Bio (Unit 4)

• Somatic cells are "body" cells, containing the normal number of chromosomes (diploid number symbolized as 2n) and are produced through mitosis, examples include muscle cells, skin cells, and nerve cells
• Gametes are "sex" cells, containing only half the original number of chromosomes (haploid number symbolized as n) and are produced through meiosis, examples include sperms (male gamete) and eggs (female gamete)
• Humans have 23 pairs of homologous chromosomes, with each homologous set made up of 2 homologues, and humans have 23 sets of homologous chromosomes
• Sex chromosomes determine the sex of the offspring, with two "X" chromosomes resulting in a female and one "X" chromosome and one "Y" chromosome resulting in a male
• Meiosis is the process of nuclear division that reduces the number of chromosomes by half, resulting in haploid cells like egg cells in females and sperm cells in males
• Meiosis involves two nuclear divisions: Meiosis I separates homologous chromosomes into separate cells, while Meiosis II separates sister chromatids of each chromosome into separate cells, resulting in 4 daughter cells with half the number of chromosomes of the parent cell
• Prophase I of Meiosis involves chromosomes condensing, homologous chromosomes coming together and overlapping in some regions where crossing over occurs, contributing to genetic variation
• Metaphase I of Meiosis sees homologous chromosomes align on the metaphase plate, with independent assortment occurring, creating genetic variation
• Anaphase I of Meiosis involves homologous chromosomes separating and moving towards the poles, while sister chromatids remain attached at their centromeres
• Meiosis II is similar to mitosis, with Prophase II, Metaphase II, and Anaphase II stages leading to the formation of haploid daughter cells
• Chromosomes replicate during interphase before prophase 1, with interphase being a stage in the cell cycle and prophase 1 a stage in meiosis
• Meiosis II is similar to mitosis, with the phases being: prophase II, metaphase II, anaphase II, and telophase II
• In meiosis II, each dividing cell (parent cell) is haploid, whereas in mitosis, the dividing cell is diploid
• Meiosis II produces 4 haploid daughter cells, which are gametes like sperm or egg
• Non-Disjunction during meiosis results in zygotes with abnormal chromosome numbers, damaging the offspring, like in Down Syndrome (Trisomy 21)
• Meiosis starts with a diploid cell with 4 chromosomes for meiosis I, and the two daughter cells from meiosis I for meiosis II
• Meiosis I and II have the same phases: prophase, metaphase, anaphase, and telophase, but differ in the ploidy (number of sets of chromosomes in a cell) of the dividing cells
• Meiosis is a genetic process
• Traits inherited from parents are determined by genes
• Genes are specific segments of DNA that control characteristics through proteins
• Genes are heritable factors that control specific characteristics through proteins
• Genes are sections of DNA located in chromosomes
• Each parent gives 1 set of chromosomes (23 in egg cell + 23 in sperm cell) = 46 chromosomes
• DNA synthesis process: DNA → RNA → Amino acid

  
• Mutation can change the nucleotide and amino acid, leading to the production of an abnormal protein
• Mutations originate in the DNA level but show their effects at the protein level
• Examples of genetic diseases caused by mutations:

  • Sickle cell anemia: due to one base change
  • Cystic fibrosis disease: gene mutation (3-base deletion), recessive gene, causes breathing difficulty, without treatment can lead to a short lifespan
• Genetic modification: uses not natural methods, like recombinant DNA technology, to change gene sequences of cells and organisms
• Examples of positive genetic modification uses:

  • Making human insulin in bacteria for healing
  • Producing spider silk protein in goat’s milk for a stronger, more elastic product
  • Producing genetically modified crop plants like golden rice, which contains β-carotene for increased nutritional value
• GMO foods can cause potential hazards like harm to the environment and humans, allergic or toxic responses, unintended health effects, and gene transfer to non-target species