Biology 30 Genetics Unit

Name

  • Danial V

BIOLOGY 30 Genetics Unit

  • Topics: Cell Division, DNA and RNA
  • Website Reference: offthemark.com

Specific Learning Outcomes for Genetics

  • Do you understand the following key concepts?
    • Cell cycle
    • Mitosis and meiosis
    • Chromosome number
    • Karyotype
    • Alternation of generations
    • Model of DNA replication
    • Transcription
    • Translation
    • Mutation
    • Genetic engineering

General Outcome 1: Mitosis and Meiosis

  1. Define and explain the significance of chromosome number in somatic and sex cells; i.e., haploidy, diploidy and polyploidy.
  2. Explain in general terms the events of the cell cycle; i.e., interphase, mitosis and cytokinesis.
  3. Describe the process of meiosis (spermatogenesis and oogenesis) and the necessity for the reduction of chromosome number.
  4. Compare the processes of mitosis and meiosis.
  5. Describe the processes of crossing over and nondisjunction, and evaluate their significance to organism inheritance and development.
  6. Compare the formation of fraternal and identical offspring in a single birthing event.
  7. Describe the diversity of reproductive strategies by comparing the alternation of generations in a range of organisms; e.g., Daphnia, sea anemone, moss, pine.
  8. Explain that science and technology are developed to meet societal needs and expand human capability (technologies related to cellular biology).

General Outcome 2: Classical Genetics at the Molecular Level

  1. Summarize the historical events that led to the discovery of the structure of the DNA molecule, including the work of Franklin and Watson and Crick.
  2. Describe in general how genetic information is contained in the sequence of bases in DNA molecules in chromosomes and how the DNA molecules replicate themselves.
  3. Describe in general how genetic information is transcribed into sequences of bases in RNA molecules and is finally translated into sequences of amino acids in proteins.
  4. Explain in general how restriction enzymes cut DNA molecules into smaller fragments and how ligases reassemble them.
  5. Explain in general how cells may be transformed by inserting new DNA sequences into their genomes.
  6. Explain how a random change (mutation) in the sequence of bases results in abnormalities.
  7. Explain how base sequences in nucleic acids contained in the nucleus, mitochondrion and chloroplast are inherited.
  8. Explain that science and technology have both intended and unintended consequences for humans and the environment.
  9. Explain that scientific research and technological development help achieve a sustainable society, economy and environment.
  10. Construct models of DNA to demonstrate the general structure and base arrangement.
  11. Perform simulations to demonstrate the replication of DNA and the transcription and translation of its information.
  12. Perform simulations to demonstrate the use of restriction enzymes and ligases.
  13. Analyze, from published data, relationships between human activities and changes in genetic information that lead to heritable mutations and cancer.

Animal Cell Perspectives in Science

**Important Perspectives:

  1. Social Perspective:** Relates to society as a whole and large groups of people rather than individual or small family groups.
  2. Cultural Perspective: Relates to behaviors, beliefs, and other aspects characteristic of a particular group of people defined by context.
  3. Environmental Perspective: Related to aspects of ecology, including ecological management and human effects on the environment.
  4. Ethical Perspective: Relates to moral principles and a sense of right and wrong.
  5. Economic Perspective: Concerns costs, benefits, and associated effects of the application of particular technology.
  6. Technological Perspective: Useful applications of science.
  • Perspectives can overlap, requiring judgment to choose the most exemplified one. More than one answer may also be acceptable in certain questions.

Topic 1: Introduction to Cell Division

  • When a cell is preparing to divide, DNA wraps around histone proteins and condenses into chromosomes.
  • Chromatin: Long strands of DNA wrapped around beads of protein (histones).
    • When preparing to divide, chromatin coils into thicker strands called chromosomes.
    • Humans possess a total of 46 chromosomes (23 pairs):
    • 44 autosomes (non-sex chromosomes).
    • 2 sex chromosomes:
      • Females = XX
      • Males = XY

Ploidy

  • Ploidy: The number of sets of chromosomes in a cell.
    • Example of definitions:
    • Diploid (2n): Total number of chromosomes in every somatic (body) cell of an organism.
    • Haploid (n): Total number of chromosomes in the egg or sperm of an organism.
  • In humans: Homologous chromosomes carry the same genes at the same location (locus) but are NOT IDENTICAL, as they can carry different forms (alleles) of the same gene.
  • Organism Diploid Number and Example:
    1. Dog - Diploid: 78, Haploid: 39
    2. Cat - Diploid: 38
    3. Shrimp - Diploid: 2
    4. Scorpion - Diploid: 256
    5. Green Ash Tree - Diploid: 23
    6. Human - Diploid: 46

Cell Division - Mitosis and Meiosis

  • Types of Cell Division: Mitosis and Meiosis
    • Mitosis: Process to make new body cells.
    • Meiosis: Process to create egg and sperm cells.
  • During mitosis, a cell duplicates its contents, including its chromosomes, to form two identical daughter cells.
  • Health issues, e.g., cancer, can arise from improper mitosis regulation.
  • Meiosis Overview:
    • Reduces chromosome number by half (from 46 to 23) to ensure continuity in generations.
    • Sperm and egg cells unite during conception, contributing 23 chromosomes each, leading to a 46 chromosomes in the embryo.
    • Causes genetic variation through DNA shuffling.
  • Nondisjunction:
    • Abnormal chromosome division during meiosis leading to conditions such as Down’s syndrome.
  • Write at least three differences between Mitosis and Meiosis:
    • Mitosis:
    • Meiosis:

Mitosis Phases: PMAT

  • Mitosis Phases: Propahse, Metaphase, Anaphase, and Telophase.
    1. Prophase: Starting cell 2n, Chromosomes already replicated
    2. Metaphase: Chromosomes line up along the metaphase plate.
    3. Anaphase: Sister chromatids separate, ending with a somatic cell with a diploid number of chromosomes
    4. Telophase: Resulting cells are somatic with a diploid number and cytokinesis occurs.

Meiosis Phases: {PMATPMAT}

  • Meiosis II and Mitosis have similar phases but are distinct processes where:
    1. Meiosis involves two divisions (reducing the chromosome number) while Mitosis involves only one.
    2. 4 viable haploid cells are produced in meiosis, and genetically distinct cells arise due to crossing over.

Cell Cycle

  • Three Phases:
  1. Interphase: Chromosomes are not visible, in chromatin form.
    • Cells undergo growth, protein synthesis, and DNA duplication.
  2. Mitosis: Cell divisions.
  3. Cytokinesis: Cell divides into two new cells.
  • Cell Specialization: Certain cells exit the cell cycle and cease to divide (e.g., neurons).

Interphase Details

  • Main Events:
    • Growth / protein synthesis
    • DNA duplication (sister chromatids formed)

Mitosis Details

Phases
  • Prophase:
    • Chromatin becomes visible and forms chromosomes
    • Nuclear membrane dissolves
    • Centrioles separate and spindle fibers form
  • Metaphase:
    • Duplicated chromosomes line up at the metaphase plate (equator)
  • Anaphase:
    • Centromeres divide and chromosomes move to opposite poles
  • Telophase:
    • Chromosomes reach opposite poles, become chromatin, spindle fibers dissolve, nuclear envelope reappears
  • Cytokinesis:
    • Cytoplasm divides, cell plate occurs in plant cells.

Review Questions

Diagram Reference Needed

  • Identify the numbers in each phase:
    • Interphase: 4, 5, 6, 8, 10, 13, 15, 16, 18
    • Prophase: 2, 14
    • Metaphase: 1, 11, 17
    • Anaphase: 7, 9
    • Telophase: 3, 12
Multiple Choice Questions
  1. The purpose of mitosis is to produce:
    A. Somatic cells that are identical
    B. Sex cells that are identical
    C. Somatic cells that have variation
    D. Sex cells that have variation
  2. Replication of DNA molecules occurs during:
    A. Prophase
    B. Metaphase
    C. Anaphase
    D. Interphase
  3. After mitosis, the number of chromosomes in the daughter cell is:
    A. Double the number of the mother cell
    B. Half the number of the mother cell
    C. Equal to the number of the mother cell
    D. Double the number of two mother cells

Cancer Cells

Normal Cells vs. Cancer Cells

  • Normal Cells:
    • Reproduce exactly
    • Stop reproducing when needed
    • Stick together correctly and specialize
  • Cancer Cells:
    • Keep reproducing and proliferate uncontrollably
    • Do not die when moved to another body part
    • Do not stick together or specialize
Cloning Overview
  • Cloning Definition: Identical offspring formed from a single parent cell (asexual reproduction)
  • Cloning Steps:
    1. Remove nucleus from egg (donor)
    2. Insert mammary cell nucleus from the animal to be cloned
    3. Use electric shock to trigger cell division
    4. Transfer zygote to surrogate uterus
    5. Genetically identical sheep develop
Can You Clone Using Hair Cells?
  • No! Cloning only possible with totipotent cells (can differentiate into any cell type).

Identical vs. Fraternal Twins

  1. Identical Twins: Result from 1 egg fertilized by 1 sperm (monozygotic).
    • Same sex, blood type, and genetic make-up.
  2. Fraternal Twins: Result from 2 different eggs and sperm (dizygotic).
    • Not genetically identical.

Stem Cell Research:

  • Stem cells can replicate and differentiate into numerous cell types (e.g., skin, muscle, nerve).
  • Sources:
    1. Embryonic Stem Cells (morula/blastula)
    2. Umbilical Cord Stem Cells
    3. Adult Stem Cells (bone marrow)

Topic 2: Meiosis

Meiosis Overview

  • Meiosis creates haploid cells (gametes).
    • Gametes include sperm (from testes) and eggs (from ovaries).
    • Meiosis occurs in two stages, producing four haploid cells.

Interphase I Details

  • Similar to mitosis; chromosomes replicate during this phase.

Meiosis I Details

  • Prophase I: Homologous chromosomes form tetrads; crossing over can occur.
  • Metaphase I: Tetrads align on the metaphase plate.
  • Anaphase I: Homologous chromosomes separate, but sister chromatids stay together.
  • Telophase I: Cells may enter interphase II; cytokinesis occurs to form two haploid cells.

Meiosis II Details

  • Similar to mitosis:
    • Prophase II: Spindle fibers form; nuclear membrane dissolves.
    • Anaphase II: Centromeres split and chromatids move apart.
    • Telophase II: Cytokinesis results in 4 haploid cells.

Gametogenesis: Males vs. Females

  1. Males: Spermatogenesis (in testes).
  2. Females: Oogenesis (in ovaries).
Compare Mitosis and Meiosis
  • Meiosis Variability:
    • Happens through processes like crossing over and independent assortment during Metaphase and Anaphase.

Fill in the Phase and Ploidy of Cells (Example Given)

Phases:

  1. Prophase II ____
  2. __
  3. __
  4. __
    Measure Ploidy:
    n =

Topic 3: DNA - The Molecule of Life

  • Genetic information exists within DNA, housed in the nucleus; unique for each individual.
  • DNA: DeoxyriboNucleic Acid.
    • Composed of:
    • Deoxyribose sugar
    • Phosphates (make DNA acidic)
  • DNA Functions:
    • Universal code for all living cells (plant, animal, bacteria, fungus).

Historical Contributions to DNA Discovery

  1. Griffith (1928): Demonstrated DNA as hereditary material.
  2. Hershey & Chase (1952): Confirmed DNA’s role through experiments.
  3. Phoebus Levene: First to define DNA's structure, claiming equal base amounts.
  4. Erwin Chargaff: Disproved Levene's theory; Introduced Chargaff's Rule (A=T, C=G).
  5. Rosalind Franklin (
    X-ray diffraction"): Discovered double-helix structure.
  6. Watson and Crick: Determined 3-D structure of DNA based on prior research.

DNA Structure

  • DNA Architecture: Twisted ladder structure.
    • Backbone: Deoxyribose & phosphate groups.
    • Rungs: Pairs of nitrogen bases (Adenine, Thymine, Guanine, Cytosine).

DNA Replication: Semiconservative nature where each strand consists of half original DNA and half newly synthesized DNA.

Steps of DNA Replication:

  1. Unwinds (helicase initiates).
  2. Unzips (hydrogen bonds are broken).
  3. Attracts complementary nucleotides.
  4. Sugars and phosphates connect to create two identical DNA strands.

Topic 4: Protein Synthesis

  • The journey from DNA to protein involves Transcription and Translation.

1. Transcription:

  • DNA code transferred to mRNA within nucleus.
  • Structural Components of mRNA detrived from DNA:
    • Comprised of sequences called codons; each codon encodes a specific amino acid.

2. Translation:

  • mRNA interacts with ribosome to assemble amino acids into polypeptides.
  • tRNA carries amino acids to mRNA based on complementary pairing.

Topic 5: Genetic Engineering

  • Genetic Engineering (Recombinant DNA technology):
    • Process of building new DNA by splicing genes from different organisms.

Key Components for Recombinant DNA

  1. Plasmids from E. coli bacteria
  2. Restriction enzymes (cut DNA)
  3. DNA ligase (glue)
  4. Desired gene segment

Applications of rDNA

  1. Agriculture: Genetically modified organisms (e.g., Roundup Ready Canola).
  2. Human Products: Expression of insulin, hormones, proteins.
  3. Gene Therapy: Replacing defective genes with functional copies.
  4. Ethical Considerations: Address concerns of technology, long-term effects, and social implications.