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28 Cards in this Set
- Front
- Back
Genes located on the same chromosome are referred to what?
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syntenic genes
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Why are syntenic genes often referred to as linked genes?
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since they are so close together their alleles cannot assort independently
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Which of the following statements about genetic linkage is generally true?
A. Crossing over is more likely to occur between linked genes that are close to one another than between genes that are farther apart on a chromosome. B. Individuals that are heterozygous for two linked genes (AaBb) will produce roughly equal numbers of recombinant and parental gametes. C. Individuals that are heterozygous for two linked genes (AaBb) will produce genetically different gametes in a ratio of 1:1:1:1. D. Genetic linkage results in the production of significantly more parental gametes, and significantly fewer nonparental (recombinant) gametes than expected by chance. |
D. Genetic linkage results in the production of significantly more parental gametes, and significantly fewer nonparental (recombinant) gametes than expected by chance.
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True or False: Crossing over during prophase I of meiosis occurs between alleles on sister chromatids
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False: Crossing over during meiosis occurs between alleles on NON-SISTER chromatids.
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Who is generally credited with creating the first genetic linkage map?
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Alfred Sturtevant
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What is the definition of a map unit?
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One percent recombination (or more precisely, one percent recombinant products of meiosis)
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How can genetic linkage be quantified?
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It can be quantified to map the positions of genes on chromosomes.
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Alleles of syntenic genes can be reshuffled when crossing over occurs between homologs to produce what?
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recombinant chromosomes
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Homologs that do not reshuffle alleles under study are called ___ or _____ chromosomes
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parental chromosomes or nonrecombinant chromosomes
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What does genetic linkage mapping accomplish?
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It plots the positions of genes on chromosomes
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True or False: Independent assortment of syntenic genes can occur if they are close together on a chromosome so that recombination occurs very frequently
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FALSE: if the are far apart on a chromosome so that recombination occurs very frequently
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TRUE OR FALSE: Incomplete genetic linkage is much more common than complete linkage
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True
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Does genetic linkage leads to the production of significantly more gametes with parental allele combinations or significantly more gametes with nonparental combinations?
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Genetic Linkage leads to significantly more gamete with PARENTAL alleles.
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genetic linkage can be recognized by comparing what?
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by comparing observed frequencies of gametes or progeny phenotypes with those expected under independent assortment.
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When does independent assortment of syntenic genes occur?
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if they are far apart on a chromosome so that recombination occurs very frequently
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Crossing over that prevents linked genes from segregating together occurs in what stage?
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during prophase I of meiosis
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TRUE OR FALSE: If genes are linked, parental allele combinations will be observed at higher frequency than predicted by chance
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TRUE
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When does complete genetic linkage occur?
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When NO CROSSING OVER occurs between linked genes; only parental gametes are formed?
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What organisms exhibit complete linkage?
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Male Drosophila (flys) -- means no crossing over.
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what is the biological basis for complete genetic linkage?
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unknown
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Morgan figured out what ____ and ____ had identified as genetic linkage
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Batsen and Punnett
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How did Morgan realize that linkage of autosomal genes in Dorosphila could be interpreted?
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Two-Point Test-Cross anaylsis
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TRUE OR FALSE: Genetic linkage is a not a physical relationship between genes located near one another on a chromosome
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FALSE: Genetic linkage is A PHYSICAL relationship between genes located near one another on a chromosome
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Genetic Linkage Mapping Is Based on what?
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Recombination Frequency Between Genes
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what is another name for a map unit?
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centiMorgan (cM)
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1% recombination = how many m.u or cM
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one
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Recombination frequency is likely a reflection what?
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physical distance between two genes
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how is recombination (r) frequency measured?
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r= number of recombinant gametes/ total number of meiosis
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