Cellular Metabolism and Reproduction: Mitosis and Meiosis 69
Glucose (^)
(C 6 H 12 O 6 ) (^)
(^) Glycolysis (^)
Cytoplasm O^2
(^) Pyruvic acid (^)
Citric acid cycle
Electron-transport chain
2 lactic acid + 2 ATP
Anaerobic respiration
Figure 4- 5 How a piece of candy gets metabolized to
ATP.
23 chromosomes and the male sperm carries the other one
half of the genetic material or the other 23 chro-mosomes.
A special kind of cellular reduction division called
meiosis- (my-OH-sis), which occurs only in the gonads,
allows this to occur. When a sperm and an egg unite in
fertilization, the genetic material is returned to its full
complement of 46 chromosomes.
Before we study these processes of cellular division, it
is necessary to understand the basic structure of the DNA
molecule, which constitutes the genetic material. We shall
also examine the history of the discovery of the structure of
DNA.
The Structure of the DNA
Molecule
To better understand the structure of the DNA molecule,
the history of the discovery of DNA and the anatomy of the
DNA molecule will be discussed.
6CO 2 + 6H 2 O + 38ATP
(^) ®
Aerobic respiration Learning
Cengage ©
The History of the Discovery of DNA
One of the most significant discoveries in biology of the
20th century was the discovery of the three-- dimensional
structure of the DNA molecule. A num-ber of scientists
made various contributions to our knowledge of the DNA
molecule. The molecule it-self was discovered in 1869 by a
German chemist, Friedrich Miescher. He extracted a
substance from the -nucleus of human cells and the sperm
of fish. He called it nuclein- because it came from the
nucleus. Because this material was slightly acidic, it became
known as nucleic acid.
It was not until the 1920s that any further discover-ies
were made. A biochemist, P. A. Levine, discovered that
DNA contained three main components: phos-phate (PO 4 )
groups, five carbon sugars, and nitrogen-- containing bases
called purines (adenine and guanine) and -pyrimidines
(thymine and cytosine).