Biology Chapter 16 Final Exam Flashcards

DNA Structure and Function

• Nucleic acids are polymers, consisting of nucleotide monomers, essential for encoding genetic information. Types include DNA and RNA.
• DNA consists of two antiparallel polynucleotide chains that form a double helix structure, stabilized by hydrogen bonds between nitrogenous bases.
• DNA nucleotides comprise a deoxyribose sugar, a phosphate group, and nitrogenous bases (adenine, thymine, cytosine, guanine).
• RNA differs from DNA by containing ribose sugar instead of deoxyribose and uracil instead of thymine; it usually exists as a single polynucleotide strand.

DNA Replication Process

• DNA replication involves unwinding the double helix at replication forks, facilitated by helicase, which breaks hydrogen bonds between base pairs.
• The replication fork is a structure where DNA is open for polymerase activity, allowing for the synthesis of new strands.
• DNA polymerase III synthesizes new DNA in a 5’ to 3’ direction, which requires short segments (Okazaki fragments) on the lagging strand due to the antiparallel nature of DNA.
• Leading strand is synthesized continuously towards the replication fork, while the lagging strand is synthesized in segments, later joined by DNA ligase.

Key Enzymes in DNA Replication

• Helicase unwinds the DNA double helix, creating a replication fork.
• Single-strand binding proteins stabilize the unwound DNA strands to prevent re-annealing.
• Primase synthesizes short RNA primers necessary to initiate DNA synthesis.
• DNA polymerases add nucleotides to the growing strand; DNA polymerase I replaces RNA primers with DNA.
• DNA ligase connects Okazaki fragments on the lagging strand to form a continuous DNA strand.

Genetic Terms and Concepts

• Genes are segments of DNA that encode instructions for protein synthesis and influence traits.
• Mutations are errors in DNA replication that can be inherited if they occur in germ cells.
• Telomeres protect the ends of chromosomes and are composed of repetitive DNA sequences.

Experimental Evidence for DNA Structure

• Rosalind Franklin’s X-ray diffraction studies were crucial in revealing the helical structure of DNA.
• The Hershey-Chase experiment demonstrated that DNA, not protein, is the genetic material, evidenced by radioactively labeled DNA entering bacterial cells.
• Griffith’s transformation experiments with S. pneumoniae showed that genetic traits could be transferred and were heritable.

Important Concepts

• Chargaff’s rules assert that the amounts of adenine equal thymine and cytosine equal guanine in DNA.
• DNA replication is described as semiconservative, meaning each new double helix has one parental strand and one newly synthesized strand.
• The structure of DNA can be likened to a pearl necklace, where the necklace is a polymer and each pearl symbolizes a nucleotide monomer.

DNA in Forensics

• DNA fingerprinting is a method used for identification in forensic science, although it is not reliable for identical twins due to their identical genetic material.

Summary

• The DNA double helix is fundamental to heredity, encoding instructions via a specific base sequence that determines cellular activities and functions.
• Enzymatic actions in DNA replication are intricate and precise, ensuring accurate genetic transmission.

Prepare for your Biology final exam with these flashcards covering Chapter 16. This quiz includes key concepts such as nucleotide excision repair, the role of helicase in DNA replication, and significant historical contributions to DNA research. Test your knowledge and ensure you're ready for the exam!