Unit 2 review Flashcards
What are the two reasons why cells have to divide?
For the cell to grow and repair.
Explain what DNA overload means
when the replication system has trouble keeping up with the demand for DNA replication
In a living cell, what part of the cell represents surface area and which part of the cell represents volume?
The call membrane and the cytoplasm
What are some adaptations that cells have developed that allow for a greater surface area volume ratio?
specialized structures that increase the amount of exchange surface available
Cell division occurs in two main stages. What are they?
Mitosis and interphase
What is the cell cycle?
series of events that take place in a cell that causes it to divide into two daughter cells (G1, S, G2) (P,M,A,T) (cytokinesis)
What are the 4 stages of the cell cycle?
G1, growth. S, DNA synthesis. G2, growth and preparation for mitosis. Mitosis, cell division.
What is the G0 stage?
Resting phase. Not dividing or preparing to divide. Cells enter this phase after they divide
Cells spend most of their lifetime in what stage?
Interphase
What are the four stages of mitosis, in order?
Prophase, metaphase, anaphase, telophase (PMAT)
Briefly describe what happens in each of the four stages of mitosis
Prophase: Chromatin condenses and coils, forming chromosomes. Nucleus disappears; the nuclear envelope breaks down. Centrioles separate and move to opposite sides of the cell. The chromosomes attach to newly formed spindle fibers. Metaphase: Chromosomes line up at the center of the cell. Each chromosome is connected to a spindle fiber at its centromere. The spindle fibers help chromosomes “move” in the next phase. Anaphase: The centromeres that join the chromatids split. Sister chromatids separate into individual chromosomes and are moved apart. Chromosomes move to opposite ends of the cell. This stage ends when chromosomes stop moving. Telophase: Chromosomes move to opposite ends of the cell and start to uncoil into chromatin again. Nuclear envelope reforms around the chromatin. Spindle fingers disappear. Nucleolus becomes visible in the daughter cell.
Briefly explain how six feet of DNA is packed into the nucleus of every cell of our body!
DNA is tightly packed within the nucleus through a hierarchical structure. DNA wraps around histone proteins to form nucleosomes, which are the basic repeating units. Nucleosomes, made up of eight histone proteins and DNA, create a “bead-on-a-string” structure called chromatin. Chromatin can exist in loosely coiled form during normal cellular activities, but when cells divide, it undergoes further condensation, becoming supercoiled to fit into the confined space of the nucleus. This intricate packaging ensures the six feet of DNA in each cell is efficiently organized and accommodated.
How many chromosomes are found in human body cells?
46
How many chromosomes are found in human sex cells (egg and sperm)?
23
What is the name of the proteins that regulate the cell cycle
Cyclins
