Cell Cycle, DNA & RNA

• DNA is deoxyribose sugar while RNA is ribose sugar.
• DNA is double-stranded, and RNA is single-stranded.
• DNA contains thymine (T), RNA contains uracil (U).
• DNA stores genetic information, and RNA helps protein synthesis.
• Both DNA and RNA are nucleic acids made of nucleotides.
• Both contain adenine (A), cytosine (C), and guanine (G).
• Both are involved in genetic information processing.

Central Dogma of Biology

• The flow of genetic information follows: DNA to RNA (Transcription), then RNA to Protein (Translation).
• In the G1 phase, genes are paired as Homologous Chromosomes
• In the G2 phase, genes are paired as Homologous Chromosomes and Sister Chromatids

Cell Cycle Events

• Sister chromatids separate during Anaphase.
• G2 Checkpoint ensures correct DNA replication.
• M Checkpoint ensures correct chromatid separation.
• G1 Checkpoint decides division or G0 phase.
• DNA duplication occurs during S Phase.
• Cells spend most of their time in Interphase.

Nucleic Acids

• The monomer of nucleic acid is a nucleotide.
• RNA Polymerase reads DNA and synthesizes complementary mRNA during transcription.
• Healthy cells divide for growth, repair, and replacement of damaged or old cells.

Cell Cycle Checkpoints

• G1 Checkpoint ensures cell size and DNA integrity; failure may result in apoptosis.
• G2 Checkpoint verifies DNA replication accuracy; failure may trigger DNA repair or apoptosis.
• M Checkpoint ensures correct sister chromatid separation; failure can lead to aneuploidy (abnormal chromosome number).

Transcription & Translation

• Given DNA sequence: ACTATA CGC CATC
• The resulting mRNA sequence is: UGAUAU GCG GUAG
• The resulting Amino Acid Chain: MET - ARG - (STOP)
• The start codon is AUG (Methionine).
• The number of amino acids in the chain in the example sequence is two (MET - ARG)

Proto-oncogenes vs. Tumor Suppressor Genes

• Proto-oncogenes promote cell division; mutations turn them into oncogenes, leading to uncontrolled growth.
• Tumor Suppressor Genes prevent uncontrolled division; mutations lead to loss of function and cancer.
• Gain of function is a mutation in proto-oncogenes, causing excessive cell growth.
• Loss of function is a mutation in tumor suppressor genes, removing growth regulation.

Cancer Treatments

• Surgery removes tumors but may not eliminate all cancer cells.
• Radiation targets cancer cells and can harm healthy cells.
• Chemotherapy uses drugs to kill cancer cells and affects rapidly dividing healthy cells (e.g., hair, digestive cells).

Cancer Risks

• Genetic cancer risks are mutations inherited from parents (e.g., BRCA1, BRCA2).
• Environmental cancer risks are carcinogens (smoking, UV rays, pollution).
• Lifestyle habits to reduce cancer risk: Healthy diet, regular exercise, avoiding tobacco, limiting alcohol, using sunscreen.

Key Vocabulary

• Gene: A segment of DNA coding for a protein.
• Nucleic Acid: DNA/RNA, molecules carrying genetic info.
• Transcription: DNA to RNA process.
• Translation: RNA to protein process.
• Frameshift Mutation: Insertion/deletion shifting the reading frame.
• Diploid vs. Haploid: Diploid (2 sets of chromosomes), Haploid (1 set).

Carcinogenesis

• Initiation: Mutation in a cell.
• Promotion: Mutated cell divides abnormally.
• Progression: Tumor grows and spreads.
• Cancer cells grow uncontrollably, ignore signals to stop dividing, and can invade other tissues, differing from healthy cells.
• Cancer treatments harm healthy cells because treatments target rapidly dividing cells, affecting hair, digestive, and immune cells.
• Advantages of genetic testing: Identifies inherited risks and allows for early interventions.
• Disadvantages of genetic testing: Psychological stress, potential insurance discrimination, and ethical concerns.

Genetic Disorders

• True statement about dominant vs. recessive disorders: Most people with recessive disorders have normal parents who are heterozygotes.
• Dominant lethal alleles are less common than recessive lethal alleles.
• A deletion mutation removes one or more nucleotides from a DNA sequence.
• A carcinogen is a cancer-causing agent found in the environment.
• In DNA base pairing, if guanine = 30%, then cytosine = 30%, leaving adenine + thymine = 40%, and adenine = 20%.
• A gene is a unit of inheritance encoded in DNA that programs the amino acid sequence of a polypeptide.
• An insertion mutation adds one or more nucleotides to the DNA sequence.

Radiation and Cancer

• Radiation damages both cancerous and healthy cells.
• Some cancer cells lose the ability to repair themselves.
• Unique DNA information is determined by the order of nucleotide bases in the helix.
• Oncogene: A gene that causes cancer.
• Cells spend 90% of their time in interphase, within the cell cycle.
• Translation: synthesis of a polypeptide from mRNA.
• In gel electrophoresis, DNA fragment #1 is shorter than fragment #2 because it traveled faster.
• Nucleic acids consist of A polymer of nucleotides.

Cancer Cells

• Some cancer cells divide indefinitely.
• Cancer starts with mutations in key genes.
• The first stage of carcinogenesis is a single cell undergoing genetic mutations affecting the cell cycle control system.
• PCR amplifies specific DNA segments, creating billions of copies.
• Benign tumors that are contained and solid are best for surgery.
• G1, G2, and S are not mitosis stages.
• Proto-oncogenes regulate cell division; when mutated, they can cause cancer.
• Nucleotides are the monomers of nucleic acids.
• RNA is single-stranded genetic material.

Genetic Testing

• Advantages of direct-to-consumer genetic testing: Lower cost, helps consumers understand genetics, encourages proactive health steps, and is non-invasive sampling.
• Mitosis phase divides both nucleus and cytoplasm.
• Metastatic tumors spread; chemotherapy treats the entire body.
• Complementary DNA Strand: ATCCGA is complementary to TAGGCT
• DNA and RNA are both made of nucleotides.
• Sample collection for genetic testing involves saliva or mouth cells via cheek swab.
• Mitosis produces genetically identical cells; meiosis does not.
• Dominant phenotypes result from AA (homozygous dominant) or Aa (heterozygous).
• Radiation in cancer treatment can be used before, during, or after surgery.