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Chromosomes

Chromosomes. Packaged Instructions for Life. Structure. Chromosomes are packages of DNA wrapped with help of proteins called histones Composed of two identical sister chromatids attached at centromere. Chromosome levels organization: dsDNA Nucleosome Coiled solenoid/nucleosome

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Chromosomes

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  1. Chromosomes Packaged Instructions for Life

  2. Structure • Chromosomes are packages of DNA wrapped with help of proteins called histones • Composed of two identical sisterchromatidsattached at centromere

  3. Chromosome levels organization: • dsDNA • Nucleosome • Coiled solenoid/nucleosome • Chromatin • Supercoiled (condensed) chromatin • Chromosome

  4. Each sister chromatid contains thousands of identical genes in the same locations on each • Gene: segment of DNA that codes for specific proteins • Ex: brown hair, green eyes, etc Gene A Gene B Gene C Gene D Gene E

  5. Each human somatic or body cell contains two copies of each chromosome • 23 sets of chromosomes x 2 = 46 total (other species differ in numbers) • Combination of all 23 is TOTAL DNA genome (3 billion base pairs)

  6. One set (23rd) contains sex chromosomes X and/or Y • Females have XX • Males have XY (Y is just shorter) Females: XX Males: XY

  7. Two sets of chromosomes is termed diploid (somatic cells) • One set of chromosomes is termed haploid (gametes) • Necessary since combination of chromosomes from egg & sperm must be diploid to produce viable (able to live) offspring • Fertilized egg = zygote haploid diploid

  8. Diploids have same gene (eye color) but may have different variations (brown vs. blue eyes) • called homologouschromatids (similar info) • One from mother, one from father gene for eye color (mom’s brown eyes) dad’s blue eyes

  9. Map of all 23 sets of chromosomes from a body/somatic cell is called a karyotype • Numbered from 1 – 23 based on length, location of centromere, and banding pattern • #1-22 are called autosomes, #23 are sex chromosomes

  10. Typical Karyotype w/ 23 Chromosome Pairs female male

  11. Karyotypes are usually only completed for cases where there might be a chromosomal abnormality • Monosomy (missing homolog) • Trisomy (Extra homolog) • Incorrect sex chromosome numbers

  12. THE END • Quiz Friday 1/17/14 • 20 multiple choice

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