Biology 2nd Semester

Mitosis and Meiosis

Mitosis

  • Definition

    • Process of cell division where one cell divides into two identical daughter cells.

  • Phases

    • Interphase

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase

  • Purpose

    • Growth, repair, and asexual reproduction.

  • Result

    • Two diploid daughter cells with the same number of chromosomes as the parent cell.

Meiosis

  • Definition

    • Process of cell division that produces gametes with half the number of chromosomes.

  • Phases

    • Meiosis I

      • Prophase I

      • Metaphase I

      • Anaphase I

      • Telophase I

    • Meiosis II

      • Prophase II

      • Metaphase II

      • Anaphase II

      • Telophase II

  • Purpose

    • Production of gametes for sexual reproduction.

  • Result

    • Four haploid daughter cells with half the number of chromosomes as the parent cell.

  • Mitosis:

    • Cell division

    • Growth and repair of tissues

    • Results in two identical daughter cells

    • Consists of prophase, metaphase, anaphase, and telophase

  • Meiosis:

    • Cell division in reproductive cells

    • Results in four genetically different daughter cells

    • Consists of two rounds of division (meiosis I and meiosis II)

    • Creates genetic diversity

    • Phases of Meiosis

      • Central Idea: Phases of Meiosis

      • Main Branches:

        1. Meiosis I

          • Prophase I

          • Metaphase I

          • Anaphase I

          • Telophase I

        2. Meiosis II

          • Prophase II

          • Metaphase II

          • Anaphase II

          • Telophase II

DNA Replication

  1. Introduction

    • Definition of DNA replication

    • Importance of DNA replication

  2. Key Players

    • DNA polymerase

    • Helicase

    • Primase

    • Ligase

  3. Steps of DNA Replication

    • Initiation

      • Unwinding of the DNA double helix by helicase

      • Binding of primase to create RNA primers

    • Elongation

      • DNA polymerase adding nucleotides to the growing DNA strand

      • Leading and lagging strand synthesis

    • Termination

      • Removal of RNA primers by exonuclease

      • Sealing of nicks by DNA ligase

  4. Semi-Conservative Nature

    • Explanation of semi-conservative replication

    • Meselson-Stahl experiment

  5. Errors in DNA Replication

    • Mismatch repair

    • Proofreading by DNA polymerase

  6. Significance of DNA Replication

    • Genetic inheritance

    • Cell division and growth

  7. Conclusion

    • Recap of the importance of DNA replication

    • Future implications and research areas

RNA Translation

  • Definition

    • Process of protein synthesis in which the genetic information encoded in mRNA is decoded to produce a specific sequence of amino acids

  • Components involved

    • mRNA: Carries the genetic information from DNA to the ribosome

    • tRNA: Transfers specific amino acids to the ribosome based on the mRNA codon sequence

    • Ribosome: Site of protein synthesis where mRNA and tRNA interact

  • Steps of translation

    1. Initiation

      • Small ribosomal subunit binds to mRNA at the start codon (AUG)

      • tRNA carrying methionine binds to the start codon

      • Large ribosomal subunit joins to form a functional ribosome

    2. Elongation

      • Ribosome moves along the mRNA, reading codons in sets of three

      • tRNA molecules bring amino acids to the ribosome based on codon recognition

      • Peptide bond formation between adjacent amino acids

    3. Termination

      • Ribosome reaches a stop codon (UAA, UAG, UGA)

      • Release factor binds to the stop codon, causing the ribosome to release the completed protein

  • Post-translation modifications

    • Folding, cleavage, and chemical modifications may occur to the newly synthesized protein to become functional

  • Importance of translation

    • Essential process for gene expression and protein synthesis in all living organisms

      Transcription

      • Definition

        • Process of transcribing DNA into RNA

        • RNA polymerase reads the DNA template and synthesizes a complementary RNA strand

      • Types of RNA

        • Messenger RNA (mRNA)

        • Ribosomal RNA (rRNA)

        • Transfer RNA (tRNA)

      • Steps of Transcription

        • Initiation

          • RNA polymerase binds to the promoter region on DNA

        • Elongation

          • RNA polymerase moves along the DNA template, synthesizing RNA

        • Termination

          • RNA polymerase reaches the terminator sequence, RNA is released

      • Differences between Prokaryotic and Eukaryotic Transcription

        • Prokaryotic

          • Transcription and translation occur simultaneously

          • No introns in mRNA

        • Eukaryotic

          • Transcription and translation are spatially separated

          • mRNA undergoes splicing to remove introns

      • Regulation of Transcription

        • Transcription factors

        • Enhancers and silencers

        • Epigenetic modifications

      • Significance of Transcription

        • Essential for gene expression

        • Plays a crucial role in protein synthesis

      • Diseases related to Transcription

        • Cancer

        • Genetic disorders

      • Techniques used in Transcription Studies

        • RNA sequencing

        • Chromatin immunoprecipitation

      • Reporter gene assays

        Genetics Outline

        • Introduction to Genetics

          • Definition of genetics

          • Importance of genetics in biology

        • Mendelian Genetics

          • Gregor Mendel's experiments

          • Mendel's laws of inheritance (law of segregation, law of independent assortment)

        • Chromosomes and Genes

          • Structure of DNA

          • Genes and alleles

          • Chromosome structure and function

        • Genetic Variation

          • Mutations and types of mutations

          • Genetic recombination

          • Genetic diversity

        • Genetic Inheritance

          • Inheritance patterns (autosomal dominant, autosomal recessive, X-linked)

          • Pedigree analysis

        • Genetic Disorders

          • Types of genetic disorders (single gene disorders, chromosomal disorders, multifactorial disorders)

          • Examples of genetic disorders (e.g., cystic fibrosis, Down syndrome)

        • Genetic Engineering

          • Recombinant DNA technology

          • Gene editing techniques (CRISPR-Cas9)

        • Ethical and Social Implications of Genetics

          • Genetic testing and counseling

          • Genetic discrimination

          • Bioethics in genetics

        • Future of Genetics

          • Advances in genetic research

          • Potential applications of genetic technologies

        • Conclusion

          • Recap of key points in genetics

          • Importance of genetics in shaping the future

          • Inheritance of traits from parents

          • Genetic mutations and their impact

          • Genetic disorders and diseases

          • Genetic testing and counseling

          • Gene editing technologies like CRISPR

          • Genetic engineering in agriculture

          • Evolution and natural selection

          • Genetic diversity in populations

          • Epigenetics and gene expression regulation

          • Ethical considerations in genetic research

          Dominant and Recessive Alleles

          • Definition

            • Dominant allele: masks the effect of the recessive allele when present

            • Recessive allele: only expressed when two copies are present

          • Inheritance

            • Dominant allele: represented by uppercase letter (e.g., A)

            • Recessive allele: represented by lowercase letter (e.g., a)

          • Phenotype

            • Dominant allele: determines the observable trait

            • Recessive allele: trait only expressed if individual has two copies

          • Examples

            • Dominant: Brown eyes (B) over blue eyes (b)

            • Recessive: Attached earlobes (e) over free earlobes (E)

          • Punnett Square

            • Used to predict offspring genotypes and phenotypes

            • Shows possible combinations of alleles from parents

          • Genotype

            • Dominant: AA or Aa

            • Recessive: aa

          • Inheritance Patterns

            • Autosomal dominant

            • Autosomal recessive

            • X-linked dominant

            • X-linked recessive

          • Implications

            • Genetic disorders

            • Genetic counseling

            • Selective breeding in agriculture

        • Incomplete Dominance, Complete Dominance, and Co-dominance

          Incomplete Dominance

          • Definition:

            • Neither allele is completely dominant over the other.

          • Phenotype:

            • Heterozygous individuals show an intermediate phenotype.

          • Example:

            • Red flower (RR) x White flower (WW) = Pink flower (RW).

          Complete Dominance

          • Definition:

            • One allele is completely dominant over the other.

          • Phenotype:

            • Heterozygous individuals show the dominant phenotype.

          • Example:

            • Red flower (RR) x White flower (WW) = Red flower (RW).

          Co-dominance

          1. Definition:

            • Both alleles are expressed equally in the phenotype.

          2. Phenotype:

          3. Heterozygous individuals show a mix of both alleles.

            • Example:

              • Black chicken (BB) x White chicken (WW) = Specked chicken (BW).

      Phases of Mitosis

      • Interphase

        • Cell prepares for division by growing and replicating DNA

      • Prophase

        • Chromatin condenses into chromosomes

        • Nuclear membrane dissolves

        • Spindle fibers begin to form

      • Metaphase

        • Chromosomes align at the cell's equator

        • Spindle fibers attach to centromeres of chromosomes

      • Anaphase

        • Sister chromatids separate and move towards opposite poles

        • Cell elongates as poles move apart

      • Telophase

        • Chromosomes reach opposite poles and decondense into chromatin

        • Nuclear membrane reforms

        • Spindle fibers disassemble

      • Cytokinesis

        • Division of cytoplasm and organelles to form two daughter cells

        • Each daughter cell has a complete set of chromosomes

    Evolution

  • Before Darwin, people believed in Aristotle’s unchanged species idea

    • He wrote “The Origin of Species”

    • He also proposed evolution of natural selection

  • Evolution - change in a population’s allele frequency over time

  • Natural Selection - different survival & reproduction skills that come from traits (survival of the fittest)

  • Fossils provide evidence of evolution

  • Homology - similar traits (w/ different species) that come from a common ancestor

  • Sexual selection gives special traits to animals during mating season

  • Genetic Drift - changing the alleles in an environment (random chance)

  • Gene Flow - certain genes flow/migrate to a new place to form a new population

  • Directional selection - populations shift one way or the other (l or r)

  • Stabilizing selection - populations want to be in the middle

  • Disruptive selection - populations don’t want to be in the middle, either l or r

  • l or r represent the end traits or the extremes of the traits

Anatomy

  1. Integumentary system - helps maintain homeostasis, body covering, & produces vitamin D

    • skin

    • hair

    • nails

    • sweat glands

  2. skeletal & muscular systems - structure, support, contractability, movement, protects vital organs

    • bones

    • ligaments

    • joints

    • cartilage

    • muscles

    • tendons

  3. nervous - quick & fast changes to things; responses to internal + external stimuli

    • brain

    • spinal cord

    • nerves

  4. endocrine - hormone secretion; long term responses/changes to things

    • testes

    • ovaries

    • pancreas

    • pituitary gland

    • adrenal glands

    • thyroid

  5. cardiovascular - transportation of blood & blood vessels (from heart) to all tissues; blood transports O2, CO2, nutrients, & hormones

    • heart

    • arteries ~ pumps away

    • veins ~ to the heart

    • capillaries

  6. lymphatic/immune - drains extra fluid out of blood, immunity ~ also houses white blood cells

    • lymphatic vessels

    • lymph nodes

    • spleen

  7. respiratory - gas exchanges (CO2 —> O2) & sound production

    • lungs

    • trachea (carries air to lungs)

    • pharnyx (throat)

    • nose

    • larynx (voice box)

    • diaphragm

  8. digestive - absorb nutrients from food, breaks down foods; excretory system

    • mouth

    • then to pharynx

    • then to esophagus

    • then to stomach

    • then to small intestine

    • then to large intestine

    • then to rectum

    • then to anus

  9. urinary - helps regulate water level, kidneys tell brain about dehydration, normal blood pressure

    • kidneys

    • ureter

    • urinary bladder

    • urethra

  10. reproductive - reproduction, make sex hormones, sex cells

    • male

      • penis

      • testes

      • scrotum

      • prostate

      • vas deferens

    • female

      • vagina

      • ovaries

      • fallopian tubes

      • uterus

      • breasts