Cell - The Unit of Life Test - 7

Histone H₁ is one of the five main histone protein families which are components of chromatin in eukaryotic cells. Though highly conserved, it is nevertheless the most variable histone in sequence across species. Unlike the other histones, H1 does not make up the nucleosome "bead". Instead, it sits on top of the structure, keeping in place the DNA that has wrapped around the nucleosome.

Secondary constriction II of chromosome is generally concerned with the synthesis of rRNA. Secondary constriction is seen at the chromosome in addition to primary constriction or centromere. Chromosome can bend only at the site of primary constriction during anaphase.

The chromosome that remains condensed during interphase is X chromosome of Barr body. A Barr body is the inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization. In humans with more than one X chromosome, the number of Barr bodies visible at interphase is always one less than the total number of X chromosomes. 

Megachromosomes are found in tobacco. Only chromosomes with large heterochromatic segments become megachromosomes and the enlarged parts themselves show at interphase and prophase, the intense staining characteristic of heterochromatin.

Lampbrush Chromosomes (LBCs) are present in the oocytes of birds, lower vertebrata and invertebrates during the prolonged prophase of the first meiotic division.

Dr. Hammerling began acetabularia in laboratories in 1930.He determine the nucleus control the development of organisms by containing hereditary information or DNA from his grafting experimentation on the Green algae.

The simple stain can be used to determine the shape , size and arrangement of the cell.Basic stain such as methylene blue, gram satfranin or gram Crystal voilet are useful for staining the most bacteria...

Nucleus controls the activity of cytoplasm by sending RNA. The nucleus pores allows the movement of large molecules such as proteins and RNA through the pores is required for both gene expression and the maintenance of chromosomes. The interior of the nucleus does not contain any membrane-bound sub compartments, its contents are not uniform, and a number of sub-nuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best-known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.

Diplotene chromosomes are the lampbrush chromosomes. Lampbrush chromosomes are a special form of chromosome found in the growing oocytes (immature eggs) of most animals, except mammals. Chromosomes transform into the lampbrush form during the diplotene stage of meiotic prophase I due to an active transcription of many genes. They are highly extended meiotic half-bivalents, each consisting of 2 sister chromatids.

Nucleoplasmin is a thermostable acidic protein with a pentameric structure which is present in the nuclear pore complex. The pentameric protein participates in various significant cellular activities like sperm chromatin remodeling, nucleosome assembly, genome stability, ribosome biogenesis, DNA duplication and transcriptional regulation. During the assembly of regular nucleosomal arrays, these nucleoplasmic transfer the DNA to them by binding to the histones. This reaction is ATP-dependant.

A swelling in the band of a polytene chromosome is an indication of gene action. Polytene chromosomes are very large chromosomes. These are developed from the specialized cells which undergo many rounds of DNA replication without cell division forming a giant polytene chromosome. Polytene chromosomes are formed when replication produce many sister chromatids that remain synapsed together. Polytene cells have multiple copies of genes permits a high level of gene expression. 

Thus, the correct answer is option A. 

A nucleoside triphosphate (NTP) is a molecule containing a nucleotide bound to three phosphates. These NTPs include ATP, GTP, CTP, UTP. They generally provide energy and the phosphate group for phosphorylation. They are stored in the nucleus.
Thus, the correct answer is option (D), 'CTP and all the above'.

Ribonucleic acid occurs in the nucleus and cytoplasm. The DNA molecules are transcribed inside the nucleus to form RNA. The RNA undergoes post-translational modification and forms different types of RNA which leave the nucleus by nuclear pore and undergo translation to form protein.

The chromatin material which takes darker stain in interphase is called Heterochromatin. Heterochromatin is a tightly packed form of DNA, which comes in different varieties. These varieties lie on a continuum between the two extremes of constitutive and facultative heterochromatin.

Each chromosome is bounded by a membrane called pellicle. It is very thin and is formed of achromatic substance.

Polytene chromosomes have characteristic light and dark banding patterns that can be used to identify chromosomal rearrangements and deletions. Dark banding frequently corresponds to inactive chromatin, whereas light banding is usually found at areas with higher transcriptional activity.

In human being secondary constriction II found on Acrocentric chromosomes. It have a centromere which is severely offset from the center leading to one very long and one very short section. Human chromosomes 13,15, 21, and 22 are acrocentric.

DNase catalyses the cleavage of the phosphodiester linkage in the DNA molecule and thus facilitates the degradation of the DNA.

The nucleolus is the largest structure present in the nucleus of eukaryotic cells where it primarily serves as the site of ribosome synthesis and assembly. Nucleoli also have other important functions like the assembly of signal recognition particles and playing a role in the cell's response to stress. Nucleoli are made of proteins and RNA and form around
the specific chromosomal regions.

The nucleolar chromatin contains the gene for rRNA and ribonucleoprotein. The nucleolus is the largest structure present in the nucleus of eukaryotic cells where it primarily serves as the site of ribosome synthesis and assembly. Nucleoli also have other important functions like the assembly of signal recognition particles and playing a role in the cell's response to stress. Nucleoli are made of proteins and RNA and form around specific chromosomal regions.

In metacentric centromere is located at centre of chromosome and therefore arm ratio is 1:1

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.
So, the correct answer is option A.

Chromosomes can be defined as thread-like structure which contains DNA and proteins which are found in the nucleus of most living cells.

They carry the genetic information in the form of genes.

The word chromosome is derived from the Greek word chroma meaning "colour" and soma meaning "body".

The term was coined by von Waldeyer-Hartz in relation to the term chromatin which was introduced by Walther Flemming.

So, the correct answer is 'Waldeyer'.

Chromosomes are the carrier of genetic information in form of DNA. The secondary constrictions are used as a point of identification of chromosomes. These are always constant in their positions and hence, can be used as markers that identify particular chromosomes. A satellite chromosome or SAT chromosome has a chromosome segment that is separated from the main body of the chromosome by such a secondary constriction.
So, the correct answer is option C.

Nucleus of a cell was discovered by Scottish botanist Robert Brown in 1831. The presence of a nucleus in an atom was discovered and proved by Nobel Laureate Dr. Ernest Rutherford through his gold leaf scattering experiment.

Linker DNA is double-stranded DNA in between two nucleosome cores that, in association with histone H1, holds the cores together. Linker DNA connects to histone H1 and histone H1 sits on the nucleosome core. Nucleosome is technically the consolidation of a nucleosome core and one adjacent linker DNA; however, the term nucleosome is used freely for solely the core. Linker DNA may be degraded by endonucleases.

Chromatin is made of nucleoprotein. Chromatin is a complex of macromolecules found in cells, consisting of DNA, protein and RNA. The primary functions of chromatin are to pack DNA into a smaller volume to fit in the cell, to reinforce the DNA macromolecule to allow mitosis, to prevent DNA damage, and to control gene expression and DNA replication. The primary protein components of chromatin are histones that compact the DNA.