Molecular Biology Quiz: Genetics and Cancer

Ames Test

• Detects the mutagenic potential of chemicals
• Uses Salmonella typhimurium strains with a mutation preventing histidine synthesis
• Detects mutations that allow the bacteria to regain the ability to synthesize histidine

DNA Repair and Xeroderma Pigmentosum

• Inherited disease caused by a defect in the UV repair pathway
• Individuals with XP are highly sensitive to UV radiation

Cancer

• Develops from a single cell that accumulates genetic changes
• Benign tumors are non-invasive and do not metastasize
• Malignant tumors invade surrounding tissues and metastasize

Oncogenes and Proto-oncogenes

• Oncogenes promote uncontrolled cell growth by being overactive
• Proto-oncogenes are normal genes that can become oncogenes when mutated
• Examples of oncogene mutations involve growth factors and receptors

Mitosis

• Cell division that produces two daughter cells genetically identical to the parent cell
• Includes the stages: prophase, metaphase, anaphase, telophase, and cytokinesis
• Involves the separation of sister chromatids, reformation of nuclear membranes, and division of the cytoplasm

Meiosis

• Cell division that produces four haploid daughter cells from a diploid parent cell
• Involves two rounds of division: meiosis I and meiosis II
• Includes the processes of synapsis, crossing over, and segregation of homologous chromosomes

Chromosome Identification

• Chromosomes are identified based on size, centromere location, and banding patterns
• Centromere location is described as metacentric, submetacentric, acrocentric, or telocentric
• Banding patterns are observed under a light microscope after staining

Chromosomal Mutations

• Deletions: loss of a chromosome segment
• Duplications: repeated segment of chromosome
• Inversions: segment is flipped in direction
• Translocations: segment attaches to another chromosome

Sex Chromosomes

• Sex chromosomes determine an individual's sex
• X-Y system: males XY, females XX
• X-O system: females XX, males X or XO
• Z-W system: males ZZ, females ZW

HIV

• Human immunodeficiency virus, causes AIDS
• Targets and destroys helper T cells, weakening the immune system
• Can be spread through sexual contact, blood transfusions, sharing of needles, and mother-to-child transmission
• Reverse transcriptase lacks proofreading function, leading to rapid mutation and making vaccine development difficult

Viroids

• Single-stranded circular RNA molecules infecting plant cells
• Replicate in the nucleus or chloroplast
• Do not encode proteins

Prions

• Infectious proteins that cause neurodegenerative diseases
• PrP protein in a different conformation causes disease
• Prions convert other normal PrP proteins to the abnormal form
• Can cause transmissible spongiform encephalopathies (TSE)

Bacterial Chromosome Compaction

• Bacterial chromosomes are supercoiled to fit within the cell
• Topoisomerases control the degree of supercoiling

Plasmids

• Small, circular pieces of DNA independent of the bacterial chromosome
• Can replicate independently and provide growth advantages
• Episomes can integrate into the bacterial chromosome
• Include resistance plasmids, degradative plasmids, virulence plasmids, and fertility plasmids

Bacterial Reproduction

• Bacteria reproduce asexually through binary fission.
• The bacterial chromosome is replicated and the cell divides into two daughter cells.
• This process is rapid and allows bacteria to quickly populate a suitable environment.