Bio 3.2.1: Meiosis in Sexual Reproduction and Genetic Variation
Meiosis leads to genetic diversity and independent assortment because the chromosomes cross over
- Crossing Over- Two chromosomes pair up and exchange segments of their genetic material
- Random Assortment-Many different qualities within your genetic structure
- Gene Mutation- Permanent change in the DNA sequence that makes up a gene
- Nondisjunction-The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis
- Fertilization- Initiating biological reproduction by insemination or pollination
- Meiosis- Sexual reproduction, humans, animals, plants, and fungi use it, genetically different, can cross over, 2 divisions, chromosome number reduced by half,
- Mitosis- Asexually, All things use it, genetically identical, can't cross over, 1 division, chromosome number remains the same
- Meiosis Steps:
- Prophase I- Homologous chromosomes pair up and form tetrad
- Anaphase I- Spindle fibers move homologous chromosomes to opposite sides
- Telophase II- Nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed
- Metaphase II- Chromosomes line up along the equator, not in homologous pairs
- Prophase I- Crossing over occurs
- Anaphase II- Chromatids separate
- Metaphase I- Homologs line up along equator
- Telophase 1- Cytoplasm divides, two daughter cells are formed
- Meiosis Virtual Lab Link:
Bio 3.2.2: Offspring Ratios Based on Patterns
- Genotype- Genetic makeup of a cell
- Phenotype- Physical characteristics of an organisim
- Dominant alleles always mask recessive alleles (i.e. Aa, AA)
- Karyotype- Number and appearance of chromosomes in the nucleus of a cell
- Codominance- Single gene has more than one dominant allele
- Incomplete Dominance- One allele for a specific trait is not completely dominant over the other allele
- Some traits are controlled by more than one pair of genes and that this pattern of inheritance is recognized by the presence of a large range of phenotypes (skin, hair, and eye color)
- Autosomal Inheritance- A pattern of inheritance in which the transmission of traits depends on the presence or absence of certain alleles on the autosomes
- An example of Autosomal Inheritance is sickle cell anemia
- Sex-Linked Traits- Originate from genes of the sex chromosome (males are most likely to express the trait
- Pedigrees- To originate ones ancestors and where diseases and more have come from
- Punnett Square Virtual Lab Link:
- http://www.mhhe.com/biosci/genbio/virtual_labs/BL_05/BL_05.html
Bio 3.2.3: Environmental Factors Causing Traits
- Examples of This is:
- Lung/mouth cancer= tobacco use
- Skin cancer= Vitamin D, folic acid and sun exposure
- Diabetes= diet/exercise and genetic interaction
- Any trait that was not caused naturally or born with
- Genetic Trait Lab Link:
- http://rhoyle.cusd.claremont.edu/mm/Course%20Assets/Biology/Labs/pdf%20-%20Observing%20Human%20Traits.pdf