Lecture 20a - Supplementary Information on Disorders Due to Chromosome Numbers (Interest Only)

Lecture 20a - Supplementary Information on Disorders Due to Chromosome Numbers (Interest Only)

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1 Lecture 20a Supplementary Information on Disorders due to Chromosome Numbers You are not responsible for this information. It will not be on the exam. During S stage, the DNA replicates. The two original strands separate and another strand is formed on each strand. This is called “semi- conservative” (half of the original strand is kept) replication. Original strand New strand The Key stage which starts everything is interphase In the two strands of DNA, the bases are also complementary The complementary strands are coiled into a helix. Since one spiral is coiled around another spiral, the structure is called a double helix. The helix is wrapped around proteins called histones. And then coiled some more.
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2 And coiled some more so that in mitosis it looks like this. The parts of a chromosome during mitosis. Note that the chromosome has already replicated. Each chromatid is really a complete chromosome. However, because they
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Unformatted text preview: are still joined together, the two chromatids are considered to be one chromosome. At the end of mitosis, they will be separated, each chromatid going into a new cell – here designated by the different colours. Cell # 1 Cell # 2 3 Summary so far Chromosome number is halved during meiosis I (not shown) n = DNA Content Summary so far DNA content is halved at the end of meiosis II Review of allele and locus. A locus is a location; an allele is a form of a gene at a locus. After replication of a single chromosome, there are two chromatids. chromatid In meiosis, the chromosomes divide and then separate and go into 4 different cells Each allele of a chromosome pair will go into separate cells at the end of meiosis II. 4 Meiosis • In meiosis there is also recombination of DNA. End of Supplementary Lecture 20a You are not responsible for this material. No exam questions will be taken from Lecture 20a...
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This note was uploaded on 06/10/2008 for the course BIOL BIOL-1F25 taught by Professor Peery during the Spring '08 term at Brock University.

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Lecture 20a - Supplementary Information on Disorders Due to Chromosome Numbers (Interest Only)

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