BIOL 1010 1st Edition Final Exam Study Guide Chapter 9 Terms and definitions Genetics The study of genes and inheritance Blending model of heredity The idea that maternal and paternal characteristics blend to produce the characteristics found in the offspring just as cream mixes with dark brown coffee to produce the beige colored caf au lait disproved by Mendelian genetics Particulate model of heredity Mendel s idea that heredity could be governed by particles that retain their identity from generation to generation Principle of segregation Mendel s first law the principle of segregation states that sexually reproducing diploid organisms have two alleles for each gene and that during the gamete formation these two alleles separate from each other so that the resulting gametes have only one allele of each gene Principle of Independent assortment Mendel s second law the random dis tribution of genes located on different chromosomes to the gametes the principle of independent assortment Gene Gr genos birth or race The biological unit of inheritance that transmits hereditary information from parent to offspring and controls the appearance of a physical behavioral or biochemical trait A gene is a specific discrete portion of the DNA molecule in a chromosome that encodes an rRNA molecule Allele One of the alternative forms of a gene Autosome A chromosome other than a sex chromosome Sex chromosomes Pairs of chromosomes where the members of the pair are dissimilar in different sexes and are involved in sex determination such as the X and Y chromosomes Sex limited A trait that is confined to one sex Carrier In genetics a heterozygous individual not expressing a recessive trait but capable of passing it on to her or his offspring Codominance The genetic situation in which both alleles in a heterozygous individual are fully expressed in the phenotype this is a characteristic of human blood types Incomplete dominance The genetic situation in which the phenotype of the heterozygote is intermediate between the phenotypes of two homozygotes Pleiotropy The condition in which a single gene affects two or more distinct and seemingly unrelated traits Epistasis The interaction between two nonallelic genes in which one gene masks the expression of the other Hybrid An offspring resulting from the mating between individuals of two different genetic constitutions Dihybrid cross A mating between two individuals in which the investigation follows the inheritance of only two traits Parental P1 generation In Mendelian genetics the individuals that give rise to the first filial F1 generation First filial F1 generation In Mendelian genetics the first generation in the line of descent Second filial F2 generation In Mendelian genetics the second generation in the line of descent Dominant In genetics an allele or corresponding phenotypic trait that is expressed in the heterozygote in other words that shows in the hybrid Recessive An allele or corresponding pheno typic trait that is hidden by a dominant allele in a heterozygote Genotype The genetic makeup of an individual Phenotype The physical appearance of an organism controlled by its genes interacting with the environment Heterozygote An organism with two different alleles for a given trait Heterozygous Gr heteros different zygotos pair Having two different alleles for a specific trait Homozygote An organism with two identical alleles for a given trait Homozygous Having two identical alleles for a specific trait Locus pl loci The location of a gene on a chromosome Linkage Alleles of two genes located so close to each other on the same chromosome that they fail to assort independently Mutation Any heritable change in the base sequence of an organism s DNA Pedigree An orderly diagram of a family s relevant genetic history Punnett square In genetics a diagrammatic way of presenting the results of random fertilization from a mating Recombinant Chromosomes of mixed ancestry contained within individual haploid cells after meiosis II Somatic gene therapy The deliberate genetic alteration of body cells not sex cells to treat disease Amniocentesis A procedure for obtaining fetal cells from amniotic fluid for the diagnosis of genetic and other abnormalities Chorionic villus sampling A procedure for removing fetal cells from the chorion in the developing placenta for the diagnosis of genetic defects Germ line gene therapy The deliberate genetic alteration of sex cells to treat disease dinoflagellates Protists with armorlike coverings and two flagella one in a beltlike groove and the other trailing behind often can cause red tides Diplomonad The group of protists that includes Giardia a common human parasite endospore A heavily encapsulated resting cell formed within many types of bacterial cells during times of environmental stress Euglenoid Green spindle shaped protists with eyespots extremophiles Prokaryotes that survive in Earth s most extreme environments foraminiferans Delicately shaped protists that live in the oceans and secrete usually whitish calcium based shells frond The leaflike structure of an individual alga that collects sunlight and produces sugars Also refers to the large divided leaf on a fern fruiting bodies A spore producing reproductive structure in many fungi gram negative cells Prokaryotes in which the peptidoglycan layer is covered by an outer sheet of proteins and lipopolysaccharides don t pick up Gram s stain gram positive cells Prokaryotes containing peptidoglycans in a single broad layer do pick up Gram s stain Gram s stain A special stain that distinguishes gram positive and gram negative organisms green algae Protists with green pigments that are closely related to plants also called Chlorophyta halophile A type of archaebacterium that can tolerate extremely high salt concentrations heterotroph Gr heteros different trophos feeder An organism such as an animal fungus and most prokaryotes and protists that takes in preformed nutrients from external sources holdfast A rootlike anchor that attaches an alga to its substrate such as a rock on the ocean floor hypha pl hyphae kelp Kinetoplastid One of many long thin filaments of cells that make up a multicellular fungus One of the largest members of the algal world a brown alga Primitive protists with long whiplike flagella includes the protist causing African sleeping sickness macronucleus In ciliates a large nucleus containing many sets of chromosomes that control cell activities methanogen A