Life sciences

FUNCTION AND NUCLEOTIDES

  • Nucleotide: the basic building block of nucleic acids, which includes DNA and RNA.

INTRODUCTION TO NUCLEIC ACIDS

  • Cell Structure: Basic unit of life consisting of various organelles.

  • Types of Nucleic Acids:

    • DNA (Deoxyribonucleic Acid): the genetic material.

    • RNA (Ribonucleic Acid): involved in protein synthesis.

  • Components of Nucleotide:

    • Phosphate group

    • Sugar (Deoxyribose in DNA, Ribose in RNA)

    • Nitrogenous base (A, T, C, G for DNA and A, U, C, G for RNA)

DNA - THE CODE OF LIFE

  • Key functions of DNA include the storing and transmitting of genetic information.

  • DNA synthesis involves the formation of new DNA strands based on existing templates.

RNA AND ITS FUNCTIONS

  • Location:

    • mRNA: nucleus and ribosome

    • tRNA: cytoplasm

    • rRNA: ribosome

  • Functions:

    • Messenger RNA (mRNA) copies the genetic code from DNA.

    • Transfer RNA (tRNA) carries amino acids to ribosomes.

    • Ribosomal RNA (rRNA) is a component of ribosomes.

PROTEIN SYNTHESIS

  • Two main stages: Transcription and Translation.

Transcription:

  1. DNA unwinds to expose the coding region.

  2. RNA polymerase synthesizes mRNA from the DNA template.

  3. RNA nucleotides link to form a polymer.

  4. mRNA moves out of the nucleus to the ribosome.

Translation:

  1. mRNA binds to a ribosome.

  2. tRNA molecules transport specific amino acids.

  3. mRNA codons match with tRNA anticodons, facilitating peptide bond formation between amino acids.

  4. Polypeptide chain is synthesized, forming a protein.

MEIOSIS VS MITOSIS

  • Meiosis: cell division that produces haploid gametes, essential for sexual reproduction.

    • Results in genetic variation due to crossing over.

    • Two stages: Meiosis I and II, which both include Prophase, Metaphase, Anaphase, and Telophase.

  • Mitosis: cell division that produces two identical daughter cells, maintaining the diploid number.

    • Occurs in somatic cells.

    • Involves one division cycle (karyokinesis and cytokinesis).

DIFFERENCES BETWEEN MEIOSIS AND MITOSIS

Similarities:

  • Both involve cell division processes.

  • Both contribute to growth and reproduction processes.

Differences:

  • Mitosis produces two genetically identical cells; meiosis produces four genetically varied cells.

  • Mitosis occurs during growth/repair, meiosis during gamete formation.

  • Mitosis involves one cycle; meiosis involves two cycles.

GAMETOGENESIS

Spermatogenesis and Oogenesis:

  • Spermatogenesis: Formation of sperm cells (spermatids mature into sperm).

  • Oogenesis: Formation of egg cells (ova).

  • Key structures involved in gametogenesis include the ovary for oogenesis and testes for spermatogenesis.

KARYOTYPE AND MEIOSIS ERRORS

  • Karyotype: representation of the number and appearance of chromosomes in somatic cells.

  • Non-disjunction: failure of chromosomes to separate properly during meiosis can lead to conditions like Down syndrome (trisomy 21).

DOWN SYNDROME

  • Caused by an extra chromosome 21 (47 instead of 46 chromosomes).

  • Characteristic symptoms include slanted eyes, flat facial profile, and increased risk for certain health issues.

AMNIOTIC EGG AND DEVELOPMENT

  • Reproductive Strategies:

    • Amniotic egg allows reproduction away from water, crucial for terrestrial life.

    • Contains several structures: yolk sac (nutrients), chorion (gas exchange), amnion (protection).

  • The presence of a hard or leathery shell helps in protection and moisture retention while allowing gas exchange.

GENERAL CONCEPTS WITH MEIOSIS

  • Meiosis introduces genetic variation through crossovers in Prophase I, where homologous chromosomes exchange segments of DNA.

  • Individual chromosome arrangement in Metaphase II leads to genetic diversity.

  • Understanding meiosis is essential for grasping fundamental biological concepts of inheritance and genetic variability.