*DNA replication is called semiconservative replication since there is one old strand and one new strand in the daughter DNA;DNA replicates in the form of a bubble
*the point where the DNA strands begin to be split apart is called the replcation fork
*DNA grows 5' to 3'
1. DNA helicase unwinds and unzips the double stranded DNA into single strands for replication by breaking the hydrogen bond between the nucleotides.
2. DNA gyrase helps to relieve the tension in the DNA as it is unwinding, by cutting both DNA strands then gluing them back together.
3. Since single stranded DNA is very unstable, single-stranded binding proteins (SSBs) help to keep the two single stranded DNA seperated. Once the DNA unzips, it immediately starts to replicate.
4. The 2 strands are seperated into two types of strands :
- Leading strand--> the strand which grows 5' to 3' into the replication fork.
- Lagging strand--> the strand that grow 5' to 3' away from the replication fork, thus can only replicate in short segments called Okazaki Fragments.
5. RNA Primase attaches itself to the DNA once it has unzipped and creates a primer (approx. 10-60 RNA segments that are complimentary to the parent DNA strand).
6. With the primer on, DNA polymerase III attaches itself to the primer and begins to add nucleotides to the parent DNA strand.
7. However on the lagging strand, the DNA must grow in short segements (Okazaki fragments) because it cannot wait for the whole DNA to unzip first then replicate, or else the DNA will degrade.
8. DNA polymerase I removes the primers once the polymerase III has finished replicating a section. it replaces the primers with the correct DNA sequences. polymerase I also checks for mistakes in the replication and replaces it with the correct sequences.
9. Finally DNA ligase glues the gaps between the okazaki segments with a phosphodiester bond.
a link that shows the process of DNA replication: http://www.youtube.com/watch?v=Yl754_TtJ_M
Friday, September 24, 2010
Saturday, September 18, 2010
5 Famous Geneticists
James Dewey Watson
Birth: Watson was born on April 6th, 1928 in Chicago,United States .
Year they became famous: In 1953 he and Francis Crick discovered that DNA was a double helix structure.
Publications that made him famous: he published "the Double Helix" which included his findings on DNA in 1968.
Contributions to the world of genetics: Watson's discovery of the double helix structure of DNA help scientists better understand how DNA functions and other categories on DNA such as cloning, hereditary traits,and genes.
Thomas Hunt Morgan
Birth: September 25th, 1866 in Kentucky, USA.
Death: December 4th, 1945
Year they became famous: He began his research on the fruit fly in 1909, and he recieved his Nobel Prize in 1933 for his research on heredity.
Publications that made him famous: He published many books, one of his first being "Mechanisms of Mendelian Heredity" in 1915.
Contributions to the world of genetics: his intensive study of the fruit fly, which teachs scientist about heredity of traits and genes.
Dr. Kary Banks Mullis
Birth: December 28, 1944 in North Carolina, United States.
Year they became famous: In 1983 he developed the Polymeraise chain reaction.
Publications that made him famous: He recieved the Nobel Prize in chemistry in 1993 for his discovery of PCR.
Contributions to the world of genetics: His discovery of PCR made a great contribution to the world of genetics; now one molecule (usually DNA) can be amplifide to billions more molecules for detailed research to be conducted.
Barbara McClintock
Birth: June 6th, 1902 in Hartford, Connecticut.
Death: September 2nd, 1992
Year they became famous: in 1930 she was the first person to explain the details of crossing over in meiosis.
Publications that made her famous: in 1931 she published the first genetic makeup of her research on maize. Also in 1950 she published a paper on how genes can change their loci on a chromosome, her paper was called "The origin and behavior of mutable loci in maize."
Contributions to the world of genetics: Her studies on genetic transposition told scientists alot about genes and how they can behave, such as "jumping" from one area of a chromosome to another area. McClintock proved that some genes don't always stay in a fixed spot on a chromosome.
Roaslind Franklin
Birth: July 25, 1920 in London, England.
Death: April 16, 1958 in London, England.
Year they became famous: 1952 when she made the first photograph of the DNA's X shape, which later paved the way to prove that DNA's structure is a double helix.
Publications that made her famous: in 1953 Roaslind Franklin published an article in Nature on the DNA which included her famous DNA x-ray.
Contributions to the world of genetics: Rosalind Franklin developed the basis of what DNA's structure is (the double helix), with her x-ray of DNA, which showed an X formation.
Birth: Watson was born on April 6th, 1928 in Chicago,United States .
Year they became famous: In 1953 he and Francis Crick discovered that DNA was a double helix structure.
Publications that made him famous: he published "the Double Helix" which included his findings on DNA in 1968.
Contributions to the world of genetics: Watson's discovery of the double helix structure of DNA help scientists better understand how DNA functions and other categories on DNA such as cloning, hereditary traits,and genes.
Birth: September 25th, 1866 in Kentucky, USA.
Death: December 4th, 1945
Year they became famous: He began his research on the fruit fly in 1909, and he recieved his Nobel Prize in 1933 for his research on heredity.
Publications that made him famous: He published many books, one of his first being "Mechanisms of Mendelian Heredity" in 1915.
Contributions to the world of genetics: his intensive study of the fruit fly, which teachs scientist about heredity of traits and genes.
Dr. Kary Banks Mullis
Birth: December 28, 1944 in North Carolina, United States.
Year they became famous: In 1983 he developed the Polymeraise chain reaction.
Publications that made him famous: He recieved the Nobel Prize in chemistry in 1993 for his discovery of PCR.
Contributions to the world of genetics: His discovery of PCR made a great contribution to the world of genetics; now one molecule (usually DNA) can be amplifide to billions more molecules for detailed research to be conducted.
Barbara McClintock
Birth: June 6th, 1902 in Hartford, Connecticut.
Death: September 2nd, 1992
Year they became famous: in 1930 she was the first person to explain the details of crossing over in meiosis.
Publications that made her famous: in 1931 she published the first genetic makeup of her research on maize. Also in 1950 she published a paper on how genes can change their loci on a chromosome, her paper was called "The origin and behavior of mutable loci in maize."
Contributions to the world of genetics: Her studies on genetic transposition told scientists alot about genes and how they can behave, such as "jumping" from one area of a chromosome to another area. McClintock proved that some genes don't always stay in a fixed spot on a chromosome.
Roaslind Franklin
Birth: July 25, 1920 in London, England.
Death: April 16, 1958 in London, England.
Year they became famous: 1952 when she made the first photograph of the DNA's X shape, which later paved the way to prove that DNA's structure is a double helix.
Publications that made her famous: in 1953 Roaslind Franklin published an article in Nature on the DNA which included her famous DNA x-ray.
Contributions to the world of genetics: Rosalind Franklin developed the basis of what DNA's structure is (the double helix), with her x-ray of DNA, which showed an X formation.
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