13.1 RNA

The main differences between RNA and DNA are that (1) the sugar in RNA is ribose instead of deoxyribose; (2) RNA is generally single-stranded, not double-stranded; and (3) RNA contains uracil in place of thymine.

In transcription, segments of DNA serve as templates to produce complementary RNA molecules.

• RNA (362)

• RNA polymerase (364)

• messenger RNA (363)

• promoter (365)

• ribosomal RNA (363)

• intron (365)

• transfer RNA (363)

• exon (365)

• transcription (364)

13.2 Ribosomes and Protein Synthesis

The genetic code is read three “letters” at a time, so that each “word” is three bases long and corresponds to a single amino acid.

Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.

The central dogma of molecular biology is that information is transferred from DNA to RNA to protein.

• polypeptide (366)

• translation (368)

• genetic code (366)

• anticodon (369)

• codon (366)

• gene expression (370)

13.3 Mutations

Mutations are heritable changes in genetic information.

The effects of mutations on genes vary widely. Some have little or no effect; some produce beneficial variations. Some negatively disrupt gene function.

Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.

• mutation (372)

• mutagen (375)

• point mutation (373)

• polyploidy (376)

• frameshift mutation (373)

13.4 Gene Regulation and Expression

DNA-binding proteins in prokaryotes regulate genes by controlling transcription.

By binding DNA sequences in the regulatory regions of eukaryotic genes, transcription factors control the expression of those genes.

Master control genes are like switches that trigger particular patterns of development and differentiation in cells and tissues.

• operon (377)

• homeotic gene (382)

• operator (378)

• homeobox gene (382)

• RNA interference (380)

• Hox gene (382)

• differentiation (381)

Think Visually Using the information in this chapter, complete the following flowchart about protein synthesis:

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