Meiosis Video Guided Notes Packet

Name: ________________________________________ Per: ____________ Animation guided notes: Mitosis (review) and Meiosis: MITOSIS AND CELL CYCLE REVIEW: Mitosis is the process by which organisms ___________, _________, and ___________body cells. During M phase, a cell will undergo mitosis to produce two new ______________ and then divide to form two new cells during ______________. Mitosis divides the duplicated ___________ of a cell into two identical __________________. ****Watch the summary but do not take notes yet until 1:27******* CELL CYCLE REVIEW Mitosis is one small part of the ______________________. For many eukaryotic cells one cell is produced every _______hours. Most of the cell’s life is spent in ______________________, which is divided into three stages: ______________, ____________, and ______________. In ____________, the cell _______________ to nearly full size and performs its ___________________________________________________. Next is the ____________ phase, where the DNA in the nucleus is ________________________. The cell enters another growth phase known as ___________. Previously, we learned that during this phase, the cell is doing final preparations for _____________________. Once the DNA is _____________________ and _____________ centrosomes appear in the cytoplasm, Mitosis can begin. For a typical cell, Mitosis takes about ____________________________. In Prophase…. During the first stage of Mitosis, chromatin becomes visible as chromosomes through a ____________________ process. Protein strands called ________________________ grow from the ____________________ (which contain the centrioles. The ________________ and the ___________________ break down. In Metaphase… Microtubules capture chromosomes at the _________________, which is a protein structure at the centromere of each _______________________________. The microtubules push the duplicated chromosomes to the _______________ of the cell (also known as the cell equator). Each sister chromatid faces _______________ poles. Now the sister chromatids are ready to be _____________________. In Anaphase…. Through a shortening of the ______________ attached to kinetochores, the _____________________are pulled APART toward opposite spindle poles. The cell also _________________, increasing the distance between sister chromatids. In Telophase … Telophase is the __________ stage of mitosis, where components of new cells begin to appear. The spindle fibers break down and release the ________________________________. A new ____________________________ appears around the chromosomes at each end of the cell. The chromosomes ________________ and return to an uncondensed state. At the end of Mitosis, _________________begins to divide the cytoplasm. MEIOSIS: Reductive division Many organisms pass their __________ to their offspring through sexual reproduction. This begins when gametes from two organisms fuse or unite to form an embryo that is genetically _____________ from both parent organisms. The offspring then grows to adulthood to pass their genetic information on to their own ________________. _________________ are formed through a process called Meiosis. The cells that undergo Meiosis to produce the gametes (sperm in the testes and eggs in the ovaries) are called __________________________. In diploid organisms, most body cells including germ cells have __________ copies of each chromosome. Germ cells undergo Meiosis to produce ________________ gametes which have only ___________ copy of each chromosome. The haploid gametes then ______________ to form a new ______________ embryo that will grow into an adult. The life cycle of a germ line cell includes Meiosis, but also includes _____________________, which also has _______, __________, and _____________ phases. The DNA in a germ line cell is ___________________ before Meiosis begins during _______________ (just like it happens for non-germ line cells preparing for Mitosis). The sister chromatids will remain attached to each other at their centromeres until the _________________ of two cell division events that occur during Meiosis. The first cell division event, _________________, results in two ______________ daughter cells with ___________ as much DNA as the parent cell. The second division, __________________, results in four unique ____________cells with only one copy of each chromosome. These four cells are the gametes that can go on to fuse with another gamete during sexual reproduction and form a unique organism. MEIOSIS I: Meiosis I begins with __________________. DNA condenses to form visible chromosome structures. Sister chromatids will remain attached to each other at their ____________________ throughout Meiosis I. Each ___________________ pair of chromosomes will undergo _______________________ to form a complex of two pairs of sister chromatids. During _______________, chromosomal material may be exchanged between the chromatid complexes. This event is called recombination, or _________________________. This occurs between one of the sister chromatids from each homologous chromosome. Once crossing over has occurred the sister chromatids are no longer ________________ to each other. This is one of the reasons why no two _____________ are genetically identical (apart from twins). Prophase I is the longest Meiotic phase, taking on average 70+ hours. Other key events in Prophase I include nuclear envelope breakdown and the migration of centrosomes to opposite ends of the cell. Spindle fibers then appear and attach to the synapsed chromosomes. The next phase of Meiosis I is called _______________________. Here, the synapsed chromosomes align at the equator of the cell, guided by the spindle microtubules. The chromosomes align ____________________ (VERY IMPORTANT), which results in different combinations of chromosomes every time Meiosis occurs. This is called RANDOM ASSORTMENT. The next stage is called _________________________, where homologous chromosomes are separated to opposite ends of the cell. Sister chromatids remain________________________________ at their centromeres. The last stages of Meiosis I are ________________________ and _________________________. Here, the original cell divides into two ___________________________ daughter cells. At the end of Meiosis I the nuclear envelope briefly reforms , the DNA decondenses and the cells fully separate. Each of the daughter cells will now undergo Meiosis II. MEIOSIS II: Meiosis II is very similar to ????__________________. During the first stage, ____________________, the nuclear envelope breaks down, the spindle poles begin to reform and the DNA again condenses. Sister chromatids are still attached to one another. The major difference between ______________ and ________________ is that in the second, cells only have one chromosome from each _____________ pair (meaning no synapsing and no crossing over). In Metaphase II, the sister chromatids again line up at the cell equator, each chromatid facing opposite spindle poles. Again this happens ___________________, so there will be many different possible ways for the chromosomes to be separated. In anaphase II, sister chromatids are ___________________ to opposite ends of the cell as the microtubules shorten. In ________________________, the nuclear membrane ___________________, the microtubules ________________, and the daughter chromosomes ________________________. The final act of Meiosis is ______________________________, which divides the cytoplasm between each pair of daughter nuclei. At the end of Meiosis II, we now have _______ unique haploid cells, or gametes. If one male gamete, _____________ ,fuses with a female gamete, _____________, a new organism will be formed. The resulting embryo will grow through development, birth and into adulthood through many rounds of ________________.