NUR 332 Exam 2 - Module 3 Genetics[ch 2,3,4 1 Chromosomes...

Module 3 - Genetics [ch. 2,3,4]
1. Chromosomes alterations and associated disorders [3]
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 normal number 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 chromosomes
rather 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% translocation
ii. 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 cancer
2. Causative factors : 75% from mother caused by error in father
iii. 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 impairment
iv. 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 DNA
Ex 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 translocation occurs 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.