HUMAN BIOLOGY

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DNA analysis requires only a few drops of blood
or a smear of epithelial cells from the skin or inside of the cheek.
It is the foundation for activities that seem routine today—studying
the genetic causes of disease, identifying crime perpetrators, even
tracing personal ancestry. Our ability to perform these scientific
marvels stems from the fact that DNA forms the genes that provide
instructions for building and operating the body. We begin this chapter
by looking at the structure of DNA and how our cells use it to guide
life processes. We also consider how scientists are using DNA-based
technologies to address a wide range of human concerns.

This chapter expands on Chapter 2’s discussion of amino
acids and the primary structure of proteins (2.11).
We’ll discuss how DNA is copied during the phase of the
cell cycle before chromosomes are duplicated and assorted
into new cells (18.2, 18.3, 18.6).
You’ll also learn more about the roles of RNA and ribosomes
in making proteins (3.6).

Key ConCepts


LinKs to earLier ConCepts


Genetic Instructions in DNA
DNA consists of two strands of
nucleotides twisted into a double
helix. A gene is a sequence of
nucleotides in DNA. Sections
21.1–21.2

Making Proteins
Genes provide the genetic code for
making proteins. First, an mRNA
molecule is transcribed from DNA.
Then mRNA is translated into a string
of amino acids, the primary structure
of proteins. Sections 21.3 –21.6

Altering and Exploring Genes
Biotechnology is a tool for changing
genes and studying their effects.
Practical applications range from
uses in agriculture to DNA finger-
printing and studying the human
genome. Sections 21.7–21.12

Top and middle: © Cengage Learning; Bottom: Tek Image/Science Source

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Dna, Genes,


anD BioteChnoLoGy


21


Science Source

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