Biology 313: Exam 2

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proband

Back 1

person from the pedigree is initiated

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consanguinity

Back 2

mating between closely related people

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concordance

Back 3

percentage of twin pairs that are concordant (both have the trait)

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amniocentesis

Back 4

procedure for obtaining a sample of amniotic fluid; analyzed for chemical, DNA, and chromosomal

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Unlinked genes

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1:1:1:1 ratio

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Partial linkage

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PAR > REC

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Complete Linkage

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PAR: 1 REC: 0

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Recombinant distance

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(# Recombinant progeny / #Total progeny) X 100

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Chance of a double cross over

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SCO1 X SCO2 = DCO

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crossover interference

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number of observed double crossovers is usually less than expected
(1-Coefficient of Coincidence)
Ex 0.6 means 60% did not occur as predicted

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Coefficient of Coincidence

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observed DCO/ expected DCO

-expected: probability of crossover (single recombination frequences, or map distance) X total progeny

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Cell fusion

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mapping technique; analysis of human tissue in culture

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LOD analysis

Back 13

mapping technique; based on pedigree

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LOD values

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STUDY power point

LOD: logarithm of odds (probability that genes are actually linked)

LOD > 3.0: linkage.
LOD < -2.0: no linkage (exclusion).
LOD between 3.0 & -2.0: inconclusive

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pericentric inversion

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chromosome inversion that includes the centromere in the inverted region

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alternate segregation

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type of segregation that takes place in heterozygote for a translocation

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allopolyploid

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condition in which the sets of chromosomes of a polyploid individual possessing more than two haploid sets are derived from two or more species

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autopolyploid

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sets of chromosomes of a polyploid individual possessing more than two haploid sets are derived from an identical species member

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AC element

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transposable element in Maize; autonomous due to a gene that it contains which encodes a transposase enzyme

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nonrecombinant gametes

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parental gametes; gametes that contain only original combinants of alleles present in the parents

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coupling

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cis configuration; wild-type alleles are found on one chromosome and mutant alleles are found on other

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repulsion

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trans configuration: each chromosome contains one wild type and one mutant alleles

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genetic maps

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chromosome maps calculated by using the genetic phenomenon of recombination

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somatic-cell hybridization

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requires the fusion of different types of cells; cells altered by viruses or tumors will divided indefinitely
provide cell line

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heterokaryon

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cell with two nuclei
*hybrid cells shed chromosomes as they divide (lost from only one species-lost of human chromosomes in human/mice tumor cross)

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episomes

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plasmids that are capable of freely replicating and able to integrate into the bacterial chromosomes

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intragenic mapping

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different sites within a single gene are mapped using techniques similar to those described for mapping bacterial genes by transduction

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High Frequency Recombination (Hfr) Strains

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-The F-factor integrates into the bacterial chromosome.
-F integration occurs at many different sites in the bacterial chromosome.

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electroporation

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used prior to transformation; creates "pores" in bacteria, allowing DNA fragments to pass through

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Mapping Phage Chromosomes

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-Recombination produces parental and recombinant phage
-Recombinant frequency is used to map phage genes.

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Map distance (phage)

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= [#recombinant plaques / # total] X100

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Fine Structure Mapping

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Mapping distances within a gene.
-each alleles: DNA sequence change

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cistron

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-segment of DNA that contains all the information for production of single polypeptide
-mutant alleles within one cistron will not complement

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complementation

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production of normal phenotype in an individual heterozygous for two closely related mutations with one on each homologous chromosome and at a slightly different position

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Retrovirus

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-virus w/ RNA genome
-reverse transcriptase

gag: viral capsid proteins
pol: integrase and reverse transcriptase
env: viral envelope proteins

may also contain oncogenes (stimulate cell divisions, cause tumors)

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HIV

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-infects T cell
-cripples immune system
-leads to AIDS

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RII locus and fine structure mapping

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RII mutants: produce r (rough) plaques on E. coli strain B but not K

Wild type: smooth plaques on E. coli strains B and K

by crossing more than one mutant type, one can tell if the mutations are on the same cistron (if not, complementation will result and the phage will revert to wild type)

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Chromosome rearrangements affect chromosome pairing in ____

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meiosis I

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Haplo-insufficient

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lower gene dosage; abnormal development

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triplo-abnormal

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too high gene dosage; abnormal development

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heterokaryon

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used in cell fusion mapping
-Human chromosomes are lost from hybrid cells, giving lines containing different human chromosomes

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paracentric inversion

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have inversion loops in Meiosis I (no centromere)

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Nucleotide

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The linked repeating unit of DNA that is made up of a sugar, phosphate, and a base.

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Retrotransposon

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(also called Class II transposons) Elements that transpose through an RNA intermediate.

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Fine structure map

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A technique for mapping DNA that uses the probability of the rarest instances of recombination to determine the order of genes and the distance between them.

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Coefficient of Coincidence

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The ratio of observed double crossovers to expected double crossovers.

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Nucleosome

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A core particle of DNA wrapped around an octamer of eight histone proteins two times. The simplest level of chromatin structure.

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Translocations

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exchanges between non-homologous chromosomes

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Robertsonian translocations

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exchanges of whole chromosome arms

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Aneuploidy

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2n +/- x chromosomes
types end in -omy

cause: Non-disjunction during the first or second meiotic division.

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Downs, Edwards

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Trisomy 21, 18

Down: mental retardation

Edwards: death prior to age one

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purines

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guanine and adenine

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pyrimidines

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cytosine, thymine, uracil

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attachment on DNA carbon ends

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phosphate: 5'
base: 1'

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Chargaff’s rule

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A/T and C/G ratios

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cytosine methylation

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key role in imprinting and gene activation (methylation inactivates)

-methyl (CH3) group added to pyrimidine cytosine (or adenine in bacteria)