Molecular Biology Quiz on Genetics and Translation

Informational Macromolecules

• Macromolecules are large molecules important for life
• Nucleic acids are a class of macromolecules
• Nucleic acids are polymers, made up of repeating units called nucleotides
• Nucleotides are made up of three subunits: a pentose sugar, a phosphate group, and a nitrogen-containing heterocyclic base
• DNA and RNA are two types of nucleic acids
• DNA is primarily found in the cell nucleus and stores and transfers genetic information
• RNA is found in all parts of a cell and is primarily involved in protein synthesis
• The five nitrogen-containing heterocyclic bases are nucleotide components: pyrimidine, a monocyclic base with a six-membered ring, and purine, a bicyclic base with fused five and six-membered rings
• The three pyrimidine derivatives found in nucleotides are thymine, cytosine, and uracil
• The two purine derivatives found in nucleotides are adenine and guanine
• Phosphate is a component of a nucleotide derived from phosphoric acid
• Nucleotide formation is a two-step process
• First, the pentose sugar and nitrogen-containing base react to form a nucleoside
• Second, the nucleoside reacts with a phosphate group to form a nucleotide
• Eight nucleosides are associated with nucleic acid chemistry; four involve ribose (RNA nucleosides) and four involve deoxyribose (DNA nucleosides)
• The primary structure of nucleic acids involves the sequence of bases, which are linked through sugar-phosphate bonds
• The backbone of a nucleic acid consists of alternating sugar and phosphate groups, with a base group projecting from the chain at regular intervals
• DNA is a double helix, made of two polynucleotide strands
• The strands are connected by hydrogen bonds, and run in opposite directions (antiparallel), one 5' to 3' and the other 3' to 5'
• Complementary base pairs are a key feature of DNA structure (A-T and G-C)
• DNA replication is the process of producing two daughter DNA molecules identical to the parent molecule
• DNA replication begins at a replication fork, where the DNA unwinds
• The enzyme DNA polymerase operates in the 5' to 3' direction
• Multiple sites for replication enable large DNA molecules to be replicated rapidly
• RNA molecules have four major differences from DNA molecules: ribose sugar instead of deoxyribose, uracil instead of thymine, single-stranded instead of double helix, much smaller in size, ranging from 75 to several thousand nucleotides
• RNA molecules perform various functions, including transcription (forming RNA from a DNA template) and translation (using mRNA to synthesize proteins)
• There are three parallels between primary nucleic acid structure and primary protein structure
• They all have backbones that do not vary in structure; the sequence of attachments to them distinguishes them
• Both have directionality (5' and 3' for nucleic acids and N-terminal and C-terminal for proteins)
• Viruses are very small disease-causing agents that are considered to be the lowest order of life
• Viruses possess nucleic acid (DNA or RNA), a protein coat, and cannot reproduce without a host cell
• A vaccine is a preparation containing an inactive or weakened form of a virus or bacterium
• Genetic engineering, or recombinant DNA technology, is the process of intentionally changing an organism's DNA at a molecular level to alter its traits

Nucleic Acids and Viruses

• The nucleic acids in viruses vary depending on the type of virus
• Genetic engineering involves a type of DNA called recombinant DNA, which contains genetic material from two different organisms
• Bacteria, like E. coli, and yeast cells are frequently used in recombinant DNA experiments

Transcription and Translation

• Transcription is the process by which DNA directs the synthesis of hnRNA/mRNA molecules that carry the information needed for protein synthesis
• The process begins when a portion of a DNA molecule unwinds (under enzyme influence), exposing a base sequence
• Free ribonucleotides align with the exposed base pairs
• RNA polymerase links the ribonucleotides
• Transcription ends when a stop signal is encountered; the hnRNA molecule is released, and the DNA rewinds to its original form
• The "edited" RNA is messenger RNA (mRNA), which serves as a blueprint for protein assembly.
• Splicing is the process of removing introns (gene segments that do not carry genetic information) from hnRNA and joining exons (gene segments that do carry genetic information) together to form mRNA
• Translation is the process by which mRNA codons are deciphered to synthesize a protein molecule
• The process uses mRNA, tRNA molecules, amino acids, ribosomes, and enzymes
• Specific steps include tRNA activation, initiation, elongation, termination, and post-translation processing
• Ribosomes, an rRNA-protein complex, serve as the site for translation.

Chromosomes

• A chromosome is an individual DNA molecule that interacts with proteins called histones to create stable structures for long DNA molecules
• Cells from different organisms have different numbers of chromosomes
• Homologous pairs are chromosomes that are matched in terms of similarities in their DNA base sequences
• Homologous chromosomes derive a copy of one from each parent, creating similar but not identical DNA base sequences