Anthropology Midterm Study Guide 1

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DNA

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

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RNA

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A single-stranded moedule, similar in stucture to DNA. Three forms of RNA are essential to proten synthesis. They are messenger RNA, transfer RNA, and ribosomal RNA.

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Nucleotide

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

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Double helix

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The coiled structure of double-stranded DNA in which strands linked by hydrogen bonds form a spiral configuration, with the two strands oriented in opposite directions.

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Cell nucleus

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A stucture (organelle) found in all eukaryotic cells. The nucleus contains chromosomes. (Nuclear DNA)

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Nuclear membrane

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The double-layered membrane enclosing the nucleus of a cell.

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Ribosomes

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

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Amino acids

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Small molecules that are the components of proteins.

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Proteins

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3-D molecules that serve a wide variety of functions through their ability to bind to other molecules.

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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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Anticodon

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A sequence of three adjacent nucleotides in transfer RNA that binds to a corresponding codon in messenger RNA and designates a specific amino acid during protein synthesis.

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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 chromosome number and/or structure.

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Point Mutation

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A chemical change in a single base of a DNA sequence.

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Genotype

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The combination of alleles located on homologous chromosomes that determines a specific characteristic or trait. AB, AA, AO, BB, BO, OO

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Phenotype

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Expressed of genotypes. AB, A, B, O.

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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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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 orginal number of chromosomes. There cells can develop into gametes.

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Mitosis

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

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Diploid

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Referring to the full complement of chromosomes in a somatic cell - both members 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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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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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 fuctional product. A gene may by made up of hundreds or thousands of DNA bases organized into coding and noncoding segments.

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Allele

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Alternate forms of a gene. Allels 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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Locus

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The position on a chromosome where a given gene occurs. THe term is cometimes used inter changeably with gene, but this usage is technically incorrect.

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Mendelian traits

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Characteristics that are influenced by allels at only one genetic locus. Examples include many blood types, such as ABO. Many genetic disorders, including sickle-cell anemia and Tay-Sachs disease, are also Mendelian traits.

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Polygenic

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Referring to traits that are influenced by genes at two or more loci. Examples of such traits are stature, skin color, and eye color. Many polygenic traits are also influenced by environmental factors.

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Homologous chromosomes

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

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Homozygous

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Having the same allele at the same locus on both members of a chromosome pair.

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Heterozygous

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Having different alleles at the same locus on members of a chromosome pair.

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Dominant

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Describing a trait governed by an allele that can be expressed in the presence of another, different allele. Dominant alleles prevent the expression of recessive alleles in heterozygotes.

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Recessive

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Describing a trait that is not expressed in heterozygotes; also refers to the allele that governs the trait. For a recessive allele that goerns the trait. For a recessive allele to be expressed, there must be two copies of the allele.

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Codominant

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The expression of two alleles in heterozygotes. In this situation, neither allele is dominant or revessive; thus, both influence the pheotype.

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X-linked traits

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Caused by recessive allele at a locus on the X chromosome.