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Chapter Chapter 3

ANTA01H3 Chapter Chapter 3: Anthropology Text Book Chapter 3 Notes

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Steven Dorland
Chapter 3

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Chapter 3 Notes: Heredity and Evolution Notes
Describe the basic structure of DNA and explain how it relates to DNA replication.
Describe the basic concepts of heredity that are found in all sexually reproducing organisms,
including humans.
Genetics is the study of how traits are transmitted from one generation to the next.
Prokaryotic cells are single-celled organisms, represented today by bacteria and blue-green
Eukaryotic cells are found in all multicellular organisms: they consist of organelles within a cell
Organelles include the nucleus: surrounded by a nuclear membrane which possess two acids
that contain the genetic information that controls the cell’s functions (DNA) and (RNA).
Cytoplasm: a gel like fluid that surrounds the nucleus and contains the other organelles.
Two types of cells are gametes: reproductive cells (eggs and sperm in animals) developed from
precursor cells in ovaries and testes.
And somatic cells: basically, all the cells in the body except those involved with reproduction.
Protein synthesis: the assembly of chains of amino acids into functional protein molecules. The
process is directed by DNA.
Protein's: Three dimensional molecules that serve a wide variety of functions through their
ability to bind to other molecules.
Zygote: A cell formed by the union of an egg and a sperm cell. It contains the full complement of
chromosomes (in humans, 46) and has the potential to develop into an entire organism.
DNA Structure and Function
The DNA molecule is composed of two chains of even smaller molecules called nucleotides.
Nucleotides consist of a sugar molecule (deoxyribose), a phosphate unit, and one of four bases.
Inside of DNA, nucleotides are stacked on top of one another to form a chain, which is
combined to another nucleotide chain. The two chains are then twisted together to form a spiral
and is thus often described as forming a double helix that resembles a twisted ladder.

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If we follow the twisted ladder analogy, the sugars and phosphates represent the two sides,
while the bases (the bonds that join the two nucleotides) form the rungs.
The four bases: A, G, T, and C
The four bases are the key to how DNA works. These bases are named adenine, guanine,
thymine, and cytosine, but they’re usually referred to by their initial letters: A, G, T, and C. In the
formation of the double helix, one type of base can pair, or bond, with only one other type: A can
only pair with T, and G can only pair with C.
DNA Replication
Before a cell can divide, its DNA must first replicate.
Before cells divide, enzymes break the bonds between bases in the DNA molecule, leaving the
DNA strands with their bases exposed. The exposed bases then attract unattached nucleotides
(that aren’t part of a strand) that are constantly being manufactured elsewhere in the cell
Complementary joining: Referring to the fact that DNA bases form base pairs in a precise
manner. For example, adenine can bond only to thymine. These two bases are said to be
complementary because one requires the other to form a complete DNA base pair.
As each new strand is formed, its bases are joined to the bases of an original strand. When the
process is completed, each new DNA molecule consists of one original nucleotide chain joined
to a newly formed chain.
Protein Synthesis
DNA directs the manufacture of proteins within the cell.
Proteins function in countless ways. Some function as structural components whilst others
regulate chemical reactions.
Hormones: substances (usually proteins) that are produced by specialized cells and travel to
other parts of the body, where they influence chemical reactions and regulate various cellular
Proteins are made up of chains of smaller molecules called amino acids. In all, there are 20
amino acids, which are combined in different amounts and sequences to produce potentially
millions of proteins.
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