My Cell Tour Project

Click on the link to see my unit 5 project I made for the standards. :)

16. Intro to Genetics

  Today we started learning about genetics. This unit is very similar to the Hardy Weinberg principle we learned. For every inherited trait (features) of an organism (all traits are inherited through meiosis or mitosis), there must be an unique type of gene in the DNA to provide instruction to determine the features, and those genes are called "alleles". If one allele overrides another in the organism, the allele is called dominant allele, and the other allele is called recessive allele. For example, if the allele for black hair for human is dominant, and allele for blond hair is recessive, a man with heterozygous alleles will have black hair, but the allele for blond hair is in the man as well. Therefore we say that the genes shown on the surface is phenotype, and the genes inside the organism is genotype.

 
    This diagram shows an example of monohybrid cross. In the diagram, T is the dominant allele and t is the recessive allele. If the father and mother are both heterozygous, the ratio of genotypes would be 1 homozygous dominant: 2 heterozygous: 1 homozygous recessive. The ratio of phenotypes would be 3 dominant: 1 recessive.

  This diagram shows an example of dihybrid cross with 2 traits. In the diagram, A & B are the dominant alleles and a & b are the recessive alleles. If the parents are AABB and aabb, all the F1 generation are heterozygous for both traits. Through self-pollination, the F1 generation will breed the next generation (F2), which has a phenotypic ratio of 9 dominant/dominant: 3 dominant/recessive: 3 recessive/dominant: 1 recessive/recessive.

- Andy Liu '15

15. Operon System

  Today in class we learned about the operon system. The operon system only exists in the prokaryotic cells (bacteria), and there are only two types of operons - repressible (on to off) and inducible (off to on).
  One example of the repressible type of operon systems is tryptophan. A regulatory gene is synthesized into an inactive repressor protein while the RNA polymerase transcribes the rest of the genes to create tryptophan. Once enough tryptophan is created, the tryptophan will connect to the repressor protein and switch it to be active. the active repressor will bond with the operator that started the transcription, and eventually RNA polymerase stops creating more tryptophan.
  The second type of operon system is inducible, and one example for that would be lactose. The repressor protein synthesized in this system is active at the beginning. And once enough lactose is created, the lactose will connect enter the repressor protein and triggers to be inactive. The repressor protein will leave the operator and allow lactase to be synthesized to reduce the amount of lactose in the body.

- Andy Liu '15

14. Protein Synthesis

  Today we talked about protein synthesis in class. Since DNA is double-stranded and has a large size, it cannot leave the nucleus to synthesize protein. So in order to convert the order of DNA bases to protein, the first step would be the process of translating DNA language to mRNA language, that is also known as "transcription". To start this process, the DNA would first have to break apart to allow access for RNA polymerase to begin translation. After this step is done, the introns in the mRNA are cut out and only exons are left in mRNA because introns are useless codes, also known as "junk DNA". Also, a cap made of Guanine (G-cap) and a tail made of multiple Adenine bases (poly-A tail) are added to the mRNA strand as well, to protect it from being eaten away by enzymes in cytoplasm.
  After the mRNA leaves the nucleus and enters the cytoplasm, the process of converting mRNA language to amino acids starts. This process, also known as "translation" begins with mRNA bonding with ribosome. The ribosome will read each codon (3-letter message) on mRNA, and match it with an anti-codon, carrying an amino acid. The message always begins with AUG (Met) and ends with UAG, UGA or UAA. After each codon is processed, the amino acid will connect to other amino acids and create a long string. When the translation is finished, the long string of amino acids will leave the ribosome, and will become protein.

- Andy Liu '15