Meiosis
Page 1
Page 2: Introduction
Topics Covered:
Meiosis (Chapter 8.3)
RNA & Protein Synthesis (Chapter 10.2 & 10.3)
Human Genetics (Chapter 12.2)
Author: Konnor Wong
Date: 2/3/25
Page 3: CH 8.3 - Meiosis Stages
Prophase I
Nuclear membrane dissolves.
Spindle fibers begin to form.
DNA condenses into visible chromosomes.
Homologous chromosomes pair up and MAY undergo crossing over.
Centrioles move to opposite poles of the cell.
Metaphase I
Spindle fibers attach to homologous chromosome pairs.
Homologous chromosome pairs line up at the center of the cell.
Anaphase I
Spindle fibers pull homologous chromosomes to opposite poles of the cell.
Telophase I
Nuclear membrane reforms.
Chromosomes may partially unwind into DNA.
Cytokinesis I occurs, resulting in two haploid (1n) cells.
Page 4: CH 8.3 - Continued Meiosis Stages
Prophase II
Nuclear membrane dissolves.
DNA condenses into visible chromosomes.
Centrioles move to opposite poles of each cell.
Spindle fibers begin to form.
Metaphase II
Spindle fibers attach to the centromeres of individual chromosomes.
Chromosomes (sister chromatids) line up at the center of each cell.
Anaphase II
Spindle fibers pull sister chromatids apart to opposite poles of the cell.
Page 5: Telophase II
Telophase II
Nuclear membrane reforms around each set of chromosomes.
Chromosomes decondense into DNA.
Cytokinesis II occurs, resulting in four genetically unique haploid (1n) cells.
Page 6: Vocabulary for Meiosis
Terms Defined:
Synapsis: Pairing of homologous chromosomes during Prophase I.
Tetrad: Each pair of homologous chromosomes.
Crossover: Exchange of DNA between homologous chromosomes.
Genetic recombination: Result of crossover.
Independent assortment: Random assortment of homologous pairs into daughter cells during Anaphase I.
Mendel’s Law of Independent Assortment: Explained.
Spermatids: Result of meiosis in males (4x 1n cells).
Spermatogenesis: Production of sperm cells.
Spermiogenesis: Maturation of spermatids.
Oogenesis: Production of mature egg cells (ova).
Polar bodies: Degenerate products of oogenesis.
Page 7: Gametes and Cells
Zygote: Cell formed when two gametes fuse during fertilization.
Gamete: Reproductive cells (sperm & egg).
Somatic: Body cells.
Binary Fission: Type of cell division in bacteria.
Page 8: CH 10.2 & 10.3 - RNA & Protein Synthesis
Protein Synthesis: Also known as gene expression; the process of synthesizing proteins.
Transcription Steps
RNA Polymerase Binds to DNA
Attaches to a promoter sequence.
DNA Strands Separate
Strands unwind; template strand is used for RNA synthesis.
RNA Nucleotides Are Added
RNA polymerase adds complementary RNA nucleotides.
Transcription Ends at a Stop Signal
RNA molecule detaches.
Types of RNA Produced:
mRNA: Carries protein-making instructions.
rRNA: Forms ribosomes.
tRNA: Brings amino acids to ribosomes.
Page 9: Translation
Translation: Genetic code in mRNA converted to amino acid sequence for protein.
Stages of Translation
Initiation
mRNA binds to a ribosome at the start codon (AUG).
Elongation
Ribosome reads mRNA in codons; tRNA brings specific amino acids.
Termination
Stop codon is reached; polypeptide detaches, folding into protein.
Page 10: Vocabulary for RNA & Protein Synthesis
Gene Expression: Process of transcribing DNA into proteins.
RNA polymerase: Enzyme for mRNA creation.
Promoters: DNA sequence marking start of transcription.
Codon: Sequence of three nucleotides coding for an amino acid.
Anticodon: Sequence of three nucleotides on tRNA.
Genetic Code: Correlation between nucleotide and amino-acid sequences.
Page 11: Human Genetics and Chromosomal Mutations
Crossover: DNA exchange between homologous chromosomes during Prophase I.
Nondisjunction Disorders:
Monosomy 23: Turner Syndrome (missing X chromosome, affects females).
Trisomy 23: Klinefelter's Syndrome (extra X chromosome, affects males).
Trisomy 21: Down Syndrome (affects development).
Trisomy 18: Edwards Syndrome (growth delays).
Trisomy 13: Patau Syndrome (multiple physical issues).
Traits
Single-allele Traits: Controlled by a single allele.
Multiple-allele Traits: Controlled by three or more alleles.
Polygenic Traits: Controlled by multiple genes.
Page 12:
Page 13: Vocabulary
Pedigree: Family record showing trait inheritance over generations.
Genetic Screening: Process for identifying genetic disorders.
Karyotype: Arrangement of chromosomes in an organism.
Page 14: Chromosome Structure
Homologous Chromosome Pairs: Two chromosomes of the same size and shape coding for traits.
Kinetochore Fibers: Attach to centromere proteins during chromosomal movement.
Polar Fibers: Extend across the dividing cell.
Key Definitions
Diploid (2n): Two sets of chromosomes.
Haploid (1n): One set of chromosomes.
Prokaryotic Chromosomes: Circular DNA molecules.
Binary Fission: Prokaryotic cell division process.
Page 15: Review Questions
Differentiate between chromosomal and homologous pairs.
Chromosome: Two identical sister chromatids joined by a centromere.
Mitosis vs. Meiosis: Mitosis involves somatic cells; meiosis involves gametes.
Cytokinesis: Varies in plant and animal cells.
Spermatogenesis: Produces four haploid cells.
Oogenesis: Involves meiotic divisions.
Comparison
Meiosis produces genetically varied daughter cells; Mitosis produces identical daughter cells.
Asexual Reproduction: No homologous chromosomes involved; Sexual Reproduction merges gametes from two parents.
Page 18: Genetic Code and Protein Synthesis
mRNA, tRNA, rRNA differences: Functions during protein synthesis.
DNA Encoding: Information for protein production.
Covalent Bonds: Exist between nucleotides.
Base Pairing Rules: A with T, C with G.
Peptide Bonds: Form between amino acids.
Transcription Location: Occurs in the nucleus for eukaryotes.
Nondisjunction Disorders Summary
Trisomy 18: Edwards Syndrome
Trisomy 23: Klinefelter Syndrome
Trisomy 21: Down Syndrome
Trisomy 13: Patau Syndrome
Monosomy 23: Turner Syndrome