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Module 3 - Genetics [ch. 2,3,4]1.Chromosomes alterations and associated disorders a.Homologous - 22 of 23 pairs are identical in appearance -sex chromosomes = 2 homologus cells X chromosomes in female and nonhomolous pair, X and Y for males - 46 chromosomes in 23 pairs ( Normal) b.Euploid [eu = good/true] cells- abnormal multiple of the normal chromosomes [normal = 46 chromosomes] ex : An embryo that contains a normalnumber of chromosomes is a 'euploid' embryo. i.Polyploid cell - when a euploid cell has more than the diploid number [ex: Triploidy ( ex: when a zygote that has 3 copies of each chromosomesrather than the normal 2) / tetraploidy (a condition in which euploid cells have 92 chromosomes c.Aneuploid cell - does not have multiple of 23 chromosomes i.Trisomy - a condition where the cells has 3 copies of 1 chromosomes ii.Partial Trisomy- in which only an extra portion of a chromosome is present in each iii.Monosomy- condition where the cell has only 1 copy of a given chromosome iv.Nondisjunction - an error where homologous chromosomes fail to separate during meiosis and mitosis ---- aneuploidy is usually a result v.Principle = loss of chromosome material has more serious consequences than duplication of chromosome material ●Zygote with no X chromosome will not survive d.Autosomal aneuploidy [disorders]i.Down syndrome - trisomy of chromosome 21 1.Systemic disorders: congenital heart disease, low immune system, increased leukemia, symptoms of Alzheimer's disease table 2-1 page 46 2.Causative factors: 97% by nondisjunction, 3% translocationii.Turner syndrome- 45 X, monosomy of x chromosomes [only females]-Sex linked 1.Systemic disorders: coarctation [narrow] aorta, edema of feet in
newborns, sterile [can’t reproduce], gonadal streaks rather than ovaries sometimes leading to cancer2.Causative factors: 75% from mother caused by error in fatheriii.Klinefelter syndrome- 47 XXY, XXY condition [males]-sex linked 1.Systemic disorders: sparse body hair, sterile, small tessticles, long limbs, breast development 2.Causative factors: 50% of nondisjunction of X in mother; XXY and XXXY karyotypes causing physical and mental impairmentiv.Cri du chat syndrome- “cry of the cat” described as the cry of the child, low birth weight, intellectual disability, microcephaly [small head], and heart defects; short arm of chromosome 5 1.Deletions - broken chromosome and lost DNAEx the zygote has one chromosome with the normal complement of genes and one with some missing 2.Duplications - less serious physical effect but causes mental retardation 3.Inversions - 2 breaks of a chromosome, reinserted, but in inverted order [ex: ABCDEFG → ABEDCFG] although it can cause position effect resulting in physical defects leading to duplication and deletions 4.Translocation- interchange of genetic material between nonhomologous chromosomes -Reciprocal translocationoccurs when breaks take place in 2 different chromosomes and material is exchange. The carrier is usually normal but his or her offspring can have duplications or deletions.