Chromosomes

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Chromosomes

• Chapter 8.1

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Objectives

• Describe the structure of a chromosome
• Identify the differences in structure between
  prokaryotic chromosomes and eukaryotic
  chromosomes
• Compare the number of chromosomes in different
  species
• Explain the difference between sex chromosomes
  and autosomes
• Distinguish between diploid and haploid cells

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Chromosome Structure

• Chromosomerod shaped structure made of DNA and
  protein
• This is the X shape you are familiar with
  seeing
• Allows the DNA to move around the cell easily
• When cells are not dividing, DNA is not wound up
  so tightly
• Chromatinless tightly wound DNA-protein complex
• Spends most of time like this

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Chromatin
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Chromosome Structure cont

• When it is time to reproduce, chromatin begins to
  coil up so it doesnt get tangled
• The wound chromatin thickens and shortens forming
  the familiar X

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histones
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Chromosome Structure cont

• Chromatid(arm) one of two strands of a
  chromosome visible during cell division
• When it divides each new cell will get one of the
  chromatids
• Centromerepoint where chromatids are attached

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Two Types of Chromosomes

• Sex ChromosomesDetermine the sex of the
  organism, genes for other characteristics may
  also be carried on these chromosomes
• Humans have 46 chromosomes, a certain two of them
  determine our sex
• If XX female
• If XY male
• AutosomesAll other chromosomes
• The remaining 44

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• Every cell produced by sexual reproduction has
  two copies of each autosome
• One copy came from mom, the other came from dad
• Homologous chromosomeschromosomes that are the
  same size, shape, and carry genes for the same
  traits, occur in pairs

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True or False

• The words cells and chromosomes can be used
  interchangeably
• FALSE

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Looking at cells based on how their chromosomes
are arranged

• Diploidcells that have chromosomes arranged in
  homologous pairs
• Body cells
• Haploidcells which contain only one chromosome
  from each pair
• Sex cells