Transcript Meiosis I
Recall the worst cut you have ever had in your life. Record the following info in your notes-> •Think of how the cut happened •Remember the healing process •Locate the scar (if any) and make observations Reproduction is the biological process by which new individual organisms are produced from pre-existing organisms. These pre-existing organisms are referred to as Parents/Parent _________ cells These new individuals are referred to as OFFSPRING _______________ Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and asexual. • an individual can reproduce without involvement with another individual of that species. • The division of one cell into two daughter cells is an example of asexual reproduction. • Not limited to single-celled organisms Most plants have the ability to reproduce asexually. • requires the involvement of two individual’s cells, typically one of each sex. • Normal human reproduction is a common example of sexual reproduction. One parent cell Two parents cells Identical ________offspring Similar _________offspring The process by which a cell duplicates the chromosomes in its cell nucleus, in order to generate two, identical, daughter nuclei the division causes the daughter cells (each) to have the genetic equivalent of the parent cell. How does mitosis effect chromosome number? Example: Human chromosome number is 46 ____ Which cells in the human body carry out mitosis? Examples: skin cells, hair cells, nerve cells, etc. These cells are called Somatic Cells Aka body cells The process of mitosis involves a series of complex and highly regulated steps The sequence of events is divided into phases These stages are interphase, prophase, metaphase, anaphase and telophase. The end of the process and start of another is signified by the complete division of the cell membrane CALLED CYTOKINESIS Looking at the phases, place them in order of how the process of mitosis occurs. A CC B D •When the chromosomes are replicated/duplicated •Periods of cell growth, to prepare for cell division • Each duplicated chromosome is seen as a PAIR of sister chromatids joined by the centromere The spindle fibers forms between the two pairs of centrioles as they migrate to opposite sides of the cell. • The nuclear envelope disappears at the end of prophase •The centrioles are at opposite poles of the cell. • The chromosomes become arranged on a plane equidistant from the two poles. Chromosomes line up in the middle Anaphase begins when the duplicated chromosomes separate, and the nowdaughter chromosomes begin moving AWAY toward opposite poles of the cell due to the action of the spindle. • At the end of anaphase, a complete set of chromosomes has assembled at each pole of the cell. • The chromosomes begin to uncoil and assume the characteristics of interphase. • A nuclear envelope reforms around each chromosome set, the spindle disappears, and the nucleolus reforms. Nuclear division by mitosis is complete at this point. •equal division of the cytoplasm, • In animal cells, cytokinesis involves the pinching of the cell membrane into two. •In plant cells, cytokinesis involves the formation of the cell plate which develops into the cell wall Label the phases shown (1-3) 2 1 3 •A.K.A. Gametes •Examples: human egg and sperm cells •Function is to fertilize •Used to carry out sexual reproduction 23 chromosomes each •Have _____ MEIOSIS Created by the process of __________ •Meiosis is the type of cell division by which gamete cells (eggs and sperm) are produced. •Meiosis involves a reduction in the amount of genetic material. •A.K.A. reduction division To maintain normal chromosome number once fertilization occurs 23 23 46 Meiosis consists of two successive nuclear divisions with only one round of DNA replication. 46 Parent cell 92 46 23 46 23 23 23 4 Daughter cells Meiosis I •Interphase •Prophase •Metaphase •Anaphase •Telophase Meiosis II •Prophase II •Metaphase II •Anaphase II •Telophase II To reduce chromosome number START 46 2n = ____ Called the Diploid # END 23 n = ____ Called the Haploid # •Animals produce gametes directly through meiosis in organs called gonads. •Males and females of a species that reproduces sexually have different forms of GAMETOGENESIS (formation of gametes) 2 Types •spermatogenesis (male) •oogenesis (female)