15.3 Notes – Linked Genes – Flashcards
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define linked genes
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genes located near each other on the same chromosome than tend to be inherited together in genetic crosses; such genes are said to be genetically linked
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define parental phenotype
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trait combination seen in P generation
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define genetic recombination
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the production of offspring with combinations of traits that differ from those found in either parent
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define parental types
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an offspring with a phenotype that matches one of the true-breeding parental generation phenotypes; also refers to the phenotype itself
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define recombinant types OR recombinants
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an offspring whose phenotype differs from that of the true-breeding P gen parents; also refers to the phenotype itself
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A 50% frequency of recombination means what
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the 2 genes are located on different chromosomes and thus are NOT linked
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what is the physical basis of recombination between unlinked gens
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the random orientation of homologous chromosomes at metaphase I of meiosis, which leads to independent assortment of the 2 unlinked genes
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the occurrence of parental types with a frequency greater than 50% indicates what
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that the genes ARE linked
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what can break the physical connection between specific allele on the same chromosome
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crossing over
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what accords for the recombination of linked genes
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crossing over
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when does crossing over occur
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in prophase of meiosis I
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what determines which genetic combinations persist over time
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the interplay between environment and genotype
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define genetic map
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an ordered list of the genetic loci along a particular chromosome. First done by Alfred H sturtervant
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the percentage of recombinant offspring is also known as what
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the recombination frequency
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the percentage of recombinant offspring (the recombination frequency) depends on what
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the distance between genes on a chromsome
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the farther apart 2 genes are, the _________ the probability that a crossover will occur
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higher, thus the higher the recombination frequency
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define linkage map
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a genetic map based on recombination frequencies
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define map units
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distance between genes, 1 map unit = a 1% recombination frequency
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define linkage groups
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groups of linked genes
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why does a linkage map portray order of genes along a chromosome, but NOT the recipe location of such gens
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because frequency of crossing over is not uniform across a chromosome
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define cytogenetic maps
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locate genes with respect to chromosomal features, such as stained bands, seen in microscope
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what is the raw material for natural selection to occur
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genetic variation
