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About how many cells are our bodies made of?

About how many cells are our bodies made of?. TRILLIONS! How many of those cells contain your DNA? All of them! All of your cells contain a complete copy of your genome (DNA)!. Your life started as just 1 cell. How do we come from 1 cell & end up as trillions?.

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About how many cells are our bodies made of?

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  1. About how many cells are our bodies made of? TRILLIONS! How many of those cells contain your DNA? All of them! All of your cells contain a complete copy of your genome (DNA)!

  2. Your life started as just 1 cell. How do we come from 1 cell & end up as trillions? That 1 cell divided over & over again as you grew! All of those new cells need copies of your DNA, right? HOW DOES THAT WORK?

  3. DNA Replication

  4. How is DNA copied? • DNA Replication: the process of copying DNA • Because DNA is double stranded, we can separate the 2 strands & create a new strand using 1 strand as a template. • Our end product is 2 identical double stranded DNA molecules! • The 2 strands are called complementary!

  5. During DNA Replication: • The DNA is unwound & unzipped (the 2 strands separate). • Each original DNA strand is used as a template (or model) to make a new DNA strand with base pairing.

  6. What do enzymes do again? • Remember! Enzymes are catalysts that help chemical reactions happen faster! • Forming & breaking chemical bonds takes energy. • Enzymes lower the amount of energy needed to make & break chemical bonds.

  7. Enzymes Used in DNA Replication • 1 enzyme, called Helicase, unzips/separates the 2 DNA strands by breaking the hydrogen bonds between the nitrogenous bases. • Another enzyme, DNA Polymerase, adds new nucleotides to the new DNA strand. • DNA Polymerase also “proofreads” the new DNA to check for errors. • The new strands of DNA are rewound.

  8. DNA Replication • When replication is complete, each DNA molecule is made of 1 old strand and 1 new strand. • The semi-conservative model of replication!

  9. Chromosome Arrangement – Prokaryotic Cells (Bacteria) • Prokaryotic cells have 1 circular chromosome that is free-floating in the cytoplasm. • Remember! Prokaryotic cells do not have a nucleus! • When prokaryotic cells copy their DNA, the process begins at 1 point in the chromosome & moves around the circle in both directions until complete.

  10. Chromosome Arrangement – Eukaryotic Cells • Eukaryotic cells have more chromosomes than prokaryotic cells & DNA Replication begins at hundreds of places & continues in both directions until each chromosome is completely copied!

  11. The point in the DNA where the 2 strands are separating & replication is occurring is called the replication fork!

  12. New DNA strand New DNA strand • DNA Polymerase only works in one direction (5’ to 3’). One strand is read and synthesized continuously while the other is synthesized in fragments! Replication Fork

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