Hardy-Weinberg Theorem

This week in AP Biology we talked about the Hardy-Weinberg Theorem. The Hardy-Weinberg Theorem states that allele and genotype frequencies  in a population will remain constant from generation to generation in the absence of other evolutionary influences. In Hardy-Weinberg, the numbers you have must add to 1. And there are two different equations  one to find the alleles is p + q = 1 and the other one to find individuals is 2pq+q(squared) = 1. You can also combine the Hardy-Weinberg theorem with the Chi Square equation.

Evolution

This week in AP Biology we talked about evolution. Evolution is a very interesting subject. Learning about common ancestors that a species has and how the species has evolved over time. Charles Darwin was one of the first people to really go in depth about evolution. He traveled around the world on the HMS Beagle and during his travels he stopped at the Galapagos Islands and started studying all of the species and fossils that lived on the island and noticed that some species had similar characteristics as other species he has seen before. Homology is when there is a similarity in characteristics resulting in a shared ancestor which is what Darwin saw. Vestigial structures is when there is a structure that is useless to the organism. For example in the Galapagos Islands there is a flightless bird called the cormorant, but there is a cormorant that can fly, but it is not in the Galapagos Island. Both are the same bird, but one can fly while the other cannot. The reason being is because the cormorant in the Galapagos Islands does not have a need to fly, since it is surrounded by water, it dives and swims for it's food. While the cormorant that can fly depends on its wings for food and other necessities. Evolution is a very interesting subject to learn about and so far it is my favorite topic this whole school year.

Viruses

This week in AP Biology we talked about viruses. Viruses are very tiny and there genomes can be double or single stranded DNA or double or single stranded RNA. Viruses have a capsid which is a protein shell that surrounds the genetic material. Some viruses have viral envelopes that surround the capsid and aid the viruses in infecting their hosts. A type of bacteria we studied the most was bacteriophages or phages. They are viruses that infect bacterial cells. Viruses can only replicate in host cells which means they can infect limited variety of hosts. There are two viral reproductions. One is called the Lytic cycle and the other is the Lysogenic cycle. The lytic cycle ends in the death of the host cell by rupturing. Bacteriophages injects its DNA into a host cell and takes over the host cell's machinery to synthesize new copies of the viral DNA. In the lysogenic cycle the bacteriophage's DNA becomes incorporated into the host cell's DNA and is replicated along with the host cell's genome.

Gene Expressin

This week in AP Biology we talked about gene expression. Gene expression is the process by which information from a gene is used in synthesis of a functional gene product. These products are usually proteins.There are three steps to gene expression. The first step is transcription and it is the synthesis of RNA using DNA as a template and also produces mRNA. The second step is RNA processing. The mRNA that was made in transcription goes to RNA processing to yield the final mRNA. The final step is translation. Translation is the production of a polypeptide chain using using the mRNA transcript.

DNA Replication

This week in AP Biology we talked about DNA replication. DNA replication is the process by which a DNA molecule is copied, and how cells repair their DNA. DNA replication is a very important process in all living things. The replication of a DNA molecule begins in particular sites called origin of replication. Initiation proteins bind to the the origin of replication and separate the two strands which form a replication bubble. Then the DNA moves in both directions of the DNA strand until it is copied. DNA polymerase adds nucelotides to the growing chain working in a 5` to 3` direction. The replication occurs continuously along the 5` to 3` strand, this is called the leading strand and the strand that runs 3` to 5` is copied in segments and it is called the lagging strand. The lagging strand is synthesized in Okazaki fragments which are sealed together by DNA ligase which then forms a continuous DNA strand.

The History of DNA

This week in AP Biology we talked about all of the different scientists and other geniuses that proved certain characteristics of DNA. The first was T.H Morgan and he worked with fruit flies and saw that genes are on chromosomes. The second person was Fredeirick Griffith and he worked to try and find a cure for pneumonia. From doing this he saw that harmless live bacteria mixed with heat-killed infectious bacteria caused disease in mice. Griffith called this substance that passed from dead bacteria to live bacteria the transforming factor or transformation. Avery, McCarty, and Macleod also looked for this transforming factor by purifying both DNA and proteins from streptococcus pneumonia bacteria. They found that when they injected protein in bacteria that there was no effect, but when they injected DNA in bacteria, they saw that it transformed harmless bacteria into virulent bacteria. Hershey and Chase, yet more scientist that worked with the transforming factor, but Hershey and Chase confirmed that DNA is the transforming factor by doing the blender experiment. They worked bacteriophage which is a virus that infects bacteria. They grew phage viruses in 2 media radioactively labeled. This blender experiment is how they confirmed that DNA is the transforming factor. Erwin Chargaff saw that all 4 bases of DNA are not in equal amounts. Adenine is 30.9%, Thymine is 29.4%, Guanine is 19.9% and Cytosine is 19.8% of a humans DNA. Watson and Crick simply developed the double helix structure of DNA. A woman named Rosalind Franklin is what gave Watson and Crick to make the double helix structure. And the final two people we discussed is Meselson and Stahl. Meselson and Stahl proved that DNA is semi conservative which is when two strands of DNA separate and one strand is a template and the new strand is laid down. All of these scientist are very important because of their discoveries about DNA.

 

Chi Square

This week in AP biology we learned a very important formula called chi square. Chi square is relating to or denoting a statistical method assessing the goodness of fit between observed values and those expected. Chi square as an odd looking formula, (which I will put a picture of at the end of the blog) the odd looking E stands for summation or the sum, the O means what was observed and the regular E means what you expected. If there are multiple observations and expectations, you add each one. For example you have 1600 cards with four suits. You would expect 400 cards of each suit, but when you count the cards, the number is completely random. So you would have to subtract the observed from the expected, then square that number, than divide that number by the expected number, and you will have to continue doing that for each suit of cards and add up each answer to get the final answer. Once you get the final answer, you have to look at your degrees of freedom chart and in our AP Biology class, we look at the .05 chart which means that we are 95% sure. A very important thing to know about the degrees of freedom is that you see how many observation there are and subtract it by one. So if there are 4 observations, you would look at the third degree of freedom. Also if the final answer you got from doing chi square is lower than the degrees of freedom, it accepts the null hypothesis and if its higher, it declines it. The null hypothesis is when there is no significant  difference between what is observed and what is observed. Chi square is pretty simple and easy to do once you get the hang of it.