 total instead of 46
loss of chromosomal material
is worse than duplication, as it results in less genetic material available for use
list the four abnormalities of structure
deletion
duplication
translocation
inversion
deletion
loss of parts of chromosomes, may cause significant congenital anomalies, intellectual and physical disability. Produces worst effects.
duplication
type of mutation that involves the production of one or more copies of a gene or region of a chromosome
inversion
when a segment breaks off and reattaches within the same chromosome, but in reverse orientation
translocation
when one chromosome breaks or loses a piece, and the fragmented pieces attach to different chromosomes or attach to each other in different places
genes
sequences of DNA, in nucleus
where does protein synthesis take place?
cytoplasm
list the 4 DNA bases
adenine A, cytosine C, guanine G, thymine T
How is new DNA formed?
Thru replication, when enzymes break the hydrogen bonds between bases, (unzipping the helix) leaving each single strand unpaired. Then the single strands pair with new peptides thru complementary base pairing, A with T and G with C. The unpaired base will only pair with the proper protein.
What is the template guide when new DNA is formed?
the single strand of DNA that remains after unwinding
list the most common genetic abnormalities
trisomy, monosomy, mosaicism
missense mutation
change in a single amino acid in a protein
nonsense mutation
when mutation introduces a premature stop codon
pedigree charts
help analyze modes of inheritance, a diagram that shows how trait or disease is passed down thru a family
sex linked recessive genetic disease
mutations/genetic conditions on the X chromosome, affects males more frequently than females, because males have only 1 X and 1 Y - if affected gene has the illness, it will be expressed
recessive
When individual inherits of a mutated gene, one from each parent, when unaffected parents have affected offspring. If males are more affected, it is sex-linked
gender determination
Combination of sex chromosomes, XX or XY. The Y chromosome carries the SRY (sex-determining region Y) gene, which triggers the development of male sex organs (testes). Begins in 6th week of gestation. In the absence of the SRY gene, the embryo develops female sex organs (ovaries). If there is an XY without the SRY, person will have female characteristics.
what causes neural tube defects?
genetic, environmental, nutritional (lack of maternal folic acid)
monozygotic
MZ, separate but identical embryos, natural clones, twins
dizygotic
DZ, fraternal twins, double ovulation with different sperm fertilizing each egg, can be different fathers, are like regular siblings and only share half their DNA
relative risk
rate of probability, not actual occurrence of disease
imprinting
only one copy of a gene in an individual (either from mother or father) is expressed, while other copy is suppressed or silenced. Unlike genomic mutations that can affect the ability of inherited genes to be expressed, genomic imprinting does not affect the DNA sequence itself. Instead, gene expression is silenced by the epigenetic addition of chemical tags to the DNA during egg or sperm formation. Epigenetic tags on imprinted genes usually stay in place for the life of the individual
Examples of imprinting
Prader-Willi, Angelman Syndrome, Beckwith-Wiedemann, Russell-Silver Syndrome, where expression of genes depends on parental origin
probability
mathematical measure of likelihood. Calculates likelihood of specific traits being inherited by offspring from parents.
punnett square
diagrams that help determine the likelihood of an offspring inheriting specific traits based on the parents’ genotypes.
how many chromosomes are same in males and females
- 23rd is the sex chromosome. Most people have 46 chromosomes, in 23 pairs.
Down Syndrome
trisomy 21. Extra copy on chromosome 21. Small stature, almond shaped eyes, flattened facial features, small ears, short neck, weak muscle tone, intellectual disability, vision/hearing problems, thyroid disease, cancer, increased risk for Alzheimer’s (because chromosome 21 produces amyloid plaques, so there is an extra chromosome producing plaques)
Turner Syndrome
45X0. Deletion of sex chromosome, 46-1= 45. When females only have 1 X chromosome. Sometimes they also have a partial Y chromosome, without the SRY portion. No period, missing or undeveloped ovaries, infertile, must adopt to have kids. No pubic hair, wide nipples, renal hypoplasia, horseshoe kidney, short stature, small mandible, high palate, low set ears, low hairline, webbed neck, 50% chance of congenital heart defects, bicuspid aortic valve, coarctation of aorta, lymphedema of hands and feet. Tx is HGH, estrogen
Klinefelter Syndrome
47 XXY, or 48 XXXY, or 49 XXXY. Male has extra X chromosome. Most common cause of primary hypogonadism, azospermia, and infertility in males. Infertile, poorly formed testicles, micro-penis, gynecomastia, tall, normal pubic and axillary hair, intellectual disability, infertility, behavioral problems, low testosterone, high FSH/LH, high risk of pulmonary disease, varicose veins, ADHD, high chance of breast and testicular cancer, high risk of high cholesterol and atherosclerosis. Tx testosterone and androgen therapy
Cri du Chat
Cry of the cat, due to high pitched cry that sounds like a cat’s meow characteristic of these babies. Not inherited. Deletion in chromosome 5, on the P arm of the chromosome. “Floppy baby.” Weak muscle tone, so will need therapy for swallowing, sucking. Ventricular septal defect, microcephaly, round face, wide eyes, hypotonia, intellectual disability, low ears, small jaw, heart defects, speech delay.
When to test genetics
When family hx indicates it. May need to refer to genetic counselor.
Women over age 35, old egg theory.
Single gene testing
to diagnose disease
Panel testing
looking for mutations, CA
genomic testing
entire genetic makeup, markers predict disease progression, how genes and environment interact are predictors of health
non-invasive prenatal testing
screening for disease in women over 35, men over 35. Blood draw from mother, also predicts twins
Ex panorama - screens for conditions like Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), and sex chromosome abnormalities (monosomy X, triploidy).
amniocentesis
sampling amniotic fluid by inserting needle into uterus, guided by ultrasound, usually between 15-20 weeks. To test for genetic or chromosomal abnormalities. Small risk of miscarriage that can be minimized if experienced pros perform procedure.
transcription
1st process
information passed from one structure to another
prerequisite for translation
unzipping of DNA
translation
2nd and last step of gene expression
mRNA interacts with tRNA to produce a protein
