Chapter 10 Bio

How many chromosomes do humans have?

46 chromosomes in 23 nearly identical pairs....additional or missing chromosomes are usually fatal.

Cytokinesis

-Cleavage of the cell into equal halves -Animal cells-constriction of actin filaments produces a cleavage furrow. -Plant cells: Cell plate forms between the nuclei -Fungi and some protists: nuclear membrane does not dissolve; mitosis occurs within the nucleus; division of the nucleus occurs with cytokinesis.

Chromosome

-Composed of chromatin: complex of DNA and protein -DNA of a single chromosome is one long continuous double-stranded fiber -Length of DNA from one human cell would be about 2m long.

Euchromatin

-Expressed -Loosened, DNA needs to be used

Interphase

-G1, S, and G2 phases -DNA has been replicated -Centrioles replicate -Cell prepares for division

Prophase

-Individual condensed chromosomes first become visible with the light microscope, condensing continues throughout prophase. -Spindle apparatus assembles: 2 centrioles move to opposite poles forming spindle apparatus (no centrioles in plants). -Asters-radial array of microtubules in animals (not plants) -Nuclear envelope breaks down

Rb protein

-Mutated in 40% of all cancers

P53 protein

-Mutated in 50% of all cancers

Heterochromatin

-Not Expressed -Wound up, don't need all of DNA

Solenoids

-Nucleosomes wrapped into higher order coils. -Leads to a fiber 30 nm in diameter. -Usual state of non dividing (interphase) chromatin -During mitosis, chromatin in solenoid arranged scaffold of protein to achieve maximum compaction. Radial looping aided by condensing proteins.

G2 (Gap phase 2)

-Organelles replicate, microtubules organize (Part of interphase).

Karyotype

-Particular array of chromosomes in an individual organism -Arranged according to size, straining properties, location of centromere, etc.

G1

-Primary growth phase, longest phase (part of Interphase)

Eukaryotic Replication

-Prior to replication, each chromosome composed of a single DNA molecule. -After replication, each chromosome composed of 2 identical DNA molecules and held together by cohesion proteins

Septation

-Production of septum separates cell's other components -Begins with formation of ring of FtsZ proteins -Accumulation of other proteins follow -Structure contracts radially to pinch cell into two -FtsZ protein found in most prokaryotes

Effects of mutations

-Protein over expressed, cell cycle overstimulated -Increases cell division -Protein absent, cell cycle not inhibited

S (synthesis)

-Replication of DNA (part of interphase)

Cytokinesis

-Separation of 2 new cells.

Bacterial replication

-Single, circular bacterial chromosome is replicated -Replication begins at the origin of replication and proceeds in 2 directions to site of termination -New chromosomes are partitioned to opposite ends of the cell. -Septum forms to divide the cell into 2 cells.

Telophase

-Spindle apparatus disassembles -Nuclear envelope forms around each set of sister chromatids, now called chromosomes. -Chromosomes begin to uncoil -Nucleolus reappears in each new nucleus.

M (Mitosis)

-Subdivided into 5 phases: PPMAT -prophase, prometaphase, metaphase, anaphase, telophase.

Nucleosome

-The combination of DNA and histone proteins -Promote and guide coiling of DNA

How do mutations in tumor-suppressor genes lead to cancer?

-The protein product of tumor-suppressor genes normally inhibit the cell cycle. A mutation of this would allow uncontrolled growth.

Prometaphase

-Transition occurs after disassembly of nuclear envelope -Microtubule attachment: 2nd group grows from poles and attaches to kinetochores. Each sister chromatid connected to opposite poles. -Chromosome begin to move to center of cell, congress ion....Assembly and disassembly of microtubules, motor proteins at kinetochores.

When do the chromosomes start to become visible?

-Visible as 2 strands held together as chromosomes becomes more condensed. -One chromosome composed of 2 sister chromatids

Haploid

1 set of chromosomes -23 in humans

What are the two irreversible points which the cell cycle has?

1) Replication of genetic material 2) Separation of the sister chromatids

Put the events of mitosis in order

1) Sister chromatids condense 2) The nuclear membrane breaks up 3) Sister chromatids align on the metaphase plate 4) Sister chromatids separate 5) The cleavage furrow forms

Cancer growth

1. A single tumor grows from a single cancer cell -Transformation and formation of a benign tumor 2. Cancer cells invade neighboring tissue -Malignant tumor 3. Cancer cells spread through lymph and blood vessels to other parts of the body. -Metastasis 4. A small percentage of dancer cells may survive and establish a new tumor in another part of the body.

How many nucleotides is the typical human chromosome?

140 million nucleotides

Diploid

2 complete sets of chromosomes, 46 total chromosomes -Humans are diploid

In which phases are cyclins synthesized?

In S through G2 phase of interphase

What does the anti-cancer drug Danorubicin do?

It binds and opens DNA structures, disallowing replication.

What happens to the cyclin component of MPF during anaphase?

It is degraded, terminating M-phase. The cell enters G1 phase.

The proteins to which the mitotic spindle attaches on a chromosome are

Kinetochores

In which stage of the cell cycle does the cell contain chromosomes consisting of 2 chromatids joined by a centromere?

Metaphase

What types of cells stay indefinitely in the G0 phase?

Nerve and muscle cells

Proto-oncogenes

Normal versions of cellular genes that promote cell growth and division, i.e. the cell cycle, when they receive the appropriate signals to do so. -These proto-oncogenes can be converted into oncogenes

Homologous

Pair of chromosomes, each one is a homologue

Centromere

Point of constriction

Histones

Positively charged and strongly attracted to negatively charged phosphate groups of DNA.

Oncogenes

Promote growth and cell division even when they don't receive a go-ahead signal. Ex: The protein Ras

Stages of mitosis in order

Prophase, metaphase, anaphase, telophase, interphase

The order in which the stages of mitosis proceed is

Prophase, metaphase, anaphase, telophase, interphase

A protein encoded by a tumor-supressor gene normally acts to

Restrict cell division

A cell that contains eight chromosomes and is undergoing mitosis will produce ______ daughter cels; each daughter cell will contain _______ chromosomes

Two; eight

The proteins to which the mitotic spindle attaches on a chromosome are what?

kinetochores

Haploid (n)

-1 set of chromosomes -23 in humans

Diploid (2n)

-2 complete sets of chromosomes -46 total chromosomes

Src kinase

-Activated by mutations in 2-5% of all cancers

Ras protein

-Activated by mutations in 20-30% of all cancers

Metaphase

-Alignment of chromosomes along metaphase plate -Not an actual structure -Future axis of cell division

Kinetochore

-Attachment site for microtubules -Each sister chromatid has a centromere -Chromatids stay attache at centromere by cohesion.

Anaphase

-Begins when centromeres split -Key event is removal of cohesion proteins from all chromosomes -Sister chromatids pulled to opposite poles -2 forms of movements: Anaphase A-kinetochores pulled toward poles Anaphase B-poles move apart

G1/S checkpoint

-Cell "decides" to divide Nutrition, size ok -Primary point for external signal influence -Specific growth factors such as PDGF -Density-dependent inhibition: cells stop dividing if too crowded -Anchorage dependence: cells must be attached to a substratum (floor) in order to divide.

Late metaphase (spindle) checkpoint

-Cell ensures that all chromosomes are attached to the spindle

G2/M checkpoint

-Cell makes a commitment to mitosis -Assesses success of DNA replication

How do bacteria divide?

Binary fission -No sexual life cycle -Reproduction is clonal

How does MPF promote mitoses?

By phosphorylating various proteins. MPF activity peaks during metaphase.

How does cytokinesis in plant cells occur?

By the formation of a cell plate. -During telophase, vesicles move along microtubules in the middle of the cell and then fuse to form the cell plate, which continues to extend until each daughter cell has its own plasma membrane.

The structure that organizes the protein subunits of mitotic spindle is the?

Centromere

What is the structure that organizes the protein subunits of the mitotic spindle?

Centrosome

How is MPF produced

Cyclins combine with Cdk's. This allows the cell to pass the G2 checkpoint.

If microtubules are prevented from polymerizing, what affect might it have on dividing cells?

Sister chromatids will not be properly separated into separate daughter cells

Replicate copies of each chromosome are called _________ and are joined at the __________.

Sister chromatids; centromere

In a karyotype, chromosomes are arranged according to what?

Size, staining properties, location of centromere, length of arm

Proto-oncogenes create proteins that?

Stimulate cell division