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153 Cards in this Set
- Front
- Back
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In general, how do cells divide?
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They must make an identical copy of their genetic material (DNA) and distribute the two copies of genetic material, as well as the remainder of the cell contents, equally between the two resulting daughter cells
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Plasma membranes are...?
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selectively permeable; allowing certain kinds of relatively small molecules to pass through them freely in both directions by diffusion and osmosis which are both passive transport processes
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Diffusion is...?
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the random movement of molecules of a substance from an area of high concentration of that substance to an area of low concentratino of that substance. This is the process by which gases are exchanged between cells and their environment, by which inorganic salts are taken up by plant and animal cells and by which ions are exchanged in kidney, muscle and nerve cells in animals.
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Osmosis?
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the movement of a solvent (usually water) through a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration. A process that affects all living orgs. It's responsible for maintaining rigidity (turgor) in plant cells, in transporting food material in phloem tissue of vascular plants and in water uptake by root cells. Involved in kidney function, exchanges of fluids between the blood and tissue in capillary beds.
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What is key to understanding the flow of water during osmosis?
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An understanding of the total solute concentrations within the cell relative to that of the external medium. iso=same so equal movement of water into and out of the cell. hyper=above so a higher solute conc than their enviro, and hypo=below. Since the conc of solutes is higher within the cell, water moves into the cell by osmosis. Conversely, if the cells have a lower solute conc than their enviro, they are said to be hypotonic and the enviro hypertonic
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What is the normal environment for a red blood cell?
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It's the liquid component of blood called plasma.
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Is the cytoplasm of the red blood cell hypotonic, hypertonic or isotonic to the plasma?
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Isotonic
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If you water a plant like Tradescantia with tap water, which is a hypotonic solution, water enters the plant's cells causing the central vacuoles to swell. What prevents the plant cells from bursting?
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Cell wall.
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Recall your study of the unicellular animal Amoeba from Lab 2. You observed the contractile vacuole, which functions in osmoregulation (control of water balance within the cell). The contractile vacuole removes excess water that continuously flows into the cell. Is the cytoplasm of Amoeba hypotonic or hypertonic to its enviro?
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Hypotonic
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What is turgor pressure?
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Concentrations of particular solutes are often higher inside cells than outside, i.e. the cell contents are hypertonic relative to the enviro. As a consequence, water tends to move into cells by osmosis. In plant cells, this net movement of water into the cell forces the plasma membrane to push outward. This force is called turgor pressure. The membrane is prevented from bursting by the presence of a somewhat elastic, but relatively rigid cell wall (which exerts pressure in the opposite direction). The crispness of leaf itssue and general rigidity of young parts of a plant body are due to this "turgid" condition of plant cells under normal circumstances.
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turgid Elodea cell in distilled water?
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plasmolysed elodea cell in 3% NaCl
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If the concentration of a particular solute becomes higher outside a plant cell than inside...?
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the result is a "flaccid" or "wilting" condition in plant tissues. The cell vacuole decreases in size and the plasma membrane pulls away from the cell wall. This is called plasmolysis and can kill plant cells if it is severe or prolonged (eg. root cells of plants growing in soils that become saline or alkaline usually become permanently plasmolysed and the plant dies). If a plasmolysed cell is immediately placed in fresh water it will often regain its turgidity and survive.
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Cell division in Prokaryotes?
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Prok and euk cells accomplish cell division in diff ways. Prok cells divide by a process called binary fission. Initially, the cell's single chromosome, which is in the form of one circular loop of DNA, will replicate. The two resulting chromosomes then seaparate and the plasma membrane and cell wall grow inward to divide the original cell into two identical daughter cells.
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Cell division in Eukaryotes
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The nucleus contains a number of chromosomes that carry the genetic material of the cell. Chromosomes are composed of DNA (deoxyribonucleic acid) and proteins. There are many specific nucleotide sequences in the DNA and these discrete units of hereditary info are called genes. Genes provide a blueprint that determines the characteristics of every organism. Most of the time chromosomes are present in the nucleus as long, thin fibres, and the combination of DNA and protein in this form is called chromatin. Well before cell division in eukaryotes the single-stranded chromosomes duplicate to form double-stranded (duplicated) chromosomes (S stage in the cell cycle). The two identical copies of the DNA structures are called sister chromatids and they are especially tightly associated at the region called the centromere.
Cell division in euks involves two major steps called mitosis and cytokinesis |
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Briefly, what are mitosis and cytokinesis?
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mitosis is the division of the nucleus, resulting in the formation of two genetically identical daughter nuclei
cytokinesis is the division of the cytoplasm between the two resulting daughter cells |
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What are some of the major functions of mitosis?
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1. The production and maintenance of multicellularity, i.e. the development of an individual from a fertilized egg (zygote) to embryo to adult.
2. Asexual reproduction (reproduction that does not involve mating or fusion of cells). Asexual reproduction produces offspring called "clones" that are genetically identical to the parent organism. We will see an example of asexual reproduction in Volvox (Section VD). 3. Replacement of old and/or damaged tissues, e.g. your own skin cells are constantly being replaced as they age and new skin cells are produced by mitosis and cytokinesis. Repairing damage to the skin (e.g. a cut or scrape) Actively dividing cells undergo a regular cycle of events called the cell cycle as they progress from one mitotic division to the next (Figure 3.2) |
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Stages of Mitosis
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Difference between a chromosome diagram and a chromosome drawing?
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Allium (onion) root tip?
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the root apical meristem is the region of rapidly dividing cells near the tip of the root, just above the empty looking cells of the protective root cap. The cells in the meristematic region are usually small and thin walled and lack large vacuoles
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(bean) root tip?
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Vicia faba
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How did we study Mitosis?
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Whitefish blastodisc. The large black spheres were oil droplets
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What is a blastodisc?
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a fertilized fish egg that has undergone many divisions to produce a multicellular embryonic stage called a blastodisc
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Multicellular organisms are thought to have evolved...
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from simple unicellular organisms. Progression began with a transition from unicellular to colonial forms.
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A colony is composed of...
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indiidual cells or organisms that adhere to teach other and may communicate with each other
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In contrast to colonial orgs, multicellular orgs are...
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single orgs that have specialized cells that perform different functions. The differentiation of the specilized cells occurs during the initial development of the organism and is not normally reversible.
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Algae are...
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photosynthetic aquatic orgs that have relatively simple body plans (ie they do not have roots, stems or leaves
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We began our study of multicellularity with...?
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the unicellular Chlamydomonas and examined increasingly complex forms culminating in the multicellular organism volvox
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Chlamydomonas
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highlighting
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each gonium colony is ...
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a small group of cells held together in a simple flat or curved plate by a gelatinous matrix.
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How many cells makes up a gonium colony?
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The number of cells is genetically predetermined and varies with the species
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Each cell of the gonium colony...
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has two flagella, a cup-shaped chloroplast, an eyespot and a pyrenoid, which is similar in structure to that of a chlamydomonas cell. Each cell of the colony secretes an envelope of gelatinous material around itself which holds the individual cells together as a colony. Adjacent cells communicate with each other via sleder cytoplasmic bridges and this communication between adjacent cells is essential for coordination of flagellar movement, which propels the colony towards the light
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While each individual cell of the gonium colony is in communication with the others, there is no...
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division of labour among cells unlike that present in the cells of multicellular orgs
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How did the simple gonium colony evolve from a unicellular org like Chlamydomonas?
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The cells of Chlamydomonas divided but did not separate. It is believed that colonial forms like Gonium arose from Chlamydomonas-type cells which divided repeatedly and adhered to each other via a gelatinous matrix.
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If you imagine that the edges of a Gonium colony join up so that...?
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the colony is now a ball of cells, with the flagella directed outward, you would have an alga similar to our next example, Eudorina which has a rolling motion.
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As with Gonium, the individual cells of the Eudorina colony are composed of...
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Chlamydomonas-type cells which are held together by a gelatinous matrix and communicate with each other via slender cytoplasmic bridges.
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Other than the shape of the colony, what differences do you notice between Gonium and Eudorina?
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MISSING INFO AND PHOTO
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To the naked eye, volvox looks like...
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green spheres suspended in the culture medium.
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Under 10x, volvox looks like...
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large, hollow spherical organisms which swim with a rolling motion. Some of the organisms may contain small green spheres ("daughter orgs") which are the result of asexual reproduction
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The org wall of Volvox is made of...?
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a single layer of cells
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As with the previous algae, the individual cells of Volvox are similar to...
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Chlamydomonas (but a lot smaller) and each cell secretes a gelatinous matrix that allows the cells to adhere to each other.
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What connects adjacent cells in Volvox?
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cytoplasmic bridges
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Each Volvox cell has two...
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flagella that project outward. The co-ordinated beating of these flagella cause the rolling motion of this organism.
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What does a Volvox look like?
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What's one of the most obvious differences between Volvox and Eudorina?
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One of the most obvious differences is the increased number of cells in Volvox resulting in the overall larger size of the org.
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Volvox has how many cell types?
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two cell types: somatic cells and reproductive cells which are formed during the early development of the organism.
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Somatic Volvox cells?
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make up the wall of the organism.
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Reproductive volvox cells?
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undergo repeated cell division to produce the small spheres we observed within the larger parent organism. These small spheres are the result of asexual reproduction and are miniature versions of the parent org. When mature, the parent org will rupture and release the small spherical "daughter" orgs. Each sphere is capable of producing its own "daughter" orgs.
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What's the most significant diff between Volvox and Eudorina?
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The irreversible specialization of cell types in Volvox, making it a multicellular org.
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Draw a chromosome diagram of a cell with six chromosomes in the G1 stage of the cell cycle, and another diagram of the same cell in the G2 stage. Show chromosomes in a condensed state, even though they would not be condensed in G1 or G2...
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Draw chromosome diagrams of a cell with three chromosomes in the metaphase stage of mitosis. Draw the same cell in the telophase stage of mitosis.
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Osmosis is...
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the passive movement of water through a selectively permeable membrane from an area of low solute conc to an area of high solute conc
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short definition of mitosis?
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division of the nucleus to create two identical daughter nuclei
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cytokinesis?
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division of the cytoplasm
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difference between plant and animal cytokinesis
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- Plant cells - cytokinesis by formation of a cell plate
- Animal cells - cytokinesis by formation of a cleavage furrow |
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The cell cycle is usually in what phases?
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G1 and G2
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What are the things called that mark the alleles?
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Lo si
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Which ones can have more than two nucleoli which throws ppl off th inking that it's dividing?
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onion cells
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easy way to tell prophase?
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looks like a bowl of noodles
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Easy way to tell anaphase?
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looks like mustaches
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Asexual reproduction of orgs is accomplished thru...?
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mitotic cell division and results in offspring which are genetically identical to the parent org.
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Asexual reproduction is advantageous if...
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the orgs are well adapted to their present environment. If enviro conditions change, asexually reproducing orgs may not be well adapted to the new conditions.
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Orgs which reproduce sexually produce...
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genetically variable offspring. They therefore have the chance of producing at least some offspring which may be gentically better able to survive in the new conditions. Thus, over time, sexually reproducing orgs are able to evolve more rapidly to adapt to a changing environment.
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The majority of plants and animals reproduce...
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sexually at some point in their life cycle.
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Meiosis is a type of nuclear division involved in_______production in animals and ______________production in plants
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gamete (egg and sperm) production in animals and spore production in plants
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When you have completd the lab you should know:
1. The events that occur in each stage of meiosis and the final products of meiotic divisions in plants and animals 2. How to identify stages of meiosis in thin sections of plant and animal reproductive organs 3. The purpose of sexual reproduction 4. The sexual life cycles of multicellular animals and plants. |
When you have completd the lab you should know:
1. The events that occur in each stage of meiosis and the final products of meiotic divisions in plants and animals 2. How to identify stages of meiosis in thin sections of plant and animal reproductive organs 3. The purpose of sexual reproduction 4. The sexual life cycles of multicellular animals and plants. |
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Ploidy refers to
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the number of "sets" of chromosomes found in a cell.
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We will most often be referring to
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diploid orgs which have two identicl sets of chromosomes in their cells
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The cells of a euk org are said to be diploid if
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for every chom in the nucleus of the cell, there is another chrom of the same size shape and carrying the same genes. These similar looking chroms are called homologous chroms.
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most cells in the human body are
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diploid and contain 46 chroms, or 23 pairs of homologous chroms
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When referring to diploid orgs or cells, we use the form...
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2n = number of chroms (eg in humans 2n=46)
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In contrast, the cells of a euk org are said to be
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haploid if there is only one of each type of chrom in the nucleus (ie no homologous partner for each chrom)
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in humans, the haploid number of chroms is
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23, so n=23
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when referring to haploid orgs or cells, we use the form...
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n = number of chroms
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Each different gene is represented by...
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a different letter of the alphabet and is located at a specific point along a chromosome using a short makre line. The particular form in which a gene exists (termed an allele) is either dominant (capital letter0 or recessive (lower case letter).
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The genotype of any cell or org is...
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simply an ordered list of the alleles it carries for any genes we are studying
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If a single chromosome has undergone DNA synthesis and is now a duplicated chromosome, ...
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the two chromatids of the duplicated chromosome carry the same allele for a given gene at the same location.
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In a homologous pair of chromosomes (either single or duplicated), one chorm may have either the same or a different ________________ for a given _______________ than its __________________ partner
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gene homologous |
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Which of the following diagrams accurately represents a correctly labelled pair of homologous chromosomes? Assume NO cross-overs. For those diagrams that you answer "no", give a reason for your answer.
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meiosis I
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Metaphase I
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Anaphase I
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Telophase I
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Meiosis I
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Halves the number of chromosomes ie diploid -> haploid
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Meiosis II
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Separates duplicated chromosomes into single chromosomes
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prophase II
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metaphase II
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Anaphase II
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Telophase II
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In plants, meiosis occurs in...
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diploid cells called sporocytes within reproductive organs called sporangia to form haploid spores
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To study the stages of meiosis in plant cells it is convenient
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to examine the production of microspore in anthers (each anther contains four male sporangia) of the lily flower
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Each anther contains...
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four round cavities called pollen sacs (or microsporangia).
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Inside the anther pollen sacs...
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are darker-stained, round cells called microspore mother cells (or microsporocytes) which are undergoing meiosis. The red structures inside them are the chromosomes
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The final product of meiosis in the lily anther is...
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four haploid cells called microspores. The four cells will separate from one another and each one will divide by mitosis to become a mature pollen grain.
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Flower buds of chives have been preserved in an...
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alcohol mixture
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discard the yellow ones because they've already started to produce...
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pollen and will not be undergoing meiosis
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the name of the stain for the chives is
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aceto-orcein stain
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The shape of cells undergoing mitosis is...
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typically square or rectangular
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Plants have a complex life cycle called...
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an alternation of generations meaning that they have distinct multicellular haploid and diploid stages
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The haploid generation of plants...
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produces gametes and is therefore called the gametophyte (greek = gamete plant)
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the diploid gen of plants produces spores...
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and thus is called the sporophyte (greek = spore plant)
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In plants, meiosis occurs in...
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diploid cells within structures called sporangia in the sporophyte plant and results in the prouction of haploid spores. The spores give rise to the multicellular haploid gametophyte generation which will produce gametes by mitosis.
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Most plants are ____________________ dominant
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sporophyte; meaning that the multicellular diploid stage is the most obvious stage of the life cycle
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We studied the life cycle of...
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the fern Polypodium which alternates between the dominant multicellular diploid stage and a smaller, independent multicellular haploid stage
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In flowering plants like.....
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lily and chives, the gametophyte generation has become greatly reduced in size, to microscopic proportions and is not free living as in the fern
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The familiar pollen grain is...
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actually the tiny male gametophyte of flowering plants
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On the fern, the leaves grow out from...
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a horizontal underground stem called a rhizome which bears many roots.
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In most ferns, brown spots called...
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sori develop on the undersides of mature leaves.
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Each sorus is made up of...
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a cluster of reproductive structures called sporangia. Inside each sporangium, diploid cells alled sporocytes undergo meiosis to form haploid cells called spores. When the spores are mature, they are discharged from the sporangia
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Life Cycle of a fern
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What did you put the spore in?
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a drop of glycerine
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Draw and lable sporangium
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Individual spores which land in a suitable area (ie moist soil) will germinate if...
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conditions are favourable and will divide mitotitcally to produce a multicellular, haploid gametophyte generation.
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The fern gmetophyte is a small heart-shaped plant called a
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prothallus
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Each prothallus develops fine, root-like structures called
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rhizoids on its undersurface
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How does the gametophyte obtain food (sugar)
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It is an independent body with its rhizoids to absorb water and other nutrients from the soil . It has green photosynthetic tissue that manufactures food via photosynthesis
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How does the gametophyte obtain water from the soil?
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hair-like transparent rhizoids extend from the plant body into the soil
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What is the size of a gametophyte
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1/5th inch
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Groups of cells on the underside of the gametophyte develop into reproductive organs called
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anterhidia (male) and archegonia (female)
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What do the antheridia and archegonia do?
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Mitosis in the antheridia gives rise to flagellat sperm cells, while single egg cell develops in each archegonium.
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draw an archegonium
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When flagellate sperm cells are mature, they are released from the antheridium...
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and swim in a film of water to the archegonium to fertilize an egg cell. After fertilization, the diploid zygote develops by repeated mitotic division into a new sporophyte plant. Inititially, the sporophyte is nutritionally dependent on the gametophyte in which it is embedded. once the sporophyte develops roots and photosynthetic leaves, the gametophyte degenerate.
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Sketch a young sporophyte emerging from a gametophyte
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In animals, meiosis occurs in...
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diploid cells in reproductive organs called ovaries (female) or testes (male), and this nuclear division results in the production of haploid gametes (eggs or sperm).
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The chiasma formation typical of crossing-over of genetic material between homologous chromosomes during Prophase I shows up particularly well in photographs of thin sections of grassphopper testes. Sketch a pair of homologous chroms with a chiasma
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In order to study the animal life cycle we studied the...
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mouse
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in animals, meiosis only occurs in the
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ovaries or testes and results in the production of haploid gametes (eggs or sperm)
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The haploid egg and sperm combine during fertilization for form...
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a new diploid cell (zygote) which develops into the new multicellular diploid individual by mitosis
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Life cycle of a mouse?
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In humans, the only haploid stage is the...
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egg and sperm
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What two events occur in Prophase I of meiosis that do not occur in Prophase of mitosis?
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- homologous chromosomes move toward each other to form bivalents
- genetic exchange occurs between homologous chromosomes during a process called crossing over (not illustrated here, see Lab 5) |
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How do the products of mitosis in one diploid cell differ from the products of meiosis in one diploid cell? (Give the number of resulting cells and the ploidy of each)
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2 diploid cells in mitosis
4 haploid cells in meiosis |
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Draw a complete set of chromosome diagrams to accurately illustrate the four stages of mitosis in a diploid (2n) plant cell with the genotype "AaBb" (Be sure to label alleles on all the chromosomes you draw)
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Draw a complete set of chromosome diagrams to accurately illustrate the eight stages of meiosis in a diploid animal cell with the genotype "AaBb" (Be sure to label alleles on all the chromosomes you draw)
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Which of the following diagrams are correct representations of cells at the metaphase I stage of meiosis, assuming that no crossovers have occured?
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Which of the following diagrams are correct representations of cells at the anaphase II stage of meiosis?
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Draw a chromosome diagram to represent the same cell in part a but at the anaphase I and anaphase II stage of meiosis
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Suppose you had an animal cell with the chromosome number of 2n=4 and you knew that the genes for eye colour were located on one pair of choms, while the genes for wing shape were locatd on another pair of chroms. Use the letters D and E to represent the genes.
a) Draw a chrom diagram to accurately represent this animal cell at the metaphase stage of mitosis if it carried only dominant alleles for eye colour, but both dominant and recessive alleles for wing shape |
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Suppose you had an animal cell with the chromosome number of 2n=4 and you knew that the genes for eye colour were located on one pair of choms, while the genes for wing shape were locatd on another pair of chroms. Use the letters D and E to represent the genes.
b) Draw the same cell described in part a if it was the metaphase II stage of meiosis. |
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Suppose you had an animal cell with the chromosome number of 2n=4 and you knew that the genes for eye colour were located on one pair of choms, while the genes for wing shape were locatd on another pair of chroms. Use the letters D and E to represent the genes.
c) Suppose the animal cell carried dominant and recessive alleles for both eye colour and wing shape. Draw a chromosome iagram at metaphase I of meiosis |
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A gene can come in differen forms called...
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called alleles
Dominant allele: A Recessive allele: a |
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Homologous chromosomes...
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- same shape
- same size - carry the same sequene of genes - they don't both have to be the same dominant or recessive but they are NOT genetically identical because we get one of the homologues from our mother and the other from our father |
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Diploid cells are
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(2n) cells with two of each kind of chromosome
- the human karyotype is that of a diploid cell 2n=46 |
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haploid is
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a cell with just one of each kind of chromosome n=23
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How are plant life cycles complex?
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They have an alternation of generations life cycle
- multicellular diploid stage = sporophyte - multicellular haploid stage = gametophyte |
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Sporophyte?
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- diploid stage
- Sorus made up of sporangia on the underside of the fern leaves. Cross section of fern leaf with sorus. Sporangium (structure where meiosis occurs) |
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Fern Gametophyte
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- indicating area where reproductive organs are formed
- notice rhizoid for water uptake... not a root - archegonium (female reproductive organ with egg cell) - antheridium (male reproductive organ with sperm cells) |
