Birth defects

chromosomal abnormalities can be … or …

chrosomal abnormalities can be structural or numerical

what is the connection between chromosmal abnormalities and sponatenous abortion after conception

30-50% aborts spontaneously,

25% of sponatenous abortion is bc of chromosomal abnormalities (dus 50% of the 50%)

what are linked genes

these are inherited together

what are some common chromosomal abnormalities

• deletions, insertions, duplications, translocations (large segments)

• sex chrom anomalies

• imprinting errors

• poly/mono-ploidies

chromosomal numerical abnormalities Trisomy 21

Trisomy 21 = Down syndrome (extra chom 21, some degree of ID, craniofacial abnormalities (eg a flat face)

triploidy

3 sets of chromosomes, lethal

Klinefelter syndrome

only in mailes, detected by amniocentesis

47 chromsomes (XXY) (soms zelf 48 chrom met XXXY) vaak door nondisjunction of X chrom & bar body (=condensend X chrom, in vrouwen is dit normaal)

features: sterilitym testicular atrophy, hyalinization of seminiferous tubules (gynecomastia)

numerical chromsomal abnormality: Trisomy 18

Trisomy 18 = Edward’s syndrome (ID, congenital heart defect, low-set ears, flecxion of fingers and hands) only 5% live +1 year

numerical chromsomal abnormality: Trisomy 13

Trisomy 13 = Patau syndrome, only 5% live +1 year

• ID,

• holoprosencephaly,

• cleft lip,

• congenital heart defects, deafness)

numerical chromsomal abnormality: Monosomy X

Monosomy X = Turner syndrome, 45 chrom, missing X, 98% spontaneously aborted, only monosomy compatible with life (women)

• absence of ovaries

• short

• webbed neck

what is the main cause of structural (chromosmal abnormalities)

environmental factors:

• viruses

• radiation

• drugs

what is a single gene mutation

type of defect caused by a mutation in just one gene

diagnostic techniques for genetic abnormalities

• cytogenetics (check chrom. nr aka ploidy)

• FISH (check specific region)

• exome sequencing (all protein coding DNA)

Primordial germ cells (2N) originate outside the embryo, migrate to gonads, and form gametes. Errors in this migration or gametogenesis can lead to genetic issues.

just a note