Campbell Biology Ch 8-10

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asexual reproduction

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The creation of genetically identical offspring by a single parent, without the participation of sperm and egg

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autosome

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a chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X or Y

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chromatin

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The combination of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing

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chromosome

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A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. All chromosomes consists of one very long piece of chromatin, a combination of DNA and protein.

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crossing over

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the exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis; also, the exchange of segments between DNA molecules in prokaryotes

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diploid

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In an organism that reproduces sexually, a cell containing two homologous sets of chromosomes, one set inherited from each parent, a 2n cell

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haploid

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in the life cycle of an organism that reproduces sexually, a cell containing a single set of chromosomes; an n cell

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homologous chromosome

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the two chromosomes that make up a pair in a diploid cell. Homologous chromosomes are the same length, centromere position, and staining pattern and possess genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother.

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gamete

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A sex cell; a haploid egg or sperm. The union of two gametes of opposite sex (fertilization) produces a zygote.

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Meiosis

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In a sexually reproducing organism, the division of a single diploid nucleus into four haploid daughter nuclei. Meiosis and cytokinesis produce haploid gametes from diploid cells in the reproductive organs of the parents

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Mitosis

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The division of a single nucleus into two genetically identical nuclei. Mitosis and cytokinesis make up the mitotic (M) phase of the cell cycle.

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somatic cell

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Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg.

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sex chromosome

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a chromosome that determines whether an individual is male or female

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sexual reproduction

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The creation of genetically unique offspring by the fusion of two haploid sex cells (gametes), forming a diploid zygote

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sister chromatids

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One of two identical parts of a duplicated chromosome in a eukaryotic cell. Prior to mitosis, sister chromatids remain attached to eachother at the centromere

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zygote

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The diploid fertilized egg, which results from the union of a sperm cell nucleus and an egg cell nucleus

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character

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A heritable feature that varies among individuals within a population, such as flower color in pea plants or eye color in humans

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chromosome theory of inheritance

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a basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.

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linkage map

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a listing of the relative locations of genes along a chromosome, as determined by recombination frequencies.

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linked genes

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Genes located near each other on the same chromosome that tend to be inherited together

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monohybrid cross

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An experimental mating of individuals differing in a single character

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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

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recombination frequency

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With respect to two given genes, the number of recombinant progeny from a mating divided by the total number of progeny. Recombinant progeny carry combinations of alleles different from those in either of the parents as a result of crossing over during meiosis.

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trait

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A variant of a character found within a population, such as purple or white flowers in pea plants

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anticodon

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On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA

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genetic code

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The set of rules that dictates the correspondance between RNA codons in an mRNA molecule and amino acids in protein

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messenger RNA

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The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences

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plasmid

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A small ring of independently replicating DNA separate from the main chromosome(s). Plasmids are found in prokaryotes and yeasts.

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prion

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An infectious form of protein that may multiply by converting related proteins to more prions. Prions cause several related diseases in different animals, including scrapie in sheep and mad cow disease.

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retrovirus

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An RNA virus that reproduces by means of a DNA molecule. It reverse-transcribes its RNA to DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA. HIV and a number of cancer-causing viruses are retroviruses.

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semiconservative model

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Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made stand

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transcription

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The synthesis of RNA on a DNA template

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transfer RNA

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A type of ribonucleic acid that functions as an interpreter in translation. Each tRNA molecule has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.

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translation

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The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of language from nucleotides to amino acids.

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Viroid

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A plant pathogen composed of molecules of naked, circular RNA several hundred nucleotides long

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Virus

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A microscopic particle capable of infecting cells of living organisms and inserting its genetic material. Viruses are generally not considered to be alive because they do not display all of the characteristics associated with life.