BIOS 110: Exam III

Prophase

Prophase

The first stage of mitosis/meiosis, nuclear envelope breaks down and chromosomes are visible under a microscope

Metaphase

The second stage of mitosis/meiosis, chromosomes are at opposite poles and aligned

Anaphase

The third stage of mitosis/meiosis, chromosomes are pulled apart by spindle fibers

Telophase

The last stage of mitosis/meiosis, nuclear membrane forms around each set of chromosomes to create 2 (mitosis) or 4 (meiosis) daughter cells

Mitosis

Cell division that creates 2 identical daughter cells, happens asexually

Meiosis

Cell division that creates 4 genetically unique daughter cells, happens sexually

Crossing over

Occurs in prophase I, interchange of sections between homologous chromosomes (only in meiosis)

Independent assortment

Randomization of chromosome location that creates genetic diversity, 2n = number of possibilities

Non disjunction

Failure of chromosomes to separate during anaphase I or II which creates unequal daughter cells, most likely occurs in women over 40

G0 Phase

"Holding state" for cells who are do not need to divide

G1 Checkpoint

Checkpoint in which the cell determines if it is able to divide based on undamaged DNA and adequate cell size

G2 Checkpoint

Checkpoint to see if cells have replicated their DNA successfully

Metaphase checkpoint

Checkpoint to see if a cell's DNA is attached to spindle fibers

Proto-oncogene

A gene that encourages cell growth

Tumor suppressor gene

A gene that blocks unscheduled or unneeded cell division

Anchorage dependence

Requirement that a cell needs to be attached to something in order to replicate (cancer cells lack this)

p53

A gene that will cause cell death (apoptosis) due to damaged DNA

Diploid

A cell containing 2 complete sets of chromosomes

Haploid

A cell containing only 1 complete set of chromosomes

Social control

Cells divide in response from other cells

E2F

Proto-oncogene, binds to Rb and enters nucleus to encourage cell division in the S phase

Rb

Tumor suppressor gene, "bouncer" for E2F that ensures it is a proto-oncogene and can enter the nucleus

Diversity dependent inhibition

Once a layer of cells have divided enough to fill a space, they will stop dividing

Contact inhibition

If a cell is touching another cell on all sides, it will not divide

Cyclins

Molecule whose concentration varies during various stages of the cell cycle

MPF

Promotes mitosis and degradation of cyclins

Apoptosis

Cell death caused by activation of p53

Oncogene

Cell with unregulated cell growth and becomes a cancer cell

DNA base pairings

A-T / C-G

RNA base pairings

A-U / C-G

Leading strand

Synthesized 5' to 3'

Lagging strand

Synthesized 3' to 5'

Telomerase

Enzyme that adds telomeres to the 3' end of DNA, only in eukaryotes

Neutral mutation

Change in base pairings, but does not affect the protein

Missense mutation

Alters a codon for one amino acid that causes it to read as a different amino acid (for example, CUG --> CGU)

Nonsense mutation

Alters a codon for one amino acid that changes it into a stop codon

Frameshift mutation

Alters the reading frame of codons that causes a domino effect for all codons after it (for example, CUG --> CCUG)

tRNA

Contains an attachment site and anticodon that are complementary to the codon

P site

Site that carries the tRNA that holds the growing chain

A site

Site that carries the tRNA carrying the next amino acid to be added to the chain

E site

Site that ejects the discharged tRNAs

Initiation

Start of the protein synthesis process, occurs once

Elongation

Addition of amino acids to the chain, occurs more than once

Termination

Ends protein synthesis process due to release factors, occurs once