congenital and genetic disorders

Question 1

what are congenital abnormalities?

Answer 1

-BIRTH defects —>
result from PROBS in DEVELOPMENT in EMBRYO
(any non-genetic defect at birth!)

Question 2

what is period of vulnerability?

Answer 2

-time in GESTATION where embryo is MOST sensitive to development ERRORS

Question 3

time period of vulnerability is?

Answer 3

busy and sensitive; organogenesis (organs begin to form)

-15 to 60 days approx post conception

Question 4

critical period is?

Answer 4

the time period for each organ system during development where they are particularly sensitive and any interruption in process may result in baby being born with congenital abnormality

Question 5

CNS critical period?

Answer 5

2-4.5 weeks

Question 6

CVS critical period?

Answer 6

2.5-5.5 weeks

Question 7

limbs critical period?

Answer 7

3.5-7weeks

Question 8

eyes critical period?

Answer 8

3.5-7.5 weeks

Question 9

external genitalia period?

Answer 9

6.5 to 10 weeks

Question 10

what is a teratogen?

Answer 10

any environmental factor causing congenital abnormality

-includes maternal environment AND environment surrounding mother

Question 11

examples of teratogens?

Answer 11

example: radiation (affects cell function)
example: drugs/ chemicals (can cross placenta)- alcohol, thalidomide effect
example: microbes (pathogens/toxins)- screened early in pregnancy like rubella virus
example: cig smoke

Question 12

are congenital abnormalities always due to a teratogen?

Answer 12

no, can be a result of a lack of something (like malnutrition)

Question 13

what are the 4 genetic abnormalities

Answer 13

1. monogenic
2. polygenic/complex trait (multifactoral)
3. mitochondrial gene disorders
4. chromosomal defects

Question 14

what is a monogenic abnormality?

Answer 14

• SINGLE gene
• caused by defective or mutant allele
• primarily affect CHILDREN
• pattern of inheritance depend on whether phenotype is DOMINANT or RECESSIVE and whether AUTOSOMAL or SEX chr
• –> leads to formation of ABNORMAL protein, or decreased protein production of gene product
• –> results in: defective enzyme or decreased amts of enzyme, defects in receptor proteins, alterations in non-enzyme proteins, mutations resulting in unsual rxns to drugs

Question 15

3 types of monogenic abnormalities?

Answer 15

a) autosomal dominant
b) autosomal recessive
c) x-linked disorders or “sex linked”

Question 16

what is autosomal dominant disorder?

Answer 16

• SINGLE mutant allele form affected parent transmitted to offspring regardless of sex
• autosomal= non-sex
• dominant= if defective allele is transmitted to offspring it will cause an abnormality
• affected parent has 50% chance of transmitting it

Question 17

what is autosomal recessive disorder?

Answer 17

• BOTH alleles affected
• both parents could be unaffected but carriers
• affects sexes equally
• if one parent fully affected, all children carriers
• if both parents carriers: 25% child affected, 25% unaffected, 50% carriers

Question 18

X-linked disorders or “sex linked”?

Answer 18

• most sex chromosome defects are on X (female) chromosome)—> males most affected because females are homogametic and have 2 X, male have one (heterogametic)
• unaffected mother carries 1 normal one mutant: 50% chance to sons, 50% chance daughters carrying
• affected father: transmits defective to daughters, does not transmit to son

Question 19

polygenic/complex trait (multifactoral inheritance disorder)?

Answer 19

• caused by multiple genes (2 or more) and in many cases environmental factors (like viral infection)
• expressed during FETAL life and present at birth, or may be expressed LATER in life
• environmental factors play greater role in disorders that develop LATER
• multifactoral= someone could have predisposition but not get it b/c of good lifestyle

Question 20

mitochondrial gene disorders?

Answer 20

• DNA not only in nucleus, some in MITOCHONDRIA
• 37 mitochondrial genes
• involved in production of ATP
• code for enzymes involved in electron transport chain (resp chain) in mitochondria
• only transmitted by MOTHER (maternal inheritance)
• b/c sperm tail falls off with mitochondrial genes in it
• most MITOCHONDRIAL defects show in NEUROMUSCULAR defects
• –> neurons and muscle cells have high requirement for OXIDATIVE metabolism (more ATP!)

Question 21

chromosomal defects?

Answer 21

46 chromosomes, 23 pairs

-defect in NUMBER or STRUCTURE of chromosomes

Question 22

what is a karytotype?

Answer 22

-TEST to identify and evaluate size, shape, number of chromosomes in sample of body cells

Question 23

aneuploidy=

Answer 23

problem related to NUMBER of chromosomes

Question 24

what is a numerical abnormality (chromosomal)?

Answer 24

aneuploidy, problem related to number of chromosomes (more or less than normal)
monosomy= one chromosome pair is LACKING
trisomy= EXTRA chromosome (downsyndrome is trisomy 21)

Question 25

turners syndrome?

Answer 25

-female has missing sex chromosome
-1 in 2500 births, gametes XO not XY
can live with turners

Question 26

klinefelters syndrome?

Answer 26

-male has extra X chromosome

XXY, 47 chromosomes

Question 27

what is a structural defect (chromosomal)?

Answer 27

• under certain circumstances SECTION of CHROMOSOME can break OFF, detached segment can do 1 of 3 things:
  1. deletion
  2. inversion
  3. translocation

Question 28

what is deletion (structural)

Answer 28

LOST a piece of chromosome (one in pair)

• detached segment does NOT reattach
• LOSS of genetic material

Question 29

what is inversion (structural)

Answer 29

-piece of chromosome INVERTS 
(top to bottom) 
-REVERSES its orientation and reattaches to original 
-two breaks in a SINGLE chromosome 
-PERICENTRIC= around the centromere
-PARACENTRIC= away from centromere

Question 30

what is translocation (structural)

Answer 30

• piece TRANSFERRED over to another chromosome
• segment BREAKS off and attaches to a non-homologous chromosome
• balanced translocation, robertsonian, isochromosomal