Bio Notes PDF

Bio lock in- otherwise you're stupid. Meiosis: Meiosis is a type of cell division that occurs in sexually reproducing organisms to produce gametes (in males & is a reproductive cell), or sperm and egg cells. Meiosis involves 2 rounds of division that result in four cells, each with a single copy of...

Bio lock in- otherwise you're stupid. Meiosis: Meiosis is a type of cell division that occurs in sexually reproducing organisms to produce gametes (in males & is a reproductive cell), or sperm and egg cells. Meiosis involves 2 rounds of division that result in four cells, each with a single copy of each chromosome. Meiosis starts with one diploid cell (a cell with 2 copies of each chromosome). A haploid cell contains half the number of chromosomes of the diploid parent cell. Sex cells, like egg and sperm, are haploid. A parent cell in meiosis has 46 chromosomes which are then arranged in 23 pairs Stages of meiosis: Prophase 1: Chromosomes pair up and exchange genetic material Metaphase 1: Homologous pairs of chromosomes line up in the middle of the cell Anaphase 1: Homologous pairs ( 2 chromosomes in a cell that are the same size and shape and contains the same genes in the same order) separate Telophase 1: Chromosomes move to opposite ends of the cell and cytokinesis produces 2 daughter cells (created after cell division and are genetically identical to the parent cell. They are the offspring of the parent cell. In meiosis, daughter cells have half the number of chromosomes of the parent cell”. Prophase 2: The centromeres (helps the cell divide up its dna during division) of the paired chromatids (one of the 2 identical halves of a chromosome that has been replicated in preparation for cell division) align along the equatorial plate in both cells Anaphase 2: The chromatids split at the centromere and migrate to opposite poles. Telophase 2: The cells pinch in the centre and divide again, producing four cells with half of the genetic material found in the original. Pedigrees: A pedigree is a diagram that shows how the traits are passed down through a family’s generations. Circle is female and the square is a male. Punnett Squares: A diagram that predicts possible genotypes and traits of offspring from a genetic cross. An allele is one of 2 or more versions of a genetic sequence at a particular region on a chromosome. Differences between a gene and an allele: Genes are sections of DNA that code for specific proteins or functional RNA. Alleles are different versions of the same gene. They can lead to variations in traits like eye colour. Genes are sections of DNA that code for specific proteins or functional RNA. Alleles are different versions of the same gene. ` Punnett Squares- monohybrid: It is a diagram that is used to estimate the genotypes of offspring produced in a genetic cross. A 2x2 square is used and there is only one specific trait(gene) being crossed. Punnett Squares- dihybrid: It is a crossing of two heterozygous individuals. A 4x4 square is used. Punnett Squares- codominance: A cross between organisms such as pink and white while equal pink and white spots. Normally all capitals. Punnett Squares- incomplete dominance: A cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits. Red and white = pink Punnett Squares- sex-linked: A “sex-linked Punnett Square” is a genetic diagram used to predict the probability of offspring inheriting a specific trait that is carried on the sex chromosomes. The traits are normally colorblindness or hemophilia. Males only carry one allele so its easy to differentiate if it is a sex-linked or not.