Polytene and lampbrush chromosomes are examples of giant chromosomes. Polytene Chromosome. Giant chromosomes were first time observed by E.G. Balbiani in the year 1881 in nuclei. of certain secretory cells (salivary glands) of Chironomas larvae (Diptera).
What is a polytene chromosome?
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.
What is the difference between polytene chromosome and Lampbrush 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 the function of Lampbrush chromosome?
Lampbrush chromosomes are also involved in the production of “masked” mRNAs for early development. The giant granular loops could either be the sites where such mRNAs are packaged or they could be sites where specific alterations of the deoxyribonucleoprotein fiber take place.
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.
Where is Lampbrush chromosome found?
Lampbrush chromosomes (LBCs) are transcriptionally active chromosomes found in the germinal vesicle (GV) of large oocytes of many vertebrate and invertebrate animals and also in the giant single-celled alga Acetabularia. These cells are all in prophase of the first meiotic division.
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 are the 4 types of chromosomes?
On the basis of the location of the centromere, chromosomes are classified into four types: metacentric, submetacentric, acrocentric, and telocentric.
Do humans have Lampbrush chromosome?
Human and other mammalian chromosomes do not form recognizable lampbrush chromosomes in their own oocytes or in any somatic cells.