Polytene chromosomes develop from the chromosomes of diploid nuclei by successive duplication of each chromosomal element (chromatid) without their segregation. The newly formed chromatids remain associated lengthwise and together form a cable-like structure, referred to as polytene chromosomes.
How many chromosomes are present in a polytene chromosome?
Polytene homologues are held together by somatic pairing. The centromeres of all four chromosomes aggregate to form a chromocentre that is seen amorphous and consists largely of heterochromatin. It is the process of making multiple copies of chromosomes without the segregation and cell division.
How do you explain what a chromosome is?
Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique.
How are polytene chromosomes formed in Drosophila?
These special chromosomes are found in the two-winged (dipteran) fruit fly (Drosophila melonagaster). Polytene chromosomes are formed by the repeated replication of homologous chromosomes, in which the replicated individual sister chromatid strands do not separate.
Do humans have polytene chromosomes?
While polytene chromosomes are most frequently found in insects, they are critical in diverse organisms from ciliates to plants to humans, and they play important roles in disease progression.
What is salivary chromosome?
Definition of salivary chromosome
: one of the very large polytene chromosomal strands made up of many chromatids that are typical of the salivary gland cells of various insects.
What is the use of polytene chromosome?
Polytene chromosomes are considered to be very useful for the analysis of many facets of eukaryotic interphase chromosome organization and the genome as a whole. They develop from the chromosomes of diploid nuclei by successive duplication of each chromosomal element (chromatid).
What is a chromosome explain to kids?
Say: kro-muh-soamz. Your body is made up of billions of cells, which are too small to see without a strong microscope. Inside most of those cells are chromosomes, which are thread-like strands that contain hundreds, or even thousands, of genes. Genes determine physical traits, such as the color of your eyes.
What are chromosome types?
Chromosomes in humans can be divided into two types: autosomes (body chromosome(s)) and allosome (sex chromosome(s)). Certain genetic traits are linked to a person’s sex and are passed on through the sex chromosomes. The autosomes contain the rest of the genetic hereditary information.
What is DNA chromosomes and genes?
Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells that contain a person’s genes. Genes are contained in chromosomes, which are in the cell nucleus.
How many polytene chromosomes are present in Drosophila?
In Drosophila the degree of polyteny is estimated to be approximately 1024 in salivary gland chromosomes, i.e., about 512 in each homolog. Polyploid chromosomes exhibit a banded structure that is reproducible from individual to individual. In Drosophila there are thousands of recognizable bands.
What is Lampbrush and polytene chromosome?
The main difference between polytene and lampbrush chromosome is that polytene chromosomes occur in the salivary glands and other tissues of insects whereas lampbrush chromosomes occur in the oocytes of vertebrates except for mammals and some invertebrates.
What is polytene chromosome write the procedure of squash preparation of Drosophila larvae for polytene chromosome?
4. Polytene chromosome squash preparation:
- Rinse larvae with water and transfer to PBS in a tissue culture dish for dissection.
- Grasp the tip of the mouth hooks with one pair of forceps, hold the body about 2/3 of the way down with the other pair, and pull on the mouth hooks so the salivary glands are exposed.
In which of the following ways do polytene chromosomes differ from other chromosomes?
In which of the following ways do polytene chromosomes differ from other chromosomes? Polytene chromosomes are replicated but not separated. … In the formation of nucleosomes, one histone class, H1, is not directly involved, yet it does associate with DNA to form higher level chromosomal structures.