Clin Med - Genetics Flashcards by Arton Azizi

Do single gene mediated d/o’s make up the majority of clinical genetic conditions?
True or False

False

They only make up for 10% and NOT the majority

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Which clinical genetic conditions have both environmental and genetic input to account for the disorders?

Polygenic or multifactorial (complex) disorders

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Which type of clinical genetic conditions make up the majority?

Polygenic or multifactorial (complex) disorders

In other words, every medical condition has a genetic component

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What is a HUGE component of non-disjunction?

Maternal age

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What is aneuploidy?

more or fewer than 46 chromosomes

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Name the conditions containing 47 chromosomes?

Trisomy 13, 18 & 21 (Down)

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Which Trisomy Syndrome has these features: cleft lip, polydactyly (post axial), rocker-bottom feet, neural tube defects with a median survival age of 2.5 days?

Trisomy 13

47, XX/XY, +13

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Which Trisomy Syndrome has is characterized by the following features:
Clenched fist (2nd & 5th digit overlap 3rd & 4th), rocker-bottom feet, low set ears?

Trisomy 18

47, XX/XY, +18

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Which Trisomy Syndrome has the following features:
Neoteny (remain infant-like), mental retardation, low set ears, epicanthal folds, single palmar crease, hypotonic, overweight later in life, congenital heart disease, risk of leukemias?

Down Syndrome
(Trisomy 21)
47, XX/XY, +21

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What syndrome has a normal phenotype, thin build, disproportionately long arms/legs
female type distribution of pubic hair, testicular dysgenesis, gynecomastia, normal IQ to MR

Klinefelter Syndrome

47, XXY

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What may be associated with a higher number of X chromosomes?

subnormal intelligence or mental retardation

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Tall male with small testicles and not doing well in school with some mental issues. What syndrome?

Klinefelter Syndrome

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What should you be sure to have on your DDX with Klinefelter Syndrome?

ambiguous genitalia

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This syndrome results from non-dysjunction at 2nd meiotic division. Features include: learning problems in school, delayed emotional maturity (aggression), very tall stature and acne.

XYY Super Male

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What are the characteristics of Turner Syndrome?

Lymphedema in feet
short stature
ovarian failure (w/ increased LH/FSH)
webbed neck (2nd to lymphedema)
increased carrying angle
shield chest (wide spaced nipples)
HTN (coarctation of aorta)

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Most Turner syndrome concepti spontaneously abort, so who are the survivors?

most likely mosaics

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What type of aneuploidy is Turner Syndrome?

monoploidy

45, X

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Does the XXX Syndrome result in unusual physical features and medical problems?

No d/t the inactivation of all but 1 X

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What are the 4 types of Mendelian inheritance patterns?

Autosomal
X-linked
Dominant
Recessive

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What is single gene inheritance referred to as?

Mendelian inheritance

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What is Autosomal inheritance?

gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes)

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What is X-linked inheritance?

gene that encodes for the trait is located on the X chromosome

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What is Dominant inheritance?

Conditions that are manifest in heterozygotes (individuals w/ just ONE copy of the mutant allele)

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What is Recessive inheritance?

Study These Flashcards

conditions are only manifest in individuals who have TWO copies of the mutant allele (homozygous)

What is Penetrance?

% of individuals having a particular genotype that EXPRESS the expected phenotype (how well the trait will penetrate or show through)

What does fully penetrant mean?

if you have the gene, you WILL develop the disease

What does incomplete penetrance mean?

Cases of individuals w the abnormal genotype who do NOT have the disease

What does expression mean?

DEGREE (you can have 100% of penetrance but degrees of expression vary) to which a phenotypic characteristic is exhibited

What is the difference between Penetrance and Expression?

Penetrance is the % of individuals having a particular genotype that express (show) the expected phenotype Expression is the degree to which a phenotypic characteristic is exhibited

What is variable expression?

Phenomena where individuals may experience differing signs, sx's & severity of the disease This may be d/t the effects of other genes or to environmental factors (altering the effect of a particular gene)

What is the Hardy-Weinberg equation for only two alleles, A & a?

p2 + 2pq + q2 = 1 | frequency of the genotypes

What does p2 correspond too?

frequency of AA

What does 2pq correspond too?

frequency of Aa

What does q2 correspond too?

frequency of aa

What are 2 genetic syndromes determined by maternal/paternal imprinting?

Prader-Willi syndrome & Angelman syndrome

Which syndrome is a result of the paternal chromosome 15 imprinted (silenced)?

Angelman Syndrome

What syndrome is seen when disruption/deletion short arm paternal chromosome 15 with maternal chromosome 15 imprinted (silenced)?

Prader-Willi syndrome

What is seen with Prader-Willi Syndrome?

Diminished fetal activity, obesity, hypotonia, MR, short stature, hypogonadotropic hypogonadism, strabismus & small hands and feet

What is seen with Angelman Syndrome?

aka Happy puppet syndrome Intellectual/developmental delay, sleep disturbance, seizures, jerky movements (hand--flapping), frequent laughter or smiling & usually a happy demeanor

For AD conditions what is the chance of passing the mutant gene to their offspring?

50% chance on inheriting the mutant allele

For AR, if 2 carriers mate, what is the chance their offspring will have the disease or be homozygous?

25% chance of being homozygous mutant (affected) Leaving 50% chance of carrier and 25% chance of unaffected homozygous wild-type (no mutant alleles at all)

What are some things to keep in mind regarding X linked Recessive?

``` fully evident in males women are rarely affected unless they have 2 copies of a mutant allele) No father to son transmission Father to daughter Mother to daughter & son ```

What are some things to keep in mind regarding X linked Dominant?

No father to son Father to daughter (she will be affected) Mother to daughter or son have 50% of inheriting the X with the mutant allele

Things to keep in mind about Mitochondrial DNA (mtDNA) inheritance

mtDNA is inherited exclusively through the maternal line (only the ovum contributed mitochondria to the offspring)

What is multifactorial inheritance?

It is numerous genetic alterations that may predispose individuals to the same disease (genetic heterogeneity)

How often will we actually see Multifactorial inheritance?

ALL THE TIME -- KNOW IT

If you see a pedigree for ovarian & breast cancer what should you automatically think?

Multifactorial!! | if you see a pedigree with cancer - the answer is ALWAYS multifactorial

What are the hallmarks of multifactorial inheritance?

most affected children have normal parents recurrence risk increases with the number of affected children in a family & severity of the defect consanguinity slightly increases the risk for an affected child risk of affected relatives falls off very quickly with the degree of relationship (vs AD with incomplete penetrance, recurrence risk falls off proportionally with the degree of relationship)

If the 2 sexes have a different probability of being affected who will most likely produce an affected offspring?

the least likely sex, if affected, is the most likely sex to produce an affected offspring ex Pyloric stenosis

What are the indications for genetic counseling?

maternal >35 paternal >50 consanguinity previous hx of child w/ birth defects or genetic d/o personal or FHx suggestive of genetic d/o high risk ethnic groups known carriers documented genetic alteration in family member U/S or prenatal test suggesting genetic d/o

What are the types of genetic testing?

FISH & Karyotype

What is FISH?

faster, can find single base mutation, no cx, inexpensive

What is karyotype?

slower, labor intensive, requires cx, limited to visible chromosomal abnormalities

What are the 3 essential elements of gene transfer?

``` Vector Trangene (gene to be delivered) Relavant target cell to which the DNA or RNA is delivered ```

Is gene therapy working?

YES

What are 2 R/Os for PDD?

Retts Syndrome & Fragile X syndrome

What is the MCC of inherited mental retardation & what is the phenotype?

Fragile X Syndrome | flat feet, flexible joints, low muscle tone, large body size, large forehead or ears with prominent jaw, long face

What should you do if your pediatric patient lost a milestone?

Send them off for genetic testing!

Clin Med - Genetics Flashcards

(58 cards)