Tag: botany

Chromosomes were discovered by Hofmeister (1848), studied by Strasburger (1875) and given the present name by Waldeyer (1888) after their staining by dyes like Janus Green. Chromosomes are a thread like structure. It is composed of DNA and protein and it is considered as a carrier of genetic characters from parents to offspring.

Chromosomes are composed of DNA, RNA, histones, non-histones. A chromosome is a packaged and organized chromatin, a complex of macromolecules found in cells, consisting of DNA and protein. The functional segments of DNA are known as genes. The DNA-bound macromolecules are proteins, which serve to package the DNA and control its functions.

The telomeres do not have any overhanging ends of nucleotides so it is known as non sticky chromosome ends called telomere. A telomere is a region of repetitive nucleotide sequences at each end of a chromatid, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. 

Chromonemata are embedded in the matrix. Chromonemata are the spirally coiled central filament of a chromatid along which the chromomeres are aligned. A chromomere is one of the serially aligned beads or granules of a eukaryotic chromosome, resulting from local coiling of a continuous DNA thread. It is visible on a chromosome during the prophase of meiosis and mitosis. 

A chromomere  is one of the serially aligned beads or granules of a eukaryotic chromosome, resulting from local coiling of a continuous DNA thread. It is visible on a chromosome during the prophase of meiosis and mitosis. The chromomeres are present during leptotene phase of prophase I during meiosis. During zygotene phase of prophase I, the chromomeres of homologs align with each other to form a homologous rough pairing. These chromomeres help provide a unique identity for each homologous pairs.

All chromosomes mentioned are large chromosomes. These chromosomes are producing large amounts of RNA for the oocyte, and most of the genes present in the DNA loops are being actively expressed. Each lateral loop contains one or several transcription units with polarized RNP-matrix coating the DNA axis of the loop.The majority of the DNA, however, is not in loops but remains highly condensed in the chromomeres on the axis, where genes are generally not expressed. This is about lampbrush chromosomes, the polytene and mega chromosomes are also larger than the other normal chromosomes.

Deoxyribonucleic acid (DNA) is the information-carrying molecule found in all living organisms. In most animal, plant and fungal cells, DNA is stored in the nucleus coiled up in thread-like structures called chromosomes.

Chromosomes are thread like structures located inside the nucleus of animal and plant cells. Each chromosome is made of deoxyribonucleic acid (DNA). Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique.

B chromosomes are called supernumerary or accessory chromosomes. It is because these chromosomes are not considered as essential for being normal. These are not found in every individual. During alloploids, it suppresses homologous pairing which reduces multiple pairing between homologous chromosomes in allopolyploids.