CHROMOSOMAL STRUCTURES Flashcards
A change in the order/sequence of nucleotide in DNA found in <1%-2% of a given population (due to errors in DNA replication, exposure to
mutagens, or other factors)
MUTATION
- Agents of mutation
MUTAGENS
A difference in DNA sequence found in 1%-2% or more of a given population
- Doesn’t take effect that much
- Example:
o Blood types in humans, color of hair and eyes, separation of most higher organisms into male and female sexes,
polymorphism used for human ID and paternity testing
POLYMORPHISM
2 TYPES OF POLYMORPHISM
BALANCE & BENIGN POLYMORPHISM
- Maintained a population through a balance of positive and
negative phenotype - Example:
o Sickle cell anemia
▪ Abnormal RBC’s resulting into resistance to
infection by Plasmodium species (malaria). - Sickle cell is a hostile environment for
plasmodium species
BALANCE POLYMORPHISM
- Does not have any detectable negative effects on an organism’s health/fitness
- Typically common in populations, do not lead to disease or other adverse phenotypic outcomes
- Example:
o Blood type (ABO blood groups), eye color, facial features,
skin pigmentation
BENIGN POLYMORPHISM
o Abnormal chromosome number
o Affect single genes and are often, but not always, small
changes in the DNA sequence
GENE MUTATION
o Abnormal chromosome number
o Affect single genes and are often, but not always, small
changes in the DNA sequence
CHROMOSOME MUTATIONS
- Process by which the long linear DNA molecules of eukaryotic chromosomes are organized and packaged into highly condensed structure.
CHROMOSOMAL COMPACT
Protective cap
o Prevents the end from being damaged
- Regulate cell division
TELOMERES
- Site of attachment for spindle fibers (anaphase/metaphase) during mitosis
CENTROMERE
CLASSIFICATION OF CHROMOSOME BASED ON SIZE AND CENTROMERE POSITION
- Centromere located at the end
TELOCENTRIC
CLASSIFICATION OF CHROMOSOME BASED ON SIZE AND CENTROMERE POSITION
- Centromere near the tip
- Satellite
o Contains many copies of gene encoding for RNA and
chromosomal proteins
ACROCENTRIC
- Feulgen, Wright, and Hematoxylin
CONVENTIONAL CYTOLOGICAL STAIN
CLASSIFICATION OF CHROMOSOME BASED ON SIZE AND CENTROMERE POSITION
- Centromere divides the chromosome into a short & long arm
SUBMETACENTRIC
- Quinacrine and quinacrine mustard
FLUORESCENT DYES
- Giemsa stain
- Pattern: G bands
CHEMICAL DYE
- Pattern: R bands (can be visualized after staining with acridine
orange)
Harsher treatment of chromosomes (87oC for 10 min, then cooling to70oC) before Giemsa staining
Centromere staining
* Pattern: C bands
ALKALI TREATMENT
- Silver nitrate
o Stain specifically at the constricted regions, or stalks, on
the acrocentric chromosomes
NUCLEAR ORGANIZING REGION (NOR) STAINING
- Indirect method of detecting genome mutations, or aneuploidy
- Measuring DNA content of individual cells
- Aneuploidy is reflected by a change in the amount of DNA
FLOW CYTOMETRY
- Binds to the surface grooves of dsDNA
- Fluorescence blue under UV light
- Chromosome & nucleus → more visualized
- Used mostly in FISH
- Microscope: Fluorescence
4’6-DIAMIDINO-2-PHENYLINDONE
- Exchange of genetic material between chromosomes
TRANSLOCATION
TYPES OF TRANSLOCATION :
RECIPROCAL & ROBERTSONIAN
- Direct method of detecting genome mutations, an aneuploidy
→ observation of metaphase chromosome structure by
arranging them according to size.
KARYOTYPING
- Loss of chromosomal material
DELETION
- Gain of chromosomal material
INSERTION
- Results from deletion of genetic regions from ends of the
chromosome and a joining of the ends to farm a ring - Sticky ends
- Affect the kids mostly
o Microcephaly
▪ Smaller brain size
RING CHROMOSOME
- Metacentric chromosome resulting from transverse splitting of
centromere during cell division
ISOCHROMOSOME
- Result from excision, flipping, and reconnecting chromosomal material within the same chromosome
INVERSION
- Translocated or otherwise rearranged parts from 2 or more
unidentified chromosomes joined to a normal chromosome
DERIVATIVE CHROMOSOMES
Example 1: 46, XX, del (7)(q13)
A female with deletion in the long arm of chromosome
7 at region 1, band 3
Example 2: 47, XX, + 21
A female with trisomy 21 (Down Syndrome)
Example 3: 46, XY, t(5:17)(p13.3:p13)
▪ A male with a translocation between the short arms of
chromosome 5 & 7 at region 1, band 3, sub-band 3,
and region 1, band 3, respectively.
- Does not include centromere
- Involve sequences within 1 arm of the
chromosome
PARACENTRIC INVERSION
Include centromere in the inverted
region
PERICENTRIC INVERSION
