KARYOTYPING Flashcards
WEEK 14 AND 15
the number and appearance of chromosomes in the nucleus of a eukaryotic cell.
also used for the complete set of chromosomes in a species, or an individual organism.
Karyotype
Karyotype analyzes
~Sex chromosomes content
~Presence or absence of individual chromosomes
~Nature or extent of chromosomal aberrations
Karyotyping Analysis
specimen for adult:
blood (WBC), bone marrow, or skin sample
Karyotyping Analysis
specimen for an unborn child:
amniotic fluid (contains stray cells) or extra-embryonic cells (from the chorionic villi)
Karyotyping Procedure:
plant-derived chemicals that stimulate mitosis
Lectins
Karyotyping Procedure:
Drug used to stop or arrest the mitotic process at metaphase. It arrests the action of spindle fiber microtubules; hence ceasing the mitotic process
Colchicine
Key characteristics used to distinguish chromosomes from one another:
~The length of the arms of the chromosome
~Shape
~General appearance of the chromosome.
Variations in Chromosome number:
a chromosome number that is a multiple of the normal haploid set.
Polyploidy
Variations in Chromosome number:
It is a deviation of an abnormal number of chromosomes in which an additional chromosome pair is added to a particular chromosome (48 chromosomes)
Tetrasomy
Variations in Chromosome number:
a chromosomal number that varies by something less than a set
Aneuploidy
Variations in Chromosome number:
having only one member of a homologous pair. (e.g., Turner syndrome)
~45 chromosomes
~one chromosome is missing
Monosomy
Variations in Chromosome number:
having three copies of a single chromosome. (e.g., Down syndrome)
~most common aneuploidy
Trisomy
Major cause of reproductive failure is
Aneuploidy
caused of Polyploidy: (EEE)
Errors in meiosis
Events after fertilization
Errors in mitosis
Type of Polyploidy
~Three sets of chromosomes
~Most common form of polyploidy
~Probably due to polyspermy
~15-18% of all spontaneous abortions
~Approximately 75% have two sets of paternal chromosomes
~1% conceptions are triploid but 99% die before birth
due to:
~egg is fertilized by a sperm with a double set of chromosomes
~the egg is fertilized by two sperms
~the egg producing cells fail to divide properly and so the mature egg contains double set of chromosomes.
Triploidy
Type of Polyploidy:
~Four sets of chromosomes (two extra chromosome set are present)
~5% of all spontaneous abortions
~Extremely uncommon in live births
~May result from failure of cytokinesis in the first mitotic division.
~Life threatening
(92 chromosomes)
Tetraploidy
___ is the failure of homologs or sister chromatids chromosomes to separate in meiosis or mitosis
Nondisjunction
Autosomal Monosomy or Autosomal Trisomy:
~Lethal condition
~Rarely seen in spontaneous abortions and live births
~Majority are lost early in development
Autosomal Monosomy
Autosomal Monosomy or Autosomal Trisomy:
~Most are lethal
~Varies by chromosome (e.g., Trisomy 13, 18, 21)
Autosomal Trisomy
Autosomal Trisomy:
~Affected infants small at birth grow slowly and are mentally retarded
~Malformation of heart, hands and feet
~80% are female
~Advance maternal age is a risk factor
Trisomy 18
Other name for Trisomy 18
Edwards Syndrome
Autosomal Trisomy:
~Lethal: mean survival time is at least 1 month
~Facial malformations, eye defects, extra fingers or toes, and large protruding heels
~Severe malformations of brain, nervous system, and heart
~Parental age only known risk factor
Trisomy 13
Other name for Trisomy 13
Patau Syndrome
Autosomal Trisomy:
~First chromosomal abnormality discovered in humans (1959)
~Leading cause of mental retardation and heart defects in US
~Wide flat skulls, skin folds in the corner of the eyes, spots on the irises, and thick-furrowed tongues.
~40% congenital heart defects.
Trisomy 21
Other name for Trisomy 21
Down Syndrome
Risks for autosomal trisomy (2)
~Advanced maternal age
~Risk increased rapidly after 35 years of age
Autosomal Trisomy:
~Features do not develop until after puberty
~Affected individuals are male with low fertility and may have mental dysfunction
~60% due to maternal nondisjunction
~Other forms XXYY, XXXY and XXXXY
Klinefelter’s Syndrome (XXY)
Autosomal Monosomy
~Females, short, wide chest, rudimentary ovaries, and abnormal sexual development
~Puffiness of hands and feet
~Abnormalities of the aorta
~No mental dysfunction
~Single X chromosome (lethal)
Turner Syndrome (X)
Autosomal Trisomy:
~Above average in height
~No established link with possible antisocial behavior
Jacob Syndrome (XYY)
inactive X chromosome in a female somatic cell
Barr Body
Cells Used for Chromosomal Analysis (STRACAL)
Skin cells
Tumor cells
Rare fetal cells from maternal blood
Any cell with a nucleus
Chorionic villi
Amniotic cells
Lymphocytes
Most common type of banding
G-banding
Types of banding:
Obtained with Giemsa stain following digestion of chromosomes with trypsin.
~The dark regions tend to be heterochromatic, late-replicating and AT rich
~The light regions tend to be euchromatic, early replicating and GC rich
G-banding
Types of banding:
the reversed of G-banding.
~The dark regions are euchromatic (guanine-cytosine rich regions)
~The bright/light regions are heterochromatic (thymine-adenine rich regions)
R-banding
Types of banding:
Giemsa binds to consecutive heterochromatin, so its stains centromeres.
C-banding
Types of banding:
a fluorescent pattern obtained using quinacrine for staining. The pattern of bands is very similar to that seen on G-banding
Q-banding
Types of banding:
Visualize telomeres
T-banding
More specific than Giemsa stain
Spectral Karyotyping
a molecular cytogenetic technique used to simultaneously visualize all the pairs of chromosomes in an organism in different colors.
this technique is used to identify structural chromosome aberrations in cancer cells and other disease conditions when Giemsa banding or other techniques are not accurate enough
(e.g., FISH typing)
Spectral Karyotyping
a technique used to quantify the DNA copy number on a genomic scale. Short sequences of DNA from specific loci all over the genome are isolated and enumerated.
This method is also known as virtual karyotyping
(e.g., PCR)
Digital Karyotyping
the number of complete sets of chromosomes in a cell
Ploidy
Where one sex is diploid, and the other haploid. It is a common arrangement in the Hymenoptera, and in some other groups.
Haplo-diploidy
A process by which chromosomes replicate without the division of the cell nucleus, resulting in a polyploidy nucleus. Also called endomitosis.
Endopolyploidy
Translocation mutation commonly associated with chronic myelogenous leukemia and less often with acute lymphoblastic leukemia.
Philadelphia chromosome
