Genetic Disorders and Disorders of Sexual Development Flashcards by Monica Fatorma

What is the karyotype of Down syndrome?

(trisomy 21)

47 XX or XY, +21

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What is robertsonian translocation?

chromosomal abnormality where the entire long arms of two different chromosomes become fused to each other.

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Mosaicism

defined as the presence of ≥ 2 population of cells within an individual

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Clinical findings of one with Down’s Syndrome.

intellectual disability,

mongoloid facial features (flat face, low-bridged nose, and epicanthal folds)

Brushfield spots (speckled appearance of the iris)

muscular hypotonia,

broad short neck,

palmar (simian) crease

congenital heart defects (endocardial cushion defect)

duodenal atresia (‘double-bubble sign”

Hirschsrpung disease

15 -20 increase chances of:

ALL

Alzheimers disease

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What are test done to see if someone has Downs syndrome?

maternal serum tests,

amniocentesis

chorionic villus sampling

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What is the karyotype of Edwards Syndrome?

trisomy 18 caused by nondisjunction

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Clinical findings Edwards Syndrome.

intellectual disability

low set ears and micrognathia

congenital heart defects

overlapping flexed fingers

rocker-bottom feet

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What is the karyotype for Patau Syndrome?

trisomy 13 caused by nondisjunction

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Some clinical features of Patau Syndrome?

intellectual disability,

cleft lip and/or palate,

cardiac defects,

renal abnormalaities,

microcephaly,

holoprosencephaly,

polydactyly

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What is the pathogenesis behind Cri du chat?

due to deletion of the short arm of chromosome 5

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Clinical findings Cri du chat syndrome?

high-pitched catlike cry,

intellectual disability,

congenital heart disease

microcephaly

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Where is the retinoblastoma gene?

13q14 gene long arm chromosome 13 deletion

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What are clinical findings in WAGR?

WAGR complex consists of:

Wilms tumor, aniridia, genitourinary anomalies, and intellectual disability (formerly known as mental retardation)

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What gene affected in WAGR?

11p13 (short arm chromosome 11 deletion)

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Name some disorders characterized by chromosomal deletions?

Cri du chat
retinoblastoma
WAGR

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What is Klinefelter syndrome caused by? It is a common cause of what presentation in males?

by meitoic nondisjunction and is common cause of male hypogonadism

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Most common karyotype for Klinefelter?

47, XXY

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Describe the hormone levels in Klinefelter?

FSH and LH are elevated while testosterone is high

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What are the clinical findings for Klinefelter?

testicular atrophy,
infertility due to azoospermia,
eunuchoid body habitus,
high-pitched voice
gynecomastia
female distribution

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What is the most common karyotype of Turner syndrome?

45, X

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What are the clinical features of Turner Syndrome?

patients fail to develop secondary sex characteristics and have short stature with widely spaced nipples, gonadal dysgenesis, atrophic streak ovaries, primary amenorrhea, and infertility

Females with Turner syndrome with a 45, X/46 XY mosaicism are at a higher risk for what conditions?

gonadoblastoma and microdeletions

How does the presence of Y chromosome determine male phenotype?

due to presence of the testes-determining factor gene (aka sex determining region Y (SRY)) on the Y chromosome)

What are Mendelian disorder?

disorders characterized by a single gene mutation.

What are common types of mutations found in mendelian disorders?

point mutations frameshift mutations

What is Lyon's hypothesis of X-inactivation?

only one is genetically active. Most though not all of the genes on the other X chromosome are inactivated

What are point mutations?

They occur with a single nucleotide base substitiution, which may produce a variety of effects

Silent mutation?

form of point mutation when a base substitution results in a codon that codes for the same amino acid

Missense mutation?

base substituation results in a new codon and change in amino acids

Nonsense mutation?

when aa base substitution produces a stop codon, and therefore produces a truncated protein

Frameshift mutation?

occurs when insertion or deletion of bases leads to a shift in the reading frame of the gene

Compare and contrast onset of AR and AD conditions?

AR: early uniform onset (infancy/childhood) AD: variable onset (may be delayed into adulthood)

Compare and contrast penetrance in AR and AD conditions.

AR: complete penetrance AD: incomplete penetrance with variable expression

Compare and contrast mutation types of AR and AD conditions.

AR: usually an enzyme protein AD: usually a structural protein or receptor

What chromosome is CFTR gene located?

chromosome 7

What is cause of damaged CFTR gene on chromsome 7?

a deletion of the amino acid phenylalanine at position 508 (ΔF508)

How can you diagnose cystic fibrosis?

sweat test (elevated NaCl) or DNA probes

What are the 3 most common infections afflicting those with cystic fibrosis?

H.influenze, P. aeruginosa and S. aureus

What is phenylketonuria (PKU)?

deficiency of phenylalanine hydroxylase resulting in toxic levels of phenylalanine and lack of tyrosine. phenylalanine hydroxylase converts phenylalanine into tyrosine.

What are the clinical features of PKU?

intellectual development disorder by 6 months light colored skin and hair mousy or musty odor

Treatment for PKU?

dietary restriction of phenylalanine

Another name for alkaptonuria?

ochronosis

Cause of alkaptonuria?

when deficiency of homogentisic acid oxidase results in accumulation of homogentisic acid homogentisic acid has an affinity for connective tissues (especially cartilage) resulting in black discoloration

Clinical features of alkaptonuria?

include urine that is initally pale yellow but turns black upon standing and black stained cartilage causing discoloration of nose and ears

What enzyme is deficient in albinism?

tyrosinase

What are glycogen storage diseases?

group of rare disease that have common deficiency of one of the enzymes necessary for the metabolism of glycogen, which results in accumulation of glycogen in liver, heart, and skeletal muscle

What are lysosomal storage diesease?

defines as a def of a lysosomal enzyme (acid hydrolase), which leads to accumulation of complex substrates within the lysosome, leading to enlarged cells that become dysfunctional

Type 1 GSD Name and condition pathogenesis.

von Gierke disease: due to deficiency of glucose-6-phosphatase and is characterized clinically by hepatomegaly and hypoglycemia

Type II GSD Name and condition pathogenesis?

Pompe disease: due to a lysosomal a-1,4 glucosidase (acid maltase) and is characterized clinically by hepatomegaly, sk. muscle hypotonia, cardiomegaly, and death from cardiac failure by 2 years

What is Type V GSD name and pathogenesis.

McArdle syndrome: due to deficiency of muscle glycogen phosphorylase and is characterized clinically by exercise-induced muscle cramps