Lab 6 Flashcards
what are the 2 major activities of the cell cycle?
interphase and cell division
what percentage does the interphase make up of the cell cycle?
90%
what subphases is the interphase made up of?
G1, S (DNA synthesis), G2
what happens during the three subphases of interphase?
the cell grows and manufactures organelles, including centrosomes and centrioles
what is Mitosis?
process by which a nucleus divides to produce two daughter nuclei identical in genetic material, generates haploid cells that has same chromosome number as its parents
what is cytokinesis?
division of cytoplasm which completes separation into two cells
where does cell division primarily occur in plants?
apical meristem at tip of shoots and roots and in cambium
what is the apical meristem located just above the root cap in plants?
embryonic region where active mitotic divisions occur, responsible for an increase in the length of the plant at the tips of roots and shoots
what is the cambium?
region of actively dividing cells, can produce new plant tissue for lateral growth (increase in diameter), found between xylem and phloem
what is the meristematic tissues?
apical meristem and cambium, tissues in plant cells that are actively dividing and is responsible for elongation and lateral growth
why is duplication of genetic information via S-phase of interphase necessary?
to make sure that the 2 daughter cells inherit same amount of chromosomes. If info not duplicated or distributed properly, daughter cells will have incomplete genetic info and will be nonfunctional
what is the root cap?
protects tip of root, where area of cell division is
where does cell division occur in animal cells?
most occur in embryo, but some somatic cells (blood, skin cells) continuously divide whereas some (nerve, certain muscle tissue) do not
what is the G1 phase?
increasing cell size so daughter cell receives sufficient cytoplasmic contents as well as creation of certain regulatory enzymes
what is the S phase?
DNA replication
what is G2 phase?
further increasing cell size so daughter cell receives sufficient cytoplasmic contents
what are the stages of mitosis?
PMAT - prophase, metaphase, anaphase, telophase
what is prophase?
chromatin condenses and shortens into chromosomes (appears as long tangled threads)
Sister chromatids are paired and held together at the centromere
spindle forms, nuclear fragments and nucleoli disappear
what is a centrosome?
organelle in animal cells that assist in cell division by organizing microtubules around it
what is a centriole?
component of centrosome made of nine microtubules, and is cylindrical in shape, formed from protein microtubules
what is metaphase?
chromosomes form a line across middle of cell (equatorial plate)
chromosomes are attached to spindle fibers at centromeres, which are aligned along equatorial plane
spindle fibres appear to originate from opposite ends of cell (poles)
what is anaphase?
the two sister chromatids of each chromosome are pulled apart at centromeres by spindle microtubules and move to opposite poles, towards direction of centrosome they are attached to
how do you count the number of chromosomes present at any stage of cell division?
count # of centromeres, not # of chromatids
how many chromosomes at each pole are present in Allium?
16
what is ploidy?
of chromosome pairs
what process turns cells from diploid to haploid?
meiosis
what process turns cells from haploid to diploid?
fertilization
how is cytokinesis in animal cells and plant cells different?
animal - formation of cleavage furrow in equatorial region of cell, indentation in membrane deepens as a ring of microfilaments contracts, resulting in two cells forming
plant - formation of cell plate in cell’s equatorial region as vesicles produced by golgi apparatus line up and begin to fuse together, cellulose accumulates in space btwn membranes of cell plate, forming new cell walls, eventually fusing with plasma membrane
what are homologous pairs?
pairs of chromosomes that are the same lengthwise, positionwise, and possesses genes for same traits
how is a cell diploid in terms of homologous pairs?
having both homologues ( two members of a pair) present in the same cell makes a cell diploid/ 2n
what is the significance of mitosis to the organism?
- allows it to grow and repair by replacing damaged cells with new ones and continuously replenish cells
- allows asexual reproduction, each cell is identical to one another
what is fertilization?
fusion of two parental cells or gametes
how is fertilization important?
genetic diversity, new gene combinations which increase diversity within a population
how are gametes produced in animals?
by meiosis
what is meiosis?
cell division that reduces number of chromosomes found in cell by half, resulting in haploid products from a diploid cell
is the reduction in chromosome number random?
No, one member from each homologous pair ( and therefore one copy of every gene) ends up in each gamete
what occurs in fertilization?
gametes fuse and each contributes a single set of chromosomes to the resulting cell, making it diploid again
what is a zygote?
diploid cell resulting from the fusing of haploid gametes through fertilization
what are the two stages of meiosis?
Meiosis I and Meiosis II
what happens in meiosis I?
the pairs of homologous chromosomes in a diploid cell are carefully matched up in a process of synapsis and then pulled apart to produce 2 haploid cells
what happens in meiosis II?
each chromosome starts meiosis with two chromatids which are pulled apart during meiosis II
how many daughter cells are produced from a diploid cell undergoing meiosis?
4 haploid cells
what happens in prophase I?
each chromosome consists of 2 chromatids held together at the centromeres
homologous chromosomes pair
paired chromosomes coil around each other, crossing-over occurs
spindle microtubules form and attach to the centromere of the short, thick chromosomes
nucleoli and nuclear membrane disappear
what is a result of crossing over during prophase I?
exchange of genetic material btwn homologues
what is a homologous pair called in prophase I?
tetrad
what happens in metaphase I?
the homologous pairs are moved to the centre of the cell by the microtubules with their centromeres on either side of the equatorial plane
what happens in anaphase I?
the homologous pairs are pulled apart and each homologue, consisting of sister chromatids, is moved to opposite poles ( each chromosome still has 2 sister chromatids)
what is reductional division?
in anaphase I, the maternal chromosome goes to one pole and paternal chromosomes goes to the other pole because the total # of chromosomes in each cell will be reduced by half
what happens in telophase I?
the chromosomes of the two daughter nuclei are grouped at opposite poles
chromosomes uncoil and pass into interkinesis, similar to mitotic interphase, however NO DNA replication occurs and cytokinesis may or may not take place
Each daughter cell is now haploid even though each chromosome is composed of a pair of sister chromatids
how are the two nuclei produced from telophase I different from those produced in telophase of mitosis?
the nuclei have chromosomes that are still composed of a pair of sister chromatids, nuclei produced by telophase of mitosis do not have sister chromatids
what is the equational division that occurs in meiosis II?
the second meiotic division, the total number of chromosomes per cell does not change with cell division
how many different end products can be produced in meiosis II without considering crossing-over?
what is crossing over?
the exchange of genetic material between homologous chromosomes. It results in new combinations of genes on each chromosome.
the number of different gametes that can be produced DOUBLES with each addition pair of chromosomes present. How can this be expressed? (math expression)
2^n , n = number of homologous chromosome pairs
how many different types of gametes can be produced in a man with 23 pairs of chromosomes?
2^23, over 8 million different gametes
how many different kinds of gametes are formed in an animal with 3 pairs of homologous chromosomes?
2^3, 8 different gametes
what is the significance of meiosis?
results in genetic diversity by producing gametes that each have different genetic combinations
results in haploid cells that allow a diploid cell to form upon fertilization
what is spermatogenesis?
production of sperm
where does spermatogenesis occur?
within the seminiferous tubules in testes
what is oogenesis?
production of eggs
where does oogenesis occur?
in the ovary
why are eggs and polar bodies produced in oogenesis?
only one viable haploid egg is produced, the three polar bodies are not viable for fertilization and disintegrate
what happens during ovulation?
oocyte/egg ruptures from its follicle
what is the difference between spermatogenesis and oogenesis in terms of end products?
spermatogenesis - 4 haploid sperm
oogenesis - 1 haploid egg and 3 polar bodies
what is alternation of generations?
meiosis and fertilization alternate and are widely separated in a life cycle
what is sporogenesis?
production of haploid spores rather than gametes which grow directly into a haploid plant which makes gametes by mitosis when mature
what is a sporophyte?
diploid, spore-producing plant
what is a gametophyte?
haploid, gamete-producing plant
what are sporangia?
specialized spore containers generally found on underside of leaves
what are sori?
clusters of sporangia
what are archegonia?
gamete-producing structures that produce eggs in gametophytes
what are antheridia?
gamete-producing structures that produce sperm in gametophytes
what do archegonia look like?
roughly bottle-shaped, wider at base with long neck, each containing a single egg at its base
what do antheridia look like?
round, produce hundreds of flagellated sperm cells
what type of cell division produced plant gametes? How is this different to animal gametogenesis?
made through mitosis b/c gametes are made by already haploid gametophytes
animal gametogenesis uses meiosis to produce haploid gametes from diploid parent cells
if the sporophyte has a total chromosome number of 24, how many chromosomes will be present in the spore?
12, sporophyte uses meiosis to make spores , spores are haploid
why is meiosis necessary in the life cycle of plants and animals?
prevents chromosome doubling where if diploid cells fuse in fertilization, a cell with a larger ploidy results
what is an advantage of exchanging gametes between two plants
genetic diversity/recombination - increases chances of adaptation to changing environmental conditions by forming new gene combinations
if the sporophyte has a total chromosome number of 24, how many chromosomes will be present in the spore?
can be time consuming requiring a lot of energy and resources to produce gametes, need external environmental factors such as wind, pollinators to spread gametes, plants may be far from one another
