Lecture--Chapter 2 Flashcards
Most of the time, a cell is in the __ or __ phase:
G1 or G2
G1 phase:
growth
G2 phase:
metabolism
The proportion of time that a cell spends in mitosis is:
1/10 of the typical cell cycle time
What is interphase?
The portion of the cell cycle that occurs between division events.
What are the 4 stages of mitosis?
- prophase
- metaphase
- anaphase
- telophase
What happens during prophase?
The nuclear membrane dissolves and the DNA condenses from loose coils into tight coils with identical chromatids joined at the centromere.
What is a chromatid?
One of the two identical copies of DNA making up a duplicated chromosome.
What happens during metaphase?
The chromosomes attach at their centromeres to the microtubules of the mitotic spindle and are positioned mid-planar within the cell.
What is the mitotic spindle?
A network of protein filaments that are attached at opposite poles of the cell, which moves and positions chromatids.
What is the centromere?
The region of DNA that occurs typically near the middle of a chromosome where two identical sister chromatids come closest in contact.
What happens during anaphase?
The sister chromatids are separated and moved to the opposite poles of the cell.
What happens during telophase?
The nuclear envelope reforms, the chromatin reappears in the nucleoli as the DNA uncoils and it compacted with histones and other proteins.
What happens after telophase?
cytokinesis
Magnification:
refers to the apparent increase in object size. The maximum magnification is reached when the finest detail an instrument can resolve with the given objectives matches the finest detail the eye can see.
Further enlargement of magnification beyond the limit of the finest detail the eye can see is:
empty magnification–results in a cloudy image
Define resolution:
the ability to distinguish objects that are close together–related to viewing distance, but it depends ultimately on the wavelength of light used for imaging and the numerical aperture of the lens.
numerical aperture of the lens:
the ability of the lens to gather light
Define contrast:
helps determine resolution by providing different optical intensities of the sample relative to its background
Define refraction:
light bending as it passes through glass
With a lens that has a shorter focal length:
the optical power is greater
Magnification depends on:
focal length and the distance from an objective to the eye piece (tube length).
