Which best matches a type of genetic material with its description?
Nucleotides form a helical structure that is called a gene.
Genes combine to form structures called nucleotides.
Chromosomes create genes.
DNA is located in the nucleus.
Answers
Answer:
the same issue of Nature in 1953.
Figure 6: The double helix looks like a twisted ladder.
How is DNA packaged inside cells?
Supercoiled DNA is tightly packed inside the chromosomes.
Figure 7: To better fit within the cell, long pieces of double-stranded DNA are tightly packed into structures called chromosomes.
Most cells are incredibly small. For instance, one human alone consists of approximately 100 trillion cells. Yet, if all of the DNA within just one of these cells were arranged into a single straight piece, that DNA would be nearly two meters long! So, how can this much DNA be made to fit within a cell? The answer to this question lies in the process known as DNA packaging, which is the phenomenon of fitting DNA into dense compact forms (Figure 7).
Chromatin
What does real chromatin look like?
Compare the relative sizes of the double helix, histones, and chromosomes
During DNA packaging, long pieces of double-stranded DNA are tightly looped, coiled, and folded so that they fit easily within the cell. Eukaryotes accomplish this feat by wrapping their DNA around special proteins called histones, thereby compacting it enough to fit inside the nucleus (Figure 8). Together, eukaryotic DNA and the histone proteins that hold it together in a coiled form is called chromatin.
A schematic shows coils of DNA wound around hundreds of nucleosomes. The DNA looks like grey thread bordering the nucleosomes, which look like red discs.
Figure 8: In eukaryotic chromatin, double-stranded DNA (gray) is wrapped around histone proteins (red).
DNA can be further compressed through a twisting process called supercoiling (Figure 9). Most prokaryotes lack histones, but they do have supercoiled forms of their DNA held together by special proteins. In both eukaryotes and prokaryotes, this highly compacted DNA is then arranged into structures called chromosomes. Chromosomes take different shapes in different types of organisms. For instance, most prokaryotes have a single circular chromosome, whereas most eukaryotes have one or more linear chromosomes, which often appear as X-shaped structures . At different times during the life cycle of a cell, the DNA that makes up the cell's chromosomes can be tightly compacted into a structure that is visible under a microscope, or it can be more loosely distributed and resemble a pile of string.
DNA forms a structure of coils within coils.
Figure 9: Supercoiled eukaryotic DNA.
How do scientists visualize DNA?
Figure 10: This karyotype depicts all 23 pairs of chromosomes in a human cell, including the sex-determining X and Y chromosomes that together make up the twenty-third set (lower right).
It is impossible for researchers to see double-stranded DNA with the naked eye — unless, that is, they have a large amount of it. Modern laboratory techniques allow scientists to extract DNA from tissue samples, thereby pooling together miniscule amounts of DNA from thousands of individual cells. When this DNA is collected and purified, the result is a whitish, sticky substance that is somewhat translucent.
To actually visualize the double-helical structure of DNA, researchers require special imaging technology, such as the X-ray diffraction used by Rosalind Franklin. However, it is possible to see chromosomes with a standard light microscope, as long as the chromosomes are in their most condensed form. To see chromosomes in this way, scientists must first use a chemical process that attaches the chromosomes to a glass slide and stains or "paints" them. Staining makes the chromosomes easier to see under the microscope. In addition, the banding patterns that appear on individual chromosomes as a result of the staining process are unique to each pair of chromosomes, so they allow researchers to distinguish different chromosomes from one another. Then, after a scientist has visualized all of the chromosomes within a cell and captured images of them, he or she can arrange these images to make a composite picture called a karyotype (Figure 10).
Watch this video for a closer look at the relationship between chromosomes and the DNA double helix
Answer:
I think it s c
Explanation: