4U Bio Genetics II Review

Page 1: Genetics Review 2022

Reproductive Processes

  • Types of Reproduction:

    • Sexual Reproduction: involves the combination of genetic material from two parents.

    • Asexual Reproduction: involves a single organism reproducing without the involvement of gametes.

Meiosis vs. Mitosis

  • Meiosis: leads to the production of gametes, reduces chromosome number by half (haploid).

  • Mitosis: results in two identical daughter cells, maintains the same chromosome number (diploid).

Mutations and Gene Function

  • Archibald Garrod (1902): Introduced the concept of "inborn errors of metabolism" to explain genetic conditions inherited as recessive traits.

  • Beadle and Tatum’s Hypothesis:

    • Proposed the "One gene, one enzyme" hypothesis to establish the role of genes in biochemical pathways.

    • Their research involved identifying genetic controls over biochemical reactions.

Definitions of Genetics Terminology

  • Allele: an alternate coding of a gene sequence, also termed "allelic variant".

Types of Mutations

  1. Single Nucleotide Polymorphisms (SNPs):

    • Substitutions: can be silent, missense, or nonsense mutations.

    • Frameshift Mutations: occur through insertion or deletion of nucleotides.

  2. Chromosomal Mutations:

    • Deletions and Additions.

    • Translocation: segments of chromosomes are rearranged.

    • Inversion: reversal of a segment within a chromosome.

  3. Aneuploidy: altered chromosome number due to non-disjunction during meiosis.

Causes of Mutations

  • Point Mutations:

    1. DNA polymerase mispairing: incorrect base pairing during replication.

    2. Tautomerization: changes the structure of bases leading to incorrect pairing.

    3. Deamination: loss of amino groups from bases causes mispairing.

  • Ionizing Radiation: (e.g., X-rays) causes breaks in the DNA structure leading to mutations.

  • Alkylating Agents: add alkyl groups, hindering polymerase activity.

  • Intercalating Agents: integrate with DNA base pairs causing frameshift mutations.

  • UV Light: causes pyrimidine dimers, preventing DNA polymerases from proceeding, which can lead to replication errors.

DNA Repair Mechanisms

  • Base Excision Repair: a key pathway to correct damaged DNA by removing and replacing damaged bases.

Outcomes of Mutations

  • Impacts: can lead to diseases or new phenotypes depending on whether mutations occur in germline or somatic cells.

  • Inheritance: only germline mutations can be transmitted to offspring.

Specific Genetic Disorders

  • Create a chart summarizing the following disorders:

    • Sickle Cell Disease

      • DNA Mutation: Single point mutation in the HBB gene.

      • Mutation Type: Missense mutation.

      • Effect on Protein: Hemoglobin structure altered (HbS).

      • Phenotypic Effect: Distorted red blood cells.

    • Cystic Fibrosis

      • DNA Mutation: Deletion of F508 in CFTR gene.

      • Mutation Type: Deletion mutation.

      • Effect on Protein: Dysfunctional CFTR protein affecting chloride transport.

      • Phenotypic Effect: Thick mucus production.

    • Huntington’s Disease

      • DNA Mutation: CAG repeat expansion in HTT gene.

      • Mutation Type: Repeat expansion.

      • Effect on Protein: Abnormal huntingtin protein.

      • Phenotypic Effect: Neurodegeneration.

    • p53 Mutation

      • DNA Mutation: Various mutations in TP53 gene.

      • Mutation Type: Diverse mutations.

      • Effect on Protein: Loss of tumor-suppressing function.

      • Phenotypic Effect: Increased cancer risk.

    • Lactase Persistence

      • DNA Mutation: Variants upstream of LCT gene.

      • Mutation Type: Regulatory mutation.

      • Effect on Protein: Continuous lactase production.

      • Phenotypic Effect: Ability to digest lactose in adulthood.

Page 2: Regulation of Gene Expression

Eukaryotic vs. Prokaryotic Gene Regulation

  • Eukaryotic Regulation:

    • Involves epigenetic mechanisms such as chromatin remodeling to regulate gene expression during cell differentiation and specialization.

  • Prokaryotic Regulation:

    • Utilizes operons to allow rapid adaptation to nutrient availability and environmental changes.

Biotech Tools

  • Restriction Enzymes: Cut DNA at specific sequences.

  • Gel Electrophoresis: Separates DNA fragments based on size.

  • Ligase: Joins DNA strands together.

  • Plasmids: Circular DNA used for cloning and expressing genes.

  • Viral Vectors: Used to deliver genetic material into cells.

  • CRISPR-Cas9: A revolutionary tool for gene editing.

  • Polymerase Chain Reaction (PCR): Amplifies DNA segments for study.

  • DNA Sequencing:

    • Chain Termination Method: Traditional method for determining DNA sequences.

    • Next Generation High Throughput: Allows rapid sequencing of large amounts of DNA.