Biology Finals S2 Vocabulary

DNA Replication

• Purpose of DNA Replication
  • Ensures each daughter cell receives identical copies of genetic material during cell division.
• Location of DNA Replication
  • Occurs in the nucleus during the S phase of the cell cycle.
• Semi-Conservative Replication
  • Each new DNA molecule consists of one original strand and one newly synthesized strand.
• Key Enzymes in DNA Replication
  1. Helicase: Unwinds and separates the DNA strands.
  2. DNA Polymerase: Adds complementary nucleotides to the template strand.
  3. Primase: Synthesizes RNA primers to initiate replication.
  4. Ligase: Seals gaps between Okazaki fragments on the lagging strand.
• Leading vs. Lagging Strand
  • Leading Strand: Synthesized continuously in the 5' to 3' direction.
  • Lagging Strand: Synthesized discontinuously as Okazaki fragments.
• Origin of Replication
  • Specific sites where DNA replication begins; multiple origins exist in eukaryotic DNA.
• Role of Telomeres
  • Protective caps at the ends of chromosomes.
  • Prevent the loss of important genetic information during replication.
• Proofreading and Error Correction
  • DNA polymerase has the proofreading ability to correct errors during replication.
• Significance of DNA Replication
  • Essential for genetic continuity and proper cell function.

Mitosis

• Purpose of Mitosis
  • Ensures equal distribution of chromosomes into two genetically identical daughter cells.
  • Functions: Growth, repair, and asexual reproduction.
• The Cell Cycle
  • Stages:
    1. Interphase: G1 (growth), S (DNA replication), G2 (preparation for mitosis).
    2. Mitosis: Division of the nucleus.
    3. Cytokinesis: Division of the cytoplasm.
• Phases of Mitosis
  1. Prophase: Chromosomes condense, spindle fibers form, nuclear envelope breaks down.
  2. Metaphase: Chromosomes align at the metaphase plate.
  3. Anaphase: Sister chromatids separate and move to opposite poles.
  4. Telophase: Nuclear envelopes reform, chromosomes decondense.
• Cytokinesis
  • Division of the cytoplasm into two cells.
  • Animal cells: Cleavage furrow forms.
  • Plant cells: Cell plate forms.
• Chromosome Structure
  • Chromatid: One of two identical halves of a replicated chromosome.
  • Centromere: Region where sister chromatids are joined.
  • Kinetochore: Protein structure on chromatids where spindle fibers attach.
• Role of Spindle Fibers
  • Attach to kinetochores and separate chromatids during anaphase.
• Control of the Cell Cycle
  • Checkpoints:
    1. G1 Checkpoint: Ensures the cell is ready for DNA synthesis.
    2. G2 Checkpoint: Checks for DNA replication errors.
    3. M Checkpoint: Ensures proper chromosome alignment and spindle attachment.
• Regulation by Cyclins and CDKs
  • Cyclins and cyclin-dependent kinases (CDKs) regulate progression through the cell cycle.
• Mitosis vs. Meiosis
  • Mitosis: Produces two genetically identical diploid cells.
  • Meiosis: Produces four genetically diverse haploid cells.
• Importance of Mitosis
  • Maintains chromosome number in somatic cells.
  • Essential for tissue repair, growth, and replacement of old cells.
• Errors in Mitosis
  • Can lead to:
    • Aneuploidy: Abnormal number of chromosomes (e.g., Down syndrome).
    • Cancer: Uncontrolled cell division due to faulty regulation.

Meiosis

• Purpose of Meiosis
  • To produce gametes (sperm and egg cells) with half the chromosome number of the parent cell.
  • Essential for sexual reproduction and maintaining chromosome number across generations.
• Meiosis vs. Mitosis
  • Meiosis: Produces four genetically diverse haploid cells.
  • Mitosis: Produces two identical diploid cells.
• Haploid vs. Diploid
  • Diploid (2n): Cells with two sets of chromosomes (e.g., somatic cells).
  • Haploid (n): Cells with one set of chromosomes (e.g., gametes).
• Stages of Meiosis
  • Two divisions: Meiosis I (reductional division) and Meiosis II (equational division).
  • Results in four haploid cells.
• Prophase I
  • Chromosomes condense, and homologous chromosomes pair up (synapsis).
  • Crossing over occurs at chiasmata, exchanging genetic material between homologs.
• Metaphase I
  • Homologous chromosome pairs align at the metaphase plate.
  • Independent assortment occurs, contributing to genetic variation.
• Anaphase I
  • Homologous chromosomes are pulled to opposite poles.
  • Sister chromatids remain attached at their centromeres.
• Telophase I and Cytokinesis
  • Nuclear membranes may reform, and the cell divides into two haploid cells.
  • Each cell contains one chromosome from each homologous pair.
• Meiosis II Overview
  • Similar to mitosis but starts with haploid cells.
  • Separates sister chromatids into individual chromosomes.
• Prophase II
  • Chromosomes condense again, and spindle fibers form in each haploid cell.
• Metaphase II
  • Chromosomes align at the metaphase plate in each haploid cell.
• Anaphase II
  • Sister chromatids are pulled apart to opposite poles.
• Telophase II and Cytokinesis
  • Nuclear membranes reform and the cytoplasm divides.
  • Four haploid cells are produced, each genetically unique.
• Crossing Over
  • Occurs during Prophase I.
  • Homologous chromosomes exchange genetic material, increasing genetic diversity.
• Independent Assortment
  • Random orientation of homologous pairs during Metaphase I.
  • Leads to different combinations of maternal and paternal chromosomes in gametes.
• Gametogenesis
  • Process of forming gametes:
    • Spermatogenesis: Produces four viable sperm cells in males.
    • Oogenesis: Produces one viable egg and three polar bodies in females.
• Importance of Meiosis
  • Reduces chromosome number by half, preventing chromosome doubling in offspring.
  • Increases genetic variation through crossing over and independent assortment.
• Genetic Variation
  • Meiosis contributes to diversity via:
    1. Crossing over.
    2. Independent assortment.
    3. Random fertilization of gametes.
• Errors in Meiosis
  • Nondisjunction: Failure of chromosomes to separate properly.
    • Can lead to aneuploidy (e.g., Down syndrome, Turner syndrome).
• Significance of Meiosis in Evolution
  • Genetic variation from meiosis is the basis for natural selection and evolution.
  • Provides the raw material for adaptation and survival in changing environments.

Genetics

• Gregor Mendel
  • Known as the "Father of Genetics."
  • Conducted experiments on pea plants to understand inheritance patterns.
• Mendel’s Laws of Inheritance
  1. Law of Segregation: Each organism has two alleles for a trait, which segregate during gamete formation.
  2. Law of Independent Assortment: Genes for different traits assort independently during gamete formation.
• Genes and Alleles
  • Gene: A segment of DNA that codes for a specific trait.
  • Allele: Different forms of a gene (e.g., dominant or recessive).
• Dominant and Recessive Alleles
  • Dominant: Expressed when present (e.g., "A").
  • Recessive: Expressed only when both alleles are recessive (e.g., "a").
• Genotype and Phenotype
  • Genotype: The genetic makeup of an organism (e.g., AA, Aa, aa).
  • Phenotype: The physical expression of a trait (e.g., tall or short).
• Homozygous vs. Heterozygous
  • Homozygous: Two identical alleles for a trait (e.g., AA or aa).
  • Heterozygous: Two different alleles for a trait (e.g., Aa).
• Punnett Squares
  • A tool to predict the probability of offspring inheriting specific traits.
  • Shows possible genotypes and phenotypes from parental crosses.
• Monohybrid Cross
  • Involves one trait.
  • Example: Crossing two heterozygous parents (Aa x Aa) results in a 3:1 phenotype ratio.
• Dihybrid Cross
  • Involves two traits.
  • Example: Crossing two heterozygous parents (AaBb x AaBb) results in a 9:3:3:1 phenotype ratio.
• Test Cross
  • Used to determine an unknown genotype by crossing with a homozygous recessive individual.
• Probability in Genetics
  • The likelihood of an event occurring:
    • Rule of Multiplication: Probability of two independent events occurring together.
    • Rule of Addition: Probability of either of two mutually exclusive events occurring.
• Incomplete Dominance
  • A situation where the heterozygous phenotype is intermediate between the two homozygous phenotypes.
  • Example: Red (RR) x White (rr) = Pink (Rr).
• Codominance
  • Both alleles are expressed equally in the phenotype.
  • Example: Blood type AB (IAIB).
• Multiple Alleles
  • A gene with more than two allele options.
  • Example: ABO blood group system (IA, IB, i).
• Polygenic Inheritance
  • Traits controlled by multiple genes, leading to a range of phenotypes.
  • Example: Skin color, height.
• Epistasis
  • One gene affects the expression of another gene.
  • Example: Coat color in Labrador retrievers.
• Linked Genes
  • Genes located close together on the same chromosome tend to be inherited together.
  • Example: Red hair and freckles.
• Sex-Linked Traits
  • Traits determined by genes on the sex chromosomes.
  • Example: Hemophilia and colorblindness (X-linked traits).
• Pedigree Analysis
  • A chart used to trace the inheritance of traits in a family.
  • Symbols:
    • Circle: Female
    • Square: Male
    • Shaded: Affected individual
• Importance of Mendelian Genetics
  • Foundation for understanding inheritance.
  • Helps predict genetic disorders and traits in offspring.

Genetic Disorders

• Definition of Genetic Disorders
  • Genetic disorders are diseases caused by abnormalities in an individual's DNA. These abnormalities may be inherited or occur due to mutations.
• Types of Genetic Disorders
  1. Single-Gene Disorders: Caused by mutations in a single gene (e.g., Cystic Fibrosis).
  2. Chromosomal Disorders: Caused by structural changes or abnormal numbers of chromosomes (e.g., Down Syndrome).
  3. Multifactorial Disorders: Result from interactions between multiple genes and environmental factors (e.g., Heart Disease).
• X-Linked Disorders
  • Caused by mutations on the X chromosome; more common in males.
  • Example: Hemophilia – A blood clotting disorder.
• Chromosomal Disorders
  • Caused by missing, extra, or altered chromosomes.
  • Example: Down Syndrome (Trisomy 21) – An extra copy of chromosome 21 leads to developmental delays and physical differences
• Diagnosis of Genetic Disorders
  • Genetic Testing: Identifies mutations in DNA.
  • Karyotyping: Analyzes chromosomes for abnormalities.
  • Newborn Screening: Detects certain genetic conditions early in life.
• Treatment and Management
  • Gene Therapy: Experimental technique that replaces defective genes.
  • Medications & Therapies: Used to manage symptoms (e.g., enzyme replacement therapy for Gaucher disease).
  • Lifestyle Changes: Can help manage multifactorial disorders.
• Ethical Considerations in Genetics
  • Issues surrounding genetic testing, privacy, and discrimination.
  • Debate over genetic engineering and modifying human genes (CRISPR technology).

Biotechnology

• Definition of Biotechnology
  • The use of living organisms, cells, and biological systems to develop technologies and products for various industries, including medicine, agriculture, and environmental science.
• Genetic Engineering
  • The direct manipulation of an organism’s DNA using biotechnology to alter genetic makeup for desired traits.
• Gene Cloning
  • Producing identical copies of a gene for research, medicine, or agriculture
• CRISPR-Cas9 Technology
  • A powerful gene-editing tool that allows scientists to precisely modify DNA sequences.
• Genetically Modified Organisms (GMOs)
  • Organisms whose DNA has been altered for agricultural or medical purposes, such as pest-resistant crops or insulin-producing bacteria.
• Gene Therapy
  • A technique that replaces, removes, or alters defective genes to treat genetic diseases.
• Stem Cell Technology
  • The use of undifferentiated cells to develop specialized cells for medical treatments and regenerative medicine.
• Biopharmaceuticals
  • Medicines produced using biotechnology, such as vaccines, monoclonal antibodies, and hormone therapies (e.g., insulin).
• Bioremediation
  • The use of microbes to clean up environmental pollutants such as oil spills and heavy metal contamination.
• Ethical Concerns in Biotechnology
  • Genetic modification, cloning, and gene editing raise ethical issues regarding safety, consent, and unintended consequences.

Darwin’s Theory of Evolution

• Charles Darwin
  • An English naturalist who proposed the theory of evolution by natural selection after his voyage on the HMS Beagle.
• Evolution
  • The process of species changing over time through genetic variation and natural selection.
• Natural Selection
  • The mechanism by which organisms with favorable traits survive and reproduce more successfully than others.
• Survival of the Fittest
  • A phrase often describes natural selection, meaning those best adapted to their environment survive and pass on their traits.
• Variation
  • Differences in traits within a population, caused by mutations, gene shuffling during reproduction, and other genetic factors.
• Adaptation
  • A trait that improves an organism's ability to survive and reproduce in its environment.
• Overproduction
  • Organisms produce more offspring than can survive, leading to competition for limited resources.
• Competition
  • The struggle among organisms for limited resources such as food, space, and mates.
• Descent with Modification
  • Over generations, species change, and descendants may look different from their ancestors.
• Common Descent
  • The idea that all living organisms share a common ancestor.
• Evidence for Evolution
  • Fossil record
  • Comparative anatomy
  • Embryology
  • DNA and molecular biology
  • Biogeography
• Homologous Structures
  • Body parts that are similar in structure but may have different functions, indicating a common ancestor (e.g., human arm, whale fin, bat wing).
• Analogous Structures
  • Body parts that perform similar functions but have different structures, showing adaptation to similar environments (e.g., bird wing and insect wing).
• Vestigial Structures
  • Body parts that no longer serve a purpose but were functional in an ancestor (e.g., human appendix, whale pelvis).
• Mutations
  • Random changes in DNA that can lead to variation and new traits in a population.
• Artificial Selection
  • The selective breeding of plants and animals by humans to promote desirable traits.
• Speciation
  • The formation of new species due to isolation, genetic divergence, and environmental pressures.
• Impact of Darwin’s Work
  • Darwin’s theory laid the foundation for modern biology, explaining the diversity of life and how species adapt to changing environments.