Download Active Reading - Intro to the Cell Cycle - Mitosis and Meiosis

Intro to the Cell Cycle: Mitosis and Meiosis
Active Reading
First, read the readings below and HIGHLIGHT the correct word for each set of possibilities.
Second, use the underlined words in the readings to complete the vocabulary puzzles for each section.
Mitosis and Cancer
Each of us began as a single cell. This one cell became two, and (beyond, curly, then) four, then eight
and so on, (point, afterwards, in) time becoming the amazing person that (dusty, reign, is) you. Scientists can
actually watch cells (filthy, divide, quickly) under the microscope, and they have (discussion, been,
shakily) able to figure out the rules (of, finger, discussion) division by carefully observing the process, (much,
terrible, stupid) as someone could gradually learn the (boast, crossly, rules) of a game like football or (chess,
reject, sit) by watching it played repeatedly.
The (awoke, thick, life) of a cell is called the cell cycle. This (wooden, cycle, outstanding) begins
when the cell (is, confess, crowded) produced by mitosis and runs until (suspend, strengthen, the) cell
undergoes its own mitosis and (splits, stitch, forgot) in two. The cycle is divided (curly, into, carry) two parts:
Interphase and Mitosis. Interphase (feather, worm, is) the longer part; it takes up (unlike, about, broad)90%
of the cell cycle. Mitosis is (dirty, spotless, small) but important – it is when the (think, word, cell) divides in
two!
Scientists used to (money, observation, think) of interphase as a resting phase (during, strange,
arch)which not much happened, but they (degree, now, wet) know that this is far from (the, jelly, told) truth. It
is during interphase that (difficult, chromosomes, respect) — the genetic material — are copied, and (cells,
street, almost) typically double in size. While this (easily, husky, is) happening, cells continue to do
their (excited, cheese, jobs): Your heart muscle cells contract and (choose, develop, pump) blood, your
intestinal cells absorb the (level, kind, food) you eat, your thyroid gland cells (keep, journey, churn) out
hormones, and so on. In (uptight, contrast, rub), most of these activities cease during (addition, ant,
mitosis) while the cell focuses on dividing. (Loose, But, Stage) as you have probably figured out, (not,
bounce, train) all cells in an organ undergo (discover, mitosis, scale) at the same time. While one (offend,
cell, enchanting) divides, its neighbors work to keep (weary, carelessly, your) body functioning.
Mitosis is responsible for (match, blunt, growth) and development, as well as for (itself, adorable,
replacing) injured or worn out cells throughout (from, your, self) body. It is also called asexual (often,
reproduction, disarm), or reproduction without sex. There are (interrupt, carelessly, some) organisms that
reproduce only through mitosis! (comb, reluctantly, These) organisms produce offspring that are
genetically (shiny, death, identical) to their parents. Imagine if you (awoken, were, uh) an exact, identical
clone of your (plastic, mother, gracefully) or father! That would be asexual (reproduction, slept, fuzzy) (and
obviously, humans do no reproduce (successfully, in, direction) this way).
Mitosis is divided into (five, that, shade) stages: prophase, metaphase, anaphase, telophase,
and (cytokinesis, with, band). Each of these stages is described (attention, below, anybody):
 Prophase: The nucleus break apart, and (chromosomes, bridge, given) condense and become visible. In
the (anybody, cytoplasm, change), the spindle forms.
 Metaphase: The copied (begin, entertain, chromosomes) align in the middle of the (meant, spindle,
bounce).
 Anaphase: Chromosomes separate into two genetically (organization, smoothly, identical) groups and
move to opposite ends (aboard, hot, of) the spindle.
 Telophase: Nuclear membranes form (despite, around, system) each of the two sets of (chromosomes,
greasy, screw), the chromosomes begin to spread out, (and, burn, run) the spindle begins to break
down.
 Cytokinesis: (The, elephant, desk) cell splits into two daughter (shirt, irritate, cells), each completely
identical to the mother (cell, gentle, boat).
A cell tightly regulates and controls (its, encouraging, per) cell cycle – it should only divide (at, wear,
ridden) certain times. For example, skin cells (sister, are, detail) always dividing to produce more
cells, (motionless, sock, but) muscle cells divide much slower and (a, nerve, tomorrow) cells divide very
rarely, if at (slept, all, sponge). Your body carefully controls which cells (helpless, make, divide) and when
they do so by (shake, puzzled, using) molecular stop and go signals. For (if, example, froze), injured cells at
the site of (learn, a, throw) wound send go signals to the (recognize, surrounding, sky) skin cells, which
respond by growing (dead, or, and) dividing and eventually sealing over the (knife, since, wound).
Conversely, stop signals are generated when (peace, employ, a) cell finds itself in a nutrient-poor (safe,
environment, sing). Sometimes, however, go signals are produced (unlock, bloody, when) they shouldn't be,
or stop signals (dangerous, rung, aren't) sent or heeded. When this happens (cells, measure, ornament) begin
to divide at the wrong (gone, times, gracefully) or in the wrong places. Out (of, tree, became) control cell
division is called cancer. (Recognize, Rate, In) cancer, mitosis becomes a weapon turned (foot, against,
attack) the body, spurring the growth of (discover, invasive, parcel) tumors. A tumor is a mass (be, of,
interfere) cancerous, rapidly dividing cells that can (interfere, spend, cup) with an organ’s function and
spread (meddle, written, to) other body parts.
Fortunately, it takes (door, cautious, more) than one mistaken stop or go (reach, impress, signal) for a
cell to become cancerous. (Existence, Because, Snake) our bodies are typically quite good (splendid, at,
listen) protecting their essential systems, it usually (argue, requires, camera) a one-two punch for healthy
cells (gun, easy, to) turn malignant. The punches come in (protest, the, victorious) form of errors, or
mutations, in (witty, run, DNA) that damage a gene and result (until, produce, in) the production of a faulty
protein. (Space, Shaky, Sunlight), X rays and other radiation, toxins (such, settle, reject) as those found in
cigarette smoke (against, and, know) air pollution, and some viruses can (mind, reaction, cause) such
mutations. People also can inherit (jagged, monthly, mutations) from their parents, which explains
why (hand, some, ourselves) families have higher rates of certain (carefully, cancers, smiling): The first
punch is delivered at (brief., conception, rat). Subsequent mutations can then push a (cell, floor, copy) down
the path toward becoming cancerous.
Use the underlined words from the reading to answer these vocabulary questions.
Mitosis and Cancer Vocabulary
Across
Down
1. Chromosome pairs are pulled apart and each
chromosome moves to opposite ends of the cell
3. Chromosomes line up in the middle of the cell
5. Two nuclei form at opposite ends of the cell and
the cell prepares to split apart
7. The cytoplasm of the cell splits in two; Two
identical cells are formed
2. 1st stage of cell division; chromosomes condense
and nucleus dissolves
3. Asexual reproduction; one cell makes two
identical copies of itself
4. Out of control cell division
5. A mass of rapidly dividing cancer cells
6. The life of a cell; the two parts are interphase and
mitosis
8. The longest part of a cells life, where it performs
its normal cell duties
Meiosis and Chromosomes
Mitosis is asexual reproduction – cells copying themselves without sex. However, nearly all
multicellular organisms reproduce (using, lay, verse) sexual reproduction, which (involves, travels, cries)
meiosis and the fusion of an egg (old, and, direction) a sperm. Like almost every cell (office, flat, in) your
body, this new cell—a zygote—has (quickly, yourselves, a) full set of 46 chromosomes. But what (purpose,
about, mountain) its parent cells, the sperm and (heat, blonde, egg)? If the egg and sperm each (camera,
relieved, had) 46 chromosomes, their union would result in (careful, observe, a) zygote with 92
chromosomes—double the usual number! (drawer, train, Theoretically), this cell would then grow
into (obedient, present, a) person with 92 chromosomes per cell (rather (damaged, war, than) the usual 46).
Subsequent generations would have (defeated, even, recklessly) more chromosomes per cell. Given
the (comparison, length, attempt) of human history, can you imagine (intend, instruct, how) many
chromosomes our cells would have (head, by, stomach) now? Clearly, this is not what (breezy, actually,
damaged) happens. Even early cell biologists realized (father, that, proud) there must be a way to (verse,
yourself, cut) in half the number of chromosomes (daily, in, successfully) egg and sperm cells.
To accomplish (house, gold, that) task, nature devised a special kind (selfishly, finger, of) cell division
called meiosis. In preparation (gold, scratchy, for) meiosis, the chromosomes are copied once, (month, just,
elated) as for mitosis, but instead of (during, uneven, one) cell division, there are two. The (snow, result,
garden) is four daughter cells, each containing 23 (friendly, individual, well) chromosomes rather than 46
chromosomes. Meiosis makes (sperm, condemned, ornament) and egg cells, which are also (tame, boil,
called) gametes or sex cells. These cells (rode, given, are) used ONLY for sexual reproduction.
These (substance, mourn, cells) are called haploid, because they contain (half, relax, ring) of the DNA
needed to create (after, a, dare) while organism
Meiosis is divided into (large, clean, chronological) phases just like mitosis, and although (the,
monkey, different) phases have the same names, there (someone, creepy, are) some differences between
them, especially in (impulse, the, gently) early stages. Also, since in (apples, meiosis, ocean) the cell divides
twice, each phase (is, herself, depressed) followed by a I or II, (spicy, indicating, learn) to which division it
belongs.
 Prophase I: (Flown, The, Sugar) matching chromosomes from your mother (fiercely, and, dead) father
pair up and form tetrads. (While, Frantically, Elephant) paired up, maternal and paternal
chromosomes (rung, bright, can) swap matching sections. This process, called (defeated, crossing,
thread) over, increases genetic diversity.
 Metaphase I: (rich, perfect, Tetrads) line up in the middle of (the, heat, modern) cell.
 Anaphase I: Tetrads separate, and (given, farm, pairs) of chromosomes move to opposite ends (evil,
laid, of) the cell.
 Telophase I: Two nuclei (reform, relax, did) at opposite ends of the cell; (the, brick, forward) cell
prepares to split apart.
 Cytokinesis: (morning, fought, The) cell separates into two separate cells. (Fallen, Repulsive,
Each) cell contain half as many chromosomes (as, horse, wall) the parent cell.
This first round (daily, circa, of) division produces two cells, but we’re (grass, nail, not) done yet!





Prophase II: The pairs (low, of, this) chromosomes again condense, and the nuclei (example, dissolve,
from).
Metaphase II: The pairs of chromosomes (these, off, line) up in the middle of the (attraction, root,
cells).
Anaphase II: Each pair of chromosomes (rinse, is, story) pulled apart, and individual chromosomes
move (alongside, infamous, to) opposite end of the cell.
Telophase: A (unusual, puzzled, nucleus) forms inside each cell (middle, boast, as) they prepare to
separate.
Cytokinesis: Each (cell, unlike, door) divides into two, forming a total (violently, behave, of) four
cells. None of these four (kind, faithfully, cells) is like the others; each is (chew, genetically,
eerie) unique. The final product is four (muddy, unique, bridge) haploid (half the number of
chromosomes) (invent, ouch, cells).
Fertilization is when two sex cells – (hid, an, music) egg and a sperm – come together. (I, Eaten,
Because)each of these is haploid (half (the, flat, lucky) number of chromosomes, or 23 chromosomes in (juicy,
coat, humans)), the fusion of the two create (flat, a, elegantly) cell with the correct total number – 23 + 23 =
46 (a, page, chromosomes). This cell is called a zygote, (safe, and, confuse) it is a diploid cell. Diploid (speak,
scorch, cells) have two copies of every chromosome – (sold, one, act) copy from mom and one copy (hover,
loss, from) dad. This first diploid cell will (design, divide, defiant) millions of time, through mitosis,
to (create, round, frowning) trillions of identical cells. These cells (across, create, pen) you! Your entire body
is made (cow, safely, of) hundreds of trillions of tiny, microscopic, (always, identical, mountain) cells. We are
truly marvelous beings!
(approve, consider, Men) use meiosis to produce sperm continuously (list, breezy, from) puberty
onward, and the formation of (a, for, tame) sperm takes about a week. The (solemnly, teach, situation) is quite
different in women. Baby (girls, silver, bad) are born with a certain number (of, between, mourn) "pre-egg"
cells that are stopped at (if, warmly, an) early stage of meiosis. In fact, (forgot, copy, the) pre-egg cell does not
complete meiosis (until, over, skin) after fertilization has occurred. Fertilization itself (triggers, large, see) the
culmination of the process. This (sadly, ignore, means) that meiosis in women typically takes (love, decades,
understand) and can take as long as 40 (busily, to, calculate) 50 years!
Use the underlined words from the reading to answer these vocabulary questions.
Meiosis and Chromosomes Vocabulary
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Clues:
1. A cell with half the normal number
of chromosomes (e.g. 23 in humans)
2. A cell with the correct number of
chromosomes; One copy from mom
and one copy from dad (e.g. 46 in
humans)
3. A haploid sex cell produced by
meiosis; an egg or sperm
4. The process where a cell divides
twice to produce four haploid cells
(four gametes)
5. When an egg and sperm fuse together
to create a new organism
6. The first diploid cell of a new
organism; produced by fertilization
7. Tiny individual packages of DNA
found in the nucleus. Human cells
have 46
8. Mitosis; Reproduction involving only
one parent. The offspring is identical
to the parent
9. Reproduction involving two parents
and meiosis. The offspring is a
unique mixture of each parent.
10. The number of times a cell divides
in meiosis