Dihybrid Cross

Once you understand monohybrid cross, dihybrid cross is basically the same thing. However, In contrast to a monohybrid cross, a dihybrid cross is a cross between F₁ offspring (first-generation offspring) of two individuals that differ in two traits of particular interest. For Dihybrid crossing, there are always 2 different traits Represented by different alphabets, for example let R be a dog with Red eyes and r be black eyes while Y be yellow skin and y be white skin. The question might be something like what are the genotype and phenotype ratios if you mate two heterozygous dogs together, which in this case would be RrYy X RrYy. And then basically you simply isolate the Rr X Rr and Yy X Yy and do the punett squares for both of them, then you multiply the results to get the ratios. Not rocket science.

Monohybrid Cross

Monohybrid cross is a really simple idea, simply take a sqaure and label all the sides with letters, which in most cases (A) means dominant trait while (a) refers to the recessive trait then you simply "multiply" them putting the terms together in the respective boxes of the sqaure and there you go, theres your genetic and phenotypic ratios.

Genotypic ratios: 1AA: 2Aa: 1aa
Phenotypic ratios: 3 dominants: 1 recessive

Unit 3 Test/ Lab

This test was pretty hard in my opinion, I forgot the RNA processing part in the free response and the multiple choice was definitely harder and more confusing than the previous tests.
As for the lab report, this is the first lab report that I actually completely did on a word document and it was a rather different yet rewarding experience since I got it done a lot faster than normal.

Operon System

Operon systems can either be inducible or repressible.

Repressible operon:

The repressor is originally inactive and the operon is on. Protein is being synthesized in repressive operons. Tryptophan is created in order for the repressor to be activate.  RNA polymerase reads DNA to create mRNA. Then RNA processing occurs and through transcription it eventually becomes a protein. Then the protein will become the co-repressor, thus activating the repressor to stop the system.

Inducible Operon:

The repressor is initially active and the system is off since RNA polymerase cannot access the gene getting blocked by the repressor. An inducer is needed to inactivate the repressor and allow the system to run again, in the pGLO lab that would be the arabinose. This would allow the RNA polymerase then go down the DNA and through protein synthesis produce the protein. Such protein is an enzyme that eats up the sugar. However, when all the sugar is gone, the repressor plugs back into its original position and activates again, turning the operon system off.

DNA Replication/ Protein Synthesis

DNA Replication is the process of replicating a DNA strand in a semi- conservative sense. First the Helicase comes in and unwind the strands by breaking the hydrogen bond. Then the RNA primase adds short sequences of RNA to both strands (the primer). Thirdly the primer allows DNA polymerase III to bind and start replication. Then DNA polymerase III adds nucleotides to each template strand in a 5'→3' direction. These nucleotides are initially deoxyribonucleoside triphosphates but they lose two phosphate groups during the replication process to release energy. One strand is replicated in a continuous manner in the same direction as the replication fork (leading strand. The other strand is replicated in fragments (Okazaki fragments) in the opposite direction (lagging strand). Then the DNA polymerase I removes the RNA primers and replaces them with DNA. Finally, DNA ligase then joins the Okazaki fragments together to form a continuous strand

Protein synthesis is one of the most fundamental biological processes by which individual cells build their specific proteins. Within the process are involved both DNA (deoxyribonucleic acid) and different in their function ribonucleic acids (RNA). The process is initiated in the cell’s nucleus, where specific enzymes unwind the needed section of DNA, which makes the DNA in this region accessible and a RNA copy can be made. This RNA molecule then moves from the nucleus to the cell cytoplasm, where the actual the process of protein synthesis take place.

DNA Structure

Today in class we discussed the DNA structure as shown below and started cutting out a paper model for it. The structure was discovered by James Waston, and we also learned that there are 4 different bases including Adenine (A), Cytosine (C), Thymine (T) and Guanine (G) and we learn that A is complementary with T while C is complementary with G.

Colored flower/ Extra fingers

According to the book Survival of the sickest, the flowers appears to be this way because of an inherited mutation in its cells. Since scientists found that mutations are inherited when they are beneficial or neutral, therefore this mutation most probably increase the chances of its survival, for example a camouflage while at the same time it may also have no effects on the survival of this species. 

As Your Inner Fish mentioned, hands with extra fingers is due to the ZPA (very similar to the sonic hedgehog genes), specifically too much skin concentrated in a ZPA zone. These genes contains the instructions for a body to construct fingers, and most probably there's extra ZPA gene thus causing more fingers to grow from the baby's hand.