Genetic and Developmental Disorders Flashcards Preview

Gen Path 300 > Genetic and Developmental Disorders > Flashcards

Flashcards in Genetic and Developmental Disorders Deck (38):
1

Egg + sperm =

zygote

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Zygote cells divide to form

Morula

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Morula develops into

Blastocyst

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Three primordial germ layers

Ectoderm
Mesoderm
Endoderm

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The critical stages of organogenesis are characterized by:

Extensive cell division, migration and interaction; and
Extreme sensitivity to external influences

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Teratogen

Any agent that causes fetal abnormalities

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Breakdown of causes of fetal abnormalities:

75% unknown
20% genetic diseases
2% chromosomal abnormalities
2% infection
1% chemical

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Exogenous teratogens

Physical (X-rays, radiation, etc)
Chemicals

9

Fetal Alcohol Syndrome

Intrauterine growth development, affecting development of brain

Typically presents with small cranium and jaw, thin upper lip, reduced mental processes

10

TORCH

Toxoplasma, Other, Rubella, Cytomegalovirus, Herpes Simplex

Microbial teratogens

11

Congenital Rubella syndrome.

Microcephaly, micropthalmia, congenital heart defects

Inflammation of liver, lungs, lymphosplenomegaly

12

Teratogenic effect of Toxoplasmosis and cytomegalovirus

Brain abnormalities; small eyes with inflammation, cataracts and calcifications

13

Teratogenic effect of Herpes

skin lesions

14

Chromosomal abnormalities can be:

1. Structural
2. Numerical
- trisomy
- monosomy

More common in sex chromosomes than autosomes

15

Trisomy 21

Downs Syndrome
Translocation or trisomy of chromosome 21
Associated with mental retardation, facial and limb abnormalities, defects in internal organs, hematologic abnormalities.

16

Turner's Syndrome

Monosomy X

Short stature, webbing of neck, normal female genitalia, except ovaries don't develop normally.

17

Klinefelter's Syndrome

XXY

Infertile males.

Atrophy of testes. Tall, effeminate, gynecomastia

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Heterozygous

Possess one recessive and one dominant copy of the allele

19

Homozygous

Possess either two recessive or two dominant copies of the gene.

20

Marfan's Syndrome

Autosomal dominant disorder primarily affecting connective tissue. Defect in gene that codes for fibrilin

1/10000

Causes skeletal, cardiovascular and occular changes

Elongated head, eye abnormalities, aortic aneurysm, floppy mitral valve, vertebral deformity, arachnodactyly

21

Familial Hypercholesterolemia

Autosomal dominant disorder primarily affecting cardiovascular system. Mutation in gene encoding LDL receptor.

LDL cholesterol removal less efficient --> deposition of lipids in arteries

1/500 people

22

Xanthomas

Lipid-rich yellow nodules, consist of macrophages that have phagocytize cholesterol

23

Cystic Fibrosis

Autosomal recessive disorder affecting gene that codes for chloride transport channel in cell membrane.

1/2500 neonates (1/25 estimated carrier)
Almost exclusively found in those with European heritage

Lack of NaCl in glandular secretions --> lack of H2) --> increased viscosity of secretions --> obstruction of organs

In pancreas --> malabsorption of nutrients
In bronchial mucosa --> abnormal respiration
Recurrent bacterial infection

24

Lysosomal Storage Diseases

Autosomal recessive disorders related to deficiency of enzymes involved in intermediary metabolism.

Metabolites that can't get fully degraded, digested or incorporated get stored in lysosomes

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Types of Lysosomal Storage Diseases

Lipodoses, glycogenoses, mucopolysaccharidoses, Tay-Sachs

Normally classified by type of pathway affected.
All characterized by accumulation of metabolites that cannot be processed

26

Tay-Sachs Disease

Lysosomal Storage Disease (autosomal recessive)

Defect in the function of hexosaminidase A --> accumulation of ganglioside in the brain

Gradual loss of brain function --> often death by age 5

27

Phenylketonuria

PKU

Autosomal recessive defect of protein metabolism.

Problem with enzyme that metabolizes phenylalanine (phenylalanine hyroxylase -- PAH) into tyrosine.

Phenylalanine cannot be metabolized and so accumulates in blood and tissues.

Can be controlled with diagnosis at birth and special diet. Without special diet --> mental retardation

28

Hemophilia

X-linked recessive disease
- internally hemorrhage, joint deformity resulting from hemarthrosis

Two types:
Hemophilia A
-- defect of Coagulation Factor VIII
-- 1/5000 boys
-- mild to severe symptoms
Hemophilia B
-- defect of Coagulation Factor IX
-- 1/20000 boys
-- always severe

29

Muscular Dystrophy

X-linked recessive disease characterized by progressive muscle wasting
-inadequate or absent dystrophin

Duchenne (most severe), Beckers (less severe)

30

Fragile X Syndrome

X-linked recessive form of mental retardation
CGG triplet repeat
Currently 80% penetrance, but seems to get more severe with successive generations

1/1250 boys, 1/2500 females

31

Anencephaly

Multifactorial development defect in which the midline structures covering the brain do not fuse, and spinal/brain development is severely disturbed

32

Diabetes Mellitus

Disturbance of intermediate metabolism --> hyperglycemia

Multifactorial

33

Forms of prenatal diagnosis

Ultrasound
Chorionic villus biopsy (fetal cells)
Amniotic fluid analysis
Maternal blood analysis (AFP - alpha-fetoprotein; triple-screen marker test)

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Prematurity

Born before 37th week, and weighing less than 2500g

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Immaturity

Less than 1500 g and cannot survive outside NICU

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Most important risk factor for prematurity

Premature rupture of amniotic membrane

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Neonatal Respiratory Distress Syndrome

In premature infants, immature lungs may not have fully developed alveoli
-- alveoli secrete surfactant to decrease surface tension and keep alveoli open
-- in immature alveoli, lack of surfactant allows alveoli to collapse. Cells die
-- necrotic cells and tissues coagulate and form a hyaline membrane, which further impedes gas exchange
-- anoxia can cause death within 48 hours

38

Sudden Infant Death Syndrome

SIDS
1/500 births [1/2000 in Canada]
More common with poverty
"Back to Sleep"