Chromosomal abnormalities (M1B1) Flashcards
what’s the most common birth defect?
Turner’s syndrome
what is the to the technique that produces an image of an individual’s chromosomes?
karyotype
what is ploidy?
The number of sets of chromosomes in a cell or an organism.
ex. haploid means one set and diploid means two sets.
monoploid > n
haploid > n
diploid > 2n
euploid > 2 or more eg. 2n, 3n 4n etc.
triploid and up is both euploid and polypoid
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a condition in which the cells of an organism have more than two paired (homologous) sets of chromosomes is called?
polyploid
rarely occurs in humans, although it occurs in some tissues (especially in the liver)
what is aneuploid?
is an abnormal number of chromosomes such as having a single extra chromosome (47), or a missing chromosome (45)
what is the difference between aneuploidy and polyploidy?
- Aneuploidy refers to a numerical change in part of the chromosome set
- polyploidy refers to a numerical change in the whole set of chromosomes
Aneuploid (not good) karyotypes are given names with the suffix -somy (rather than -ploidy, used for euploid karyotypes), such as trisomy and monosomy.
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trisomy is when a person has three of a particular chromosome, instead of the usual two. monosomy is when they just have one chromosome instead of the usual two.
The most well-known trisomy is?
trisomy 21, or Down syndrome
what are autosomes and sex chromosomes?
autosomes are the 22 similar chromosomes between both genders while sex chromosomes which is 23 is XX for female and XY for male
what is genotype and phenotype?
- genotype is the set of genes the individual carries
- phenotype is the external appearance of an individual as determined by his genotype
what is non-disjunction?
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution
When a person has more than one type of chromosomal makeup, that is called?
Mosaicism
(In Down syndrome, mosaicism means that some cells of the body have trisomy 21, and some have the typical number of chromosomes)
causes of down syndrome?
- Meiotic nondisjunction - 95% (trisomy 21)
- Unbalanced translocation- 4% b/w 21 and 13,14,15
- Mosaicism due to mitotic non dysjunction-1%
infants who have trisomy 18 (edward syndrome) usually die by the age of? what are the symptoms?
- 2 months
- Mental retardation, congenital heart defects, low set ears, flexion of fingers
infants who have trisomy 13 usually die by the age of? what are the symptoms?
- 3 months
- mental retardation, holoprosencephly(when the face doesn’t fully close), congenital heart defects
cause of klinefelter’s syndrome? who does it affect? symptoms?
-Nondisjunction of XX
homologue
-males only
-Sterility, testicular atrophy, hyalinization of seminiferous tubules, gynecomastia (having boobs)
no. of chromosomes? causes of turner syndrome? who does it affect?
-45 X karyotype
-females
-Structural abnormalities of X chromosome, One X chromosome is
missing, Mitotic nondisjunctiom
structural abnormalities occur when the chromosome’s structure is altered, this can take several forms like?
Translocation, deletion or duplication of
chromosomes
two main types of translocations?
Reciprocal and Robertsonian
what are the differences between Reciprocal and Robertsonian translocation?
•reciprocal translocation, two different chromosomes have
exchanged segments with each other.
•Robertsonian translocation, an entire chromosome attaches to another at the centromere
chromosomal deletions are caused by?
environmental factors
cause of cri-du-chat syndrome? symptoms?
- Partial deletion of chromosome 5
- High pitched cat like cry, a small head size , low birth weight, mental retardation and congenital heart disease
why do cri-du-chat patients have cat like cry?
larynx of the child is improperly
developed.
