Abeka Biology chapter 24

Explain the roles of DNA and the three main types of RNA in protein synthesis.

*DNA - contains the master "blueprints" for the protein; used as a template to make mRNA *mRNA (messenger RNA) - carries the genetic information for constructing a particular protein molecule from the nucleus to the ribosomes *rRNA (ribosomal RNA) - forms much of the structure of the ribosome, which serves as the "factory" that actually makes the protein *tRNA (transfer RNA) - carries amino acid molecules to the ribosomes to be assembled into proteins

Describe five structural differences between DNA and RNA.

*DNA contains the sugar deoxyribose; RNA constains the sugar ribose. *DNA consists of two strands and has a double-helix structure; RNA consists of one strands and may assume a variety of shapes. *RNA contains the base uracil instead of thymine. *DNA is found inside the nucleus; RNA may be found outside the nucleus. *There is only one type of DNA; several types of RNA are known.

What are the four types of bases found in a DNA molecule? what type pairs only with adenine? with guanine?

*guanine, cytosine, adenine, thymine *Thymine pairs only with adenine. *Cytosine pairs only with guanine.

Briefly describe the structure of a DNA molecule.

Answers will vary. Each DNA molecule consists of two long chains of smaller molecules that are twisted about one another (like a twisted ladder). The strands that form the "legs" of the DNA ladder consists of alternating sugar molecules and phosphate molecules. Each "rung" of the ladder consists of a pair of nitrogen-containing bases.

How does the process of base pairing help ensure that DNA is replicated and transcribed correctly?

Answers will vary. Only one type of base will fit another. As the new DNA or RNA strand is assembled, base pairing ensures that only the proper nucleotides bond to the available nucleotides on the old strand of DNA.

Why are mutations in somatic (body) cells not transmitted from generation to generation?

Answers will vary. The genetic information is transmitted from one generation to the next by the germ (reproductive) cells; only the DNA that these cells contain will be passed on to the offspring. Because mutations in somatic cells have no effect on the DNA of germ cells, these mutations are not passed along to the next generation.