Ch.13 Meiosis Flashcards
explain in general terms how traits are transmitted from parents to offspring.
offspring acquire genes from parents by inheriting chromosomes; through heredity/inheritance
distinguish between asexual and sexual reproduction
- asexual: form of reproduction which does not involve meiosis, ploidy reduction, or fertilization without fusion of gametes
- sexual: It is characterized by two processes: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve genetic recombination
distinguish between the following pairs of terms:
- somatic cell and gamete
- autosome and sex chromosome
- somatic cell: Two chromosomes of each type, known as homologous chromosomes.
gamete: egg and sperm
- autosome: Chromosomes other than the sex chromosomes.
explain how haploid and diploid cells differ from each other. State which cells in the human body are diploid cells differ from each other. State which cells in the human body are diploid and which are haploid
- haploid cells: Gametes, egg and sperm (contain a single set of chromosomes).
- diploid cells: Somatic cells (one from each parent)
explain why fertilization and meiosis must alternate in all sexual life cycles
Meiosis produces unique reproductive cells called gametes, which have half the number of chromosomes as the parent cell. Fertilization is the fusion of haploid gametes, from two individuals, and restores the diploid condition.
distinguish between the three life cycle patterns characteristic of eukaryotes, and name one organism that displays each pattern
Diploid-Dominant Life Cycle - the only haploid cells are the gametes
Haploid-Dominant Life Cycle - make up the tissues of the dominant multicellular stage are formed by mitosis
Alternation of Generation - found in terrestrial plants and some algae in which subsequent generations of individuals alternate between haploid and diploid organisms.
list the phases of meiosis I and meiosis II and describe the events characteristic of each phase
Meiosis I
- Prophase I: Replicated homologous chromosomes.
-Metaphase I: Chromosomes line up on the metaphase plate (horizontally).
-Anaphase I: Chromosomes separate on opposite poles of the cell.
-Telophase I/Cytokinesis: The cleavage furrow forms and the cell is split into two haploid cells.
Meiosis II
- Prophase II: Sister chromatids are paired up
-Metaphase II: Sister chromatids line up on the metaphase plate (vertically)
-Anaphase II: Sister chromatids get pulled away by spindle apparatus to opposite poles of the cell.
-Telophase II/Cytokinesis: Nuclei form and the cell in split into four haploid cells.
Recognize the phases of meiosis from diagrams or micrographs
Describe the process of synapsis during prophase I and explain how genetic recombination occurs
The pairing of two homologous chromosomes that occurs during meiosis. The genetic material is rearranged by crossing over between nonsister chromatids.
Three events that occur in meiosis I but not during mitosis
Synapsis and Crossing Over
Homologs Align
Homologs Separate
Explain how independent assortment, crossing over, and random fertilization contribute to genetic variation in sexually reproducing organisms
Independent assortment basically means that the chromosomes can align in any free willed way. There is no set place in the metaphase plate that a specific chromosome must be. Because of this, during crossing over, two chromosomes with two completely different genes on them can swap genes, and now change the genetic info that the new cells will get. The random fertilization is that any one of the new gametes can fertilize the egg so the chances of it getting different genetic info is high.
Explain why heritable variation is crucial to Darwin’s theory of evolution by natural selection.
new combination of genes –> more possibilities for traits for offspring –> more chance to find correct traits for environmental success
