Cellular Reproduction Flashcards
Describe the process of binary fission in prokaryotes
-circular DNA is replicated
-reproduction is clonal
-new chromosomes partitioned to opposite parts of the cell
-origin of replication and proceeds in two directions to site of termination
-septum forms to divide the cell into two cells
Describe how the cell cycle is controlled by both positive and negative mechanisms.
Positive:
Cyclins interact with Cdks and function to push through the checkpoints and allow cell cycle to succeed. (Were they inhibited, cell would not progress through cell cycle.)
Negative:
Protein p53 (tumor suppressor gene) halts cell cycle, can program cell death. Rb
Distinguish between chromosome forms, homologous pairs and sister and non-sister chromatids
Sister chromatids:
-Dyad chromosomes consist of 2 sister chromatids.
-The kinetochore is a protein complex that attaches to the centromeres of the sister chromatids.
-They stay attached through the protein cohesin.
Non-sister chromatids:
-Two chromatids from two different homologous chromosomes
Describe the structure of prokaryotic and eukaryotic genomes
Genome: A cell’s genetic information encoded in DNA as one or more double-stranded molecules.
A genome can consist of a single DNA molecule (common in prokaryotic cells) or multiple DNA molecules (common in eukaryotic cells)
Describe the structures that underlie the various levels of chromosome compaction
-Each chromosome consists of DNA tightly coiled by proteins called histones.
-This DNA histone complex is called a nucleosome and is connected by linker DNA.
-Nucleosomes are coiled into a chromatin fiber that is uncondensed during interphase.
Describe the eukaryotic cell cycle
Interphase (G1, S, G2)
M (mitosis)
C (cytokinesis)
When it exits the cell cycle, it is considered to be in G0.
Describe the three phases and key events of interphase
G1 (gap phase 1):
-primary growth phase
-longest phase
S (synthesis):
-replication of DNA
-centrosome is duplicated
G2 (gap phase 2):
-organelles replicate
-microtubules organize
Explain how the cytoplasmic content is divided during cytokinesis
Cytoplasmic contents divide by using the cleavage furrow with the pinching method,
pinches inward along the cell’s equator until two daughter cells form. In plant cells, a cell
plate forms along the equator of the parent cell, then a new plasma membrane and cell
wall form along each side of the cell plate.
Distinguish the role of checkpoints in the control of the cell cycle
G1/S checkpoint:
-cell “decides” to divide
-primarily influenced by internal and external signals
G2/M checkpoint:
-cell makes a commitment to mitosis
-assesses success of DNA replication
Late metaphase (spindle) checkpoint:
-cell ensures that all chromosomes are attached to the spindle
Explain how the three internal control checkpoints occur at the end of G1, at the G2/M
transition, and during metaphase
G1/S checkpoint:
-cell “decides” to divide
-primarily influenced by internal and external signals
G2/M checkpoint:
-cell makes a commitment to mitosis
-assesses success of DNA replication
Late metaphase (spindle) checkpoint:
-cell ensures that all chromosomes are attached to the spindle
Prophase
-chromosomes condense and become visible
-centrioles move to opposite poles to form spindle fibers
-nuclear envelope breaks down
-nucleolus disappears
Prometaphase
-chromosomes continue to condense
-kinetochores appear at the centromeres
-mitotic spindle microtubules attach to kinetochores
Metaphase
-mitotic spindle is fully developed
-chromosomes are lined up at the metaphase plate
-each sister chromatid is attached to a spindle fiber originating from opposite poles
Anaphase
-key event is cohesin proteins binding the sister chromatids together break down
-sister chromatids are pulled towards opposite poles
-non-kinetochore spindle fibers lengthen, elongating the cell
Telophase
-spindle apparatus disassembles
-nuclear envelope forms around each set of monad chromosomes
-chromosomes begin to uncoil
-nucleolus reappears in each nucleus
-golgi and ER reform
