The Cell From Chapter 3 Of Introduction To Anthropology

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Organelles

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Structures contained within cells, surrounded by a membrance. There are many different types, and each performs specific functions.

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Nucleus (Plural: Nuclei)

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A structure (organelle) found in all eukaryotic cells. The nucleus contains chromosomes (nuclear DNA).

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Molecules

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Sturctures made up of two ormore atoms. Molecules can combine with other molecules to form more complex stuctures.

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Deoxyribonucleic acid (DNA)

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The double-stranded moleculest that contains the genetic code. DNA is a main component of chromosomes.

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Ribonucleic acid (RNA)

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A single-stranded molecule, similar in structure to DNA. Three forms of RNA are essential to protein synthesis. They are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

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Cytoplasm

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The portion of the cell contained within the cell membrance, excluding the nucleus. The cytoplasm consists of a semifluid material and contains numerous stuctures involved with cell function.

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Proteins

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Three-dimensional molecules thatserve a wide variety of functions through their ability to bind to other molecules.

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Protein synthesis

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The assembly of chains of amino acids into fuctional protein molecules. The process is directed by DNA.

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Mitochondira (Singular: Mitochondrion)

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Stuctures conained within the cytoplasm of eukaryotic cells that convert evergy, derived from nutrients, into a form that is used by the cell.

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Ribosomes

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Structures composed of a form ofRNA called ribosomal RNA (rRNA) and protein. Ribosomes are found in the cell's cytoplasm and are essential to the manufacture of proteins.

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Mitochondrial DNA (mtDNA)

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DNA found in the mitochondria; mtDNA is inherited only from the mother.

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Somatic cells

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Basically, all the cells in the body except those involved with reproduction.

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Gametes

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Reproductive cells (eggs and sperm in animals) developed from precursor cells in ovaries and testes.

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Zygote

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A cell formed by the union of an egg and a sperm cell. It contains the full complement of chromosomes and has the potential of developing into an entire organism.

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Nucleotides

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Basic units of the DNA molecules, composed of a sugar, a phosphate, and one of four DNA bases.

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Complementary

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Referring to the fact that DNA bases form base pairs in a precise manner. For example, adenine can bond only to thymine. Threse two bases are said to be complementary because one requires the other to form a complete DNA base pair.

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Replicate

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To duplicate. The DNA molecule is able to make copies of itself.

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Enzymes

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Specialized proteins that initiate and direct chemcial reactions in the body.

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Hemoglobin

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A proteins molecule that occurs in red blood cells and binds to oxygen molecules.

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Hormones

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Substances (usually proteins) that are produced by specialized cells and that travel to other parts of the body, where they influence chemical reactions and regulate various cellualar fuctions.

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Amino acids

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Small molecules that are the components of proteins.

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Messenger RNA (mRNA)

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A form of RNA that is assembled on a sequence of DNA bases. It carries the DNA code to the ribosome during protein synthesis.

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Codon

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A triplet of messenger RNA bases that refers to a specific amino acid during protein synthesis.

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Transfer RNA (tRNA)

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The type of RNA that binds to specific amino acids and transports them to the ribosome during protein synthesis.

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Gene

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A sequence of DNA bases that specifies the order of amino acids in an entire protein, a portion of a protein, or any functional product. A gene may be made up of hundreds or thousands of DNA bases organized into coding and noncoding segments.

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Polypeptide chain

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A sequence of amino acids that may act alone or in combination with others as a functional protein.

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Mutation

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A change in DNA. Mutation refers to changes in DNA bases (specifically called point mutations) and also to changes in chromosomes number and /or stucture.

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Homeotic genes

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An evolutionarily ancient family of regulatory genes that directs the devlopment of the overall body plan and the segmentation of body tissues; aslo called homeobox or Hox genes.

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Sickle-cell anemia

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A severe inherited hemoglobin disorder that results from inheriting two copies of a mutant allele. This allele results from a single base substitution in the DNA.

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Point mutation

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A chemical change in asingle base of a DNA sequence.

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Interphase

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The portion of a cell's cycle during which metabolic processes and other cellular activities occur. Chromosomes are not visible as discrete stuctures at this time. DNA replication occurs during interphase.

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Chromatin

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The loose, diffuse form of DNA seen during interphase. When it condenses, chromation forms into chromosomes.

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Chromosomes

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Discrete stuctures composed of DNA and protein found only in the nuclei of cells. Chromosomes are only visible under magnification during certain phases of cell division.

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Centromere

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The constricted portion of a chromosome. After replication, the two strands of a double-stranded chromosome are joined at the centromere.

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Homologous

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Referring to members of chromosomes pairs. Homolgous chromosomes carry loci that govern the same traits. During meiosis, homologous chromosomes pair and exchange segments of DNA. They are alike with regard to size, position of centromere, and banding patterns.

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Locus (Plural: Loci)

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The position on a chromosome where a given gene occurs. The term is sometimes used interchangeably with gene, but this usage is technically incorrect.

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Alleles

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Alternate forms of a gene. Alleles occur at the same locus on homologous chromosomes and thus govern the same trait. However, because they are different, their action may result in different expressions of that trait. The term is sometimes used synonymously with gene.

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Autosomes

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All chromosomes except the sex chromosomes.

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Sex chromosomes

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In mammals, the X and Y chromosomes.

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Karyotype

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The chromosomal complement of an individual or that which is typical for a species. Usually displayed in a photomicrograph, the chromosomes are arranged in pairs and according to size and position of the centromere.

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Mitosis

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Simple cell division; the process by which somatic cells divded to produce two identical daughter cells.

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Meiosis

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Cell division in specialized cells in ovaries and testes. Meiosis involves two divisions and results in four daughter cells, each containing only half the original number of chromosomes. These cells can develop into gametes.

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Diploid

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Referring to the full complement of chromosomes in a somatic cell - both member of each pair.

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Haploid

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Referring to a half set of chromosomes, one member of each pair. Haploid sets are found in gametes.

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Recombination (crossing over)

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The exchange of genetic material between homologous chromosomes during meiosis.

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Random assortment

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The chance distribution of chromosomes to daughter cells during meiosis; along with recombination, the source of variation resulting from meiosis.

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Nondisjuction

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The failure of homologous chromosomes or chromosome strands to separate during cell division.

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Polymerase chain reaction (PCR)

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A method of producing thousands of copies of a DNA segment using the enzyme DNA polymerase.

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Recombinant DNA technology

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A process in which genes from the cell of one species are transferred to somatic cells or gametes of another species.

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Clone

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An organism that is genetically identical to antother organism. The term may also be used to refer to genetically identical DNA segments, molecules, and cells.

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Human Genome Project

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An international effort aimed at sequencing and mapping the entire human genome.

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Genome

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The entire genetic makeup of an individual or species. In humans, it is estimated that each individual possesses approximately 3 billion DNA nucleotides.