Chapter 12 Flashcards
how do unicellular organisms reproduce?
the division of one cell reproduces the entire organism
what is the cell cycle?
the life of a cell from formation to its own division
what does cell division result in?
most cell division results in daughter cells with identical genetic information or DNA
what is an exception in cell division?
meiosis: a special type of division that can produce sperm and cell eggs; the daughter cells are not genetically identical
what is a genome?
all the DNA in a cell constitutes the cell’s genome; can consist of a single DNA molecule (prokaryotic) or a number of DNA molecules (eukaryotic)
what is chromatin? what consists of chromatin?
eukaryotic chromosomes consist of chromatin
- chromatin is a complex of DNA and protein that condenses during cell division
what are somatic cells:
somatic cells are non-reproductive cells that have two sets of chromosomes
what are gametes?
gametes are reproductive cells (sperm and eggs) that have half as many chromosomes as somatic cells
what happens in preparation for cell division?
Dna is replicated and chromosomes condense, each duplicated chromosome has sister chromatids (joined copies of the original chromosome), and the centromere is the waist where two chromatids are most closely attached
what happens to sister chromatids during cell division?
the two sister chromatids of each duplicated chromosome separate and move into two nuclei, once separate they are called chromosomes
what does eukaryotic cell division consist of?
mitosis: the division of the genetic material in the nucleus
cytokinesis: the division of the cytoplasm
how are gametes produced?
gametes are produced by a variation of cell division called meiosis
what does meiosis yield?
meiosis yields nonidentical daughter cells that have half as many chromosomes as the parent cell
what are the phases of the cell cycle?
- the mitotic (M) phases: mitosis and cytokinesis
- interphase: cell growth and copying of chromosomes in preparation for cell division
how can interphase be divided into subphases?
- G1 phase (first gap)
- S phase (synthesis); cells are duplicated only in this phase
- G2 phase (second gap)
where are chromosomes duplicated?
in the S phase
what happens during different phases of mitosis?
prophase: chromosomes shorten and thicken
metaphase: chromosomes line up in center of cell
anaphase: chromatids break up and move to opposite poles
telophase: two nuclei formed after nuclear envelopes reform around each group of chromosomes
what is the mitotic spindle?
a structure made of microtubules that controls chromosome movement during mitosis
what happens during interphase?
the centrosome replicates, forming 2 centrosomes that migrate to opposite ends of cell in prophase
what is an aster?
a radial array of short microtubules that extend from each centrosome
what are kinetochores?
protein complexes associated with centromeres
where do chromosome line up at metaphase?
at the metaphase plate, a plane midway between the spindle’s two poles
what happens in anaphase?
cohesins are cleaved by an enzyme called separase; sister chromatids separate and move toward opposite ends of cells
what happens in telophase?
identical daughter nuclei form at opposite ends of cells
when does cytokinesis begin?
during anaphase or telophase and the spindle eventually dissasembles
how does cytokinesis occur in animal cells?
cytokinesis occurs in animal cells by a process known as cleavage, forming a cleavage furrow
how does cytokinesis occur in plant cells?
a cell plate forms during cytokinesis
What is binary fission?
prokaryotes reproduce by a type of cell division called binary fission
what happens in binary fission?
chromosome replicates (begins at origin of replication), and daughter chromosomes actively move apart, the plasma membrane pinches inward and divides the cell into two
Which 2 regulatory proteins are involved in cell cycle control?
Cyclins and Cyclin-dependent kinases (Cdks)
what is MPF?
maturation-promoting factor: is a cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase
what checkpoint seems to be the most important?
the G1 checkpoint, if it receives a go-ahead signal it goes to complete S, G2, and M; if it does not receive go ahead, it exits cell and switches to G0 phase
