Cell Division and Asexual Reproduction

Cell Division

• Cell division involves mitosis and cytokinesis, resulting in two identical daughter cells.
• Mitosis is a process of nuclear division, followed by cytokinesis, which divides the cytoplasm to create two separate cells.
• Each daughter cell contains a complete set of chromosomes from the parent cell.
• The process ensures that each daughter cell receives a full set of genetic material.

Asexual Reproduction

• Asexual reproduction involves a single parent producing genetically identical offspring.
• Common in plants, including runners, rhizomes, tubers, bulbs, corms, and spores.
• Some simple animals (starfish, flatworms) can regenerate from fragments.
• Parthenogenesis: development of an unfertilized ovum into a new organism (e.g., some shrimp, bees, ants).
• Binary fission: cell division used by unicellular organisms for asexual reproduction.
• Budding: an outgrowth or asymmetric cell division leading to new individuals.
• Advantages: Only one parent required, rapid population growth.
• Disadvantages: Lack of biodiversity within a population, potential for overpopulation.

Sexual Reproduction

• Involves the fusion of two different types of gametes (male and female).
• Occurs widely in animals and seed-bearing plants, including angiosperms (flowering) and gymnosperms (cone-bearing).
• Also occurs in primitive plants like ferns, mosses, and liverworts.
• Fungi may reproduce sexually under unfavorable conditions.
• Male gamete is smaller and more mobile, while the female gamete is larger and contains food reserves.
• The female gamete develops into a seed or egg for the embryo.
• Fertilization unites male and female gametes, creating a zygote.
• The zygote develops through mitotic cell divisions and differentiation into an embryo.
• Population growth in sexual reproduction often depends on the number of females and their reproductive cycles.
• Occurs in eukaryotes.

Polypeptide Synthesis

• Inheritance and species continuity rely heavily on polypeptide synthesis.
• Polypeptide synthesis translates genetic information encoded in DNA into cellular structures and functions.

Phenotypic Expression

• Genome: the total base composition and arrangement of DNA in an organism.
• Genotype: the genetic makeup of an organism.
• Phenotype: the observable traits of an organism, such as height and eye color.
• Environmental factors can influence phenotypic expression, alongside genetic influences.

Research on Environmental and Genetic Impacts

• Environmental influences in the womb can have lasting effects on health.
• Literacy development can be influenced by both genetics and environmental factors.
• Genetic mutations can be involved in specific diseases, even epilepsy.
• Research is ongoing to understand the interaction of environmental and genetic factors in various conditions, such as amyloid plaque development.

Types of Mutations

• Point mutation involves a change in a single nucleotide in the DNA sequence.
• Can occur spontaneously during DNA replication or induced by environmental factors.
• Can lead to amino acid substitutions in proteins or alter gene expression.
• Other point mutations include insertions or deletions, potentially resulting in frame-shift mutations.

Chromosomal Mutations

• Occur in cells undergoing division due to exposure to radiation, chemicals, or spontaneous errors.
• Involve chromosome rearrangements and changes in chromosome numbers.
• Main types: deletion, duplication, inversion, translocation.
• Can impact offspring in case of germ-line cell mutations.
• Can lead to cell death or loss of function in somatic cells, potentially contributing to cancer.

Somatic Mutations

• Occur in somatic or normal body cells after conception.
• Not inherited by offspring.
• Affect specific cells and tissues.
• Can cause cancer and disease in individuals.
• Do not directly change allele frequencies in a gene pool.

Germ-line Mutations

• Occur in germ-line cells (gametes) responsible for transmitting genetic material to offspring.
• Can be inherited by offspring.
• Result in inherited diseases and disorders.
• Have the potential to alter allele frequencies in a gene pool.

Causes of Genetic Variation

• Mutations: the ultimate source of new alleles and genetic change.
• Fertilization: combines different alleles.
• Meiosis: random segregation and crossing over create new allele combinations.
• Genetic variation is essential for adaptation and evolution.
• In-vitro fertilization and genetic screening are used to minimize the risk of genetic diseases.

The Effect of Mutation, Gene Flow, and Genetic Drift

• Diversity within a gene pool is influenced by population size, mutations, natural selection, gene flow, and diverse environments.
• Small populations are more susceptible to the effects of mutations, genetic drift, and gene flow.

Biotechnology

• Past uses include selective breeding, fermentation, and extraction of substances from plants and animals.
• Present uses include: Agricultural applications: Transgenic crops, improved nutritional content, and pest resistance; Medical applications: Gene therapy, diagnostics, pharmaceuticals; Industrial applications: Biofuels, bioplastics.
• Future uses include: Personalized medicine, synthetic biology, and bioremediation.