DNA Replication Enzymes

DNA Replication Enzymes

1.     Helicase: DNA helicases bind to ssDNA at the replication forks and move into the adjacent double stranded regions forcing the two strands apart and unwinding the helix. Helicases require ATP as an energy source

2

.     DNA Polymerase III: In prokaryotes, chain elongation is catalyzed by DNA Polymerase III on both strands. The high processivity of the polymerase is the result of the β-subunit of the polymerase acting as a sliding clamp on the DNA template. On the lagging strand, Pol III elongates until it encounters a RNA primer.

3

.     DNA Polymerase I: DNA repair and some replication. Highest concentration

4

.     RNA Primase: Replicates/synthesizes the start of a new strand, the primer. Uses RNA in a 3'-5' way

5. Ligase:    Supplies final phosphodiester bond that seals the new strands together.

Survival of Sickest chapter 6 summary

    DNA can be purposely modified or just by random mutation. Barbara McClintock discovered the “ jumping genes” – whole sequences of DNA that moved from one place to another during times of some environmental stress.  These jumping genes are constantly “cut and paste” and “copy and paste. Also, what we consider as the “junk” DNA ( DNA that does not code for proteins) actually is the main source of jumping genes.

    Retroviruses are made of RNA, and can be written into DNA.  For example, HIV is a retrovirus and the drug “cocktail” therapy used to resist HIV by stopping the enzyme that helps the retroviruses become part of DNA. The retroviruses that are part of our DNA are called HERV, and it’s function is to produce a healthy placenta 

“ From Atoms to Traits”

Kevin Lin 

Mr. Quick 

A Block 

“ From Atoms to Traits”

1. One of these principles, now called Mendel's law of segregation, states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.

 A gene can exist in more than one form.

Organisms inherit two alleles for each trait.

When gametes are produced (by meiosis), allele pairs separate leaving each cell with a single allele for each trait.

When the two alleles of a pair are different, one is dominant and the other is recessive.

2. Watson and Crick first discover the structure of DNA.

3.

1) The substitution of a single letter for another at a particular position in the polymer

Example:

ACTGCC…

ACGCCC…

Every three letters is a amino acid, so it could cause the change of protein

 2) Insertion: The addition of extra base pairs in the sequence

Example: A smooth pea and a wrinkled pea

 3) Gene Copy Number: Difference in the number of duplication of an entire sequence

Example: the genes for starch digestion in chimpanzees and humans

 4) Duplication: Difference in the number of duplication of a base pair

Example: Signal receptor for pigment cells in pigs

 5) Regulatory changes: the change in the formation of gene sequences during the organism's development

Example: …

4. Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different organisms to determine the ancestral relationship between them, and to discover how developmental processes evolved. It addresses the origin and evolution of embryonic development; how modifications of development and developmental processes lead to the production of novel features, such as the evolution of feathers; the role of developmental plasticity in evolution; how ecology impacts development and evolutionary change; and the developmental basis of homoplasy and homology.

5.   If a person has been constantly rejecting lactose products while he was growing up, then he will be lactose intolerant because his body lacks the mutant form of lactase enzyme. 

“Traces of a Distant Past”

Kevin Lin

Mr. Quick

A Block

Oct 22^nd

     Darwin knew that individuals were variable, so each individual in a population carried a unique set of traits. However, he did not discover that the reason behind it is genetic differences. Variation in the genes of individuals arises from several sources. Mutation, the alteration of existing genes to form new alleles, can arise from copying errors during DNA replication, DNA damage, and repair or recombination during cell division. Varation also arises from sexual reproduction, wherein new combinations of DNA are created through the independent assortment of genes. 

   In the Documentary movie “ The Journey of Man”, Spencer Wells, a geneticist, adheres to the out of Africa theory in which all of mankind stemmed from a single person who originated in Africa 60,000 years ago. His question is that how human possibly travelled from Africa and end up spread out in the rest of the world and also to find genetic evident to backup his theory. He is also wondering what caused human immigration. From his basis understanding, he believes that on genetic markers in Y chromosomes, which are only found in males. The idea behind this is that sons inherit Y chromosomes identical to that of their fathers. However occasionally mutations occur in the DNA and form a genetic marker which can be traced. By looking for different markers and analysing DNA in people all over the world today, a picture can be formed of where our ancestors were at certain points in time and this enables us to track their journey and the origins of man.

The article “Traces of a Distant Past” once again proof Spencer Wells idea that humans left Africa and gradually fanned out across Asia to Australia and then up to Europe; and then say 15,000 years ago, they crossed over what was then a land bridge to the Americas and gradually worked their way down to South America. Also, due to fast speed of globalization, discovering how genetics related to evolution is becoming an important issue. That has been the perspective of a number of population geneticists who have felt that we really need to carry out this research as soon as possible because of globalization, because of the mixing of peoples. That was the reason that in the early '90s, a very well-known population geneticists, Luca Cavalli-Sforza, suggested that at the same time that we begin a Human Genome Project, we begin something called the Human Genome Diversity Project that would go out and collect samples from many, many different indigenous populations from around the world and then have a basis for comparing that genetic diversity for researching the hypothesis that we're talking about, that humans originated in Africa and gradually spread out with this decreasing genetic diversity. There was a problem with that. Many of the people who they approached were not eager to have their blood sampled or to give samples of sputum because they felt that, one, this may be taking something that is intrinsic to their own belief systems, which is there are some groups that believe that taking the blood is in essence robbing the soul in some ways. Others had had bad experience with people coming and wanting to take plants and other types of materials that they've been using and patenting them.

Class 11 quiz

Class 11 Quiz

1.   This picture demonstrates the evolution of whale. 55 million years ago, Mesonychid was a mammal that lived on land. Its four limbs allowed it to walk. Ambulocetus evolved from Mesonychid. The structure of its head is flatter and its mouth was longer and sharper. The limbs of Ambulocetus adapted to amphibian environment that it was able to go to near land area yet still hunt in the water. The eyes of Ambulocetus were on the sides so that they can see better in the water. Rodhocetus evolved from Ambulocetus. The body structure of Rodhocetus was more streamlined, allowing it to swim in water. Its tail was divided into two parts to balance the body while swimming. The limbs changed to fins because fingers were not needed in water. Finally, Basilosaurus evolved from Rodhocetus. The structure of the body was more streamlined. All four of the fins grew smaller.

2.     E.

3.     Dragonfly, birds and bats are all able to fly. However, bats  is the only organism have finger structure in the wings. The limbs of birds are more stronger than bats and dragonfly because they need to stand on their feet. The neck of bird is long so it allows the bird to pick up its food from the ground. The long tail of dragonfly also allows it to balance its body

4.     The sequences of Cytochrome C of different organisms demonstrate the relationship between them. The fewer differences between two organisms, the more closer they are to the common ancestor because DNA mutations take place over time. The less time available for mutations to happen, the closer two organisms are to their more recent common ancestor. For example, there is only one difference in amino acid between human and Rhesus monkey.

5.     Homology shows two organisms have similar structures or genes which indicates that they share a common ancestor. For example, modern toothed whale and Rodhocetus have the same tail structures.