Nucleic Acids and Proteins Quiz

Nucleic Acids and Proteins

• Nucleic acids are polymers of nucleotides, which have a phosphate group bonded to the -OH on C5'
• They have a unique base sequence in RNA, called the primary structure
• They carry information between cells

Primary Structure of Nucleic Acids

• Nucleotides are joined by 3'-5' phosphodiester bonds
• The 3'-OH group of one nucleotide bonds to the 5'-phosphate group of the next
• An example of sequence is 5'-A-C-G-U-3', joined by phosphodiester bonds, starting with adenine (free 5'-phosphate end)
• In nucleic acid chains, each sugar in the sugar-phosphate backbone is attached to a base
• The bases extend out from the nucleic acid backbone
• Bases are labeled from the 5' end to the 3' end

Double Helix of DNA & DNA Replication

• DNA contains complementary base pairs, with equal amounts of A and T, and equal amounts of G and C
• Adenine (A) is always linked by two hydrogen bonds with thymine (T)
• Guanine (G) is always linked by three hydrogen bonds with cytosine (C)
• Two strands of nucleotides wind together to form a double helix
• The double helix is held in place by hydrogen bonds between the base pairs A-T and G-C
• The bases along one strand complement the bases along the other

DNA Replication

• In DNA replication, genetic information is maintained during cell division
• DNA strands unwind and each parent strand bonds with a new complementary base
• Exact copies of the parent DNA are formed
• The separate strands of the parent DNA act as templates for complementary stands which produces two exact copies (daughter DNAs)

DNA Fingerprinting

• Enzymes cut DNA chains into sections
• Resulting fragments are separated by size and treated with a radioactive isotope that adheres to specific base sequences
• This creates a pattern of bands called a DNA fingerprint
• Used in forensic science to connect suspects to crimes

RNA Types

• Ribonucleic acid (RNA)
• Is a single-stranded nucleic acid similar to DNA, but with a single, helical strand of bases and role in turning DNA instructions into functional proteins
• Made up of nucleotides: ribose, phosphate group, and nitrogenous bases (adenine, uracil, guanine, cytosine)

Types of RNA

• Messenger RNA (mRNA): carries genetic information from DNA in the nucleus to the cytoplasm for protein synthesis
• Transfer RNA (tRNA): links between mRNA and growing chains of amino acids in protein synthesis
• Ribosomal RNA (rRNA): part of the ribosome which reads the order of amino acids and links them together

Protein Synthesis

• Transcription is the process of copying a segment of DNA into mRNA
• First step in gene expression that creates proteins
• In mRNA synthesis, in a eukaryotic cell, RNA polymerase binds to a promoter region
• Copying the basis on the DNA template strand to form new complementary RNA strand
• In prokaryotic cells, it's the same except the termination region signals when to stop

Nucleotides

• Nucleotides are the building blocks of nucleic acids, playing a key role in the structure and function of DNA and RNA
• Single stranded template RNA, coding strand, and template strand parts of the DNA molecule.
• The coding strand is the template strand.
• The molecules of RNA and DNA are composed of nucleotide monomers.

Maturation of Pre-mRNA

• Pre-mRNA undergoes modifications before translation (e.g., 5' capping, splicing, poly-A tail addition)
• Crucial for maturation, stability, and eventual translation of mRNA.

Regulation of Transcription

• Genes are expressed timely, in correct cells, and at appropriate levels by regulating transcription
• DNA template provides the genetic information
• RNA polymerase synthesizes RNA from the DNA template using a promoter region
• Transcription factors help initiate transcription
• Promoters are located near the start site of the gene, while enhancers and silencers increase or decrease transcription

Transcription Factors

• Activators bind to enhancer regions for increased transcription
• Repressors bind to silencer regions to decrease transcription
• General transcription factors are necessary for basic transcription
• Specific transcription factors are activated by signaling pathways

Remodeling of Chromatin

• DNA is wrapped around histones to form chromatin for gene regulation
• Splicing increases protein diversity by producing different protein isotypes from a single gene

Lac Operon

• Codes for enzymes involved in lactose catabolism
• Inducible operon; lactose presence activates it
• Operon has three enzymes (lac Z, lac Y, lac A)

Function of Lac Operon

• In absence of lactose, a repressor protein blocks transcription
• Lactose presence causes allolactose formation and repressor removal, allowing RNA polymerase to bind
• When both glucose and lactose are present, RNA polymerase is less stable during binding

Mutations

• Incorrect codons result in defective proteins and enzymes
• Causes genetic diseases (e.g., Huntington's, Cystic Fibrosis)

Translation

• Process converting genetic info (DNA/RNA's genetic code) to proteins
• Genetic code is read as triplets (codons)
• Specific amino acids correspond to specific codons
• Codons, each correspond to an amino acid or signal

2 Major Processes of Translation

• tRNA activation (aminoacylation): Charging tRNA molecules with their corresponding amino acids
• Translocation: Ribosome moves along mRNA, with dipeptide shifts to P site and empty tRNA to E site

Termination of Translation

• Polypeptide chain continues until a stop codon (e.g., UAA, UAG, UGA) appears
• Stop codons have no corresponding tRNA, causing termination
• Polypeptide is cleaved from tRNA

Viruses and Reverse Transcription

• Viruses are small particles that need a host cell to replicate
• They cause infection by releasing their DNA or RNA into the host cell
• Some viruses use reverse transcription to synthesize viral DNA in the host

HIV and AIDS Treatment

• Treatment for AIDS involves targeting HIV's life cycle
• AZT, similar to thymidine, inhibits reverse transcriptase
• Lexiva is a protease inhibitor that prevents protein synthesis

DNA Fingerprinting and Polymerase Chain Reaction (PCR)

• Technique identifies individuals by DNA characteristics
• PCR amplifies small DNA amounts for further testing