Chromosomal Mutations. A mutation is considered chromosomal if it is large enough to be seen with a...
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![Page 1: Chromosomal Mutations. A mutation is considered chromosomal if it is large enough to be seen with a light microscope using stains and/or fluorescent.](https://reader030.fdocuments.in/reader030/viewer/2022032606/56649eb35503460f94bbb5b4/html5/thumbnails/1.jpg)
Chromosomal Mutations
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A mutation is considered chromosomal if it is large enough to be seen with a light microscope using stains and/or fluorescent tags to highlight missing, extra, or moved material.
Too much or too little genetic material, particularly on the autosomes, can cause syndromes.
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Cytogenetics is a subdiscipline within genetics
Deals with chromosome variations In general, excess genetic material has milder effects on health than a deficit(Trisomies are not as bad to have as a monosomy)
Still, most large-scale chromosomal abnormalities present in all cells disrupt or halt prenatal development
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Made up of: DNA, replication enzymes, histone proteins, transcription factors, and RNA.
Organized according to size and centromere location.
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Centromere = point of attachment for spindle fibers during mitosis and meiosis. Repetitive sequence that may help orient chromosomes during division.
Metacentric = equal armsSubmetacentric = one long arm and one short arm
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Acrocentric = pinches off only a small amount toward one end
Telocentric = centromere at one end
Telomere = A chromosome tip
Position of the centromere in (A) metacentric; (B) submetacentric; (C) acrocentric; and (D) telocentric chromosomes.
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Stains are used to distinguish chromosomes.
Heterochromatin – darker-staining region. More highly coiled & more repetitive. May play a role in maintaining structure. (near centromere and telomeres)
Euchromatin – lighter-staining. Protein encoding genes.
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Portrait of a Chromosome
Figure 13.1
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Karyotype – size-order chart of chromosomes. They can:
confirm diagnosis.I.D. relatives with specific chromosomal abnormalities.
sometimes reveal the effects of environmental toxins.
clarify evolutionary relationships. Banding patterns are more similar in species that are more closely related.
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GET CELLS: Any cell other than red blood cells (no nucleus).
White blood cells (easy)
Red blood cell (left) and white blood cell (right)
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FETAL CELLS commonly tested AMNIOCENTESIS (1966) needle passes
through abdomen and fetal cells are obtained from the amniotic fluid.
Chorionic Villus Sampling Fetal Cell Sorting (from mom’s blood)
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Put cells in a hypotonic solution so they fill with water.
Drop the cells onto a slide and add a glass coverslip.
Photograph cells and make a print.
Cut out chromosomes and arrange by size. Now use software.
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Count the number. (46 in humans)
Use a combination of stains and DNA probes (labeled piece of DNA that binds to its complementary sequence)
Shorthand - # of chrom, Sex chrom, type of error
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Most frequent cause of spontaneous abortion.
POLYPLOIDY – Extra chromosome sets
2/3 from egg fertilized by two sperm.
Also from formation of a diploid gamete.
Some infants survive for a few days, but most are never born.
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ANEUPLOIDY – An extra or missing chromosome
“not good set” (Euploid – “good set”)
Result from NONDISJUNCTION (chrom. not separated properly during meiosis)
Most result in spont. Abortion.
Most survivors have mental retardation.
Sex chromosome aneuploidy is less severe.
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TRISOMY – an extra chromosomeDown syndrome – Trisomy 21Klinefelter syndrome – XXY, XXXY, XXXXY or XXX, XXXX, etc.
XYY Syndrome Trisomy 13 & 18
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MONOSOMY – one missing - Turner Syndrome – X
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Deletion – Part of chromosome missing
Duplication – Part of chromosome present twice
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Inversion – Gene Sequence Reversed
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