Genetics - Genetics

Pyrimidine bases include cytosine, thymine, and uracil (RNA), and are monocyclic. Purine bases include adenine and guanine, and are bicylic with two rings in the molecular structure.

The correct answer here is uracil. Remember that in DNA replication, the nucleic acids present are TCGA. When we switch over to RNA production, the thyamine is replaced by uracil to form UCGA. If you chose any of the other options, remember that each one has a pair (AT and CG) and in RNA it switches over to UA and CG. If you remember that, you will always recall that uracil replaces thyamine in RNA sequencing

Nucleotide excision repair corrects DNA that turns into pyrimidine dimers. These are usually caused by ultraviolet radiation and result in sizable DNA adducts.

The correct answer here is meiosis. Some of the options look challenging because you could assume RNA or DNA replication would result in gametes. However, the term gamete singularly refers to a sex-germ cell that is the direct result of meiosis. We can cancel out mitosis because that is specifically to replicate non sex related cells.

CDK levels remain relatively constant, but activity varies. Cyclin levels vary to which the CDKs must bind to become active. Also, the activity depends on cyclin levels, CDK inhibitors, and phosphorylation of CDKs.

Viral RNA polymerases do not have the same proof-reading ability as DNA polymerases. This is a contributing factor to the difficulty of making vaccines from RNA viruses.

Retroviruses do have a single-stranded RNA genome, but they use DNA intermediates in replication. Retroviruses utilize reverse transcriptase to convert viral RNA into complementary DNA, which is then copied to produce double-stranded viral DNA.

G1 checkpoint acts as the restriction point where the cell commits to cell cycle entry. This phase needs favorable environment in order to function properly. The G2/M checkpoint involves chromosome alignment on spindle in metaphase. This process requires adequate size for mitosis entry. The S checkpoint includes DNA quality control looking for proper duplication.

Failure to meet the checkpoint requirements may lead to delays from DNA damage, improper nutrients, or cell size. it may also lead to exiting the cell cycle and apoptosis (cell death). Necrosis is unprogrammed cell death, usually caused by inflammation, disease, or lack of oxygen/blood.

Telomeres are repetitive DNA sequences at the end of chromosomes and they shorten which each division. Poly-a-tails are added to RNA at the end of transcription. 5' caps are nucleotides added to mRNA aiding in translation. The kinetichore is a protein structure on chromatids that allow spindle fiber attachment.

Mutations can lead to lack of regulation, which overall, leads to genomic instability providing opportunities for uncontrolled growth — for example, cancer from the loss of cell cycle control. Proto oncogenes are normal genes that promote and regulate cell growth. Mutations to the proto oncogene itself could lead to oncogenes, which are cancer promoting.

Proto oncogenes promote proteins via proliferation with regulation. Oncogenes promote cell proliferation without regulation, leading to genomic instability, which can lead to cancer. A mutagen is a physical or chemical substance that can increase the frequency of mutations. A carcinogen is a substance that is directly involved in causing cancer.

p53 is a famous tumor suppressor, which blocks cell cycle progression preventing damaged/mutated DNA from being duplicated. Proto oncogenes are normal genes that regulate cell growth and proliferation. Oncogenes are mutated proto oncogenes that lead to unregulated cell proliferation. The checkpoints are in the S, G1, G2/M phases.

A transition mutation represents a purine-to-purine mutation or a pyrimidine-to-pyrimidine mutation. This could be a change of A to T, or vice versa. It could also be a change of C to G, or vice versa. Remember, a transition mutation does not insert or delete any bases. It simply changes a base.

Since colorblindness is a sex-linked gene, female children need to have the sex-linked gene from both their mother and father in order to be colorblind. In this case, the mother will donate a colorblinded gene to half of all offspring, while the dad will give his colorblind gene to all his female children. This means that one out of every two female children will have this trait.

Karyokinesis is the division of the cell's nucleus during mitosis. A similar (but different meaning) word is cytokinesis. Cytokinesis is the division of the cell cytoplasm, which occurs at the end of mitosis. The other answer choices do not reflect the meaning of karyokinesis.

The central dogma of biology is best described by DNA is transcribed to RNA, which is translated to protein. The genetic material (DNA) is transcribed into mRNA (RNA) which is than translated into proteins. The central dogma is an important principle in molecular biology, and it helps explain why DNA plays such an important role in genetic expression.

Transcription begins when RNA polymerase binds to promoter DNA sequences on a gene. This leads to the production of a RNA chain, complimentary to the original (template) DNA strand.

RNA is transcribed 5' to 3' ALWAYS, meaning that the template DNA strand is read from the 3' to 5' direction.

Eukaryotes are more complex cells than prokaryotes and have 3 different polymerases for the different RNA classes, while prokaryotes only have one RNA polymerase that handles RNA transcription for the whole cell.