Genetic... chromosomes, chromosomes, and chromosomes!!!

This week in AP Biology we further travelled through genetics. We learned about sex-linked traits, co-dominance, incomplete dominance among other things. From there we went even deeper into the chromosomal basis of inheritance.

                Sex-linked traits are genes that are located on the x or y chromosome.  These genes on the chromosomes bring forth diseases such as hemophilia and color blindness. Co-dominance in genetics is when both alleles are expressed. This is exemplified in the blood type AB and calico cats. Calico cats are also always female which makes it a sex-linked trait. Incomplete dominance is when the dominant allele doesn’t completely mask the other such creating a sort of blending. This can be seen in blending a red and white snapdragon together and it producing a pink.

                The chromosomal basis of inheritance is connected with Thomas Hunt and the, Chromosome Theory of Inheritance which states that Mendelian genes have specific loci on chromosomes that undergo segregation and independent assortment. Thomas Hunt Morgan contributed a lot to his specific subject. He produced a lot of research with fruit flies that had to do with linked genes. Link genes are genes that tend to be inherited together because they are so close on the chromosomes.  He also helped with recombinant offspring. These are offspring that have features from both parents.

                We also looked at genetic disorders such as Huntington’s and Down Syndrome. The fertilization of these gametes cells that produce these disorders is called aneuploidy.

Genetics

This week for AP Biology we reviewed and studied genetics. On Tuesday we went to Sam Ryan's genetic conference at Lubbock High. At the conference we went over genetics and the recent discoveries in the field. 

An interesting thing I learned about was Barr bodies. Barr bodies are little black dots in female cells. They're only in females because the bodies are a disabled X chromosome. When a cell begins to form it randomly picks an X to follow and then disables the other one. This lead to questions about fixing Down syndrome by taking the third chromosome at 21 and disabling it so that it would turn into a Barr body. 

A fun fact I learned was that our phenotype which is the physical representation of our genotype is actually expressed in all of our cells.  

Another concept that I was enlightened about was that you can take skin cells and turn them into stem cells by reprogramming the cell. This can lead to many things. Such as growing new organs and allowing blind people to see again. The stem cells that have been reprogrammed can form new organs by using scaffolds of organs. If an organ cannot be replicated perfectly they use a dead organ and drain the cells out of it. The stem cells can also be used to replace corneas that have become too cloudy for people to see out of and thus making it possible for the replacement of their vision. This procedure has already been done in a young boy. The procedure requires no stiches or blood and the patient is under local anesthesia and last around thirty minutes. 

I also learned about alternative splicing which allows our genes to code for different proteins and telomerase. 

 Telomerase is an enzyme that builds up the telomeres which are caps at the end of chromosomes. Every time a cell divides the telomeres get shorter and shorter until eventually there is next nothing there. At that point the chromosome stops dividing, unless it has telomerase. The shortening of the telomeres is a major component in age. Unfortunately telomerase is only found in testis, ovaries, and cancer cells. If researchers can discover a way to put telomerase in all areas there might be a chance to postpone aging. 

 The Genetics Conference was super interesting and I advise everyone to take the opportunity to go to it if they can. 

What time is it? LAB TIME!

 This week in AP Biology we did the mitosis and meiosis lab. As I previously discussed in my last blogs, mitosis which is when two genetically identical diploid daughter cells are produced and meiosis is the process which produces four genetically different haploid daughter cells. To began this lab we modeled mitosis and meiosis. We then prepared garlic for another activity. After following that we looked at onion root and fish egg cells to locate cells in the various stages of mitosis. We then proceeded to prepare the garlic root tip squash lab. In this part of the lab we took the garlic we had previously prepared by putting it into a sand and water mixture and placing it into a dark drawer, and cut off around 2 mm of the root tip. After that we put the root tip and hydrochloric acid on a slide  and passed it through an open flame for five seconds. Then we put a chemical that was bright pink and fuchsia in the name on the slide and passed it over an open flame for 2 minutes. We then squished the root tip and put it under a microscope to see if we could locate cells in the various stage of mitosis, but unfortunately we were unable to. That then concluded the lab.


(I will publish pictures separately.)

Meiosis

 This week in AP Biology we went over meiosis. Meiosis is divided into 2 different parts, meiosis 1 and meiosis 2. Meiosis 2 is the most similar to mitosis. In meiosis 1 there are four stages prophase 1, metaphase 1, anaphase 1, and telophase 1. In prophase 1 chromosomes condense, homologous chromosomes attach, crossing over between chromosomes, and centrioles move to opposite ends. In metaphase 1 the tetras line up at the metaphase plate. During anaphase 1 the homologous chromosomes are separated and taken to opposite poles. After anaphase 1, telophase occurs and the sister chromosomes continued to be pulled. Cytokinesis then takes place. After that meiosis 2 takes place which is very similar to mitosis. 

 Mitosis and meiosis differ greatly in their end products; mitosis results in 2 genetically identical diploid cell and meiosis results in 4 genetically different haploid cells. 

Message Passing and Reproducing in Cells

 This week in AP Biology we reviewed cell to cell communication and the cell cycle. 

 There are three types of cell to cell communication no distance, short distance, and long distance. In no distance communication the cells are touching and can send messages to one another. Plants have holes in there cell wall that allows the message to pass. When there is a short distance in cell to cell communication a local regulator is used to pass on the message, neurotransmitters are an example. When there is a long distance to pass on a message a hormone is used. The hormone is sent all around but only passes the message on to the right cells. 

After we went over cell to cell communication we then went to the cell cycle. The cell cycle is made up of the G1 phase, S phase, G2 phase, mitosis, and cytokinesis. There is also a G0 phase that some cells go into. G1, S, and G2 phase all make up interphase. In G1 phase the cell is working normally as the cell progresses into G2 it starts copying its DNA. When the cell starts S phase it again goes through its normal process. Then the cell gets to mitosis.  When mitosis and cytokinesis are combined it is called the mitosis (m) cycle the first phase is prophase. In prophase the chromatin becomes more clear and thicker and the centrioles become visible. Metaphase follows prophase in which the chromatin which has turned into sister chromatids are lined up in the middle of the cells with the centrioles at opposite ends and the mitotic spindle is forming. Anaphase which is the third phase is when the sister chromatids are pulled apart by kinectchores and nonkinectchores elongate the cell. The fourth and finall stage of mitosis (m) cycle is telophase and cytokinesis which is when the nucleus splits apart and start to reform the nuclear wall. And the cytoplasm splits thus creating another cell identical to its self. 

 To help control mitosis and prevent uncontrollable division there are checkpoints that the cell must pass before it can proceed into different phases. The are also internal and external  mechanisms that help to control uncontrollable division which can lead to cancer. 

Lab Time!!!

This week in AP Biology we did a photosynthesis lab. The first portion of out lab tested the different pigments in spinach leaves. The next portion of our lab tested the rate of photosynthesis in spinach leaves. 

The first lab where we tested for the different pigments showed four different pigments. There was chlorophyll a, chlorophyll b, xanthophyll, and carotene in the spinach leaves. We then tested for a constant that measured how far the chromatography solvent travelled divided by how far the pigment travelled. 

Part two of the lab tested the rate of photosynthesis in spinach leaves. At the first of the lab we took ten spinach leaf discs and put them in a syringe with a bicarbonate solution with dish soap. We them created a vacuum inside the syringe to compress the mesophyll cells so the leaf discs would sink. We then placed the discs into another bicarbonate solution. Every thirty seconds we checked for leaf discs that we're floating. This would mean the mesophyll cells had  air in them and that photosynthesis was occurring. 

The Food-Making Plant Process

               

 This week in AP Bio we went over Photosynthesis. Photosynthesis is an anabolic and endergonic process that plants use to produce food (glucose). The process is done in two reactions, the light reaction and the Calvin Cycle. The chemical equation of this process is:

6 CO₂ + 6 H₂O à C₆H₁₂O₆ + 6O₂

                The first reaction in Photosynthesis is the light reactions. In this reaction solar energy is converted into chemical energy in the thylakoid membrane. This starts with water being split, and because of this it provides a source of electrons and protons and gives off O₂ as a by-product. Light is then absorbed by chlorophyll which excites the electrons in a domino effect until finally the electrons are accepted by the primary electron acceptor. All of this takes place in photosystem two. The electrons are then passed via electron transport chain to photosystem one. The fall of the electrons to a lower energy level provides enough energy for the synthesis of ATP. As the electrons do through part of the electron transport chain a proton gradient of H⁺ is produced and which is often used in chemiosmosis. Light energy meanwhile is transferred by light harvesting complexes and is used to excite electrons in photosystem one until they are accepted by the primary electron transport. The electrons in photosystem’s one primary electron acceptor are then transferred through redox reactions to another electron transport chain, although this one does not produce a proton gradient. The electrons are then transferred to NADPH.

                The second reaction in Photosynthesis is the Calvin Cycle. The Calvin Cycle performs carbon fixation where it takes CO₂ from the air and it to the enzyme RuBP. Then through a series of reactions the ATP and NADPH produced by the light reactions are used up and recycled back. After all these reactions a sugar called G3P is produced which eventually is used to make glucose.