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31 Cards in this Set
- Front
- Back
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Define gene
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"a heritable factor that controls a specific characteristic"
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What is the relationship between genes, chromosomes, and alleles?
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Chromosomes are very long pieces of DNA packed with proteins. The majority of the DNA is not genes; it is repetitive sequences. There can be thousards of genes on a chromosome. A particular gene will have an "address" (location where it is always found) on a chromosome called its locus. For a particular gene there can be slightly different versions of the DNA sequence called alleles; which alleles a person has for a gene (genotype) will determine what trait (phenotype) is seen in the person.
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Define allele
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"one specific form of a gene, differing from other alleles by only a few bases and occupying the same gene locus as other alleles of the gene"
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Define locus
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"the particular location on homologous chromosomes of a gene" (plural=loci)
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Define genome
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"the whole of the genetic information of an organism"
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Define genotype
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"the alleles of an organism"
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Define phenotype
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"the characteristics of an organism"
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Define dominant allele
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"an allele that has the same effect on the phenotype whether it is in the homozygous or heterozygous state"
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Define recessive allele
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"an allele that only has an effect on the phenotype when present in the homozygous state"
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Define codominant alleles
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"pairs of alleles that both affect the phenotype when present in a heterozygote" (don't use the term incomplete dominance)
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Define homozygous
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"having two identical alleles of a gene"
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Define heterozygous
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"having two different alleles of a gene"
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Smooth pea pods are dominant over wrinkled pea pods. What genetype(s) result in wrinkled pea pods?
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ss
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Smooth pea pods are dominant over wrinkled pea pods. What genetype(s) result in smooth pea pods?
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SS and Ss
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Define carrier
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"an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele"
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Tay-Sachs disease is caused by an autosomal recessive allele. A person has the genotype nn. What is the person's phenotype?
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The person has Tay Sach's disease
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Tay-Sachs disease is caused by an autosomal recessive allele. What is the genotype of a carrier for Tay-Sachs?
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Nn
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Define test cross
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"testing a suspected heterozygote by crossing it with a know homozygous recessive" (don't use the term backcross)
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Smooth pea pods are dominant over wrinkled pea pods. Describe a test cross with this organism.
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In a test cross you would have a smooth pea plant with an unknown genotype (SS or Ss) and you would cross it with a wrinkled pea plant (ss). If all of the offspring were smooth then you would know the smooth parent plant was SS; if the offspring were a mix of wrinkled and smooth then the smooth parent was Ss.
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Define autosomes
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a chromosome that is not a sex chromosome (chromosome pairs 1-22 in humans)
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How many autosomes does a normal human have?
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44
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What sort of chromosomes control gender?
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sex xhromosomes; XX is normal female and XY is normal male. (In cases with nondisjunction; as long as there is a Y chromosome the person is male. You need a minumum of 1 X chromosome to live.
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Define X-linked
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a gene found on the X chromosome
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Define Y-linked
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a gene found on the Y chromosome
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Define sex linkage
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genes for a trait are located on the sex chromosomes
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Define sex chromosomes
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a chromosome involved in determining the sex of the individual (the X and Y chromosomes in humans)
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How many chromosomes does a normal human have?
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46
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How many sex chromosomes does a normal human have?
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2 (either XX or XY)
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Define linkage group
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genes found together on the same chromosome close enough that they tend to be inherited together (required for IB; not required for CP)
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Define polygenic inheritance
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additive effect of 2 or more genes on a single phenotypic character
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Define multiple alleles
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having more than 2 alleles for a gene
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