What is the function of constitutive heterochromatin?
What is the function of constitutive heterochromatin?
Constitutive heterochromatin is found more commonly in the periphery of the nucleus attached to the nuclear membrane. This concentrates the euchromatic DNA in the center of the nucleus where it can be actively transcribed.
What causes banding patterns on chromosomes?
Banding patterns are patterns of light and dark transverse bands on chromosomes. The light and dark bands become apparent by staining the chromosome with a chemical solution and then viewed under a microscope. These bands describe the location of genes on a chromosome.
Which of the banding techniques is not used to observe plants?
Note: Different banding techniques are used for the identification of chromosomes in plants and animals. However, G and R banding techniques don’t work on plant chromosomes.
What is Q banding used for?
QFQ-banding (Q banding). This fluorescent staining method, which uses quinacrine, is used to identify individual chromosomes and their structural anomalies, given the resulting banding pattern. The characteristic banding pattern can be used to identify each chromosome accurately.
What causes a dark band on a chromosome?
A karyotype analysis usually involves blocking cells in mitosis and staining the condensed chromosomes with Giemsa dye. The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a dark band.
What are the different banding techniques?
The most common methods of dye- based chromosome banding are G- (Giemsa), R- (reverse), C- (centromere) and Q- (quinacrine) banding. Bands that show strong staining are referred to as positive bands; weakly staining bands are negative bands.
Where is constitutive heterochromatin found?
The majority of constitutive heterochromatin is found at the pericentromeric regions of chromosomes, but is also found at the telomeres and throughout the chromosomes.
Why does constitutive heterochromatin stain darker?
The constitutive heterochromatin stains darker because of the highly condensed nature of the DNA. Constitutive heterochromatin is not to be confused with facultative heterochromatin, which is less condensed, less stable, and much less polymorphic, and which does not stain when using the C-banding technique.
What is facultative heterochromatin?
Facultative heterochromatin is a type of reversible heterochromatin found in a cell. It is not a conserved factor to a particular set of cells. Additionally, the genes in facultative heterochromatin have the potential to undergo expression at a particular level of development.
What are histone modifications and where are they found?
Histone modifications are one of the main ways that the cell condenses constitutive heterochromatin. The three most common modifications in constitutive heterochromatin are histone hypoacetylation, histone H3-Lys9 methylation (H3K9), and cytosine methylation. These modifications are also found in other types of DNA, but much less frequently.
