Ch 7: Genetic and Developmental Diseases

Question 1

Nondisjunction

Answer 1

2 homologous chromosomes go to one gamete and none to the other. Fertilization then results in trisomy or monosomy.

Question 2

Translocation

Answer 2

DNA fragment exchanges places with sequence on non-homologous chromosome

Question 3

Mosaicism

Answer 3

Cells with differing chromosomal makeup due to nondisjunction, translocation, deletion/duplication

Question 4

Mutation

Answer 4

chemical alteration in a sequence of DNA

Question 5

Sex-linked

Answer 5

genes located on X or Y chromosome (others called autosomal)

Question 6

Nonpenetrance

Answer 6

Abnormal dominant gene or pair of recessive genes fails to result in abnormal trait

Question 7

Variable expressivity

Answer 7

an abnormal trait can be expressed differently in individuals with identical genotype

Question 8

Embryonic development

Answer 8

• First 8 weeks after fertilization

- cells very sensitive to cytotoxic/mutagentic insults

Question 9

Fetal period

Answer 9

-8th week to birth

Question 10

Congenital

Answer 10

abnormalities present at birth but not necessarily genetic in origin

Question 11

Gestational age

Answer 11

fertilization plus 2 weeks (dated from last menstrual period)

Question 12

Perinatal period

Answer 12

2 weeks before birth to 4 weeks after birth

Question 13

Neonatal period

Answer 13

birth to 4 weeks after birth

Question 14

Monogenic disease

Answer 14

• caused by single abnormal gene, can be traced through families (eg phenylketonuria, sickle cell anemia)
• Can be autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive
• autosomal & recessive more common

Question 15

Chromosomal Disease

Answer 15

• microscopically visible changes in chromosomes
• usually incompatible with embryonic development (account for 1/3 spontaneous abortions)
• eg) Down Syndrome, abnormal # sex chromosomes

Question 16

Polygenetic Disorders

Answer 16

• inheritance patterns not clear-cut, influenced by environmental factors
• Eg) diabetes mellitus, cleft lip, congenital heart disease

Question 17

teratogens

Answer 17

environmental factors that can interfere with fetal development

Question 18

TORCH

Answer 18

• Toxoplasma
• Other (syphilis)
• Rubella
• Cytomegalovirus
• Herpes simplex virus

Question 19

erythroblastosis fetalis

Answer 19

mother produces antibodies to fetus’ RBC’s

Question 20

chorioamniotis

Answer 20

infection of placental membranes, usually by bacteria

Question 21

Cerebral palsy

Answer 21

brain damage to fetus in late fetal or perinatal period

-abnormal muscular coordination with or without mental retardation or seizure disorders

Question 22

5 major causes of death of infants in US

Answer 22

1) congenital/chromosomal abnormalities 2) prematurity/low birth weight 3) SIDS 4) complications of maternal diseases 5) diseases of placenta, cords, and membranes

Question 23

karyotyping

Answer 23

induce cells to grow in culture, arrest dividing cells during mitosis, squash and stain to view under microscope
-used to diagnose chromosomal diseases

Question 24

triple screen test / quad test

Answer 24

performed on serum of pregnant women to -measure substances present in abnormal concentrations if the fetus has neural tube defect or trisomy 21

• triple screen measures alpha fetoprotein, human chorionic gonadotropin, and estriol
• quad test adds inhibin-A

Question 25

Hemosiderosis

Answer 25

• monogenetic disease affecting iron storage – the intestine absorbs greater than normal amounts of iron, which accumulates in various tissues including liver and heart, organs gradually fail
• treated with bloodletting or chelation therapy (coat iron to make it more easily cleared)

Question 26

Phenylketonuria

Answer 26

• autosomal recessive disease resulting in increased levels phenylalanine
• causes mental retardation
• avoidance of this amino acid in diet can prevent neurologic impairment

Question 27

Duchenne Muscular Dystrophy

Answer 27

• sex-linked disorder (primarily males)
• abnormality in muscle protein dystrophin
• skeletal muscles degenerate, pts develop muscle weakness, heart failure, orthopedic/pulmonary problems

Question 28

Cystic fibrosis

Answer 28

• autosomal recessive disorder caused by mutation in gene that codes for cystic fibrosis transmembrane regulator conductor
• thick mucus, plugged airways, infection
• pneumonia, lungs destructand become unable to function normally
• poor digestion of food, failure to thrive due to blockage of pancreatic ducts

Question 29

Down Syndrome (Trisomy 21)

Answer 29

• 1/1000 newborns, most common genetic cause of mental retardation
• 3 copies chromosome 21
• round face, narrow palpebral fissures, cardiac defects, predisposition to leukemia/Alzheimers/dementia

Question 30

Klinefelter syndrome

Answer 30

• male XXY
• diagnosed at puberty, lack of male sexual development and breast development (risk of breast cancer)
• may have delay in language development

Question 31

Turner

Answer 31

• Female X
• fail to undergo normal female secondary sex development
• short stature, broad neck, normal mentation

Question 32

Fragile X syndrome

Answer 32

• non-medelian, most common cause of MR in males
• trinucleotide repeats on X
• long faces, enlarged ears, MR

Question 33

What is the most common kind of embryonic anomaly?

Answer 33

Congenital Heart Disease

Question 34

Cyanosis

Answer 34

decreased oxygenation in blood, gives skin blue hue

Question 35

Tetralogy of Fallot

Answer 35

-defect between ventricles, misplacement of aorta, obstruction of outflow tract of RV, hypertrophy of RV

Question 36

Meckel’s Diverticulum

Answer 36

outpouching of distal small intestine

Question 37

Meningomyelocele

Answer 37

outpouching of spinal cord and meninges

Question 38

Syphilis

Answer 38

• caused by spirochetes

- causes death or stillbirth, MR, skeletal deformities