Cell Reproduction - Biology

what does cell division increase the number of?

somatic cells

what are somatic cells

cells in the body other than sperm/eggs

what is a zygote

one cell

what is mitosis

division of the nucleus

what is cytokinesis

division of cytoplasm

what is apoptosis

programmed cell death to get rid of faulty cells

what is the cell cycle

orderly set of stages that occur between the time a cell divides and the time the resulting daughter cells divide

what are daughter cells?

genetically identical celsl formed when a cell undergoes division by mitosis

what is interphase

when the cell is not being divided/daily work

what are the phases of interphase

G1, S, G2

what is the mitotic stage

mitosis and cytokinesis

what is growth 1 phase/gap 1?

when the cell is quickly growing and carrying out metabolic activity

what is synthesis phase?

DNA replication; when the cell copies its DNA exactly so there is 2 identical copies

what are sister chromatids

the identical copies formed by DNA replication

what is growth 2 phase

when the cell rebuilds its energy reserves and preparing for division by manufacturing necessary molecules

what cells do not complete the cell cycle?

muscle and nerve cells

why are muscle and nerve cells not completed by the cell cycle?

because they are not able to divide due to a lack of centrioles; they are permanently arrested in interphase and said to enter G0 phase

what is chromatin

tangled mass of threadlike DNA in a non-dividing cell

what are chromosomes

condensed DNA molecules observed in dividing cell

what is a diploid (2n)

cells have a pair (2) of each type of chromosome

what is a haploid (1n)

cells have half the diploid number of chromosomes

what is a duplicated chromosome

chromosome that contains two sister chromatids joined at a centromere (two sister chromatids are identical)

how much chromosomes does a normal human receive from their parents

23 from mother
23 from father

what are homologous (pairs that look the same) chromosomes called

autosomes (22 pairs)

what is the 23rd pair of chromosomes

sex chromosme

what are the chromosomes of a female

XX

what are the chromosomes of a male

XY

what do homologous pairs contain?

the same genes, the same length, the same centromere location, and bonding pattern

what is karyotyping

a visual display of an individual's chromosomes

what is a gene

an area of dna that carries specific genetic information for a certain trait

what are diploid cells

cells that have homologous pairs of chromosomes (all human somatic cells)

what are haploid cells

cells that only have half the diploid number of chromosomes; one chromosome per pair

what is the haploid number of a species

n

what is the diploid number of a species

2n

what is the haploid and diploid number for humans

n = 23, 2n = 46

what is polyploid

when organisms have more than 2 sets of homologous chromosomes

what does cell division start and end with

starts with mitosis (the division of the contents of the nucleus into two identical and complete sets) and finishes with cytokinesis (the division of the cytoplasm and organelles into 2 separate cells)

what do body's cells have to do?

growth, maintenance, and repair of body cells/tissues

what is prophase

getting the cell ready to divide

what happens to chromatin in prophase?

condenses to chromosomes

what occurs to the nuclear membrane and nucleolus during prophase?

nuclear membrane: breaks down
nucleolus: disappears

what occurs to centrioles in prophase?

may move to opposite poles of the cell and may lay down a network of fibers called spindle apparatus (made of microtubules) which attach to centromeres

what are microtubules

fibers that compose the mitotic spindle

what is metaphase

the stage where chromosomes become attached to the spindle fibers

what occurs to the spindle apparatus in metaphase?

guides chromosomes to the equator or midline of the cell so that chromosomes are lined up with one sister chromatid facing one pole and the other facing the other

where is the spindle fiber attached in metaphase

attached to each side of the centromere

what is anaphase

the stage where chromosomes move away from one another to opposite poles of the spindle

how does anaphase start

when centromeres split

what occurs to sister chromatids in anaphase

they separate and each are now called its own chromosome

what occurs to the spindle fibers in anaphase

shorten, pulling chromosomes to opposite poles of the cell

what occurs to other spindle fibers in anaphase

they lengthen, forcing poles apart

what is telophase

the stage where the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed

how does telophase start

when chromosomes reach opposite poles of the cell

what occurs to the chromosomes in telophase

begin to unwind to chromatin

what occurs to the nuclear membrane in telophase

forms around each nucleus, causing a nucleolus to appear

what is cytokinesis not apart of

mitosis but a part of cell division

how does the cytoplasm in animals divide?

by the formation of a cleavage furrow

what is a cleavage furrow

when cell membrane pinches inward with contractile ring to separate daughter cells

what phase of interphase does separate identical daughter cells enter?

G1

what does and doesn't form in plant cell division?

does: spindle apparatus
doesn't: centrioles

what forms between the two daughter cells in plant cell division

a cell plate that signals the location of the new cell membrane and cell wall in cytokinesis

what is the function of the cell plate

divides the cytoplasm instead of a cleavage furrow as cell walls are too rigid to furrow

what appears in cytokinesis in plant cells

flattened, small disk appears between daughter cells

what does the golgi apparatus do in plant cells during cytokinesis

produces vesicles which move to disk

what occurs to molecules in ck in plant cells

released to build new cell walls

what membrane completes another membrane?

vesicle membranes complete plasma membrane

what is binary fission

asexual reproduction by a separation of the body into two new bodies

how much chromosomes do prokaryotes have

a single chromosome

when does chromosomal replication occur

before division

what occurs to the cell in cell division of prokaryotes?

elongate to twice its length

what does the cell membrane do until division is complete

grows inward

what is cancer

uncontrolled, rapid cell division produces masses of non-functional cells called tumours

what should the cell cycle be regulated by

specific signals; internal and external

what are cyclins

signaling proteins that increase and decrease as the cell cycle continues and must be present to proceed from G2 to M and G1 to S

what are the 3 checkpoints?

g1, g2, metaphase

what is the g1 checkpoint

when the cell cycle stops before S if DNA is damaged - repair is attempted otherwise apoptosis

what is the g2 checkpoint

when the cell cycle stops before M if DNA has not finished replicating or is damaged and needs to be repaired

what is m checkpoint

when mitosis stops if chromosomes are not properly aligned to proceed to daughter cells

why do cells undergo apoptosis

when they cannot complete mitosis or respond to external signals

what occurs to cells in apoptosis

rounds up and loses contact with neighbours. nucleus fragments, membrane blisters, cell fragments and pieces engulfed by white blood cells

what are capases

enzymes that bring about apoptosis and are routinely kept in cells

what are capases checked in check by

inhibitors until unleashed by internal/external signals

what are initiators

things that receive signals and activate executioners

what are executioners

turn on enzymes and dismantle the cell

what is meiosis

process that occurs in the life cycle of sexually producing organism

what does meiosis do to chromosomes

reduces the chromosome number

what does meiosis provide to offspring?

a different combination of traits from that of either parent

how is meiosis a special form of cell division

a diploid cell divides to produce 4 haploid cells instead of 2 diploid daughter cells

why does meiosis occur in humans

to produce haploid gametes that recombine in fertilization to accomplish sexual reproduction

what are the two meiosis outcomes

reduction division and recombination

what is reduction division

when daughter cells have fewer chromosomes than parent cells

what is recombination

when daughter cells have different combination of genes compared to each other and parent cells

what are the phases of meiosis

two rounds of PMAT phases: meiosis I and meiosis II

which germ cells undergo meiosis to produce haploid gametes

diploid germ cells

what duplicates during interphase and why?

DNA duplicates during interphase so the germ cell has 2n times 2 of the amount of DNA (each chromosome is made of two identical chromatids like in mitosis)

what occurs to homologous chromosomes in prophase I?

(similar to the events of prophase)
when homologous chromosomes align side to side by synapsis

what are 4 chromatids called?

tetrad

what occurs to spindle fibers in metaphase I?

spindle fibers from opposite ends attaches to each homologue's centromere, guiding the tetrad to the equator of the cell

what is independent assortment?

maternal or paternal member could be aligned facing either pole of the cell

what occurs to spindles in anaphase I?

as they shorten, maternal and paternal homologous chromosomes are pulled to opposite poles of the cell (disjunction - separation)