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103 Cards in this Set

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A unicellular organism with a relatively simple cell structure.
Prokaryote
Has a compartmentalized cell structure divided by intracellular membranes and may be unicellular or multicellular.
Eukaryote
This group includes Archaea and Eubacteria
Prokaryotes
___ may be evolutionarily closer to eukaryotes than to eubacteria.
Archaea
Has a nuclear envelope.
Eukaryote
Lacks a nuclear envelope
Prokaryote
In Eukaryotes, DNA is closely associated with a special class of proteins to form tightly packed chromosomes.
Histones
The complex of DNA and histone proteins.
Chromatin
___ limit the accessibility of enzymes and other proteins that copy DNA, but they enable to DNA to fit into the nucleus.
Histones
In addition to eukaryotes, ____ also have histones, but the makeup of their chromatin is much different than that of eukaryotes.
Archaea
Have membrane bound organelles.
Eukaryotes
Have no membrane bound organelles
Prokaryotes
Have a cytoskeleton
Eukaryotes
Lack cytoskeleton
Prokaryotes
Place on a bacterial chromosome where replication initiates
Origin of replication
Two chromosomes which correspond, one from the male and one from the female.
Homologous Pairs
Humans have ____ homologous pairs of chromosomes.
23
Cell with two sets of chromosomes
Diploid
Cell with one set of chromosomes
Haploid
Filaments responsible for moving chromosomes during cell division.
Spindle Microtubules
The attachment point for the spindle microtubules.
Centromere (or more specifically, the kinetochore on the centromere)
The natural ends, or tips of the chromosome
Telomeres
Serve to stabilize the chromosome ends
Telomeres
Two initially identical copies of a chromosome, held together at the centromere.
Sister Chromatids
Period in the cell cycle in which the cell grows, develops and prepares for cell division.
Interphase
Period of active cell division.
M Phase, or Mitotic Phase
Includes Mitosis and Cytokinesis.
M Phase, or Mitotic Phase
Includes G1, S, and G2 Phases.
Interphase
Extended period of development between cell divisions.
Interphase
The cell grows, and proteins necessary for cell division are synthesized (part of Interphase).
G1
After this checkpoint is passed, the cell is committed to divide.
G1/S Checkpoint
Nondividing Phase
G0
During this phase, each chromosome duplicates and DNA synthesis takes place.
S Phase
After the cell passes this checkpoint, it is ready to divide.
G2/M
During this part of cell division, chromosomes are in a relaxed state and cannot be seen with a microscope.
Interphase
After this checkpoint is passed, the cell is committed to divide.
G1/S Checkpoint
Nondividing Phase
G0
During this phase, each chromosome duplicates and DNA synthesis takes place.
S Phase
After the cell passes this checkpoint, it is ready to divide.
G2/M
During this part of cell division, chromosomes are in a relaxed state and cannot be seen with a microscope.
Interphase
Part of the cell cycle in which the copies of the cell's chromosomes (sister chromatids) separate and the cell undergoes division.
M Phase
Chromosomes condense and mitotic spindles form.
Prophase
The spindle which forms in Prophase grows out of the ____.
Centrosomes
Disintegration of the nuclear membrane marks the start of this phase.
Prometaphase
Spindle Microtubules enter the nuclear region in this phase.
Prometaphase
Microtubules anchor to the kinetochores of sister chromatids in this phase.
Prometaphase
During this phase, the chromosomes arrange themselves in a single plane.
Metaphase
This checkpoint ensures that each chromosome is aligned on the metaphase plate and attached to spindle fibers from opposite poles.
Spindle-Assembly Checkpoint
In this phase, the sister chromatids separate and move towards opposite poles.
Anaphase
This phase is marked by the arrival of the chromosomes at the spindle poles.
Telophase
Microtubules are composed of subunits called ____.
Tubulin
The ____ end of the microtubule is oriented toward the centrosome.
Negative
The ____ end of the microtubule is always oriented away from the centrosome.
Positive
The ____ ends of the microtubules make contact with the kinetochores.
Positive
Throughout Prophase, Prometaphase, and Metaphase, the sister chromatids of mitosis are held together by ____.
cohesin
At the onset of this phase, cohesin breaks down.
Anaphase
Specialized kinesin proteins are present at both ends of spindle microtubules and function as ____ ____.
Molecular Motors
Enzymes that activate or inactivate other proteins by adding phosphate groups to them.
CDKs (Cyclin Dependent Kinases)
CDKs are only functional when they associate with a protein called ____.
Cyclin
The G2/M Checkpoint is regulated by ____.
Cyclin B
Combines with CDK to form MPF.
Cyclin B
When Cyclin B binds with CDK it forms _____.
MPF (Mitosis Promoting Factor)
After MPF is formed, it must be activated by:
Removal of a phosphate group from one of the amino acids of CDK.
Cyclin B levels stay low until late in ____ phase.
G2
At the end of ____, Cyclin B is abruptly degraded and the cycle starts over again.
Metaphase
In general, low levels of MPF bring a return to ____ conditions.
Interphase
To determine the number of chromosomes in a cell, count the ____.
Centromeres
To determine the number of DNA molecules in a cell, count the number of ____.
Chromatids
Process that leads to gametes in which the chromosomes number is reduced by half.
Meiosis
Two haploid gametes fuse and restore chromosome number to its original dipliod value.
Fertilization
Genetically identical cells are produced during ____.
Mitosis
Genetically variable cells are produced during ____.
Meiosis
This is termed the reductional division.
Meiosis I
This is sometimes termed the equational division.
Meiosis II
In this part of Prophase I, the chromosomes contract and become visible.
Leptotene
In this part of Prophase I, the chromosomes continue to condense, and homolgous chromosomes pair up and begin synapsis.
Zygotene
A very close pairing association between chromosomes.
Synapsis
Synapsis occurs in ____.
Zygotene
Homologous pair of synapsed chromosomes.
Tetrad or Bivalent
In which part of Prophase I does the synaptonemal complex develop?
Pachytene
Crossing over is initiated in ____ of Prophase I.
Zygotene
The centromeres of the paired chromosomes move apart during ____ of Prophase I.
Diplotene
Chiasmata move towards the ends of the chromosomes as the strands slip apart.
Diakinesis
List the five stages of Prophase I in order.
Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis
Initiated when homolgous pairs of chromosomes line up along the metaphase plate.
Metaphase I
Marked by the separation of homologous chromosomes.
Anaphase I
Chromosomes arrive at the spindle poles, and the cytoplasm divides.
Telophase I
The period between Meiosis I and Meiosis II is called ____.
Interkinesis
Chromosomes condense, the mitotic spindle forms, and the nuclear envelope disintegrates.
Prophase II
Individual chromosomes line up on the metaphase plate.
Metaphase II
Cohesin is broken down by ____.
Separase
____ keeps separase inactive.
Securin
The production of gametes in a male animal.
Spermatogenesis
Diploid primordial germ cells divide mitotically to produce ____ (male).
Spermatagonia
A spermatagonium that enters Prophase I is called a _____.
Primary Spermatocyte
When a primary spermatocyte completes Meiosis I and enters Meiosis II it is a ____.
Secondary Spermatocyte.
The male gametes produced from Meiosis I and Meiosis II are called ____.
Spermatids
____ grow up to become sperm.
Spermatids
The production of gametes in the female
Oogenesis
Diploid primordial germ cells in the ovaries divide mitotically to produce ____.
Oogonia
When Oogonia enter Prophase I they are called ____.
Primary Oocytes
At the end of Meiosis I in a female, there will be:
One secondary oocyte and a polar body.
At the end of Meiosis II in the female, there will be:
An Ovum and a second polar body.