dna/genetics

• The DNA double helix is held together by hydrogen bonds between complementary base pairs.
• DNA is a deoxyribonucleic acid molecule located in the nucleus of cells that contains the genetic information responsible for the development and function of an organism
• Gene is a distinct sequence of nucleotides forming part of a chromosome which is a unit of heredity that is transferred from a parent to offspring
• Chromosome is a threadlike structure of nucleic acids found in the nucleus of living cells, which carries genetic information in the form of genes
• Cell division is the division of a cell into two daughter cells with the same genetic material. It may be mitosis (clone copy) or meiosis (for reproduction)
• Gametes are reproductive cells of plants and animals which are haploid because they contain only one set of chromosomes
• Zygote is a fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm)
• Somatic cell are cells of the body which do not include gametes. These are diploid because they contain two sets of chromosomes
• Phenotype is an individual's observable trait, determined by both their genomic makeup (genotype) and environmental factors
• Autosomes are all of the numbered chromosomes of the cell which do not include the sex chromosomes. They contain the bulk of the cell’s information required to function
• Homologous chromosomes pair during replication and have the same structural features and pattern of genes
• Trisomy is having three copies of a chromosome instead of the normal pair of two, e.g., the addition of a number 21 chromosome that results in Down syndrome within each cell. Monosomy is having only one copy of a particular chromosome
• Karyotype is the number and general appearance (size, shape, and banding) of a set of chromosomes in a somatic cell
• Nucleotides are compounds (DNA building blocks) containing a sugar part (deoxyribose or ribose), a phosphate part, and a nitrogen-containing base that varies
• Base-pair Rule states that in DNA, every adenine (A) binds with a thymine (T), and every cytosine (C) binds to a guanine (G)
• Triplet is a sequence of three nucleotides in DNA that can code for one amino acid. For example, the triplet base sequence CAA codes for the amino acid, valine
• Diploid is the paired set of chromosomes within a somatic cell, e.g., 23 pairs in each body cell. Sex cells have only one copy of each chromosome in the cell, referred to as the haploid number
• Variation is the differences of characteristics shown in individuals due to various reasons. Inheritance of these variations or phenotypes may be favorable to increase the chance of survival
• Alleles are alternative forms of a gene for a particular characteristic. Each allele is characterized by a slightly different nucleotide sequence
• Homozygous is having two identical alleles for a characteristic within the genotype
• Heterozygous is having two different alleles for a characteristic within the genotype
• Number of combinations

  • The chromosomes could be divided up into gametes
• stages of prophase

  - Dna X shaped structures form and chromosmes become visible -Nuclear membrane breaks down
• stages of interphase

  - Chromosomes replicate - Chromosomes are not visible
• metaphase-  Chromosomes line up along the equator of the cell  Spindle fibres attatch to centromere of each chromosome
• Anaphase

  -       Centromere divides

  -       Sister chromatids are separated and moved to opposiite poles

  -       Sister chromatids are now called chromosomes
• Telophase

  -       Two nuclei form, each with a diploid number of chromosomes (46 each side)
• Cytokinesis

  -       Cytoplasm separates

  -       Membranes form separating the two nuclei into the two daughter cells for growth and repair of somatic cells

  -       END RESULT!
• Biodiversity

  Variation in the many different communities and their environments on Earth
• Selective pressures


  Factors that contribute to selecting which variations will provide the individual with an increase chance of surviving over others
• Selective agents


  • Living (biotic)
  • Non-living (abiotic)
• Natural Selection

  A species gives rise to new species that has characteristics that make them better adapted for survival in a particular environment
• Theory of Evolution

  A theory about how change occurs in the inherited characteristics of a group of organisms
• Genetic drift

  Changes due to chance events such as floods and fires
• gene flow - the transfer of genetic material from one population to another (emigration- loss of alleles from a population) and immigration (introduction of alleles into a population)
• gene pool- all of the genetic information for a particular species. For example frogs in a pond, or trees in a forrest
• replication- the process of copying a cells dna prior to cell division.
• species diversity- number of species in an ecosystem
• genetic diversity- the range of genetic characteristics within a species