1. 12-2 Chromosomes and DNA Replication
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2. DNA and Chromosomes
Eukaryotic DNA is located in the cell nucleus inside chromosomes.
The number of chromosomes varies in each species.
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3. DNA and Chromosomes Chromosome Structure
Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin.
Chromatin consists of DNA tightly coiled around proteins called histones.
DNA and histone molecules form nucleosomes.
Nucleosomes pack together, forming a thick fiber.
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4. DNA and Chromosomes Eukaryotic Chromosome Structure Chromosome
Nucleosome
DNA double helix
Coils
Supercoils
Eukaryotic chromosomes contain DNA wrapped around proteins called histones. The strands of nucleosomes are tightly coiled and supercoiled to form chromosomes.
Histones
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5. DNA Replication DNA Replication
Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing.
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6. DNA Replication
The sites where separation and replication occur are called replication forks.
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7. DNA Replication Duplicating DNA
Before a cell divides, it duplicates its DNA in a process called replication.
Replication ensures that each resulting cell will have a complete set of DNA.
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8. DNA Replication
During DNA replication, the DNA molecule separates into two strands, then produces 2 new complementary strands following the rules of base pairing.
Each strand of the double helix of DNA serves as a template for the new strand.
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9. New Strand Original strand Nitrogen Bases Growth Growth
During DNA replication, the DNA molecule produces two new complementary strands. Each strand of the double helix of DNA serves as a template for the new strand.
Replication Fork
Replication Fork
DNA Polymerase
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10. DNA Replication How Replication Occurs
DNA replication is carried out by enzymes that “unzip” a molecule of DNA.
Hydrogen bonds between base pairs are broken and the two strands of DNA unwind.
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11. DNA Replication
The principal enzyme involved in DNA replication is DNA polymerase.
DNA polymerase joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand.
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