Bio Test 5

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Genotype

Back 1

actualgenetic make up of an individual.

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dominant

Back 2

expressionthat is alwaysexpressed if its gene is present in the genotype.

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Recessive

Back 3

expressionthat is expressed onlywhenits allele is the only form of the gene present in the genotype.

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incompletedominance

Back 4

Neitherallele is dominant to the other, thus each is expressed in theheterozygous genotype producing an intermediate phenotype. EX. Red(RR) and White (R’R’) snapdragons produce pink (RR’).

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Epistasis

Back 5

Acondition in which one gene pair has theability to mask or prevent the expression of another gene pair. EX.Coat color and pigment deposition in mice

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Co-dominance

Back 6

inheritancecharacterized by full expression of both alleles in the heterozygote.

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homozygous

Back 7

conditionwhere both members of a pair of gene are the same (ex. AA or aa )

Front 8

heterozygous

Back 8

conditionin where two expressions of a gene pair are different (ex. Aa)

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alleles

Back 9

differentforms of the same gene.

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locus

Back 10

locationof the gene on the chromosome.

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gene-

Back 11

Theunit of DNA along a chromosome that codes for a singlecharacteristic (Mendelian definition) or the unit of DNA thatcodes for a specific polypeptide (molecular definition).

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synapsis

Back 12

Pairingof homologous chromosomes

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cross-over

Back 13

Theexchange or mixing of similar genetic

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chiasmata

Back 14

criss-crossingof the non-sister chromatids

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karyotype

Back 15

displayof metaphase chromosomes where homologs are paired together andphotographed.

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pleiotrophy

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Theability of a single gene pair to have multiple effects. EX. Gene for Sickle-cell Anemia.

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sexchromosomes

Back 17

chromosomesinvolved in sex determination. in males they're the X and Ychromosomes.

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polygenicinheritance

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Acharacteristic that isdetermined by the quantitative effect of multiple pairof genes.

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Duplication

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Inthis situation a portion of a chromosomebreaks and attaches to its homologue, thus those genes arerepresented twice on the chromosome carrying the duplicated segment. Having an abnormal number of genes is often lethal in animals.

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Translocation

Back 20

n a portion of a chromosomebreaks and rejoins with a non- homologous chromosome. This type ofabnormality can result in an increased number of genes in a gamete orcan impact coordination of a metabolic path

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deletion

Back 21

Aportion of a chromosome is lost fromthe genome, thus these genes are not present in the gamete. The loseof genes from the genotype is serious and often lethal.

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Inversion

Back 22

inan inversion a section of a chromosomebreaks and rejoins with the same chromosome, but in a reversedorder. The proper sequence of genes is often important in thecoordination of metabolic pathways. If the inversion affects such apathway then it can have a serious impact.

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linkedgenes

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Refersto genes located on the same chromosome;Linked genes do not normally assort independentofeach other. Linked genes usually assort together. Independentassortment of chromosomes and unlinkedgenes.

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autosomes

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chromosomesnot involved in sex determination although they may carry genes forsecondary sexual characteristic.

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independentassortment of homologous chromosomes

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statesthat the members of one pair of homologous chromosomes segregateindependent of all other homologous pair during gamete formation.

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Genotype

Back 26

actualgenetic make up of an individual.

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Phenotype

Back 27

actualexpression of a characteristic.

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Characteristic

Back 28

heritablefeature such as flower color.

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trait

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variationsof a character such as white or purple flowers.

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truebreeding

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plantsself pollinate,offspring are identicle to parents

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hybrid

Back 31

matingof individuals with different expressions of a character

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lawof segregation-

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statesthat the members of a gene pair separate during gamete formation meaning that each gamete receives only one gene from each pairduring meiosis.

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testcross

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crossbetween an individual expressing a dominant phenotype with anindividual expressing the recessive expression of the same character

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ruleof addition

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Theprobability of an event that can occur in two or more ways is the sumof the separate probabilities of the different ways. EX. Parents areboth heterozygous for a given characteristic "Aa". What isthe probability of their having a child that is also "Aa"? The probability of the "A" allele being in the egg and "a"in the sperm is 1/2 X 1/2 = 1/4. The probability of the "a"allele being in the egg and the "A" in the sperm is 1/2 X1/2 = 1/4. Thus the probability of an "Aa" child is 1/4 +1/4 = 1/2.

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rule of multiplication

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The probability that independent events will occur simultaneously is the product of their individual probabilities. EX. The probability of giving birth to a daughter is 1/2 at any one birth. The probability of three consecutive daughters being born to a couple is 1/2 X 1/2 X 1/2 = 1/8.

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multiple alleles

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In this type of inheritance there are more than two alleles for the same characteristic in the general population, although any one individual only has two genes for the characteristic. EX. ABO blood group.

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Pedigrees

Back 37

Family history for a particular trait.Shows the relationship of parents to children over many generations.

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Barr body

Back 38

Condensed inactivated X chromosome.