In eukaryotic DNA,

along a 6000-bp segment of DNA, approximately how many molecules of each kind of histone protein do you expect to find? Explain your answer.

Verified step by step guidance

1. <Understand the structure of a nucleosome: A nucleosome consists of DNA wrapped around a histone octamer, which includes two molecules each of H2A, H2B, H3, and H4, and one molecule of H1 per nucleosome.>
2. <Determine the length of DNA associated with one nucleosome: Approximately 146 base pairs (bp) of DNA are wrapped around the histone octamer, and about 20-80 bp of linker DNA is associated with the H1 histone, making a total of roughly 200 bp per nucleosome.>
3. <Calculate the number of nucleosomes in a 6000-bp segment: Divide the total length of the DNA segment (6000 bp) by the length of DNA per nucleosome (200 bp) to find the number of nucleosomes.>
4. <Determine the number of each histone type: Multiply the number of nucleosomes by the number of each type of histone per nucleosome. For H2A, H2B, H3, and H4, multiply by 2, and for H1, multiply by 1.>
5. <Summarize the expected number of histone molecules: Based on the calculations, summarize how many molecules of each histone type (H2A, H2B, H3, H4, and H1) are expected in the 6000-bp segment.>

Key Concepts

Histone Proteins

Histone proteins are essential components of chromatin in eukaryotic cells, serving as spools around which DNA winds. They play a crucial role in packaging DNA into a compact, organized structure, allowing for efficient storage and regulation of genetic material. There are five main types of histones: H1, H2A, H2B, H3, and H4, each contributing to the formation of nucleosomes, the fundamental units of chromatin.

Nucleosome Structure

A nucleosome consists of a segment of DNA wrapped around a core of histone proteins, specifically two copies each of H2A, H2B, H3, and H4. This structure is fundamental to DNA packaging, as it allows for the compaction of DNA into a more manageable form. Each nucleosome typically contains about 147 base pairs of DNA, and the arrangement of nucleosomes influences gene expression and DNA accessibility.

DNA Length and Histone Ratio

In eukaryotic cells, the average ratio of DNA to histone proteins is approximately 1.5 to 1, meaning that for every 200 base pairs of DNA, there are about 1.5 histone molecules. Given a 6000-bp segment of DNA, one can estimate the number of nucleosomes and, consequently, the number of histone proteins present. This calculation involves dividing the total base pairs by the number of base pairs per nucleosome and multiplying by the number of histone types involved.