Question
A typical mammalian cell has 2.2m long DNA molecule, whereas the nucleus in which it is packed measures about 10m. Explain how such a long DNA molecule is packed within a tiny nucleus in the cell.
✓
Answer
- In the mammalian cells (or eukaryotes) there is a set of positively-charged basic proteins, called histones.
- Histones are organised to form a unit of eight molecules, called histone octamer.
- The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure, called nucleosome.
- A typical nucleosome contains 200 bp of DNA helix.
- The nucleosomes constitute the repeating units of chromatin, which appear as beads-on-string structure under an electron microscope.
- These are further packaged to form the chromatin fibres, which condense to form chromosomes.
- The packaging of chromatin at higher levels requires additional set of proteins called non-histone chromosomal (NHC) proteins.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Define Lactation.
Explain with suitable examples the homology and analogy found in the plant or its parts.
Describe the process of microsporogenesis.
Answer the following questions:
Why is geitonogamy also referred to as genetical autogamy?
Why is geitonogamy also referred to as genetical autogamy?
Study the graph given below and answer the questions that follows.
- Write the status of food and space in the curves A and B.
- In the absence of predators, which one of the two curves would appropriately depict the prey population?
- Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line.
The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. Explain with example.
- One of the codons on mRNA IS AUG. Draw the structure of RNA adapter molecule for this codon.
- Name the RNA polymerase that transcribes RNA in eukaryotes.
- What is unique about the amino acid this RNA binds with?
What is geitonogamy? Give its one similarity to autogamy and xenogamy.
Seeing a crowd of students in one corner of the school, the principal rushed to see the matter and found some children beating and chasing a small lizard. On seeing the principal, all the children fled to their classes except Alok who requested the principal to arrange for some medical assistance for the injured animal. The principal rewarded Alok for his attitude to save guard our biodiversity.
- Mention the factors resulting in loss of biodiversity
- Was Alok an indisciplined boy, who did not run to the class on seeing the principal? What values does the act promote?
- Explain any two defence mechanisms plants evolved against their predators.
- How does predation differ from parasitism?