Inheritance and Evolution Revision Notes

DNA and Base Pairing

  • DNA stands for deoxyribonucleic acid.
  • DNA is found in the nucleus of cells.
  • Base pairing rules:
    • Adenine (A) pairs with Thymine (T).
    • Cytosine (C) pairs with Guanine (G).

Genes and Chromosomes

  • A gene is a segment of DNA that codes for a specific trait.
  • A chromosome is a structure containing DNA; genes are located on chromosomes.

Complementary DNA Strand

  • Given DNA strand: G A T C C A T G A G T T A C
  • Complementary strand: C T A G G T A C T C A A T G

DNA Sequence, Codons, and Amino Acids

  • Original DNA strand: CGGATTATAGGCTAC
  • Complementary strand: GCCTAATATCCGATG
  • Codons: GCC-UAA-UAU-CCG-AUG
  • Amino acids: (determined using the amino acid table based on the codons)

Mitosis

  • Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.
  • Cells undergoing mitosis: Somatic cells (body cells).
  • Number of daughter cells produced: Two.

Meiosis

  • Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes as the parent cell, as in the production of gametes and plant spores.
  • Cells undergoing meiosis: Germ cells (cells that produce gametes).
  • Number of daughter cells produced: Four.

Genotype and Phenotype

  • Genotype: The genetic makeup of an organism.
  • Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.

Dominant and Recessive Alleles

  • Dominant allele: An allele that expresses its trait even when paired with a recessive allele.
  • Recessive allele: An allele that expresses its trait only when paired with another recessive allele.

Heterozygous and Homozygous Genotypes

  • a) Bb: Heterozygous
  • b) Cc: Heterozygous
  • c) dd: Homozygous recessive
  • d) EE: Homozygous dominant
  • e) AA: Homozygous dominant

Genetic Variation

  • Genetic variation: Differences in DNA sequences between individuals within a population.
  • Importance: Provides the raw material for natural selection and adaptation.

Homologous and Analogous Structures

  • Homologous structures: Structures in different species that have a similar underlying anatomy due to shared ancestry, but may have different functions.
  • Analogous structures: Structures in different species that have similar functions but different underlying anatomy and evolutionary origins.

Artificial and Natural Selection

  • Artificial selection: Selective breeding of plants and animals by humans to promote desirable traits.
  • Natural selection: The process by which organisms better adapted to their environment tend to survive and reproduce more successfully.

Evolution

  • Evolution: The change in the heritable characteristics of biological populations over successive generations.

Natural Selection and Peppered Moths

  • Original state: Peppered moths were predominantly white.
  • Industrial Revolution: Pollution darkened tree bark.
  • Natural selection:
    1. Variation: There was variation in color among peppered moths (white and black).
    2. Inheritance: Color is a heritable trait.
    3. Selection: Black moths had a survival advantage on darkened trees because they were camouflaged from predators.
    4. Time: Over time, black moths became more common due to differential survival and reproduction.

Speciation

  • Speciation: The process by which new species arise. This often occurs when populations are isolated and diverge genetically over time.

Finches in the Galapagos Islands

  • Founder effect: A small group of finches colonized the Galapagos Islands.
  • Adaptive radiation: The finches diversified into many different species, each adapted to a different ecological niche.
  • Natural selection: Different beak shapes evolved in response to different food sources.