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44 Cards in this Set
- Front
- Back
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how do cell reproduce?
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through the division of their parents cells, and most cells divide in turn to produce daughter cells
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Usually this occurs during
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Mitosis - when the genetic material is duplicated and one copy is passed on to each daughter cell. - |
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Mitosis is generally followed by.....
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Cytokinesis: or cytoplasmic division - in which the rest of the cell divides in half to form two new cells |
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In animals and plants that reproduce sexually, two sex cells...
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or gametes, fuse to produce the zygote. The zygote has twice as much genetic material as the gamete.
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Therefore, before fertilization occurs....
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the genetic material must be reproduced by half so that the amount of genetic material stays the same from one generation to the next.
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This reduction in nuclear material occurs through the process of....
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Meiosis! - only germ cells carry out meiosis - the gametes resulting from this process contain only one-half of the genetic material of their parent cells. |
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The events from the beginning of one cell division to the beginning of the next division are called?
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the cell cycle - the cell cycle is divided into four stages: G1, S, G2 and M |
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Interphase consists of.....
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G1, S, G2 - the M (mitosis Stage) represents the division of the nucleus and the cytoplasm. |
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Modeling the Cell Cycle and Animal Mitosis:
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building models of the cell cycle to enhance our understanding of the behavior of chromosomes and other cell parts involved in the process. - Using pipe cleaners to represent Sister Chromatids and beads to represent the centromeres. - our model will start with a diploid cell (2N) with 4 chromosomes. - we will then have two homologous pairs of chromosomes. |
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During interphase, a cell preforms several functions that prepare it for the next mitotic division. As the phase begins....
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the cytoplasm in the cell is approximately half the amount present before division. - the cell has a nucleus surrounded by a nuclear membrane and contains chromosomes in an uncoiled state. In this condition, DNA and associated proteins are called Chromatin. |
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G1 phase....
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the cytoplasm increases and will continue to do so throughout interphase. Macromolecules such as arbohydrates and proteins are synthesized, new organelles are formed and mitochondria grow and divide
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Phase S (Synthesis)
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duplicate the chromosomes in the nucleus makes a cell in the Synthesis phase
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G2 phase
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the cell continues to increase in size. Enzymes and other proteins for cell division are synthesized at this time.
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In M or the Mitosis phase
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the nucleus and cytoplasm divide. Division of the nucleus is called MITOSIS.
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Mitosis is divided into 4 phases....
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1. prophase 2. metaphase 3. anaphase 4. telophase |
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the division of the cytoplasm is called....
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cytokinesis
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As the cell enters PROPHASE...
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the chromatin condenses into visible threads, eventually appearing as chromosomes. The nucleoli disappear and the nuclear membrane breaks down - by the end of the phase, the centrioles have migrated to opposite pole with the chromosomes beginning to move to the center of the cell - the MITOTIC SPINDLE starts to appear |
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Metaphase
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during metaphase, the spindle forms and the chromosomes arrange themselves on the equatorial plane of the spindle. The equatorial plane is imaginary in the middle of the cell halfway between the two poles. - each double stranded chromosomes is attached to a SPINDLE FIBER at its centromere |
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Anaphase
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the sister chromatids seperate and begin to move towards opposite poles. - Metaphase enda and anaphase begins when the centromere of each chromosome divides and the new single-stranded chromosomes moves away from each other toward opposite poles of the cell. -Spindle microtubules, attached to the centromeres, cause chromosomes to move with the arms of the chromosomes trailing passively behind -ANAPHASE ENDS when the chromosomes reach the poles. |
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Telophase
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the daughter chromosomes gather at the poles and begin to form the daughter nuclei. Since each original chromosome in the cell contributed a chromosome identical to itself to each new nucleus, the two daughter nuclei will be identical to the nucleus of the parent cell - the nuclear membrne begins to reform, the nucleoli reappear and the chromosomes bein to unwind. - at the end of telephase, the nuclei look like interphase nuclei |
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Cytokensis
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or division of the cytoplams, usually accompanies telophase. - In Animal Cells: the membrane consists in a ring around the middle of the cell, and eventually pinches the cell in two. the cytoplasm and all its constituents are divided so that each cell gets about half the material and organelles in the cell - In Plants: a cell plate begins to form in the center of the equatorial plane and grows until it extends across the cell, dividing the cytoplasm |
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An animal cell about to undergo mitosis has already replcated its DNA during....
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Interphase
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In animal cells, the centriole has replicated during... |
Interphase - the newly replicated centrioles called daughter centrioles, move to opposite poles of the cell. - The position of the centriole determines how chromosomes will move during mitosis with the chromosomes moving toward the centrioles and the cell dividing in a plane perpendicualr to a line joining them |
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Mitochondria importance
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mitosis requires a great del of energy, so there are many mitochondira to provide ATP for synthesis and chromosome movement
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During Interphase
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the genetic material is in the form of fibers of DNA that form a tangled mass called chromatin - the nucleus is bounded by the nuclear membrane and contains nucleoli |
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Differences between Mitosis in animal cells vs plant cells
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Interphase: the nuclei look similar to the animal but may have a different number of nucleoli Prophase: no centrioles in plant cells Metaphase: similar to animal Anaphase: similar Telophase: similar but in plants telophase cells can be easily distinguished becasue you will see two nuclei within a cell that is about the same size as the othe cells that have two nuclues. the two new daughter cells together are the same size as the parent cell, and growth of the cells will occur later Cytokinesis: Completely different! |
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Cytokenesis in plant cells
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the parent cell does not pinch in or change shape at all. Instead, a cell plate forms, which initiates the new cell wall, dividing the two daughter cells - Cellulose is laid down along the plate to eventually form a cell wall between the two new cells - each cell then begins to elongate in its dimension until it is as big as the parent cell and can enter another cycle of mitosis |
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Percentage of Cells in Each Stage
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- determine the stage of mitosis in 100 cells using onion root tip slide - onion root tip cells take 16 hours to complete the mitotic cycle - by determining the percentage of cells in each cells in each stage of mitosis and in interphase, you can calculate the amount of time spent in each stage |
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In diploid organisms such as human beings, that are two sets of genes...
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2N in the adult - Meiosis produces cells that have only a single set of genes (N) which are consequently haploid |
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chromosomes undergoing meiosis...
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the chromosomes do not act independently but join together in a homologous pair during meiosis I, the 1st meiotic division -homologous pairs |
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Plant: During the 1st meitoic division....
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the two members of the pair seperate but the chromosomes do not split in half as they do in mitosis abd they remain double-stranded. Thus there is no need for DNA synthesis before meiosis II |
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Plnt: Meiosis II
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the two sister chromatids of each chromosome seperate so that each daughter cell receives one single-stranded chromosome. The four daughter cells produced whnen a cell undergoes meiosis are usuallynot identicel, in contrast to the casrbon copy daughters produced during mitosis. These four daughter cells are HAPLOID rather than DIPLOID and contain only one set of the genetic material.
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Plant: During Mitosis, each chromosome acts...
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independently -sister chromatids seperate during anaphase and two genetically identical cells are produced. |
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Plant: During Meiosis, there is pairing of .....
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homologous chromosomes and the daughter cells formed are not identical to the parent cell
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Pipe cleaners are used to represent....
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sister chromatids of the chromosomes and beads to represent centromeres.
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In animals, meiosis occurs only in...
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Gonads
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In males the sperm are formed with each cell undergoing....
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spermatogenesis - which produces four sperm cells. |
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Oogenesis, in females
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a single large egg cell is produced which carries the energy for the development of the zygote after fertilization. - nuclear division occurs in the same way but cytoplasmic division is very unequal - a nucleus with a small amount of memebrane and a cytoplasm is discarded after meiosis I as the first Polar Body. - a second polar body is discarded after meiosis II. - if the 1st polar body undergoes division, there may be two or three polar bodies stuck onto the outside of the ovum, or egg cell. - Thus in a female, meiosis gives rise to a single gamate, the ovum and three polar bodies. |
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In humans, sex and other traits are determined by....
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sex chromosomes - Males have one X chromosome and a tiny Y chromosome that contains very few genes - Females have two X chromosomes, however, early in the development of a female embryo, one of the X chromosomes becomes inavtive in each cell, so that only one of the two X chromosomes is actually active. - the inactive chromosome is still replicated and passed on to all daughter cells. |
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The condensed X Chromosome can be seen in ceratin cells as...
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Barr Body - if a female is normal, only one Barr Body in many of the cells - None found in males - Abnormal male with an extra X chromosome will have a Barr body and an abnormal female with an extra X chromosome will have two Barr bodies |
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Karyotype
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is the display of a person's chromosomes - because each cell is supposed to have the same set of chromosomes, in theory, a karyotype could be made from any cell in petaphase - Karyotypes from adults can be made from cheek cells or white blood cells - in fetal evelopment, karyotype can be determined by studying cells removed from amniotic fluid during amniocentesis - chromosomes must be paired in correct goups according to their size and relative length of their arms |
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children with down syndrome have
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three copies of chromosome 21 - since then, many human genetic disorders have been traced to an abdnormal chromosome complement |
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An abnormal number of chromosomes in an individual is often the result of...
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an error in meiosis during which an egg or sperm cell with an incorrect number of chromosomes is produced. - when the homologous chromosomes pair during meiosis I, it is possible that the members of the pair fail to seperate properly during anaphase I, so both members of the pair eventually end up in the same gamate. |
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the fail of chromosomes to separate is called...
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nondisjunction - and results in gametes with extra or missing chromosomes |
