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General Biology: DNA, Genetics & Evolution

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  • What is DNA and why is it important?

    DNA (deoxyribonucleic acid) is the molecule of inheritance that carries genetic information for the development and functioning of living organisms.

  • Where is DNA located within a cell?

    DNA is located in the nucleus and mitochondria of a cell.

  • What is the role of DNA in organisms?

    DNA codes for proteins that determine inherited characteristics in organisms.

  • What are nucleotides and how do they form DNA?

    Nucleotides are the building blocks of DNA, each consisting of a sugar, phosphate, and nitrogenous base; they form the DNA double helix by pairing complementary bases.

  • List the four nitrogenous bases and their complementary pairings.

    The four bases are adenine (A), thymine (T), cytosine (C), and guanine (G). A pairs with T, and C pairs with G.

  • Differentiate between DNA, chromosomes, and genes.

    DNA is the molecule, genes are segments of DNA coding for traits, and chromosomes are structures made of DNA and proteins that carry genes.

  • Describe the process of DNA replication and key enzymes involved.

    DNA replication involves unwinding the double helix by helicase, synthesizing new strands by DNA polymerase, and joining fragments with ligase.

  • Compare the structure and function of DNA and RNA.

    DNA is double-stranded with thymine, stores genetic info; RNA is single-stranded with uracil, involved in protein synthesis.

  • What is mitosis and its purpose?

    Mitosis is the division of somatic cells for growth and repair, producing two identical diploid daughter cells.

  • Name and describe the stages of mitosis.

    Stages: Prophase (chromosomes condense), Metaphase (chromosomes align), Anaphase (chromatids separate), Telophase (nuclei reform), Cytokinesis (cell divides).

  • Define gamete and identify where male and female gametes are produced.

    Gametes are sex cells; male gametes (sperm) are produced in testes, female gametes (eggs/ova) in ovaries.

  • Explain fertilisation and the formation of a zygote.

    Fertilisation is the fusion of male and female gametes, resulting in a zygote with a full set of chromosomes.

  • Define homologous pairs, diploid, and haploid.

    Homologous pairs are chromosome pairs with the same genes; diploid (2n) cells have two sets of chromosomes; haploid (n) cells have one set.

  • Outline major events of meiosis and its significance.

    Meiosis reduces chromosome number by half and creates genetic variation through two divisions producing haploid gametes.

  • Compare mitosis and meiosis.

    Mitosis produces two identical diploid cells for growth; meiosis produces four genetically varied haploid cells for reproduction.

  • What are mutations and their effects?

    Mutations are sudden, permanent changes in genes that can create new alleles and contribute to genetic variation.

  • List the three main types of mutagens with examples.

    Mutagens include physical (e.g., UV radiation), chemical (e.g., tobacco smoke), and biological (e.g., viruses).

  • Define key genetic terms: allele, genotype, phenotype, dominant, recessive, homozygous, heterozygous.

    Allele: gene variant; genotype: genetic makeup; phenotype: observable traits; dominant: expressed allele; recessive: masked allele; homozygous: identical alleles; heterozygous: different alleles.

  • How are Punnett squares used in genetics?

    Punnett squares predict possible genotypes and phenotypes from monohybrid crosses, including complete dominance, co-dominance, and incomplete dominance.

  • Explain sex determination in humans.

    Sex is determined by X and Y chromosomes; males are XY, females XX; inheritance patterns can be shown using Punnett squares.

  • What is a pedigree and how is it used?

    A pedigree is a diagram showing family relationships and inheritance of traits, used to determine genotypes and phenotypes.

  • Compare Lamarck’s and Darwin’s theories of evolution.

    Lamarck proposed acquired characteristics are inherited; Darwin proposed natural selection based on variation and survival of the fittest.

  • Define artificial selection with examples.

    Artificial selection is selective breeding by humans to enhance desired traits in plants and animals.

  • Explain the process of natural selection.

    Natural selection involves variation, competition, survival, and reproduction of the fittest individuals in a population.

  • How do mutations contribute to natural selection?

    Mutations create genetic variation, providing new traits that may increase survival and reproduction in natural selection.

  • Describe speciation and its key factors.

    Speciation is the formation of new species through isolation, variation, and selection over time.

  • What is a gene pool and gene flow?

    A gene pool is the total genetic diversity in a population; gene flow is the transfer of genes between populations.

  • How are fossils formed and dated?

    Fossils form under specific conditions; their age is determined by relative dating (rock layers) and absolute dating (radiometric methods).

  • What evidence supports evolution?

    Evidence includes comparative anatomy (homologous/analogous structures), vestigial organs, embryology, and DNA/protein comparisons.

  • How does continental drift support evolutionary theory?

    Continental drift explains biogeographical distribution of species, supporting common ancestry and evolution.