Bio 1113 Exam 3

what are reasons cells divide?

reproduction, growth, tissue renewal, maintain SA:V ratio

types of cellular division

asexual and sexual

types of of asexual reproduction

mitosis and binary fission

types of sexual reproduction

meiosis

How many base pairs?

3 billion base pairs

how much dna is genes (stuff that is acted upon)?

2%

genome

the DNA of a cell

genome of prokaryotes (bacteria) is packed into

a singular circular chromosome

how is the genome of eukaryotes organized?

into linear chromosomes and often two copies of each chromosome (homologous chromosomes)

chromatin

long strand of DNA wrapped around proteins (histones)

how does chromatin become chromosomes?

chromatin coils and condenses so two chromosomes are equally divided

what does the structure of a chromosome include?

centromere, telomere, kinetochore

centromere

condensed region of the chromosome (center where sister chromatids are held together)

telomere

region of repetitive DNA sequences at the end of the chromosome

does the centromere contain a lot of protein coding genes?

no

T/F: every time DNA is replicated, telomeres get shorter

true

what is different about the telomeres in cancer?

cancer cells have the ability to reactivate telomerase so their telomeres don’t shorten and they can divide indefinitely while maintaining telomere length

kinetochore

disc-shaped protein that spindle fibers attach to

chromosomes are duplicated before division which result in

sister chromatids

what is pulled apart during mitosis?

sister chromatids

how does bacterial cell division work?

1. dna is copied and protein filaments attach
2. dna copies are separated; ring of protein forms
3. ring of protein draws in membrane
4. fission complete :)

which two major phases make up the eukaryotic cell cycle?

interphase and mitosis

components of interphase

G1, S, G2, and G0

gap 1 (G1)

growth, protein synthesis, organelle synthesis \*\*entire cell is doubling and growing except dna

synthesis (S)

DNA is duplicated

gap 2 (G2)

growth, synthesis of microtubules, cell cycle checkpoints

G0 “resting state”

cells not preparing to divide but are metabolically active

once cells replicate dna, does the chromosome number double?

no, the chromosome number does not double but the number of chromatids doubles

how much time do cells spend in interphase?

90%

what is the goal of mitosis?

nuclear division

what comes after mitosis?

cytokinesis

the goal of cytokinesis

division of organelles and cytoplasm

product of mitosis

2 identical daughter cells (all diploids)

5 phases of mitosis

prophase, pro metaphase, metaphase, anaphase, telophase

prophase

* chromosomes begin to condense’
* spindle apparatus begins to form (located in the cytoplasm)

what is the spindle apparatus?

the “machine” responsible for pulling apart the chromatids

what is the spindle apparatus composed of?

microtubules and proteins

prometaphase

* **nuclear envelope disassembles**
* spindle fibers attach to kinetochores

why is it important that the nuclear envelope disassembles?

so that the microtubules that are in the cytoplasm can reach to and connect to the kinetochores of the chromosomes located in the nucleus

metaphase

chromosomes **align** along the metaphase plate, “tug of war” between two poles through the attached microbes

anaphase

the cohesin holding sister chromatids together is cut by enzymes which allows for the chromatids to be pulled to the opposite poles

what does the cell look like during anaphase?

cell takes on an ovular shape due to microtubules pressing against opposite edges

why are cut sister chromatids pulled to opposite poles of the cell?

because the microtubules start shortening which results in the pulling motion

telophase

reversal of prophase events

what does the cell look like in telophase?

the cleavage furrow is created, nuclear envelope and nucleolus is reforming

why is cytokinesis not a part of mitosis

because of the goal of mitosis and cytokinesis are different

difference between animals and plants for cytokinesis

* for animals, cleavage furrow pinches off separated nuclei


* for plants, new cell wall formed and Golgi-derived vesicles bring materials to middle - fuse to form cell plate

t/f: tight regulation is crucial for normal growth and development

true

what are the 2 main regulatory molecules of the cell cycle?

cyclins and cyclin-dependent kinases (cdks)

when are cdks present? when are cdks activated?

cdks are present at constant concentrations but they become activated by attaching to cyclins

when is MPF present in high concentrations

right after the G2 checkpoint

what are the targets of mpf?

condensins and lamins

how many checkpoints are there and what are they?

g1, g2, and m phase

when does g1 checkpoint occur?

after g1 phase

what does the g1 checkpoint check?

is the cell big enough? are conditions favorable? is there any DNA damage?

what happens if a cell doesn’t pass the G1 checkpoint?

the cell exits cell cycle, enters G0

how do growth factors impact the cell cycle?

the ras pathway:

* Rb is bound to genes that are needed for s phase so they aren’t transcribed
* a growth factor signals the ras pathway which initiates the binding of cyclin and cdk
* Rb protein is phosphorylated and unbinds to the E2F gene
* this allows for gene transcription and mrna translation of enzymes and other proteins required for s phase

in dividing cells, when does most of the cell growth occur?

interphase

what are the two opposite controlling center during mitosis?

centrosomes

what also must form after DNA replicates in G2?

the centrosomes must duplicates

is the condensation of chromosomes related to sister chromatids?

no it is not

what is the difference between nonkinetochore and kinetochores?

kinetochores attach to the chromatids and shorten during anaphase while nonkinetochores push past each other and lengthen in order to elongate the cell

what is the significance of cohesin compared to kinetochores?

cohesin simply separates (cuts apart) the sister chromatids while kinetochores pull the split chromatids to opposite poles

t/f: a chromatid contains a single molecule of double stranded dna

true

what is cancer?

uncontrolled cell proliferation (growth)

what causes cancer?

damages (mutations) to DNA and viruses (small percentage)

what are the mutations caused by?

errors during replication and mitosis OR carcinogens

what cancer does HPV cause?

cervical cancer

what cancer does mono/epstein Barr virus cause?

lymphoma

herpes and an impaired immune system causes

cancer

tumor

a mass of cells (an overgrowth)

benign tumor

confined locally (has not spread yet)

malignant tumor

invades surrounding tissues, spreads to other tissues, and comes back

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metastasis

spread of cancer cells

so which tumor means cancer?

malignant

on average how many mutations does it take to get cancer

varies, but 5-7

t/f: incidence of cancer increases with age

true bc you have had more time to accumulate mutations

what are the 2 types of genes most often associated with cancer?

oncogenes and tumor suppressors

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oncogenes

gas pedal, accelerate cell division

tumor suppressor genes

brake, slow down cell division

proto-oncogene

gene that when mutated or over expressed can contribute to turning a normal cell into a cancer cell

what are the 3 types of activation of proto-oncogenes into oncogenes

mutation which changes protein structure, increase in protein concentration, chromosomal translocation

what type of genes are typically proto-oncogenes?

genes involved in growth and differentiation: growth factors, RTKs, GTPases, transcription factors

start at tumor suppressors.