Transcript Genetics: Mitosis/Meiosis

Part 2
• Cell reproduction of somatic cells (all cells except sperm/egg)
• This is how we grow, develop, and repair
• Involves chromosomes: Complex structure of coiled DNA that carries all
genetic information (genes)
• Chromosome #
• Each species has a characteristic # of chromosomes
• Humans: 23 pairs (46 total)
• Dogs: 39 pairs
• Corn: 20 pairs
• Diploid: Pairs of similar
chromosomes (from parents)
• Haploid: one of each type of
chromosome
• Gametes (egg 23 / sperm 23)
Types:
Autosomes: Do not determine
sex (1-22)
Sex Chromosomes:
determine sex (X,Y 23)
Male = XY
Female = XX
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
• Longest phase of cell’s life cycle
• Increase in mass
• Increase # of organelles
• Replication of chromosomes (DNA)
• G1 Phase: Gap prior to DNA replication
• S Phase: DNA replication
• G2 Phase: After DNA replication
• Chromosomes are copied
(#doubles)
• Chromosomes appear as
threadlike coils
(chromatin) at the start,
but each chromosome
and it’s copy (sister
chromosome) change to
sister chromatids.
• Mitosis begins (cell
begins to divide)
• Centrioles (poles)
appear and move to
opposite ends of cell.
• Spindle fibers form
between the poles.
• Nuclear membrane
breaks apart.
• Chromatids (pairs of
chromosomes) attach to
the spindle fibers.
• They are aligned in
middle of cell.
• Chromatids separate
and begin to move to
opposite ends of the cell.
• Two new nuclear
membranes (nuclei) form.
• Chromosomes appear as
chromatin (threads).
• Cell membrane begins to
pinch together.
• Cell membrane continues
to move inward to create
two daughter cells.
• Each daughter cell has it’s
own nucleus with identical
chromosomes.
• Modern Biology Books: Pg. 140
Review ? 1-8 (graded)
• A type of cell division in which the chromosome # is reduced by
half.
• Production of gametes (sex cells) – these cells have half the #
of chromosomes.
• 2 Major sections of Meiosis:
• Meiosis I – reductive division
• Interkinesis – 2 cells form each with only one chromosome from the
pair.
• Meiosis II - Double stranded chromosomes become single stranded
chromosomes.
• Cytokinesis – 4 haploid cells are formed which will become sperm or
eggs.
• Fertilization: Fusion of gametes = reconstitutes the proper # of
chromosomes.
• Trait: Genetic characteristic of an organism.
• Gene: DNA sequence that codes for a protein (may lead to a
trait).
• Allele: Different forms of a gene.