Cell Reproduction

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Chapter 8

• Cell Reproduction
• Section 8.1

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Chromosomes

• DNA- deoxyribonucleic acid
• Consists of six billion pairs of nucleotides

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Eukaryotic Cells

• During cell division, DNA is coiled into compact
  chromosomes
• Chromosomes are rod-shaped structures made of DNA
  and proteins

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• Each chromosome is a single DNA molecule wrapped
  around proteins called histones
• Histones maintain the shape of the chromosome

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• Nonhistone proteins are involved in controlling
  the activity of specific regions of the DNA

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Chromosome Structure

• Each half is called a chromatid
• The constricted area is called a centromere

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• When a cell divides, each of the two new cells
  receives one chromatid from each chromosome

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Prokaryotic Cells

• DNA usually consists of only one chromosome
• DNA molecule is circular

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Chromosome Numbers

• Each species has a characteristic number of
  chromosomes
• Examples fruit fly 8
• cat 32
• human 46

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Sex Chromosomes

• Determine the sex of an organism
• In humans, sex chromosomes are either X or Y
• Normal females are XX
• Normal males are XY

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Autosomes

• The other 44 chromosomes are autosomes
• Every cell of an organism produced by sexual
  reproduction has two copies of each autosome (one
  from each parent)

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Homologous Chromosomes

• Refers to the two copies of each chromosome
• Same size and shape
• Carry genes for the same trait

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Karyotype

• A photomicrograph of the chromosomes in a
  dividing cell found in a normal human
• 46 human chromosomes exist as 22 homologous pairs
  of autosomes and two sex chromosomes

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Diploid

• Cells that have two sets of chromosomes
• All normal human cells, except for reproductive
  cells, are diploid
• Abbreviated as 2n
• For humans, the diploid (2n) number is 46

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Haploid

• Cells that contain only one set of chromosomes
• Includes sperm and egg cells
• Abbreviated as 1n
• The haploid number (1n) of humans is 23

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Introduction to Cell Reproduction

• http//www.youtube.com/watch?vvjAdiUMc96w