Biology 141 Genetics

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mitosis

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process of nuclear division in eukaryotic cells. conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.

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mitotic phase

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the phase of the cell cycle that includes mitosis and cytokinesis.

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monohybrid

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an organism that is heterozygous with respect to a single gene of interest.

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chiasma

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the x shaped microscopically visible region representing homologous chromatids that exchanged genetic material through crossing over during meiosis.

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MPF

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(maturation-promoting factor) a protein complex required for a cell to progress from late interphase to mitosis.

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growth factor

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a protein that must be present in the extracellular enviornment for the growth and normal development of certain types of cells.

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binary fission

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type of cell division by which prokaryotes reproduce. each dividing daughter cell receives a copy of the single parental chromosome.

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cell cycle control system

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cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle.

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checkpoint

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a critical control point in the cell cycle where stop and go-ahead signals can regulate the cycle.

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aster

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radial array of short microtubles that extends from each centrosome toward the plasma membrane in a cell undergoing mitosis.

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chromosomes

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packaged DNA molecules
thread like gene carrying structure found in the nucleus.

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sister chromatid

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replicated forms of a chromosome joined together by the centromere.

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chromatin

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complex of DNA and proteins that make up chromosomes when the cell is not dividing.

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kinetochore

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specialized region on the centromere that links each sister chromatid to the mitotic spindle.

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centrosome

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nonmembraneous organelle that functions throughout the cell cycle to organize the cell's microtubules.

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telophase

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5th stage of mitosis in which daughter nuclei are forming and cytokinesis has typically begun.

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prometaphase

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2nd stage of mitosis in which discrete chromosomes consisting of identical sister chromatids appear, the spindle microtubles attach tot he kinetochore, nuclear envelope fragments.

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prophase

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1st stage of mistosis in which chromatin condenses and mitotic spindl forms but nucleus is still intact.

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S phase

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the synthesis phase of the cell cycle in which DNA is replicated.

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G2 phase

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2nd growth phase of the cell cycle, consisting of the portion of interphase.

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G1 phase

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1st growth phase of the cell cycle.

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metaphase

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3rd phase of mitosis, the spindle is complete and the chromosomes are attached to the microtubules at the kinetochore. they are aligned on the metaphase plate.

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anaphase

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4th stage of mitosis in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.

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G0 phase

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a nondividing state in which a cell has left the cell cycle.

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Interphase

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accounts for 90% of the cell cycle. cell grows and copies its chromosomes in preparation for cell division.

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cyclin

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a regulatory protein whose concentration fluctuates cyclically.

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cyclin dependent kinases (Cdks)

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a protein kinase that is active only when attached to a particular cyclin.

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anchorage dependence

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the requirement that to divide a cell must be attached to the substratum.

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density dependent inhibition

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the phenomenon observed in normal animal cells that causes them to stop dividing when they come in contact with one another.

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haploid cell

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a cell containing only one set of chromosomes.

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diploid cell

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a cell containing 2 sets of chromosomes.

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somatic cell

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ant cell in multi-cellular organisms except a sperm or egg cell.

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homologous chromosomes

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chromosome pairs of the same length, centromere position and staining patternn that possess alleles of the smae genes at corresponding loci.

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asexual reproduction

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a type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into 2 or more parts.

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gametes

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a haploid cell such as a sperm or egg cell.

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malignant tumor

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a cancerous tumor that is invasive enough to impair the functions of one or more organs.

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benign tumor

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a mass of abnormal cells that remains at the site of origin.

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transformation

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conversion of a normal animal cell to a cancerous one.
a change in genotype and phenotype due to the assimilation of external DNA by a cell.

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metastasis

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the spread of cancer cells to locations distant from their original site.

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alternations of generations

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a life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte. characteristic of plants and some algae.

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gametophyte

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the multicellular haploid form that mitotically produces haploid gametes that unite and grow into the sporophyte generation.

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synapsis

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the pairing of replicated homologous chromosomes during prophase 1 of meiosis.

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crossing over

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the reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis.

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tetrad

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a paired set of homologous chromosomes, each composed of 2 sister chromatids.

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recombinant chromosomes

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a chromosome created when crossing over combines the DNA from 2 parents into a single chromosome.

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zygote

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the diploid product of the union of haploid gametes in conceptin

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gametophyte

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the multicellular haploid form that mitotically produces haploid gametes that unite and grow into the sporophyte generation.

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synapsis

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the pairing of replicated homologous chromosomes during prophase 1 of meiosis.

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crossing over

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the reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis.

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tetrad

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a paired set of homologous chromosomes, each composed of 2 sister chromatids.

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recombinant chromosomes

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a chromosome created when crossing over combines the DNA from 2 parents into a single chromosome.

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zygote

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the diploid product of the union of haploid gametes in conceptin

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gametophyte

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the multicellular haploid form that mitotically produces haploid gametes that unite and grow into the sporophyte generation.

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synapsis

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the pairing of replicated homologous chromosomes during prophase 1 of meiosis.

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crossing over

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the reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis.

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tetrad

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a paired set of homologous chromosomes, each composed of 2 sister chromatids.

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recombinant chromosomes

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a chromosome created when crossing over combines the DNA from 2 parents into a single chromosome.

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zygote

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the diploid product of the union of haploid gametes in conception

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fertilization

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the union of haploid gametes to produce a diploid zygote

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sporophyte

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in organisms undergoing alternation of generations the mutlicellular diploid form that results from a union of gametes and that mitotically produces haploid spores that grow into the gametophyte generation.

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codominance

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the situation in which the phenotypes of both alleles are exhibited in the heterozygote.

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complete dominance

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the situation in which the phenotypes of the heterozygote and the dominant homozygote are indistinguishable.

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law of independent assortment

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Mendel's seond law stating that each pair of alleles segregates independently during gamete formation.

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dihybrid

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an organism that is heterozygous with respect to two genes of interest. all the offspring from a cross between parents doubly homozygous for different alleles are dihybrid.

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testcross

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breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

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genotype

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the genetic makeup or set of alleles of an organism.

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Punnett Square

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a diagram used in the study of inheritance to show the results of random fertilization in genetic crosses.

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phenotype

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the physical and physiological traits of an organism which are determined by its genetic makeup.

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homozygous

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having 2 identical alleles for a given gene.

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heterozygous

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having 2 different alleles for a given gene.

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law of segregation

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Mendel's 1st law stating that each allele in a pair separates into a different gamete during gamete formation.

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recessive allele

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an allele whose phenotyic effect is not observed in a heterozygote.

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dominant allele

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allele that is fully expressed in the phenotype of a heterozygote.

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alleles

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alternative versions of a gene that produce distinguishable phenotypic effects.

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F2 generation

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offspring resulting from interbreeding og the hybrid F1 generation.

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F1 generation

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the 1st filial or hybrid offspring in a series of genetic crosses.

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P generation

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the parent individuals from which offspring are derived in studies of inheritance.

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hybridization

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the mating or crossing of 2 truebreeding varieties.

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True-breeding

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refer to plants that produce offspring of the same variety when they self pollinate.