chromosomes, chromosome abnormalities and birth defects

Question 1

define karyotype

Answer 1

22 autosomes, 1 sex from each parent

Question 2

structural

Answer 2

translocations (interchange of genetic material between non-homologous chromosomes) of 2 different chromosomes (when balanced, not generally deleterious as genes are normally switched and fused equally); may also be due to duplication, deletion, inversion or formation of ring

Question 3

Robertsonian translocation

Answer 3

long arms (q) fuse to form single, large acrocentric (satellite short arms containing rRNA genes) chromosome with single centromere

Question 4

numerical

Answer 4

aneuploidy: monosomy: -1 (nearly always fatal); disomy: 0 (normal), trisomy: +1 (feasible in chromosomes 13 - Patau, 18, 21 - Down); tetrasomy: +2

Question 5

mosaicism

Answer 5

individual has 2 genetically different populations of cells (different cell lineages); occurs due to non-disjunction (caused by radiation and age related decrease in immunological competence) in mitosis

Question 6

Turner’s syndrome: sex chromosome aneuploidy

Answer 6

monosomy X (45, X); significant loss of X or Y in parental meiosis; predominantly female, renal problems, short stature

Question 7

Klinefelter’s syndrome: sex chromosome aneuploidy

Answer 7

(47, XXY); predominantly males, development of breasts, infertility, small testicles