DNA & RNA (Chapter 8) Flashcards

DNA Structure and Function

• DNA is described as a double helix, resembling a twisted ladder.
• Composed of four nitrogen bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
• DNA consists of two strands, while RNA has a single strand.
• Nucleotides are the monomers of DNA, containing a sugar (deoxyribose), a phosphate group, and a nitrogen base.

Base Pairing

• Thymine pairs with Adenine (A-T), and Cytosine pairs with Guanine (C-G) in DNA.
• In RNA, Uracil replaces Thymine; thus, Adenine pairs with Uracil (A-U).
• Codons consist of three mRNA bases in sequence, and each codon codes for a specific amino acid.

RNA and its Functions

• mRNA (messenger RNA) conveys genetic information from DNA to ribosomes for protein synthesis.
• tRNA (transfer RNA) brings amino acids to the growing polypeptide chain.
• rRNA (ribosomal RNA) is a component of ribosomes, facilitating protein synthesis.

Transcription and Translation

• Transcription occurs in the nucleus, converting DNA into mRNA.
• Translation happens in the cytoplasm on ribosomes, decoding mRNA and forming polypeptides.
• Every mRNA strand starts with Methionine and ends with a stop codon.

Gene and Proteins

• A gene is a DNA segment that codes for a particular protein.
• Proteins are macromolecules formed from amino acids linked into polypeptides.

DNA Replication

• DNA replication occurs before cell division, ensuring that genetic information is passed on to daughter cells.
• DNA polymerase is the enzyme facilitating nucleotide binding during replication.

Mutations

• Mutations represent changes in DNA; they can be point mutations (affecting a single nucleotide) or frameshift mutations (shifting the reading frame by insertion/deletion).
• Frameshift mutations are often more severe, potentially affecting multiple downstream codons.

Gene Regulation

• Operons are groups of prokaryotic genes operating together.
• Exons are important DNA sequences coding for proteins, while introns are non-coding sequences without known functions.

Genetic Code

• The central dogma of molecular biology is DNA → RNA → Protein, involving replication, transcription, and translation.
• RNA polymerase synthesizes RNA strands by bonding nucleotides together during transcription.

Cellular Locations

• DNA resides in the nucleus, while RNA is found in the nucleus, ribosomes, and cytoplasm.
• DNA's large size prevents it from exiting the nucleus directly; RNA serves as the messenger carrying code to ribosomes.