Cell organelles

To learn more about cell organelles please view my prezi on this topic:
Cell Tour


Also to view my project on beta-thalassemia click here:
Beta-thalassemia

PGlo Lab

Here is a link to my lab report on the Green Fluorescent Protein Lab.
pglo lab

What is the genotype of the father?

Based on our knowledge of genetics, I can decipher the genotype of the father of the puppies. From the picture, we can tell that the mother has yellow fur, brown nose, and possibly brown eyes, meaning that her genotype is eebb (recessive). The puppies in the pictures have black and brown fur, brown and black ears, brown and black noses, and possibly brown eyes. Based on these phenotypes of the puppies, the father's genotype is most likely EEBb.

eebb (mom) x EEBb (dad)

	EB	EB	Eb	Eb
eb	EeBb	EeBb	Eebb	Eebb
eb	EeBb	EeBb	Eebb	Eebb
eb	EeBb	EeBb	Eebb	Eebb
eb	EeBb	EeBb	Eebb	Eebb

The genotype for the puppies are eight EeBb (black lab- phenotype) and eight Eebb (chocolate lab- phenotype).

 

Meiosis

Meiosis involves two nuclear divisions that produce four haploid cells. Meiosis I is the reduction division. It reduces the chromosome number from diploid to haploid and separates the homologous pairs. Meiosis II separates the sister chromatids and the result is four haploid gametes. N is the haploid number. The fist phase of Meiosis I is called interphase. Here DNA synthesis or DNA replication. Each chromosome is now made up of two strands, or chromatids, joined together at the centromere region. Next phase is prophase I. Homologous chromosomes now come together and synapse (crossing over) along their entire length. A tetrad (4 chromatids) is formed. The result of crossing over is called a chiasma. A tetrad is two chiasmata. The next phase is metaphase I. Here the crossed over tetrads line up in the center of the cell. The next phase is anaphase I. Here the homologous chromosomes separate and are "pulled" to opposite sides of the cell. The next phase is telophase I. Here there is a formation of a nuclear envelope and possibly the division of the cytoplasm (cytokinesis). 2 haploid cells have formed and each chromosome is composed of two chromatids. Then Meiosis II happens. The first phase is called interphase II or Interkinesis. This is a period of rest for the cell. Here DNA replication does not happen. Also, the amount of time in rest depends on the type of organism. The next phase is called prophase II. Here replicated centrioles separate and move to opposite sides of the chromosome groups. The next phase is called metaphase II. The chromosomes are centered in the middle of each of the daughter cells. The next phase is anaphase II. Here the centromere regions of the chromatids now appear to be separate. The chromatids are separated and the daughter chromosomes are pulled toward the opposite sides of each of the daughter cells. The final phase is called telophase II. Here the chromosomes are at the opposite sides of the dividing cell. A nuclear envelope forms and the cytoplasm divides.

     

Mitosis

There are five main stages to mitosis (cell division). The first stage is called interphase. In this phase there is a non dividing cell. The nucleus of the cell is filled with chromatin (fine network of threads). There are three parts to interphase. The first part, G1, is the growth stage, S is where DNA replication occurs, and G2 is where the cell gets ready for mitosis and the organelles double. Then next stage is called prophase. The chromatin threads start to thicken and condense into chromosomes. Each chromosome is made up of two chromatids joined at the centromere. As this stage or phase continues, the chromatids shorten and thicken. The nuclear envelope starts to disappear.  The first sign of a spindle appears in the cytoplasm, and the spindle apparatus is made up of microtubules. The microtubules pull the chromosomes toward the poles of the spindle where two daughter nuclei will form. The nest phase is called prometaphase. Here, the nucleus membrane breaks apart into numerous "membrane vesicles" and the chromosomes inside form protein structures called kinetochores. The centrioles begin to move apart as well. The next phase is metaphase. Here the chromosomes move to the center of the spindle and the centromere attaches to the spindle. The centromeres of all the chromosomes lie at the same level of the spindle, the metaphase plate. The next phase is called anaphase. Here the centromere regions of each pair of chromatids separate and are moved by spindle fibers toward opposite poles of the spindle, dragging the rest of the chromatid behind them. The daughter chromosomes (split chromatids) continue their poleward movement until they form two compact clumps, one at each spindle pole. The last phase of cell division is called telophase. Here there is a pronounced condensation of the chromosomes, followed by the formation of a new nuclear envelope around each group of chromosomes. The chromosomes gradually uncoil to form the fine chromatin network like in interphase. After cell division occurs, another step might happen. It is called cytokinesis, which is the division if the cytoplasm into two cells. The old cell will pinch off in the middle along a cleavage furrow to form two new daughter cells.

    

Protein Synthesis!

There are two steps to protein synthesis. The first step is called transcription. In this step, the DNA strand is transformed into mRNA  because DNA is too big to pass through the cell membrane because of the double helix. RNA polymerase (enzyme) is used for the processes. This reads 3' to 5'. Then the mRNA goes under RNA processing where the introns ("non-coding" materials) are spliced out with splicesomes. Then the mRNA creates caps on its ends and Poly-A tails so that once out of the cell the important information is not "eaten". Then once out of the cell, the mRNA goes into a ribosome. The ribosome is where the final step happens. This step is called translation. The ribosomes read from 5' to 3'. There are three stations in a ribosome. The start codon is always AUG. The second station is where the anti-codon start attaching the amino acids together with polypeptide bonds. Then once the stop codon is reached, the amino-acids break off, and then the anti-codon exits the ribosome.

   

DNA Replication

DNA replication is an important process because before a cell can reproduce, it has to replicate. An important factor that affects DNA replication is whether the cell is a prokaryote (no nucleus) or a eukaryote (yes nucleus). DNA replication takes place in the nucleus for a eukaryote and in the cytoplasm for a prokaryote. There are five basic steps to replication. The steps use five different enzymes and reads from 3 prime or 3 Carbon end (OH-) to the 5 prime or 5 Carbon end. THe beginning enzyme for the first step is called Helicase, which unwinds the double stranded DNA by breaking down the hydrogen bonds between nitrogen bases. Then RNA primase (enzyme) makes a polar end for DNA polymerase III and puts down RNA nucleotides. Then DNA polymerase III proof reads to make sure the replication has no mistakes. Then DNA polymerase I replaces RNA with DNA because DNA is too big to pass the cell membrane. Finally the enzyme Ligase attaches the Okazaki fragments (short fragments of DNA synthesized on the lagging strand) together.

Here is a link to a youtube video animation of DNA replication:
DNA replication animation on youtube
http://www.youtube.com/watch?v=teV62zrm2P0

Survival of the Sickest Chapter 6

 All human being start off with one cell, or a zygote, that is the product of the union of two other cells, a sperm cell from the father and an egg cell from the mother. That one cell contains every single genetic instruction  to manufacture the proteins used to build a human being. Our genes are organized by twenty- three pairs of chromosomes, so forty- six in total. One set of the chromosomes come from the father and one comes from the mother. They carry instructions for our bodies to carry out tasks. Also, many advances are happening. Scientists now think that "junk DNA" is not useless. Also, evolution is not random  because there are cells that proofread the process of copying genes, and errors rarely happen. Nobel-prize winning scientist, Barbara McClintock found that corn genes mutated faster when the corn was under stress like drought or extreme heat and this is called “jumping genes”, which is when the cell suppresses the proofreading cells so mutation will occur. Viruses also contribute to evolution because jumping genes occur in viruses which is called retrotransposons, there is also another kind of jumping genes called DNA transposons. 

From Atoms to traits

1. Mendel's experiment is important because he was able to get some proof for Darwin's theory of evolution through natural selection. Through his experiment with peas he was able to show us that variants in species are inheritable and that genetic variants reappear in future generations, not blend away.

2. James Watson and Francis Crick were the ones who discovered the double helix structure of DNA.

3. A variation in DNA is called a homopolymer, which are stretches of DNA with eight or more identical letters in a row are prone to copying errors during DNA replication and an example of this is microsatellites which consist of sequences of two or more nucleotides in a row. Another variation is called “jumping” elements, which change gene activity patterns by creating new regulatory sequences, and an example is the wrinkly seeds of peas.Another is when the bases change from A to G, and an example of this is in peas when the variation occurs it shortens growth. Another is the change in regulatory genes that regulate cell division, and an example is the differences between the maize plant and the tesinte plant. Finally, the last one is the variation is change in pigment cell, and an example is the change in human skin color.

4. Evo-devo is the study of the effects and changes in important gene developments and their role in evolution.

5. The ability to digest milk is only found in infants. Different lactose tolerant have different mutations in key regions. Because humans rely on milk, the mutation is still active. 

Founder Mutation

Founder Mutations is the genetic legacy of a founder of a population, which is passed on through inheritance. People who have founder mutations have damaged DNA embedded in a larger stretch of DNA that is identical to that of the founders. This region of shared DNA is called a haplotype. If you share a haplotype with someone then that means that you guys share a common ancestor and are related. One can determine the age of a founding mutation by the length of the haplotype because over time the haplotype becomes shorter. The haplotype in the founder is an entire chromosome that contains the mutation. The hot spot is different because it is a DNA base pair that is prone to mutation. People who have hot spots are not related, so the rest of their DNA varies, unlike in people who have the founder mutation that do share some DNA.

The reason people have genetic mutations is because the mutations gives people an advantage in warding off diseases. If you have the dominant trait of a mutation you could have an unwanted disease, but if you have the recessive trait, that will help you. People who carry a single copy of the sickle cell disease are much less likely to contract malaria. Individuals with two copies of the mutation die off soon, but people with one copy live longer because their copy helps them fight off diseases. This is called balancing selection. This chart will give more examples of how mutations can help:

            The ability of identifying founder mutations helps doctors identify certain patients to be tested for diseases. Also, geneticists can use the haplotype to trace back the origins of populations and their migration tracks. They can look back at a certain time and region to help find the connections between all humans.