Genetics Flashcards
Ploidy
Number of sets of chromosomes
Aneuploidy
Abnormal # of chromosomes, either due to extra or missing chromosomes
Monoploidy
Loss of the entire set of chromosomes
Euploidy
Gain of one or more complete sets of chromosomes
Haploid
When a cell has half the usual/expected number of chromosomes
Diploid
Cell with paired chromosomes, one coming from each parent (ie. our cells are diploid with 23 pairs of chromosomes)
Turner Syndrome
*Cause?
*Chromosome Abnormality
*Key Findings
*Cause: Non-disjunction during gametogenesis
- Mosaicism = some cells missing an X, some are not = milder symptoms
*Chromosome Abnormality: Pt has only 1 X Chromosome (45, X)
*Key Findings:
- Short stature
- Lymphedema of hands + feet (also seen w/ Kawasaki)
- Webbed neck
- Low-set hairline
- Ovarian Dysgenesis
- Pre-ductal coarctation
- Bicuspid Aortic Valve
- Horseshoe kidney
Cri-du-Chat
*Cause:
*Sx’s:
*Cause: Partial deletion of the short arm of chromosome 5
- Abnormal development of larynx & nervous system
*Sx’s: High-pitched, cat-like cry
- Microcephaly
- Hypotonia
- Low birth weight
- Developmental Delays
- Intellectual disability
Acrocentric Chromosomes
Chromosomes 13, 14, 15, 21, 22
Patau Syndrome (Trisomy 13)
*Cause:
*Findings:
*Screening:
*Cause:
- Robertsonian Translocations (of acrocentric chromosomes: 13, 14, 15, 21, 22)
*Findings:
- Cleft Lift + Cleft Palate
- Polydactyly
- Rocker Bottom feet
- Umbilical Hernia or Omphalocele
- Cardiac Defects
- Deafness
- Eye defects
- Holoprosencephaly
- Sloping forehead
*Screening:
- 1st trimester
- Decreased Beta-HCG & Dec. PAPP-A
Edwards Syndrome (Trisomy 18)
*Cause:
*Findings
*Screening
*Cause: Chromosomal Non-disjunction = Three copies of Chromosome 18
- Mosaics are possible but rare
*Findings:
- Clenched fists w/ overlapping fingers
- Rocker bottom feet
- Micrognathia
- Microcephaly
*Screening:
- Dec. Beta-HCG, Dec. PAPP-A in 1st trimester, Dec. Alpha-fetoprotein, dec. estriol, dec./normal inhibin A
Down Syndrome (Trisomy 21)
*Cause:
*Findings:
*Screening:
*Cause: Meiotic Non-Disjunction
- Mosaicism is common
*Findings:
- Intellectual disability
- Low set ears
- Palpebral fissures
- Flat nasal bridge
- Protruding tongue
- Low muscle tone
- Wide space between big & 2nd toe
- Joint laxity
- Brushfield spots
- Single palmar crease
- Shorter than average
- Higher risk of obesity than average
- Cardiac abnormalities: ASD + VSD + Endocardial cushion defect
- Greater risk for atherosclerosis
- GI: Duodenal stenosis, atresia, annular pancreas, esophageal atresia + tracheoesophageal fistula, Hirschsprung Disease
- Elevated Risks for Cancers: ALL, Leukemia, AML-M7
*Screening:
- 1st Trimester: Inc. Beta-HcG, Inc. Nuchal translucency, Dec. PAPP-A
- 2nd Trimester: ^ B-hCG, ^ inhibin A, Dec. alpha feto-protein, dec. estriol
Klinefelter Syndrome
*Cause:
*Findings:
*Screening:
*Cause: Male hypogonadism, reduced spermatogenesis, male infertility
- Karyotype: (47, XXY)
*Findings:
- Dec. sperm production due to seminiferous tubule damage
- Dec. testosterone production due from Leydig cell damage
- Above average height
- Poor insight
- Poor judgement
- Normal language skills w/ limited vocabulary
*Screening:
- Elevated FSH & LSH, Dec. testosterone
DiGeorge Syndrome
*Cause:
*Findings: (Mnemonic)
*Screening:
*Cause: Deletion of a large part of Chromosome 22
- Damage to TBX1 gene
*Findings: CATCH-22
- C: Cardiac Abnormalities
(Tetralogy of Fallot)
- A: Atypical Facies
- T: Thymic hypoplasia
- C: Cleft palatate
- H: Hypocalcemia/Hypoparathyroidism
*Screening:
Elevated FSH & LH (bc dec. testosterone so no negative feedback)
Prader-Willi Syndrome
*Cause:
*Findings:
*Screening:
*Cause: Paternal deletion on chromosome 15
- 75% from imprinting (1 parental chromosomal = methylated the other is silenced) & 25% uniparental disomy
*Findings:
- Obesity
- Severe hypotonia during infancy
- Delayed motor milestones
- Hyperphagia
- Delayed + absent secondary sexual characteristics throughout adolescence
*Screening:
