YR 12 Biology

• Mutations can be beneficial, harmful, or have no effect on the organism's fitness.
• Genetic mutations are permanent changes in the DNA sequence that make up an organism's genome.
• Cell walls are rigid structures that give plants their shape and support them against gravity.
• Mutations can arise from errors during DNA replication, environmental mutagens, or spontaneous changes in DNA.
• The cell wall is made up of polysaccharides, mainly cellulose.
• The endocrine system is made up of glands that secrete hormones into the bloodstream.
• Plant cells have chloroplasts which contain the pigment chlorophyll used to capture light energy during photosynthesis.
• Hormones are chemical messengers produced by cells or organs, which travel through the blood to target tissues where they bind with receptors on cell surfaces.
• Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries (in females), testes (in males).
• Microfibrils form a lattice structure that provides strength to the cell wall.
• The cell wall is made of cellulose fibers held together by hemicelluloses and pectin.
• DNA is coiled tightly around eight histone molecules to form nucleosomes.
• Chromosomes carry genetic information in the nucleus.
• Chromatin is composed of DNA wrapped around histone proteins.
• Cell walls protect plant cells from bursting due to water uptake.
• Fertilization is when the female gamete and the male gamete fuse to form a zygote
• Steps of fertilization:

  • Capacitation
  • Acrosome reaction
  • Polyspermy block
  • Completion of meiosis II
  • Zygote formation
• Cleavage is the process that takes a zygote to an embryo

  • Zygote has one cell
  • Cleavage results in two cells, then four cells, then a morula (12-16 cells)
• Cleavage happens following fertilization in the fallopian tube by mitosis

  • Nucleus to cytoplasmic ratio increases
  • Surface area to volume ratio increases
  • Two types of cleavage: determinate and indeterminate
• Indeterminate cleavage (free will) allows the cell to give rise to any type of cell

  • Example: monozygotic twins are always identical in sex
  • Monozygotic twins originate from one zygote
• Blastulation is the formation of the blastocyst or blastula

  • Blastocyst has an inner cell mass (embryoblast) and outer cell mass (trophoblast)
  • Blastocyst cavity is filled with fluid
• Implantation is the attachment of the embryo to the wall of the uterus

  • Trophoblast gives rise to the chorion which forms the placenta
  • Fertilization occurs in the ampulla of the fallopian tube, discovered by Gabrielle Fallopio
• Cytokinesis involves the formation of a cleavage furrow and division of cytoplasm into two daughter cells.
• Glycolysis occurs in the cytoplasm and produces two ATP molecules per glucose molecule.
• Animal cells are surrounded by plasma membrane only, while plant cells also have a cell wall.
• Plant cells have a rigid cell wall, while animal cells do not.
• Nucleotides are monomers of DNA and RNA.
• Cell division occurs when DNA is duplicated and then divided equally between two daughter cells.
• Genetic material consists of DNA, RNA, proteins, and carbohydrates.
• Chromatin fiber condenses even more to become chromosome.
• The first stage of gastrulation is invagination where the ectoderm folds downwards forming the primitive streak
• During gastrulation, the mesoderm develops between the endoderm and ectoderm
• Nucleosomes are further compacted into chromatin fiber.
• Genetic variation occurs when there are differences between individuals within a population due to variations in alleles.
• The structure of DNA includes a double helix made up of four bases - adenine, thymine, cytosine, guanine.
• DNA consists of nucleic acids (nucleotide) with phosphate groups attached to sugar-phosphates.
• Mitosis is the process of nuclear division during which chromosomes duplicate and separate to form two identical nuclei.
• Carbohydrates are the body's main source of energy and contain carbon, hydrogen, and oxygen
• Carbohydrates come in two forms: simple sugars (monosaccharides) and complex sugars (disaccharides and polysaccharides)
• Simple sugars provide immediate energy but lack other nutrients, examples include glucose