Chromosomes
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Chromosomes PowerPoint PPT Presentation


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Chromosomes. During cell division, DNA must be neatly packed into structures called chromosomes Chromosomes- rod shaped structures made of DNA and proteins Contain our genes. Chromosome structure Consists of 2 identical halves Each half- chromatid Each chromatid represents one DNA molecule

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Chromosomes

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Chromosomes

Chromosomes

  • During cell division, DNA must be neatly packed into structures called chromosomes

    • Chromosomes-rod shaped structures made of DNA and proteins

      • Contain our genes


Chromosomes

  • Chromosome structure

    • Consists of 2 identical halves

      • Each half- chromatid

      • Each chromatid represents one DNA molecule

    • Two chromatids of chromosome are attached at a point called a centromere

    • Chromatin- uncoiled DNA; present in between cell divisions


Chromosomes

  • Chromosome Numbers

    • Each species has a characteristic number of chromosomes in each cell ( ex: humans = 46; dogs = 78)

    • Sex Chromosomes- chromosomes that determine sex of organism

      • Human females have two X chromosomes

      • Males have one X and one Y chromosome


Chromosomes

  • Autosomes- all other chromosomes in an organism

    • Every cell has two copies of each autosome, one from each parent

    • The 2 copies of each autosome called homologous chromosomes

    • Homologous chromosomes are same size, shape and carry genes for same traits


Chromosomes

  • Chromosome numbers

    • Karyotype- photomicrograph of chromosomes in a normal dividing human cell


Chromosomes

  • Chromosome numbers

    • Diploid- cells having 2 sets of chromosomes

      • 2 autosomes for each homologous pair

      • 2 sex chromosomes

      • Abbreviated 2n

      • In humans, diploid or 2n number is 46- 22 pairs of homologous autosomes and 2 sex chromosomes

    • Haploid- cells containing only one set of chromosomes (ex. Sperm and egg)

      • Only one autosome of each homologous pair and only one sex chromosome

      • Abbreviated - n

      • n number = 23 in humans


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