Mitosis & Meiosis Flashcards
Genetic continuity between generations of cells and between generations of sexually reproducing organisms is maintained through the processes of mitosis and meiosis, respectively.
An organism’s DNA, with its arrays of genes, is organized into
structures called
Chromosomes.
When cells are not undergoing division, the genetic material making up chromosomes 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
Plasma membrane
provides biochemical identity at the surface of cells
give examples
Glycocalyx or cell coat
ex. AB, Rh, and MN antigens
act as recognition sites that transfer specific chemical signals across the cell membrane into the cell
Receptor molecules
an amorphous component where ribosomal RNA (rRNA) is synthesized and where the initial stages of ribosomal assembly occur.
Nucleolus
portions of DNA that encode rRNA are collectively referred to as the
nucleolus organizer region, or the NOR
The remainder of the eukaryotic cell within the plasma membrane, excluding the nucleus, is referred to as
cytoplasm
In the cytoplasm, a nonparticulate, colloidal material referred to as the _______ surrounds and encompasses the cellular organelles.
cytosol
provides a lattice of support structures within the cell
Consisting primarily of microtubules, which are made of the protein tubulin, and microfilaments, which derive from the protein actin
this structural framework maintains cell shape, facilitates cell mobility, and anchors the various organelles.
Cytoskeleton
compartmentalizes the cytoplasm, greatly increasing the surface area available for biochemical synthesis.
endoplasmic reticulum (ER)
The ER appears smooth in places where it serves as the site for synthesizing _______ and ______
fatty acids
phospholipids
serve as sites where genetic information contained in messenger RNA (mRNA) is translated into proteins.
Ribosomes
are the sites of the oxidative phases of cell respiration. These chemical reactions generate large amounts of the energy-rich molecule adenosine triphosphate (ATP).
Mitochondria
are associated with photosynthesis, the major energy-trapping process on Earth.
Chloroplasts
In some organisms, the centriole is derived from another structure, _________
the basal body
Each chromosome contains a constricted region called the ________, whose location establishes the general appearance of each chromosome.
centromere
chromosomes are classified as _____, ______, ______, or _______ on the basis of the centromere location.
metacentric, submetacentric, acrocentric, or telocentric
mitotic chromosomes have been photographed, cut out of the print, and matched up, creating a display called a ________
karyotype
Collectively, the genetic information contained in a haploid set of chromosomes constitutes the _____ of the species.
genome
Gene sites are called
locus (loci)
inheritance from two parents
biparental inheritance
alternative forms of the same gene
Alleles
single-celled fertilized eggs
zygotes
Nuclear division
Karyokinesis
cytoplasmic division
Cytokinesis
the initial stage of the cell cycle, as the interval between divisions.
the replication of the DNA of each chromosome happens here
interphase
period, during which DNA is synthesized, occurs before the cell enters mitosis and is called the
S phase
the time spent in each interval of one complete cell cycle of a human cell in culture.
Hours
5 - G1
7 - S Phase
3 - G2
1 - Mitosis
Mitosis mins.
36 - Pro
3 - Met
3 - Ana
18 - Tel
Cells that enter ___remain viable and metabolically active but are not proliferative.
G0
Sister chromatids are held together by a multi-subunit protein complex called _______. This molecular complex is originally formed between them during the S phase of the cell cycle when the DNA of each chromosome is replicated.
cohesin
_______, is the midline region of the cell, a plane that lies perpendicular to the axis established by the spindle fibers.
metaphase plate
________, an assembly of multilayered plates of proteins associated with the centromere.
kinetochore
Once properly attached to the spindle fibers, cohesin is degraded by an enzyme, appropriately named ______,
separase
protects cohesin from being degraded by separase at the centromeric regions.
Shugoshin
The microtubules most directly responsible for chromosome migration make contact with, and adhere to, kinetochores as they grow from the centrosome region.
kinetochore microtubules
the shortest stage of mitosis
Anaphase
The cell plate laid down during telophase becomes a structure called the
Middle lamella
Many mutations are now known that exert an effect at one or another stage of the cell cycle. First discovered in yeast, but now evident in all organisms, including humans, such mutations were originally designated as ________
cell division cycle (cdc) mutations
The normal products of many of the mutated genes are enzymes called ______that can add phosphates to other proteins.
kinases
Each synapsed pair of homologs is initially called a ________
bivalent
As prophase I progresses, each pair of sister chromatids within a tetrad is seen to pull apart. However, one or more areas remain in contact where chromatids are intertwined. Each such area, called a __________
chiasma (pl., chiasmata)
◉ basic unit of heredity
Gene
◉ threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell
Chromosome
set of hereditary information encoded in the DNA of an organism, including both the protein-coding and non–protein-coding sequences
Genome
○ Transmission of traits from generation to generation
Heredity
○ Genetic differences between organisms
Variation
Substages of prophase I
- Leptonema = Chromosomes begin to condense
- Zygonema = Homologous pairing (Synapsis)
- Pachynema = Homologous chromosomes fully paired (Crossing over)
- Diplonema = Homologous chromosomes separate except at chiasmata
- Diakinesis = further condensation and attach to spindle fibers
Uncoiled DNA found in the nucleus
Chromatin
What causes the cleavage furrow in animal cells to constrict?
Actin filaments
Which cell during oogenesis must be fertilized by a sperm if it is to become a mature egg?
Secondary oocyte
The centrioles migrate and establish poles at opposite ends of the cell. After migration, the centrosomes, in which the centrioles are localized, are responsible for organizing cytoplasmic microtubules into the spindle fibers that run between these poles, creating an axis along which chromosomal separation occurs.
For complete disjunction to occur:
(1) shugoshin must be degraded, reversing its protective role;
(2) the cohesin complex holding the centromere region of each sister chromosome is then cleaved by separase; and
(3) sister chromatids of each chromosome are pulled toward the opposite poles of the cell
results in genetic exchange between members of each homologous pair of chromosomes prior to one or the other finding its way into a haploid gamete or spore.
crossing over
Since crossing over is thought to
occur one or more times in each tetrad, mosaic chromosomes are routinely created during every meiotic event.
In general, meiotic telophase is much shorter than the corresponding stage in mitosis.
