2: Mitosis and Meiosis

mitochondrion

"power house" of the cell; a self-reporducing, DNA-containing, cytoplasmic organelle in eukaryotes involved in generating the high-energy compound ATP

histocompatibility antigens

(HLA) cell-surface proteins produced by histocompatibility loci and involved in the acceptance or rejection of tissue and organ grafts and transplants

The size of the human genome is approximately

3 billion base pairs

The size of the E coli (prokaryotic) genome is

4-5 million base pairs

in vitro

Literally means "in glass"; outside the living organism; occurring in a artificial environment

nondisjunction

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

cdc mutation

a cell of cell division cycle (cdc) mutations in yeasts that affect the timing of and progression through the cell cycle

telocentric chromosome

a chromosome in which the centromere is located at its very end

submetacentric chromosome

a chromosome with the centromere placed so that one arm of the chromosome is slightly longer than the other

shugoshin

a class of protein involved in maintaining cohesion of the centromeres of sister chromatids during mitosis and meiosis

chromomere

a coiled, beadlike region of a chromosome, most easily visualized during cell division -the alignment of chromomeres of polytene chromosomes are responsible for their distinctive banding pattern

diploid (2n) number

a condition in which each chromosome exists in pairs; having two of each chromosome ∙humans have a diploid number of 46 *a cell that is 2n=46 undergoes the process of meiosis. If all goes correctly, the daughter cells will be: 2n=46 *the complete set of an individual's chromosomes is most correctly referred to as their: 2n number

Centriole

a cytoplasmic organelle composed of 9 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 -organize spindle fibers for movement of chromosomes during meiosis and mitosis *during mitosis in animal cells, the spindle fibers originate from the: Centrioles

equational division

a division stage where the number of centromeres is not reduced by half by where each chromosome is split into longitudinal halves that are distributed into two daughter nuclei. -chromosome division in mitosis and the second meiotic division are examples of equational divisions

kinetochore

a fibrous structure with the size of about 400 nm, located within the centromere; it's the site of microtubule attachment during cell division *during mitosis/meiosis of mammalian cells, the chromosomes are connected to the spindle apparatus/fibers through specialized structures called: kinetochores

mitosis

a form of cell division producing two progeny (daughter) cells genetically identical to the parental cell ∙production of two cells from one, each having the same chromosome complement as the parent cell *the proper order of phases during mitosis is: prophase, prometaphase, metaphase, anaphase, and telophase

Endoplasmic Reticulum (ER)

a membranous organelle system in the cytoplasm of eukaryotic cells -in rough ER, the outer surface of the membrane is ribosome-studded; in smooth ER, it is not

tetrad analysis

a method that analyzes gene linkage and recombination in organisms with a predominant haploid phase in their life cycle

folded-fiber model

a model of eukaryotic chromosome organization in which each sister chromatid consists of a single chromatin fiber composed of double-stranded DNA and proteins wound together tightly

G0

a nondividing by metabolically active state (G-zero) that cells may enter from the G1 phase of the cell cycle

adenosine triphosphate (ATP)

a nucleotide that is the main energy source in cells

G1 checkpoint

a point in the G1 phase of the cell cycle when a cell becomes committed to initiating DNA synthesis and continuing the cycle or withdrawing into the G0 resting stage

cohesin

a protein complex that holds sister chromatids together during mitosis and meiosis and facilitates attachments of spindle fibers to kinetochores

ribosome

a ribonucleoprotein organelle consisting of two subunits, each containing RNA and protein molecules; are the site of translation of mRNA codons into the amino acid sequence of a polypeptide chain

chloroplast

a self-replicating cytoplasmic organelle containing chlorophyll; the site of photosynthesis

gamete

a specialized reproductive cell with a haploid (n) number of chromosomes *the ultimate product(s) of a cell undergoing meiosis is a: Gamete

zygotene

a stage of meiotic prophase I in which the homologous chromosomes synapse and pair along their entire length, forming bivalents -the synaptonemal complex forms at this stage

synaptonemal complex (SC)

a sub-microscopic structure consisting of a tripartite nucleoprotein ribbon that forms between the paired homologous chromosomes in the pachytene state of the first meiotic division *the structures that are assembled in the regions between homologous chromosomes during the early phases of meiosis I are called: synaptonemal complexes

spore

a unicellular body or cell encased in a protective coat. Produced by some bacteria, plants, and invertebrates. Capable of surviving in unfavorable environmental conditions and give rise to a new individual upon germination. ∙In plants, spores are the haploid products of meiosis

plasma membrane

an outer covering that defines the cell boundary and delimits the cell from its immediate external environment ∙actively controls the movement of materials into and out of the cell

homologous chromosomes

chromosomes that synapse or pair during meiosis and that are identical with respect to their genetic loci and centromere placement

glycocalyx (cell coat)

covering over the plasma membrane in animal cells ∙provides biochemical identity at the cell surface and coat components under genetic control (cell-ID markers, AB, Rh, MN, histocompatibility antigens)

spindle fibers

cytoplasmic fibrils formed during 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 -originate from the centrioles contained in the centrosome *the fibers of a mitotic spindle are composed of: Tubulin *during mitosis and meiosis in animal cells, the spindle apparatus originates from a specialized region/complex called the: Centrosome (which contains centrioles)

Prophase I

first meiotic division ∙has 5 substages (leptonema, zygonema, pachynema, diplonema, diakinesis) ∙at the completion of prophase I, the centromeres of each tetrad structure are present on the equatorial plate *At what point during cell division/replication does genetic recombination/crossing over occur?: Prophase I of meiosis *the chromosomes condense during what phase of meiosis I?: Prophase I *At the end of prophase I, the homologous pairs of chromosomes are held together by: Terminal Chiasma *during meiosis, chromosomes migrate to the equatorial plate during: Diakinesis (Prophase I) *during which of the following phases of mitosis/meiosis does synapsis occur?: Prophase I *When does the cell carry out the process referred to as Homology Search?: Meiosis Prophase I

cyclins

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

cell wall

in plant cells is the outer covering of the cell, composed of mostly the polysaccharide, cellulose

chromosome

in prokaryotes, 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 meiosis

haploid (n) number

one member of each pair of homologous chromosomes; also referred to as the gametic chromosome number

allele

one of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects

Metaphase II

phase during the second meiotic division in which the centromeres are positioned on the equatorial plate *a human cell is observed to have 23 chromosomes, each with two chromatids. This cell is most likely: in Metaphase II

oogenesis

process in which female gametes are produced in the ovary *in the case of humans, polar bodies are formed during: oogenesis *nearly all of the oocytes found in the ovary of a teenage human female will be: suspended in Prophase I

polar body

produced in females at the first and second meiotic division of gametogenesis, a discarded cell that contains one of the nuclei of the division process, but almost no cytoplasm as a result of an unequal cytokinesis

asexual reproduction

production of offspring in the absence of any sexual process

centrosome

region of the cytoplasm containing a pair of centrioles *during mitosis and meiosis of animal cells, the spindle apparatus/fiber originates from a specialized region/complex called the: centrosome

sexual reproduction

reproduction through the fusion of gametes, which are the haploid products of meiosis

Anaphase II

stage in meiosis II when the sister chromatids of each dyad are pulled to opposite poles, initiated by the degradation of the Shugoshin complex *during which phase of meiosis do the centromeres uncouple and sister chromatids migrate to opposite poles of the cell?: Anaphase II

Anaphase

stage of mitosis or meiosis in which chromosomes begin moving to opposite poles of the cell *during which phase of mitosis/meiosis do the chromosomes migrate to opposite poles?: Anaphase

Metaphase I

stage when condensed chromosomes lie in a central plane between two poles of the cell and during which chromosomes become attached to the spindle fibers *during the short time that would constitute metaphase I, one of the two sister chromatids that make up the two homologous chromosomes of a tetrad are connected to each other at/by: Terminal Chiasmata *a pair of homologous chromosomes during metaphase I (meiosis) is referred to as a/an: Tetrad *during which phase of meiosis are the tetrads of homologous chromosomes aligned at the center of the dividing cell?: Metaphase II

bivalents

synapsed homologous chromosomes in the first prophase of meiosis

Tetrad

the 4 chromatids that make up paired homologs in the prophase of the first meiotic division -in eukaryotes with a predominant haploid stage (algae and fungi) a tetrad denotes the 4 haploid cells produced by a single meiotic division *Tetrads are most easily observed mammalian cells during Metaphase of Meiosis I

nucleoid

the DNA-containing region within the cytoplasm in prokaryotic cells *the region of the E. coli cell where the chromosome is found is called the: nucleoid

ribosomal RNA (rRNA)

the RNA molecules that are the structural components of the ribosomal subunits -in prokaryotes, these are the 16S, 23S, and 5S molecules; in eukaryotes, they are the 18S, 28S, and 5S molecules

karyotype

the chromosome complement of a cell of an individual -an arrangement of metaphase chromosomes in a sequence according to length and centromere position

reductional division

the chromosome division that halves the number of centromeres and this reduces the chromosome number by half. Which process is considered a reduction division in the context of genetics?: Meiosis I

chromatin

the complex of DNA, RNA, histones, and nonhistone proteins that make up uncoiled chromosomes, characteristic of the eukaryotic interphase nucleus

zygote

the diploid cell produced by the fusion of haploid gametic nuclei

cytokinesis

the division/separation of the cytoplasm during mitosis or meiosis; cytoplasmic division -differs from karyokinesis (nuclear division) *during mitosis, the formation of a cleavage furrow and the actual separation of the cytoplasm of the two daughter cells is called: cytokinesis

diakinesis

the final stage of meiotic prophase I, in which the chromosomes become tightly coiled and compacted and move toward the periphery of the nucleus

Prophase

the first stage of mitosis or meiosis in eukaryotic cell division, during which the nuclear envelope breaks down and strands of chromatin form into chromosomes. *during mammalian cell division the nuclear membrane disappears during: prophase

leptotene

the initial stage of meiotic prophase I, during which the replicated chromosomes become visible; they are often arranged with one or both ends gathered at one spot on the inner nuclear membrane (bouquet configuration)

Interphase

the initial stage of the cell cycle, includes ∙S phase, during which DNA is synthesized ∙G1 and G2, two gap phases ∙G0, a point in G1 where cells enter a non dividing but metabolically active state ∙characterized by the absence of visible chromosomes *At what point in the cell cycle does DNA replication occur?: S phase *a mammalian cell you are studying has not dividing in several days and is unlikely to divide in the next few. It's most likely in what phase: S phase

nucleus

the membrane-bound cytoplasmic organelle of eukaryotic cells that contains the chromosomes and nucleolus

terminalization

the movement of chiasmata toward the ends of chromosomes during the diplotene stage of the first meiotic division

nucleolus

the nuclear site of ribosome biosynthesis and assembly; associated with or formed in association with the DNA comprising the nucleolar organizer region (NOR) *the site of ribosomal RNA synthesis in a eukaryotic cell is the: Nucleolus

synapsis

the pairing of homologous chromosomes at meiosis

locus (pl. loci)

the place on a chromosome where a particular gene is located

meiosis

the process of cell division in gametogenesis or sporogenesis during which the diploid number of chromosomes is reduced to the haploid ∙leads to genetic variation ∙random distribution of maternal and paternal chromosomes ∙crossing over during Prophase I *Meiosis I is not an equational division *Meiosis I is a reductional division

karyokinesis

the process of nuclear division; main process of cellular division -differs from cytokinesis (cytoplasmic division) *karyokinesis refers to the process of: dividing the genetic material during mitosis

Dyad

the products of tetrad separation or disjunction at meiotic prophase I -each consists of two sister chromatids joined at the centromere

disjunction

the separation of chromosomes during the anaphase stage of cell division

cell cycle

the sequence of growth phases in a cell; divided into G1 (gap I), S (DNA synthesis), G2 (gap II), and M (mitosis) -a cell may temporarily or permanently withdraw from the cell cycle (it enters the G0 stage)

Centromere

the specialized heterochromatic chromosomal region at which sister chromatids remain attached after replication using the protein complex cohesin, and the site to which spindle fibers attach to the chromosome during cell division ∙location of the centromere determines the shape of the chromosome during the anaphase portion of cell division ∙also known as the primary constriction *two sister chromatids of a chromosome are connected to each other through a specialized structure called a: centromere

pachytene

the stage in meiotic prophase I when the synapsed homologous chromosome split longitudinally (except at the centromere), producing a group of 4 chromatids called a tetrad

Anaphase I

the stage in the first meiotic division during which members of homologous pairs of chromosomes separate from one another ❗️Chromosome dyads migrate to opposite poles of the cell during anaphase I

Telophase I

the stage in the first meiotic division when duplicated chromosomes reach the poles of the dividing cell *during Meiosis I the chromosomes are observed to be in groups at opposite poles of the cell. This cell is most likely in: Telophase I

Metaphase

the stage of cell division in which condensed chromosomes lie in a central plane between the two poles of the cell and during which the chromosomes become attached to the spindle fibers

Telophase

the stage of cell division 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 -the stage ends during cytokinesis, which divides the cytoplasm and splits the parental cell into two daughter cells *during mitosis the chromosomes are in two groups at opposite poles of the cell. The cell is most likely in: Telophase *you are observing a living cell that is presently in Telophase. What you see is: two groups of chromosomes at opposite poles of the cell

diplotene

the stage of meiotic prophase I immediately following pachytene. -sister chromatids begin to separate, and chiasmata become visible -these cross like overlaps move toward the ends of the chromatids (terminalization) as the stage proceeds

metaphase plate

the structure formed when mitotic or meiotic chromosomes collect at the equator of the cell during metaphase