Unlv, 196, Chapter 8 Review

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Character

Back 1

Observable physical fearure: flower color, seed shape)

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Trait

Back 2

particular form of a character (purple flowers or white flower, wrinkled seeds)

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Heritable trait

Back 3

the proportion of observed differences on a trait among individuals of a population that are due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics (in their "phenotypes").

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true-breeding

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have two copies of the same allele(homozygous; SS or ss)

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parental generation(P)

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the individuals that mate in a genetic cross. Their offspring are the first filial generation

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first filial generation(F1)

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The immediate progeny of the parent generation

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second filial generation(F2)

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the immediate progeny of a mating between members of the F1 generation

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Dihybrid cross

Back 8

The Punnett square that determines the genotype for two genes on one chromosome

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Dominance

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in genetics, the ability of one allelic form of a gene to determine the phenotype of a heterozygous individual in which the homologous chromosomes carry both it and a different allele.

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recessive

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in genetics an allele that does not determine phenotype in the presence of a dominant allele

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pariculate theory

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each determinant was physically distinct and remained intact during fertilization

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blending theory

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gametes contained determinants that blended when gametes fused during fertilization

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diploid(2n)

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having a chromosome compliment consisting of two copies (homologs) of each chromosome. Designated 2n

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Haploid

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having a chromosome complement consiting of just one copy of each chromosome; designated n

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gene

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a unit of heredity. Used here as the unit of genetic function which carries the information for a polypeptide or RNA

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alleles

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a specific form of a gene at a given locus on a chromosome. smound multiple possicle forms.

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locus(loci)

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in genetics, A specific location on a chromosome. May be considered synonymous with gene

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homologous pair

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a pair of matching chromosomes made up of a chromosome from each of the two sets of chromosomes in a diploid organism

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Heterozygous

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in diploid organisms, having different alleles of a given gene on the pair of homologs carrying that gene (Ss or Tt)

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Homozygous

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in a diploid organisms, having identical alleles of a given gene on both homologous chromosomes. An individual may be a homozygote with respect to one gene and a heterozygote with respect to another.(SS=eye color while Bb= hair color)

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Phenotype

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the observable properties of an individual resulting from both genetic and enviornmental factors

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Genotypes

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an exact description of the genetic constitution of an individual, either with respect to to a single trait or with respect to a larger set of traits

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law of segregation

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in genetics, the separation of alleles, or of homologous chromosomes, from each other during meiosis so that each of the haploid daughter nuclei produced contains one or the other member of the pair found in the diploid parent cell, but never both. This principle was articulated by Mendel as his first law

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Punnett square

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method of predicting the results of a genetic cross by arranging the gametes of each parent at the edges of a square

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test cross

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ating of a dominant phenotype individual(who may be either heterozygous or homozygous with a homozygous-recessive individual)

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dihybrid cross

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a mating in which the parents differ with respect to the alleles of two loci of interest

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law of independent assortment

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during meiosis the random separation of genes carried on non-homologous chromosomes into gametes so that inheritance of these genes is random. This principle was articulated by mendel as his second law

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multiplication rule

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the probability of two independent outcomes occurring together is found by multiplying the two individual probabilities

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addition rule

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he probability of an event that can occur in two or more different ways is the sum of the individual properties of those ways

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pedigree

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the pattern of tranmission of a genetic trait with in a family

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mutations

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a change in the genetic material not caused by recombination

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wild-type

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geneticists' term for standard or reference type . Deviants from the standard even if the deviants are found in the wild, are usually referred to as mutant. (note this terminology is not usually applied to human genes).

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polymorphic

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coexistence in a population of two or more distinct traits

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incomplete dominance

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Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.

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e

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condition in which two alleles at a locus produce different phenotypic effects and both effects appear in heterozygotes

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pleiotrophy

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s when one gene influences multiple, seemingly unrelated phenotypic trait, an example is being phenylketonuria, which is a human disease that affects multiple systems but is caused by one gene defect.

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epistasis

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interaction between genes in which the presence of a particular allele of one gene determines how another gene will be expressed(different from pleitrophy)

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hybrid vigor

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superior fitness of heterozygous offspring as compared with that of their dissimilar homozygous parents. Also called heterosis

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quantitative trait loci

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phenotype determined by mulple genes

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recombinant frequencies

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proportion of offspring of a genetic cross that have phenotypes different from the parental phenotypes due to crossing over between linked genes during gamete formation

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genetic map

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"Any method used for determining the location of and relative distances between genes on a chromosome." The essence of all genome mapping is to place a collection of molecular markers onto their respective positions on the genome. Molecular markers come in all forms.

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map units(centimorgans)

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is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions (also termed, loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01.

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sex chromosomes

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in organisms with ta chromosomal mechanism of sex determination, one of the chromosomes involved in sex determination

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autosomes

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any chromosome(in eukaryotes) other than a sex chromosome

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hemizygous

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in adiploid organism, having only one allel for a given trait, typically the case for W-linked genes in male mammals and Z-linked genes in female birds(contrast with homozygous and heterozygous)

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sex-linked inheritance

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inheritance of a gene that is carried on a sex chromosome. Also called sex linkage

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carrier

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someone who is not affected by the chromosome but still carries the genes for the disease.

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sex pilus

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a thin connection between two bacteria through which genetic material passes during conjugation

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conjugation tube

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the tube that forms between prokaryotes for bacterial conjugation

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plasmids

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a DNA molecule distinct from the chromosomes; that is , an extra chromosomal element; found in many bacteria. May replicate independently of the chromosome.

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Genotypic ratio

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the ratio for the genetic out come of an organism(3:2:1)

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phenotypic ratio

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the ratio for the phenotypic response of the genes(Ss vs SS=S, since the S is dominant)

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What were the pre-Mendelian concepts of inheritance?

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Blending theory-gametes contained hereditary determinants that blended when the gametes fused during fertilization

Particulate theory- each determinant had a physically distinct nature; when gametes fused in fertilization the determinants remained intact

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how did mendel investigate inheritance

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mendel worked with true breeding lines of garden peas crossed the homozygous dominant and the recessive to expose certain characteristics: reound vs wrinkled then round vs wrinkled and yellow vs green

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how many alleles does a true-breeding plant have? Why?

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2 alleles, but they both express the same gene. This plant inherited the dominant or recessive homozygous genes from the parental line