InSight
D N A
Figure 2.14
DNA is located in the cell's nucleus a. The structure of
Chromatin
Nuclear -
envelope
Nucleolus
Nuclear pore
700x
700x
Centromere
Loop
DNA is essential to its function and replication b.
a.
Location of the DNA in a cell
2. Electron micrograph of a
nucleus showing the chromatin
that contains the DNA. In a
non-dividing cell, the DNA is
unwound in the chromatin, like
a long ribbon.
about 10,000x CSM
1.
Light micrograph of a
non-dividing cell (outlined)
showing the nucleus
(stained pink).
Histones
(proteins)
DNA double helix
Chromatin
fiber
Chromatin
___
I
____________
3. Light micrograph of a
dividing cell (outlined)
showing the condensed
chromosomes (stained
black).
Nucleosome
4. When a cell divides,
the DNA gets wound
around histone proteins
into nucleosomes, which
get tightly packaged into
chromosomes.
»
DNA is the cell’s genetic material. It contains all the information
necessary to make another cell or organism.
»
In a non-dividing cell, it is found in the nucleus as chromatin.
»
In a dividing cell, the nucleus disappears and the chromatin
condenses into chromosomes.
Linker
DNA
Chromatid Chromatid
Chromosome
Nucleic Acids Carry Genetic Instructions
Nucleic acids (noo-KLE-ic) were first discovered in the
nuclei of cells (Figure 2.14a). They are huge organic
molecules that contain carbon, hydrogen, oxygen, nitro-
gen, and phosphorus. A nucleic acid molecule is composed
of repeating building blocks called nucleotides (Figure
2.14b). Each nucleotide consists of three parts:
40 CHAPTER 2
Introductory Chemistry
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