AP BIOLOGY

Detailed explanation-1: -The unwinding of native chromatin isolated from HeLa cell nuclei occurs both in the absence and in the presence of linker histone H1. These results suggest that as helicases unwind DNA, they facilitate nuclear processes by acting to clear DNA of histones or DNA-binding proteins in general.

Detailed explanation-2: -Answer and Explanation: As the DNA unwinds, it forms a structure called a replication bubble. The replication bubble is the section of DNA that is unwound and has separated so that the nucleotide bases are no longer attached, and the DNA strands are not touching.

Detailed explanation-3: -Chromatin is a substance made up of DNA or RNA and proteins, such as histones. It condenses during cell division (mitosis or meiosis) and becomes a chromosome. Chromatins are “unwound” condensed structures whereas chromosomes are highly packaged and more condensed than chromatins.

Detailed explanation-4: -Chromatin Chromatin refers to a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms. Many of the proteins-namely, histones-package the massive amount of DNA in a genome into a highly compact form that can fit in the cell nucleus.

Detailed explanation-5: -Chromatin Is Coiled into Higher-Order Structures The packaging of DNA into nucleosomes shortens the fiber length about sevenfold. In other words, a piece of DNA that is 1 meter long will become a “string-of-beads” chromatin fiber just 14 centimeters (about 6 inches) long.