neurotransmitters

Acetylcholin

-Two functions of Acetylcholin

  1. in the peripheral nervous system

    : responsible for skeletal muscle movement and regulation of smooth muscle and cardiac muscle.

  2. in the central nervous system

: involved in learning, memory, and mood

- First neurotransmitter ever identified

-discovered by Henry Hallet Dale and Otto Loewi in 1914.

- an ester of acetic acid and choline; CH₃COOCH₂CH₂N+(CH₃)₃

-If the acetylcholine increases, heart rate decreases and the production of saliva increases.

Serotonin

-also called 5-Hydroxytryptamine (5-HT)

-affects mood, emotion, sleep and appetie

-involved in the control of many behavioural and physiological functions

-to treat depression, medications are used for changing action of serotonin

-found in blood platelets, intestinal mucosa, the pineal body, and the central nervous system

Endolphins

-more than 20 types of endorphins are identified in humans

-Found in pituitary gland, other parts of brain, and throughout nervous system

-Secretion of endolphin :

   1. decrease feelings of pain

   2. modulate appetite

   3. release sex hormones

   4. enhance immune response.

Norepinephrine

- 4-(2-amino-1-hydroxyethyl)benzene-1,2-diol

- also called noradrenaline

-secreted by adrenal medulla

-secretion of norepinephrine increases heart rate, blood pressure, and the sugar level of the blood.

-Plays a role in attention and focus

-People with ADD/ADHD use medications that increase level of norepinephrine, such as Ritalin and  Dexedrine

DNA replication

DNA replication is a semilconservative replication where a double helix replicates 2 daughter strands where each of the daughter strands has one old strand and one newly made strand.

Steps of DNA replication

1. DNA helicase unwinds and unzips the double helix by breaking hydrogen bonds.

2. At the same time, DNA gyrase relieves the tension in the DNA

3. After the DNA is separated into  2 single stranded DNA, which is very unstable. Therefore, single-stranded binding proteins(SSB) prevents DNA from degenerate.

4.RNA primase attaches itself to DNA after its unzipped and creates primer.

5. Primer acts as a signal to sign DNA polymerase 3 to attach nucleoside to the 3' end of unzipped single DNA strand.

6. There are 2 different types of replication going at this stage.
At the lagging strand, which grows away from the replication fork, there are many  okazaki fragments formed in order to let the DNA strand to grow in 5' to 3' direction. At the leading strand, which grows towards the replication fork, the newly formed DNA strand grows continuously in 5' to 3' direction.

7. Once the polymerase 3 finishes to replicate, polymerase 1 comes in to remove the primase and attach correct nucleosides at the gap. In addition, it checks the mistakes in the replicated strands.

8. Lastly, DNA ligase glues the gap between okazaki fragments in the lagging strand with the phosphodiester bond.


NOTE: LIST OF ENZYMES USED IN DNA REPLICATION
Helicase
Gyrase
Primase
DNA polymerase 3
DNA polymerase 1
Ligase

VIDEO CLIP OF REPLICATION
http://www.youtube.com/watch?v=teV62zrm2P0

Famous Geneticists5: Erwin Chargaff

Erwin Chargaff

(1905-2002)

Year of Fame:1947

Publications that make him famous: Heraclitean Fire: Sketches from a Life Before Nature (1978)
Contributions to the world of genetics: He discovered 2 rules regarding DNA. He found out that in DNA, the number of Adenine approximately equals the number of thymine, and the number of Guanine equals the number of Cytosine. These rules helped Wastons and Crick to realize the double helix structure of DNA.

Famous Geneticists4:Barbara Mcclintok

Barbara Mcclintok

(1902-1992)

Year of Fame: 1983

Publications that make her famous: "A cytological and genetical study of triploid maize"

Contributions to the world of genetics: She discovered transposition, which suggests that trans- posable elements can jump between chromosomes. This discovery proved the gene’s ability to turn the physical characteristics on and off.

Famous Geneticists3:Gregor Mendel

Gregor Mendel

(1822-1884)

Year of Fame: After his death(1900: rediscovery of his work)

Publications that make them famous: Experiments with Plant Hybrids

Contributions to the world of genetics: He proved that the inheritance of traits was not random, but followed the particular rules (The law of segregation of characteristics, and The law of independent assortment)

Famous Geneticists2:James Watson

James Watson

(1928-)

Year of Fame: 1962(won Novel Prize in Physiology and Medicine)

Publications that make them famous: The Double Helix(1968), The Molecular Biology of the Gene (1965), Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic(1953)

Contributions to the world of genetics: With the help of Crick, Franklin, and Wilkins, he discovered the complete structure of DNA

Famous Geneticists1:Rosalind Franklin

Rosalind Franklin

(1920 - 1958)

Year of Fame: after her death (1958)

Publications that make them famous: Franklin worked on deciphering the structure of DNA by using X-ray crystallography. Her work provided the key clue in figuring out the DNA structure to Watson and Crick. Her work was published under her supervisor’s name, Maurice Wilkins, not hers.

Contributions to the world of genetics: Her photograph of DNA structure provided Watson and Crick the last clue to the discovery of the DNA structure.