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15 Cards in this Set
- Front
- Back
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plasmid
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small loops of DNA that carry extra copies of genes found on the chromosome in prokaryotes.
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chromatin
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the form that DNA is in at all times apart from division. Consists of loosely packed DNA associated with histone proteins
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nucleosome
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a structure formed by DNA coiled twice around eight histone proteins. When DNA is uncoiled, nucleosomes look like beads on a string.
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histone proteins
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a protein involved in DNA coiling
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homologous chromosomes
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Two chromosomes, similar in size, banding pattern and position of centromeres, with the same genes but maybe different alleles. One of a pair comes from the father and the other comes from the mother.
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diploid
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The condition when a cell has two versions of every chromosome, the two versions of each chromosome are homologous. In humans 2n=46
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haploid
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The condition when a cell has only one version of each chromosome. These are normally gametes (sex cells) such as sperm and eggs.
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karyogram
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Photo or diagram of the chromosomes present in an individual in the homologous pairs in decreasing length
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karyotype
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a description of the number, appearance and types of chromosomes present in a nucleus
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Down's syndrome
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a genetic disorder caused by having three copies of chromosome 21 rather than the normal two (trisomy 21)
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sex chromosomes
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chromosomes that determine sex
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autosomes
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chromosomes that do not determine sex (i.e. normal chromosomes)
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Cairns' technique
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3H-thymidine, a nucleotide similar to thymine, contains a radioactive form of hydrogen. This can be detected by autoradiography to form an image of the DNA and therefore determine its length. Developed by John Cairns in 1962.
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autoradiography
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a technique in which radiation from a substance is captured on photographic film or by a camera sensor
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genome size
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total length of DNA in a single cell of an organism
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