Genetics quiz

• Genetics


  The study of heredity and the variation of inherited characteristics
• Cell cycle


  The series of events that a cell goes through from the time it is first formed until it divides into two new cells
• Why does a cell divide


  • Growth
  • Repair of damaged tissues and organs
  • Replace dying or dead cells
• Cell division time


  Can range from 8 minutes to over a year (e.g. liver cells), average is 12-24 hours
• Stages of the cell cycle

  • Interphase
  • Mitosis
  • Cytokinesis
• Interphase


  • Period between cell division
  • Cell functions normally during this period
• Phases of Interphase


  • G1 phase (growth)
  • S phase (Synthesis - DNA synthesis and replication)
  • G2 phase (growth 2 - cell prepares for division)
• Cell cycle movement through stages is a continuous process
• Cell division occurs in somatic cells (body cells)
• Cell division occurs in healthy animal cells
• Interphase


  DNA is in the form of uncondensed strands called chromatin
• Chromatin


  • Thin
  • Long
• Once mitosis begins, chromatin will condense to form chromosomes
• Replicated chromosomes are attached to each other at the centromere
• Mitosis


  Ensures that the two daughter cells created are identical to each other and to the original
• Genetic continuity


  The transmission of hereditary material through cell division
• Mitosis requires both the division of genetic material and the division of the cytoplasm
• Mitosis Stages


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• In prophase, chromatin condenses into visible chromosomes, the nuclear membrane breaks down, and the nucleolus disappears
• In metaphase, chromosomes move and line up in the middle of the cell, and spindle fibers attach to the centromere of each pair of chromatids
• In anaphase, centromeres divide and chromatids move to opposite poles as spindle fibers shorten
• In telophase, chromosomes lengthen and intertwine, losing their distinct shape, the spindle fibers dissolve, and the nuclear membrane begins to form around each mass of chromosomes
• Cytokinesis


  Marks the end of telophase, the division of cytoplasm and cell contents into roughly equal portions, creating two genetically identical daughter cells
• Animal cell cytokinesis


  • Cytoplasm pinches in at the equator producing a cleavage furrow
• Plant cell cytokinesis


  • A cell plate forms at the equator which will develop into a new cell wall, no centrioles, astral rays or astral fibers
• Cell division in prokaryotic cells

  Occurs through binary fission, no true nucleus
• DNA


  Deoxyribonucleic acid, double helix structure with deoxyribose (sugar) and phosphate backbone, four nitrogen bases
• Complementary base pairing


  Adenine always bonds to thymine, guanine always bonds to cytosine
• DNA replication


  Occurs in interphase, each strand serves as a template for a new strand, new strands created according to complementary base pairing
• Chromatin


  DNA coils around proteins to form chromatin, chromatin folds up to make chromosomes
• The number of chromosomes in a cell varies between species, but the number of chromosomes does not reflect the complexity of the organism
• Homologous chromosomes


  Each chromosome is part of a homologous pair, one from each parent
• Sex chromosomes


  X and Y chromosomes determine the gender of the individual
• Autosomes


  All chromosomes other than the sex chromosomes
• In karyotyping, autosomes are arranged from largest to smallest and labelled 1 through 22, sex chromosomes are placed at the end and identified as X or Y
• Somatic cells


  Non-reproductive cells that form the body of the organism, created by mitosis
• Asexual reproduction


  Requires only one parent and produces genetically identical offspring
• Sexual reproduction


  Requires reproductive cells to combine during fertilization to form a zygote, produces offspring genetically different from either parent
• The zygote has the same number of chromosomes as the somatic cells of that organism
• Gametes


  Reproductive cells that contain half the number of chromosomes (haploid) compared to somatic cells (diploid)