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BIOL 2153, Chapter 2 (Smith)

Terms in this set (204)

What are the three types of cellular reproduction?
meiosis, mitosis, binary fission
MEIOSIS, MITOSIS, or BINARY FISSION?
A eukaryotic diploid (two copies of each chromosome) turns haploid after division
meiosis
MEIOSIS, MITOSIS, or BINARY FISSION?
a eukaryotic haploid stays haploid after division
mitosis
MEIOSIS, MITOSIS, or BINARY FISSION?
a prokaryotic haploid (single copy of chromosome) stays haploid after division
binary fission (PROKARYOTIC)
MEIOSIS, MITOSIS, or BINARY FISSION?
a eukaryotic diploid stays diploid after division
diploid
state of having two copies of each chromosome
diploid
state of having a single copy of each chromosome
haploid
How does the DNA of prokaryotic organisms differ from that of eukaryotic organisms
Prokaryotic organisms have genetic material in a singular, circular strand of DNA (single, circular chromosome), while eukaryotic organisms have multiple chromosomes
How does DNA replicate via the process of binary fission in prokaryotes?
DNA is duplicated along the circular formation, creating two circles of DNA attached to the plasma membrane of the cell; the plasma membrane and cell elongates so that the chromosomes separate, and the cell pinches in two
What type of cellular division to prokaryotes undergo?
binary fission
What is the DNA inside of prokaryotes referred to as?
nucleoid (somewhat condensed DNA within a region of the prokaryotic cell)
"somewhat condensed" DNA in a circular form within a central region of the prokaryotic cell
nucleiod
T/F: Eukaryotic organisms have nucleoids.
False; they don't have nucleoids, but they have chromosomes (a more condensed form of DNA)
Why are two strands of DNA in a chromosome identical to one another?
one of them is a copy of the other
What is the structure of the DNA molecule?
double helix; two strands of DNA connected by nitrogenous bases
In eukaryotic DNA (chromosomes), what structure is responsible for the bundling "beads on a string" phenomenon that occurs?
histone proteins
Histone proteins condense DNA in a "beads on a string" structure until the formation of which structure?
chromatid (half of the chromosome)
When is the only time that we ever see a chromosome in its highly condensed X structure?
during metaphase of mitosis
chromosome material of different density from normal (usually greater), in which the activity of the genes is modified or suppressed; chromosome material in the "x structure" (replicated) formed during metaphase of mitosis
heterochromatin
chromosome material which does not stain strongly except during cell division; It represents the major genes and is involved in transcription; chromosome material in its single (un-replicated) form
euchromatin
EUCHROMATIN or HETEROCHROMATIN
replicated chromosome
heterochromatin
EUCHROMATIN or HETEROCHROMATIN
unreplicated chromosome
euchromatin
On which type of chromosome (replicated/unreplicated) is the centromere present? Why?
Replicated (heterochromatin); holds the two sister chromatids of the structure together
arrangement of DNA chromosomes from biggest to smallest; allows one to see the full genetic makeup of an individual
karyotype
The typical x structure of chromosomes is only visible in what phase of mitosis?
metaphase
How does the position of the centromere affect a chromosome (heterochromatin)?
determines the shape of the chromosome
shape of a chromosome with the centromere located in the middle of the chromosome
metacentric
shape of a chromosome with the centromere located between the middle and end of the chromosome
submetacentric
shape of a chromosome with the centromere located close to the end of the chromosome
acrocentric
shape of a chromosome with the centromere located at the end of the chromosome
telocentric
How many pairs of chromosomes do humans have?
23 pairs
How many chromosomes are found in every SOMATIC cell?
46
How many chromosomes are found in every SEX cell? Why?
23, they are haploid (gametes)
Why is it somewhat of a misnomer to call the X and Y sex chromosomes present in a male a pair?
they are different shapes (X is much larger than the Y)
two chromosomes that have the same shape (same chromosome in the species, just from different parents)
homologous chromosomes
two DNA molecules that make up a duplicated DNA molecule
sister chromatids
two chromatids from different duplicated chromosomes
nonsister chromatids
How do sister chromatids differ (and compare) genetically?
Sister chromatids carry the same set of genes, but have different alleles
chromosomes that contain the same set of genes (that may carry different alleles) within a species
homologous chromosomes (homologs)
chromosomes that carry completely unrelated sets of genes within a species
nonhomologous chromosomes
What are chromosomes made up of?
genetic material (DNA and proteins)
During cell division, what must be maintained and transmitted in order to ensure a properly functioning cell?
genetic material (in the form of chromosomes)
What are the three phases of interphase?
G1, S, G2
What are the three major phases of the cell cycle?
interphase, mitosis, cytokinesis
What general process ensures that every cell in an organism carries the same chromosomes?
mitosis
repeating pattern of cell growth and division; alternates between interphase and mitosis
cell cycle
What two phases does the cell cycle alternate between?
interphase and mitosis
period of cell cycle between divisions; cells grow and replicate chromosomes
interphase
phase of interphase in which there is the birth of the cell that grows until the onset of chromosomes replication
G1 (Gap 1)
phase of interphase where DNA is duplicated
S (synthesis)
phase of interphase that occurs from the end of chromosomes replication to the onset of mitosis
G2 (gap 2)
T/F: Interphase is a part of mitosis
False; interphase is not a part of mitosis
By the time a cell has entered mitosis, what has happened to the DNA?
DNA has been replicated
What things happen during interphase in the cell cycle?
1) Cell grows larger and accumulates more cytoplasmic material
2) The cell continues daily metabolic pathways (gap phases)
3) the cell duplicates DNA (synthesis)
4) the cell stores energy to divide in mitosis (gap 2)
What happens in the G1 phase (gap 1) of interphase?
the cell grows larger, accumulates more organelles and cytoplasm, and stores energy for the duplication of DNA
What happens in the G2 phase of interphase?
Cell gets bigger and energy is stored for cell division (mitosis)
Most of the time, what phase of the cell cycle does a cell exist in?
interphase
separate phase within interphase where after a cell has replicated, a cell pulls out of the process of cell division (could never re-enter or could re-enter in the future)
G0 (Gap 0)
What is the most "important" part of interphase? Why?
S phase (synthesis); chromosome replication occurs
In interphase, how does the DNA/chromosomes appear, even after S-phase duplication (but before mitosis)?
thin un-condensed fibers = chromatin
thin uncondensed fibers of DNA/chromosomes that exist in an uncoiled state (before mitosis)
chromatin
What three things happen during prophase of mitosis?
1. Centrioles migrate to poles (in animal cells only); most plant cells do not have centrioles, but ALL cells have a centrosome, which is an organizing center for microtubules
2. Nuclear envelope disappears
3. Chromatin fibers begin to condense into chromosomes
a cytoplasmic organelle composed of nine groups of microtubules, generally arranged in triplets; function in the generation of cilia and flagella and serve as foci for the spindles in cell division
centrioles
the region of the cytoplasm containing a pair of centrioles
centrosome
What happens in prometaphase of mitosis?
1. microtubules (spindle fibers) originate at the centrosomes and bind the condensed chromosomes at their kinetochore
2. chromosomes begin to move toward the equatorial plate
3. chromosomes are clearly double structures
4. centrioles reach the opposite poles
What happens during metaphase of mitosis?
1. Chromosomes (centromeres) line up along the metaphase plate
general term for kinetochore microtubules and polar microtubules; cytoplasmic fibrils formed during prometaphase of cell division that attach to and are involved with separation of chromatids at the anaphase stage of mitosis and meiosis as well as their movement toward opposite poles in the cell; composed of arrays of microtubules consisting of polymers of the protein tubulin
spindle fibers
What protein polymer is found within microtubules (within kinetochore/polar microtubules aka spindle fibers)?
tubulin
spindle fibers that physically attach to the centromere of the chromosome (responsible for pulling the sister chromatids apart)
kinetochore microtubules
spindle fibers that do not attach at the centromere and push against each other and the cytoplasm (responsible for elongating the cell)
polar microtubules
What is true of both the centromere and the kinetochore?
occur at the same point in a duplicated chromosome (but refer to different things)
constricted attachment point between two sister chromatids (area where the sister chromatids are attached)
centromere
the functional center on sister chromatids that contains proteins that aid in cell division and attach to spindle fibers during mitosis
kinetochore
T/F: The kinetochore is located within the centromere
true
What happens during Anaphase of mitosis?
1. sister chromatids separate (disjunction)--shugoshin degrades, cohesin is cleaved by separase, and sister chromatids are pulled apart
2. kinetochore microtubules shorten
the separation of chromosomes during the anaphase stage of cell division
disjunction
What three things occur during disjunction (anaphase)?
1. shugoshin (protecting cohesin at the centromere region), is dissolved
2. cohesin is cleaved by the protein separase
3. kinetochore microtubules shorten and pull sister chromatids apart (now called daughter chromosomes)
How do daughter chromosomes migrate during anaphase?
shortening of the kinetochore microtubules (disassembling)
After sister chromatids separate in anaphase, what are each migrating chromatid referred to as?
daughter chromosomes
After disjunction, what is the ploidy and number of the chromosome attached to the spindle fibers?
two single/individual chromosomes (nonduplicated)
What happens during telophase of mitosis?
1. daughter chromosomes make it to the poles
2. cytokinesis occurs (division of the cytoplasm)--constriction of cytoplasm (animal cells) or cell plate is made, precursor to cell wall (plant cells)
How does cytokinesis occur in animal cells?
the plasma membrane pinches inward to form a cleavage furrow. The two cells eventually separate (constriction of cytoplasm)
How does cytokinesis occur in plant cells?
a cell plate is made, which eventually forms into the cell wall (separating the cells)
How many checkpoints exist in the cell cycle to check on the proper growth and duplication of the cell? What are they?
Three:
1) G1/S checkpoint (monitors size and DNA integrity)
2) G2/M checkpoint (cell monitors DNA synthesis and damage)
3) M checkpoint (cell monitors spindle formation and attachment to kinetochores)
What happens if at any checkpoints in the cell cycle the cell fails the checkpoint?
cell division is shut taken (enters "quiescence" in the G0 phase
period of nondivision within the cell cycle that usually occurs after a cell has failed a checkpoint or reaches maturity
quiescence (G0 phase)
What does the G1/S checkpoint monitor for in the cell cycle?
correct size and DNA integrity (to continue to synthesis/DNA duplication)
What does the G2/M checkpoint monitor in the cell cycle?
correct DNA synthesis and damage to the cell (before going through division)
What does the M checkpoint monitor in the cell cycle?
spindle formation and attachment to kinetochores
How do cell checkpoints in the cell cycle relate to the formation of cancerous cells?
often time cancer results from defective cell division, which occurs at a failure in any checkpoint
Why do we need meiosis (general)?
To maintain a normal diploid state following reproduction; -if the DNA was not halved in the creation of gametes, then all offspring created after fertilization would have double the amount of ploidy than necessary
How many chromosomes exist in a diploid human cell (diploid number)?
46
How many chromosomes exist in a haploid human cell (haploid number)?
23 chromosomes
After meiosis (reduction to haploid), how is the diploid number of the cell restored?
fusion of the nuclei during fertilization of gametes
What are the stages of mitosis?
prophase, prometaphase, metaphase, anaphase, telophase
What are the stages of meiosis?
Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II
What happens during Prophase I of meiosis I (first division of meiosis?
1. Chromatin condenses into chromosomes (like mitosis)
2. nuclear envelope disappears
3. centrioles move to poles
4. spindle fibers attach to the centromeres of homologous pairs
4. homologous chromosomes synapse (form a pair, tetrad)
5. Crossing over occurs between chromatids of synapsed homologs (two non-sister chromatids)
How many daughter cells are produced from one parent cell in meiosis?
four
How many cell divisions are there in meiosis?
two
In Anaphase I, what structures are separated during disjunction?
tetrads (pairs of recombined homologous chromosomes) are separated into dyads
In Anaphase II, what structures are separated during disjunction?
dyads (sister chromatids with recombination) are separated into monads
What is the first division of meiosis (meiosis I) referred to as? Why?
reductional division; the number of centromeres halves (diploid to haploid)
What is the second division of meiosis (meiosis II) referred to as? Why?
equational/equatorial division (same number of centromeres, but goes from common to individual--ploidy doesn't change)
What is another term for the crossing over (of genetic material) that occurs in Prophase I of meiosis?
recombination
splicing of a section of DNA from a non-sister chromatid in the homologous pair and switching them; essentially new chromosomes are formed with new alleles (Prophase I)
crossing over (recombination)
What is true of the state of genes and alleles during/after crossing over in Prophase I?
the genes in the chromosomes are the same (which is why they are homologous pairs) but the alleles may be different, which is why recombination yields unique offspring
What happens during metaphase I of meiosis I?
Homologs (tetrads) align together at the cell center (metaphase plate), and microtubules in the spindle are attached to each homolog
What happens during Anaphase I of meiosis I?
Homologous chromosomes (tetrads) separate into dyads (BUT NOT CENTROMERES)--the homologous pairs split, not the chromosomes
What happens during telophase I of Meiosis I?
1. nuclear envelopes reform
2. cytoplasm separates
What happens in Metaphase II and Anaphase II of meiosis II?
the duplicated chromosomes (sister chromatids) line themselves along the metaphase plate and are pulled apart (steps resemble mitosis)
At the end of meiosis (after telophase II), what remains?
four haploid gametes with un-replicated DNA (individual/single DNA)
In what two ways does meiosis contribute to genetic diversity?
independent assortment and crossing over
How does independent assortment in meiosis contribute to genetic diversity?
Independent Assortment of nonhomologous chromosomes creates different combinations of alleles among chromosomes; it is completely random how homologous pairs orient themselves within a cell, thus, completely random how they align themselves along the metaphase plate in Metaphase I and Metaphase II
How does crossing over in meiosis contribute to genetic diversity?
Crossing Over between homologous chromosomes creates different combinations of alleles within each chromosome.
Why is crossing over considered to be randomized genetic diversity?
-Crossing over is random because it occurs in areas where the genes of two non-sister chromatids in homologous pairs are similar, but there are no set genes that always are recombined
-The genes that undergo recombination are randomly selected
Why is independent assortment considered to be randomized genetic diversity?
How the chromosomes align themselves along the metaphase plate is completely random and yields different gametes with different random orientations (diversity)
Which chromosome arms in a tetrad undergo recombination?
non-sister chromatids within the homolog
the creation of gametes
gametogenesis
the creation of male gametes (male gametogenesis)
spermatogenesis
the creation of female gametes (female gametogenesis)
oogenesis
Explain the process of Spermatogenesis (along with ploidy and DNA content, with unreplicated number x), starting with the spermatogonium.
1. Spermatogenesis starts with a spermatogonium, a diploid cell with un-replicated DNA destined for gametogenesis (2x DNA content)
2. After the DNA of the cell is replicated, the primary spermatocyte is formed (diploid but with 4x DNA content)
3. Meiosis 1 creates two secondary spermatocytes which are now haploid but still have replicated DNA (2x DNA content)
4. Meiosis II creates four total spermatids that are haploid with un-replicated DNA (x DNA content)
5. Through differentiation, the spermatids turn into spermatozoa (sperm) with flagella for movement
How many sperm are produced from each primary spermatocyte?
4
Why are there four sperm cells created from one primary spermatocyte?
two divisions of meiosis along with equal distribution of DNA (the goal is not to make a long lasting cell with additional nutritional value, but many cells)
How many ova (eggs) are produced from each primary oocyte?
1
How many polar bodies are produced from each primary oocyte?
2
Why is there asymmetric division of the cytoplasm in oogenesis?
To provide a lot of nutrients and energy to the developing embryo; that ovum needs the extra nutrition and support to house a zygote after fertilization with the spermatocyte (The more nutrition the ovum has, the more likely that the zygote, then embryo, then human will have a healthy development)
What are the structures that eliminate diploidy during oogenesis?
first polar body and second polar body
What is the role of the polar bodies within the process of oogenesis?
Polar bodies serve to eliminate one half of the diploid chromosome set produced by meiotic division in the egg, leaving behind a haploid cell—they help to reduce the ploidy number so that the gamete has the proper haploid state to merge with a spermatocyte
Explain the process of oogenesis, starting with the oogonium,
1. Starts with a diploid oogonium that has un-replicated DNA (2n, 2x DNA content)
2. DNA replicates and the primary oocyte is formed; the cell also grows very large (2n, 4x DNA content)
3. Meiosis I creates the secondary oocyte and the first polar body; the first polar body does not divide; ploidy is reduced to haploid (but DNA still duplicated, n and 2x DNA content)
4. Meiosis II creates the ootid and the second polar body; the second polar body does not divide; the cell is still haploid but has less a DNA content (n and x)
5. Differentiation creates the ovum, which is haploid
What is the starting structure of spermatogenesis and oogenesis, respectively?
spermatogonium and oogonium
vehicles for transmitting genetic information
chromosomes
in bacteria, a DNA molecule containing the organism's genome; in eukaryotes, a DNA molecule complexed with RNA and proteins to form a threadlike structure containing genetic information arranged in a linear sequence; a structure that is visible during mitosis and meiosi
chromosome
segments in the underlying linear structure of the DNA (and chromosomes) that direct the metabolic activities of cells
genes
the process of cell division in gametogenesis or sporogenesis during which the diploid number of chromosomes is reduced to the haploid number
meiosis
a unicellular body or cell encased in a protective coat. Produced by some bacteria, plants, and invertebrates, they are capable of surviving in unfavorable environmental conditions and give rise to a new individual upon germination; in plants, they are the haploid products of meiosis
spores
What two types of cells can meiosis lead to the production of?
gametes and spores
the complex of DNA, RNA, histones, and nonhistone proteins that make up uncoiled chromosomes, characteristic of the eukaryotic interphase nucleus
chromatin
How does genetic material appear in eukaryotic cells when they are not undergoing division?
unfolds and uncoils into a diffuse network within the nucleus, generally referred to as chromatin
an outer covering that defines the cell boundary and delimits the cell from its immediate external environment; not passive but instead actively controls the movement of materials into and out of the cell
plasma membrane
outer covering of plant cells
cell wall
What is the major component (polymer) that makes up the cell wall in plants?
cellulose
covering over the plasma membrane in most animal cells; Consisting of glycoproteins and polysaccharides, this covering has a chemical composition that differs from comparable structures in either plants or bacteria; provides biochemical identity at the surface of cells
glycocalyx
What is the defining characteristic of eukaryotic organisms?
The presence of a nucleus and other membranous organelles
the membrane-bound cytoplasmic organelle of eukaryotic cells that contains the chromosomes and nucleolus (genetic material)
nucleus
the nuclear site of ribosome biosynthesis and assembly; associated with or formed in association with the DNA comprising the nucleolar organizer region
nucleolus
What are the two major groups of prokaryotic organisms?
eubacteria and archaea
What are the defining characteristics of prokaryotic organisms?
lack a nuclear envelope and membranous organelles
the DNA-containing region within the cytoplasm in bacterial cells
nucleoid
The remainder of the eukaryotic cell within the plasma membrane, excluding the nucleus, including a variety of extracellular organelles
cytoplasm
a nonparticulate, colloidal material that surrounds and encompasses the cellular organelles
cytosol
Fibers composed of tubulin, bunches of which are part of the structural framework of the cytoplasm (the cytoskeleton) and also which compose spindle fibers that facilitate chromosome migration during mitosis and meiosis
microtubules
the specialized heterochromatic chromosomal region at which sister chromatids remain attached after replication, and the site to which spindle fibers attach to the chromosome during cell division; the location determines the shape of the chromosome during the anaphase portion of cell division; also known as the primary constriction
centromere
What is another name for the centromere?
primary constriction
shorter of the two arms extending from the centromere of the chromosome
p arm (p for "petite")
longer of the two arms extending from the centromere of the chromosome
q arm
the identical number of chromosomes that all somatic cells of a species have
diploid number (2n)
chromosomes that synapse or pair during meiosis and that are identical with respect their genetic loci and centromere placement
homologous chromosomes
What two characteristics determine that two chromosomes are homologs?
identical genetic loci and centromere placement
the chromosome complements of a cell or an individual; an arrangement of metaphase chromosome in a sequence according to length and centromere position; Display of human mitotic chromosomes that have been photographed, cut out of the print, and matched up
karyotype
the number of homologous chromosome pairs characteristic of an organism or species
haploid number (n)
the set of hereditary information encoded in the DNA of an organism, including both the protein-coding and non-protein-coding sequences; term for all the genetic information in a haploid set of chromosomes in a species
genome
the place on a chromosome where a particular gene is located
locus
What type of inheritance is responsible for the fact that each diploid organism contains two copies of each gene?
biparental inheritance (inheritance from two parents)
one of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects
alleles
What shows a common exception to homologous pairs of chromosomes in humans?
the sex-determining chromosome, which is often not homologous in size, centromere placement, arm ratio, or genetic content (X and Y in males are not strictly homologous; the Y is smaller and lacks most of the gene loci contained on the X); however, they behave as homologous and have homologous regions
the diploid cell produced by the fusion of haploid gametic nuclei
zygotes
Multicellular diploid organisms begin life as single-celled fertilized eggs called ___.
Zygotes
the process of nuclear division; process precedes cytokinesis
karyokinesis
the division or separation of the cytoplasm at the end of cell division (mitosis and meiosis); follows karyokinesis
cytokinesis
The sequence of growth phases in a cell; divided into G0, G1 (gap I), S (DNA synthesis), G2 (gap II) and M (mitosis). A cell may temporarily or permanently withdraw from the cell cycle, in which case it is said to enter the G0 stage
cell cycle
the initial stage of the cell cycle and the interval between divisions
interphase
the "synthesis" portion of the cell cycle following the G1 phase during which DNA is replicated
s phase
the phase during the cell cycle following the S phase, during which the cell, having replicated its DNA, prepares for mitosis
G2 (gap II)
What is the shortest phase of the cell cycle?
mitosis
a nondividing but metabolically active state (G-zero) that cells may enter from the G1 phase of the cell cycle
G0 stage
the initial stage of cell division (mitosis and meiosis) during which the nuclear envelop breaks down, the nucleolus disintegrates, centrioles are formed and migrate to opposite ends of the cell, cytoplasmic microtubules are organized into spindle fibers, and diffuse chromatin fibers begin to condense into chromosomes.
prophase
a pair of identical chromatids visible during mitosis and meiosis that are formed following replication of DNA of one member of a homologous chromosome pair
sister chromatids
What protein complex are sister chromatids held together by?
cohesin
a protein complex that holds sister chromatids together during mitosis and meiosis and facilitates attachments of spindle fibers to kinetochores; formed during S phase of cell cycle
cohesin
the midline region of the cell, a plane that lies perpendicular to the axis established by the spindle fibers
metaphase plate
stage of cell division (mitosis and meiosis) during which the spindle fibers are assembled and attach to the centromeres of chromosomes, which begin their migration to the equatorial plane
prometaphase
stage of cell division (mitosis and meiosis) in which condensed chromosomes lie in a central plane between two poles of the cell and during which the chromosomes become attached to the spindle fibers
metaphase
a protein structure that assembles on the centromere during mitosis and meiosis; it is the site of microtubule attachment during cell division; forms on opposite sides of each paired centromere, in intimate association with the two sister chromatids
kinetochore
enzyme that degrades cohesion in sister chromatids after attached to the spindle fibers in prometaphase (but not at centromere region until anaphase)
separase
protein family that protects cohesion from being degraded by separase at the centromeric regions (from the Japanese meaning "guardian spirit")
shugoshin
the stage of cell division (mitosis and meiosis) in which chromosomes begin moving to opposite poles of the cell
anaphase
specialized proteins that facilitate the movement of cellular components; responsible for the movement of daughter chromosomes to opposite poles in anaphase with kinetochore microtubules
molecular motors (motor proteins)
a. the stage of cell division (meiosis and mitosis) in which the daughter chromosomes have reached the opposite poles of the cell and reverse the stages characteristic of prophase, re-forming the nuclear envelopes and uncoiling the chromosomes; ends during cytokinesis, which divides the cytoplasm and splits the parental cell into two daughter cells
telophase
the division or partitioning of the cytoplasm
cytokinesis
After the cell plate is laid down in telophase, what does it become in the daughter cells?
middle lamella
At the completion of telophase, what stage does the cell enter?
interphase
The study of what has shown that there are cell-cycle checkpoints?
cell division cycle mutations (CDC mutations) caused by dysfunctional kinases and cyclins
a broad class of enzymes that phosphorylate a substrate molecule such as a protein, nucleic acid, carbohydrate, or lipid; they serve as "master control" molecules functioning in conjunction with proteins called cyclins
kinases
in eukaryotic cells, a class of proteins that are synthesized and degraded in synchrony with the cell cycle and regulate passage through stages of the cycle
cyclins
regulated transitions from one stage to another during the cell cycle
cell cycle checkpoints
the exchange of chromosomal material (parts of the chromosomal arms) between homologous chromosomes by breakage and reunion; the exchange of material between non-sister chromatids during meiosis is the basis of genetic recombination
crossing over (aka recombination)
the paring of homologous chromosomes at meiosis
synapsis
name for synapsed homologous chromosomes in the first prophase of meiosis
bivalent (condensed into a tetrad)
the crossed strands of non-sister chromatids seen in the first meiotic division; regarded as the cytological evidence for exchange of chromosomal material, or crossing over; represents a point where nonsister chromatids undergo genetic exchange during crossing over
chiasma
non-identical chromatids visible during mitosis and meiosis where each chromatid represents one or the other of the two members of a homologous pair of chromosomes
non-sister chromatids
a cell division error in which homologous chromosomes (in meiosis) or the sister chromatids (in mitosis) fail to separate and migrate to opposite poles; responsible for defects such as monosomy and trisomy
nondisjunction
Where does spermatogenesis take place in the human body?
testes (male reproductive organs)
Where does oogenesis take place in the human body?
ovaries, the female reproductive organs
proteins associated with DNA in chromosomes; allow for the condensing of the genetic material from chromatin to chromosome form
histones
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