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129 terms

12, 13, 14, 15, w/ beginning of 19

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cell division
reproduction of cells
cell cycle
the life of a cell from its origin in the division of a parent cell until its own division into two
genome
a cell's endowment of DNA, its genetic information; prokaryotic ones are often a single long DNA molecule while eukaryotic ones usually consist of a number of DNA molecules
chromosomes
DNA are packaged into these which makes the replication and distribution of DNA more manageable; every eukaryotic species has a characteristic number of these
somatic cells
all body cells except reproductive cells; in humans contain 46 chromosomes each
gametes
sperm cells and egg cells (reproductive); in humans contain 23 chromosomes
chromatin
a DNA-protein complex which is organized into a long, thin fiber. After a cell duplicates DNA in preparation for division; this fiber condenses and becomes densely coiled and folded, making the chromosomes shorter and so think we can see them with a light microscope
sister chromatids
two bodies containing identical copies of the chromosome's DNA molecule and are initially attached by proteins all along their lengths, later they are divided and become the new chromosomes
centromere
the place where sister chromatids narrow in their condensed form; a specialized "waist"
mitosis
the division of the nucleus
cytokinesis
the division of the cytoplasm
meiosis
a variation of cell division which yields daughter cells that have half as many chromosomes as the parent cell; occurs only in the ovaries and testes
mitotic phase (M)
the shortest phase of the cell cycle in which the nucleus is divided and chromosomes are distributed into their nuclei; this phase includes both mitosis and cytokinesis
interphase
90% of the cell cycle in which the cell gros and copies its chromosomes in preparation for cell division; 3 subphases: G₁ phase, S phase, G₂ phase
G₁ phase
phase in which the cell grows by producing proteins and cytoplasmic organelles
S phase
synthesis phase in which chromosomes are duplicated
G₂ phase
phase in which the cell completes its preparations for division
prophase
chromatin fibers become more tightly coiled; nucleoli disappear; duplicated chromosome appears as sister chromatid; mitotic spindle begins to form; centrosomes move away from each other
prometaphase
nuclear envelope fragments so that the microtubules of spindle can now interact with the chromosomes; bundles of microtubules extend from each pole toward them middle of the cell; some microtubules attach to kinetochores causing chromosomes to begin jerky movements
kinetochores
a specialized structure located in the centromere region which, when attached to microtubule bundles, can cause jerky movements
metaphase
centrosomes are now at opposite poles of the cell; chromosomes convene by their centromeres on the metaphase plate; kinetochores of sister chromatids are attached to microtubules coming from the opposite poles of the cell
metaphase plate
an imaginary plate that is equidistant between the spindle's two poles
anaphase
begins suddenly; paired entromeres of each chromosome separate and sister chromatids are detached, each now a full chromosome; chromosomes move towards the opposite poles of of cell-centromeres first; poles of cell move farther apart a non-kinetochore microtubules lengthen; both poles have equivalent and complete collections of chromosomes
telophase and cytokinesis
nonkinetochore microtubules elongate the cell more and daughter nuclei form at the two poles of the cell; nuclear envelopes form from fragments of the parental nuclear envelope; chromatin fiber of each chromosome becomes less tightly coiled; mitosis is now complete; cytokinesis has usually already begin by now so two daughter cells appear shortly after mitosis; in animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two
mitotic spindle
a structure that consists of fibers made of microtubules and associated protiens which begins to form in the cytoplasm during prophase; spindle microtubules elongate by incorporating more subunits of the protein tubulin
centrosome
a nonmembranous organelle that functions throughout the cell cycle to organize the cell's microtubules
cell plate
in plant cells, during telophase, vesciles from the Golgi move along microtubules to the middle of the cell where they coalesce to produce this and eventually fuse with the surrounding membrane to form a cell wall and two separate daughter cells
binary fission
prokaryotic cell division, "division in half"
origin of replication
copies of the first replicated region of prokaryotic DNA
cell cycle control system
a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
checkpoint
a critical control point in the cell cycle where stop and go-ahead signals can regulate the cycle
G₀ phase
a nondividing state a cell enters if it does not receive a go-ahead signal at the G₁ checkpoint; most cells of the human body are in this phase
cyclin
a protein that gets its name from its cyclically fluctuating concentration in the cell
cyclin-dependent kinases (Cdks)
kinases that drive the cell cycle and are actually present in constant concentration in the growing cell, but much of the time they are in inactive form-to be active, such a kinase needs to be attached to a cyclin
MPF (maturation-promoting factor)
a Cdk-cyclin complex that acts as an M-phase promoting factor because it triggers the cell's passage past the G2 checkpoint and into the M phase
growth factor
a protein released by certain body cells that stimulates other cells to divide
density-dependent inhibition
a phenomenon in which crowded cells stop dividing
anchorage dependence
a phenomenon in which in order to divide, cells must be attached to a substratum, such as inside a culture jar or the extracellular matrix of a tissue
transformation
the process that converts a normal cell to a cancer cell
tumor
a mass of abnormal cells within otherwise normal tissue
benign tumor
a tumor that does not cause serious problems and can be completely removed with surgery; a lump of abnormal cells that remain at the original site
malignant tumor
a tumor which becomes invasive enough to impair the functions of one or more organs; if you have this type of tumor, you are said to have cancer
metastasis
the spread of cancer cells to locations distant from their original site
heredity
the transmission of traits from one generation to the next; inheritance
variation
offspring differ somewhat in appearance from parents and siblings
genetics
the scientific study of heredity and hereditary variation
genes
a unit of heredity
locus
a gene's specific location along the length of a chromosome
asexual reproduction
a single individual is the sole parent and passes copies of all its genes to its offspring
clone
a group of genetically identical individuals
sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
life cycle
the generation-to-generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring
karyotype
a display of chromosomes arranged in pairs starting with the longest chromosomes
homologous chromosomes
chromosomes that make up a pair-that have the same length, centromere position, and staining pattern
sex chromosomes
X and Y
autosomes
all the chromosomes that are not X and Y and therefore do not determine the sex of the organism
haploid cell
a cell with a single chromosome set
fertilization/syngamy
union of gametes-haploid sperm cell and haploid ovum
zygote
fertilized egg-the result of fertilization or syngamy
diploid cells
the zygote and all other cells having two sets of chromosomes
alternation of generations
a type of life cycle that includes both diploid and haploid multicellular stages
sporophyte
the multicellular diploid stage of the alternation of generations life cycle
spores
haploid cells produced by meiosis in the sporophyte stage
gametophyte
the multicellular haploid stage of the alternation of generations life cycle
meiosis I
the first of the cell divisions in meiosis, which results in two haploid cells with replicated chromosomes
meiosis II
the second of the cell divisions in meiosis, which results in 4 haploid cells with unreplicated chromosomes
synapsis
a process during prophase I of meiosis in which the duplicated chromosomes pair with their homologues
tetrad
when four closely associated chromatids of a homologous pair are joined along their length by synapsis
chiasmata
x-shaped regions which represent a crossing of nonsister chromatids
nonsister chromatids
two chromatids belonging to separate but homologous chromosomes-physical manifestations of a genetic rearrangement called crossing over
crossing over
a process that produces recombinant chromosomes; begins very early in prophase I of meiosis
recombinant chromosomes
chromosomes that combine genes inherited from our two parents
character
a heritable feature, such as flower color, that varies among individuals
trait
each variant for a character, such as purple or white color for flowers
true-breeding
when plants self-pollinate, all their offspring are of the same variety
hybridization
the mating, or crossing, of two true-breeding varieties
P generation
true-breeding parents in hybridization
F₁ generation
the hybrid offspring of two true-breeding parents
F₂ generation
when F₁ hybrids self-pollinate, they produce this generation
alleles
alternate versions of a gene
dominant allele
a trait that is fully expressed in an organism's appearance
recessive allele
a trait that has no noticeable effect on the organism's appearance
law of segregation
two alleles for each character segregate during gamete production- ovum and sperm each only get one of the two alleles that are present in the somatic cells of the organism
Punnett square
a handy diagram for predicting the results of a genetic cross between individuals of known genotype
homozygous
an organism who has a pair of identical alleles for a character
heterozygous
organisms who have two different alleles for a gene
phenotype
an organism's traits-what it looks like and its physiological makeup
genotype
an organism's genetic makeup
testcross
the breeding of a recessive homozygote with an organism of dominant phenotype but unknown genotype
monohybrids
the F₁ hybrids produced in a cross in which only a single character is followed
dihybrids
an organism that is heterozygous for both characters being observed
Mendel's law of independent assortment
the independent segregation of each pair of alleles during gamete formation
incomplete dominance
when hybrids display appearances that are somewhere in between the phenotypes of the two parental varieties
complete dominance
when phenotypes of a heterozygote and dominant homozygote are indistinguishable
codominance
when two alleles affect the phenotype in separate, distinguishable ways
pleiotropy
the ability of a gene to affect an organism in may ways
epistasis
a situation in which a gene at one locus alters the phenotypic expression of a gene at a second locus
quantitative characters
characters that vary in the population along a continuum making an either-or classification impossible
polygenic inheritance
an additive effect of two or more genes on a single phenotypic character
norm of reaction
a range of phenotypic possibilities over which there may be variation due to environmental influence
multifactorial
when many factors, both genetic and environmental, collectively influence phenotype
pedigree
as much information as possible is collected about a family's history for a particular trait, and this information is assembled into a family tree describing the interrelationships of parents and children across the generations
carriers
heterozygotes who are phenotypically normal with regard to a disorder but may transmit the recessive allele to their offspring
amniocentesis
a technique used to extract amniotic fluid from the womb of an at least 14 week old fetus and tested for certain chemicals that can identify certain disorders
chorionic villus sampling
a test of the chorionic villi of the placenta (extracted through the cervix) used for karyotyping and certain biochemical tests
chromosome theory of inheritance
a theory that states that Mendelian genes have specific loci on chromosomes and it is the chromosomes that undergo segregation and independent assortment
wild type
the most common character, the phenotype most common in natural populations
sex-linked genes
genes located on a sex chromosome
linked genes
genes located on the same chromosome that tend to be inherited together in genetic crosses because the chromosome is passed along as a unit
genetic recombination
the general term for the production of offspring with new combinations of traits inherited from two parents
parental types
the phenotypes of the P generation plants; non-recombinants
recombinants
offspring that show different phenotypes than the P generation
genetic map
an ordered list of the genetic loci along a particular chromosome
linkage map
a genetic map based on recombination frequencies
map units
one of these is equivalent to a 1% recombination frequency, often called centimorgans
cytological maps
maps of chromosomes which locate genes with respect to chromosomal features, such as stained bands, that can be seen in a microscope
Barr body
only one X chromosome is active in embryonic development of a female, the other becomes a compact object that lies along the inside of the nuclear envelope and are reactivated in the ovary cells that give rise to ova
nondisjunction
an error in meiosis in which members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids to separate during meiosis II, resulting in unequal distribution of homologues in gametes.
aneuploidy
when a gamete receives an abnormal chromosome number
trisomic
if a chromosome is present in triplicate in the fertilized egg
monosomic
if a chromosome is missing in a fertilized egg
polyploidy
organisms that have more than two complete chromosome sets
deletion
when a chromosomal fragment lacking a centromere is lost during cell division
duplication
when a chromosomal fragment becomes attached as an extra segment to a sister chromatid
inversion
when a chromosomal fragment reattaches to the original chromosome but in the reverse orientation
translocation
when a chromosomal fragment joins a nonhomologous chromosome
genomic imprinting
when a gene on one chromosome is somehow silenced, while its allele on the homologous chromosome is left free to be expressed
histones
proteins that are responsible for the first level of DNA packing in eukaryotic chromatin
nucleosome
the basic unit of DNA packing consisting of histone bead and its adjacent DNA