Vocabulary chapter 17

allele: One of two or more molecular forms of a gene that arise by mutation and code for different versions of the same trait.

allele frequency: For a given gene locus, the relative abundances of each kind of allele among all the individuals of a population.

antibiotic: Metabolic product of soil microbes that kills bacterial competitors for nutrients.

balanced polymorphism: Form of selection in which two or more alleles for a trait are being maintained in a population over time.

biogeography: Scientific study of the world distribution of species.

bottleneck: Severe reduction in the size of a population, brought about by intense selection pressure or a natural calamity.

catastrophism: Idea that abrupt changes in the geologic or fossil record were divinely invoked.

comparative morphology: Scientific study of comparable body parts of adults or embryonic stages of major lineages.

directional selection: Mode of natural selection by which allele frequencies underlying a range of

phenotypic variation: shift in a consistent direction, in response to directional change or to new conditions in the environment.

disruptive selection: Mode of natural selection by which the different forms of a trait at both ends of the range of variation are favored and intermediate forms are selected against.

evolution: Genetic change in a line of descent. Outcome of microevolutionary events: gene mutation, natural selection, genetic drift, and gene flow.

fitness: Increase in adaptation to environment as brought about by genetic change.

fixation: Loss of all but one kind of allele at a gene locus for all individuals in a population.

fossil: Recognizable, physical evidence of an organism that lived in the distant past.

founder effect: A form of bottlenecking. By chance alone, a few individuals that establish a new population have allele frequencies that differ from those of the original population.

gene flow: Microevolutionary process; alleles enter and leave a population as an outcome of immigration and emigration, respectively.

gene pool: All genotypes in a population.

genetic drift: Change in allele frequencies over the generations due to chance alone. Its effect is most pronounced in very small populations.

genetic equilibrium: In theory, a state in which a population is not evolving. Compare Hardy-Weinberg rule.

Hardy-Weinberg rule Allele: frequencies stay the same over the generations when there is no mutation, the population is infinitely large and isolated from other populations of the species, mating is random, and all individuals are reproducing equally and randomly.

inbreeding: Nonrandom mating among close relatives that share many identical alleles.
lethal mutation Mutation with drastic effects on phenotype; usually causes death.

microevolution: Of a population, any change in allele frequencies resulting from mutation, genetic drift, gene flow, natural selection, or some combination of these.

mutation rate: Of a gene locus, the probability that a spontaneous mutation will occur during or between DNA replication cycle.

natural selection: Microevolutionary process; the outcome of differences in survival and reproduction among individuals that differ in details of heritable traits.

neutral mutation: A mutation with little or no effect on phenotype, so natural selection can't change its frequency in a population.

polymorphism: The persistence of two or more qualitatively different forms of a trait (morphs) in a population.

population: All individuals of the same species that are occupying a specified area.

sampling error: Use of a sample or subset of a population, an event, or some other aspect of nature for an experimental group that is not large enough to be representative of the whole.

sexual selection: A microevolutionary process; a type of selection that favors a trait giving an individual a competitive edge in attracting or keeping a mate. stabilizing selection: Mode of natural selection by which intermediate phenotypes in the range of variation are favored and extremes at both ends are eliminated.

theory of uniformity: Early theory that the earth's surface changes in gradual, uniformly repetitive ways. Has since been replaced by plate tectonics theory.

DNA...Chapters 13 & 14!!

1.adenine:A purine; a nitrogen-containing base in certain nucleotides. Base pairs with thymine in DNA.
2.cytosine:Pyrimidine; one of the nitrogen-containing bases in nucleotides.
3.guanine:Nitrogen-containing base in one of four nucleotide monomers of DNA or RNA.
4.thymine:A nitrogen-containing base; one of the nucleotides in DNA.




5.bacteriophage:Category of viruses that infect bacterial cells.
6.cloning:Making a genetically identical copy of DNA or of an organism.
7.deoxyribonucleic acid:Of cells and many viruses, the molecule of inheritance. H bonds join its two helically twisted nucleotide strands, one of which has instructions for synthesizing all of the enzymes and other proteins required to build and maintain cells.

8.DNA ligase:Enzyme that seals new base-pairings during DNA replication.
9.DNA polymerase:Enzyme of replication and repair that assembles a new strand of DNA on a parent DNA template.
10.DNA repair:Enzyme-mediated process that fixes small-scale alterations in a DNA strand by restoring the original base sequence.
11.DNA replication:Any process by which a cell duplicates its DNA molecules before dividing.
12.nucleotide:Small organic compound with deoxyribose, a nitrogenous base, and a phosphate group. Monomer for adenosine phosphates, nucleotide coenzymes, and nucleic acids.
13.x-ray diffraction image:Pattern that forms on film exposed to x-rays that have been directed at a molecule; reveals positions of atoms, not the molecular structure.
14.anticodon:Series of three nucleotide bases in tRNA; can base-pair with an mRNA codon.
15.base sequence:Sequential order of bases in a DNA or RNA strand.
16.base-pair substitution:One amino acid has replaced another during protein synthesis.
17.carcinogen:Any substance or agent that can trigger cancer.
18.codon:One of 64 possible base triplets in an mRNA strand. A code word for an amino acid in a polypeptide chain; a few codons also act as START or STOP signals for translation.
19.deletion:At cytological level, loss of a segment from a chromosome. At molecular level, loss of one to a few base pairs from a DNA molecule.
20.exon:One of the base sequences of an mRNA transcript that will become translated.
21.gene mutation: A small-scale change in the nucleotide sequence of a DNA molecule.
22.genetic code:The correspondence between nucleotide triplets in DNA and specific sequences of amino acids in a polypeptide chain; the basic language of protein synthesis in cells.
23.insertion:Insertion of one to a few bases into a DNA strand. Also, a movable attachment of muscle to bone.
24.intron:A noncoding portion of a pre-mRNA transcript; excised before translation.
25.ionizing radiation:High-energy wavelengths.
26.RNA:A single strand of ribonucleotides transcribed from DNA, then translated into a polypeptide chain. The only RNA encoding protein-building instructions.
27.mutation rate:Of a gene locus, the probability that a spontaneous mutation will occur during or between DNA replication cycles

Human Genetics!!

1.abortion:Premature, spontaneous or induced expulsion of the embryo or fetus from uterus.

2.aneuploidy: Having one extra or one less chromosome relative to the parental chromosome number.

3.autosome: Any chromosome of a type that is the same in males and females of the species.



4.crossing over: At prophase I of meiosis, an interaction in which non-sister chromatids of a pair of homologous chromosomes break at corresponding sites and exchange segments; genetic recombination is the result.

5.deletion: At cytological level, loss of a segment from a chromosome. At molecular level, loss of one to a few base pairs from a DNA molecule.

6.disease: Outcome of infection when defenses aren't mobilized fast enough and a pathogen's activities interfere with normal body functions.

7.double-blind: study Different investigators independently collect, then compare data.


8.duplication: Gene sequence repeated several to many hundreds or thousands of times. Even normal chromosomes have such sequences.

9.genetic abnormality: A rare or less common version of a heritable trait.

10.genetic disorder: Any inherited condition that causes mild to severe medical problems.


11.genetic recombination: Result of any process that puts new genetic information into a DNA molecule (e.g., by crossing over).

12.homologous chromosome: Of cells with a diploid chromosome number, one of a pair of chromosomes identical in size, shape, and gene sequence, and that interact at meiosis. Nonidentical sex chromosomes (e.g., X and Y) also interact as homologues during meiosis.


13.in-vitro fertilization: Conception outside the body (''in glass'' petri dishes or test tubes).

14.independent assortment: Mendelian theory that by the end of meiosis, each pair of homologous chromosomes (and linked genes on each one) are sorted before shipment to gametes independently of how the other pairs were sorted. Later modified to account for the disruptive effect of crossing over on linkages.


15.inversion: Part of a chromosome that became oriented in reverse, with no molecular loss.

16.karyotype: Preparation of metaphase chromosomes sorted by length, centromere location, other defining features.

17.linkage group: All genes on a chromosome.

18.mosaicism: Cells of same type express genes differently, so phenotypic differences emerge in same type of tissue. E.g., occurs by X chromosome inactivation in female mammals; also by nondisjunction in any cell after fertilization (only descendants of altered cell inherit the abnormal chromosome number).


19.Non-disjunction: Failure of sister chromatids or a pair of homologous chromosomes to separate during meiosis or mitosis. Daughter cells end up with too many or too few chromosomes.

20.polyploidy: Having three or more of each type of chromosome in the nucleus of a eukaryotic cell at interphase.


21.reciprocal cross: A paired cross. In the first cross, one parent displays the trait of interest. In the second, the other parent displays it.

22.sex chromosome :A chromosome with genes that affect sexual traits. Depending on the species, somatic cells have one or two sex chromosomes of the same or different type (e.g., in mammals, XX females, XY males).


23.syndrome: A set of symptoms that may not individually be a telling clue but collectively characterize a genetic disorder or disease.
translocation Of cells, movement of a stretch of DNA to a new chromosomal location with no molecular loss. Of vascular plants, distribution of organic compounds by way of phloem.


24.X chromosome: A type of sex chromosome. An XX mammalian embryo becomes female; an XY pairing causes it to develop into a male.

25.Y chromosome: A type of sex chromosome. An XX mammalian embryo becomes female; an XY pairing causes it to develop into a male.

Observing Patterns in Inherited Plants!!

Glossary





1.allele: One of two or more molecular forms of a gene that arise by mutation and code for different versions of the same trait.





2.codominance: In heterozygotes, simultaneous expression of a pair of nonidentical alleles that specify different phenotypes.

3.continuous variation: Of a population, a more or less continuous range of small differences in a given trait among its individuals.



4.dihybrid cross: An intercross between two F1 heterozygotes that are identical for two gene loci; the dihybrids are offspring of parents that bred true for different versions of two traits.

5.epistasis: Interaction among the products of two or more gene pairs.

6.F1: The offspring of an initial genetic cross.

7.F2: The offspring of parents who are the first filial generation from a genetic cross.




8.gene: Unit of information for a heritable trait, passed from parents to offspring.

9.genotype: Genetic constitution of an individual; a single gene pair or the sum total of an individual's genes.

10.heterozygous: Having a pair of nonidentical alleles at a gene locus (that is, on a pair of homologous chromosomes).


11.homozygous dominant: Having a pair of dominant alleles at a gene locus (on a pair of homologous chromosomes).

12.homozygous recessive: Having a pair of recessive alleles at a gene locus (on a pair of homologous chromosomes).

13.hybrid: offspring Of a genetic cross, offspring having a pair of nonidentical alleles for a trait.

14.incomplete dominance:Condition in which one allele of a pair is not fully dominant; a heterozygous phenotype somewhere between both homozygous phenotypes emerges.

15.independent assortment: Mendelian theory that by the end of meiosis, each pair of
homologous chromosomes (and linked genes on each one) are sorted before shipment to gametes independently of how the other pairs were sorted. Later modified to account for the disruptive effect of crossing over on linkages.


16.monohybrid cross: Intercross between two F1 heterozygotes that are identical for one gene locus; offspring of two parents that breed true for different forms of a trait.

17.multiple allele system: Three or more slightly different molecular forms of a gene that occur among individuals of a population.

18.phenotype: Observable trait or traits of an individual that arise from gene interactions and gene-environment interactions.

19.pleiotropy: Positive or negative effects on two or more traits owing to expression of alleles at a single gene locus. Effects may or may not emerge at the same time.

20.probability: The chance that each outcome of a given event will occur is proportional to the number of ways the outcome can be reached.


21.Punnett-square: method Construction of a simple diagram as a way to predict probable outcomes of a genetic cross.

22.segregation: Mendelian theory. Sexually reproducing organisms inherit pairs of genes (on pairs of homologous chromosomes), the two genes of each pair are separated from each other at meiosis, and they end up in separate gametes.

23.testcross: Experimental cross to determine whether an individual of unknown genotype that shows dominance for a trait is either homozygous dominant or heterozygous.

24.true-breeding lineage: Of sexually reproducing species, a lineage in which only one version of a trait appears over the generations in all parents and their offspring