What is salivary gland chromosome?
salivary-gland chromosome Polytene, chromosome found in the interphase nuclei of the salivary-gland cells in larvae of Diptera. These chromosomes undergo complete somatic pairing to form units of identical chromosomes joined along their length (in parallel) to one another.
Why are polytene chromosomes found in Salivary Glands?
Polytene chromosomes are a strongly amplified form of interphase chromosomes, found, for example, in salivary gland cells of Drosophila and Chironomus. They arise through many rounds of DNA replication without subsequent separation of daughter chromatids. The chromatids run through the entire length of a chromosome.
Why might polytene chromosomes be useful in a larval insect?
Polytene chromosomes, consequently, have been used to reveal morphologically similar species (i.e., sibling species) through the absence of hybrids. The evolutionary relationships of insects also can be reconstructed on the basis of uniquely shared banding sequences.
Where are polytene chromosomes found?
Polytene chromosomes have been found in many tissues of the representatives of two orders of insects: Diptera and Collembola, in the macronuclear anlagen of Infusoria, in certain organs and tissues of mammals and also in the cells of the synergids, antipods and endosperm of angiospermous plants.
What are Balbiani rings?
Balbiani rings are exceptionally large puffs on the polytene chromosomes in the dipteran Chironomus tentans. These puffs are particularly well suited for studies of the structure of active genes and the synthesis and transport of specific RNA-protein (RNP) particles.
Do humans have polytene chromosomes?
This concept is confirmed by comparative studies of human, mink, and fox polytene chromosomes. The final step of the trophoblast giant cell differentiation is characterized by a transition from polyteny to polyploidy, with subsequent fragmentation of the highly polyploid nucleus into fragments of low ploidy.
Do humans have giant chromosomes?
Polytene chromosomes are formed when the products of multiple rounds of S-phase remain tightly associated to form one supersized chromosome. We also note that polytene chromosomes can form in cells that undergo transient nuclear envelope breakdown without subsequent chromosome separation (Cantero et al.
What is the smallest human chromosome?
Chromosome 21 is the smallest human chromosome, spanning about 48 million base pairs (the building blocks of DNA) and representing 1.5 to 2 percent of the total DNA in cells.
Which chromosome has highest DNA content?
Chromosome 1 is the largest human chromosome, spanning about 249 million DNA building blocks (base pairs) and representing approximately 8 percent of the total DNA in cells.
What is the 1st chromosome?
Chromosome 1 is the designation for the largest human chromosome. Humans have two copies of chromosome 1, as they do with all of the autosomes, which are the non-sex chromosomes. Chromosome 1 spans about 249 million nucleotide base pairs, which are the basic units of information for DNA.
Whats bigger DNA or chromosome?
If we talk about the uncoiled DNA, then DNA is larger than the chromosome. And if we talk about the coiled DNA, then DNA is smaller than the chromosome. When DNA gets coiled, it becomes smaller in size just in order to fit the nucleus of the cell.
What is the main difference between Chromatin and Chromosomes?
Chromatin is a complex formed by histones packaging the DNA double helix. Chromosomes are structures of proteins and nucleic acids found in the living cells and carry genetic material. Chromatin is composed of nucleosomes. Chromosomes are composed of condensed chromatin fibers.