Question

Genomics: Analyze cellular and chromosomal events that occur during the eukaryotic cell cycle and gamete formation. Analyze the basic structures and mechanisms of DNA and RNA including replication, transcription, and translation.

Answer 1

#. DNA

A list of instructions. A long, double-stranded, helical molecule composed of building blocks called deoxyribonucleotides that are linked together via phosphodiester bonds. It also has a sugar phosphate backbone. Must remain in the nucleus. Contains a deoxyribose sugar. Double-stranded. Larger than RNA. Only has one function: storing genetic information. Also found in mitochondria (mtDNA).

- deoxyribonucleotides

Composed of a pentose sugar (deoxyribose), one of four nitrogenous bases (adenine, guanine, cytosine, or thymine) and a phosphate group.

- mtDNA

Contains fewer genes than nDNA. Only inherited through females. More plentiful than nDNA because each cell contains hundreds, even thousands of mitochondria.

- deoxyribose

The pentose sugar lacking oxygen.

- nitrogenous bases

Adenine, guanine, cytosine, or thymine. They form hydrogen bonds with one another. Adenine forms two hydrogen bonds with thymine. Guanine forms three hydrogen bonds with cytosine.

- phosphate group

Attached to the 5' carbon of the deoxyribose.

- purines

Double ringed nitrogenous bases; adenine and guanine

-pyrimidines

Single ringed nitrogenous bases; cytosine and thymine

- genetics

The study of genes and how traits are transmitted from one generation to the next.

- codons

A unit of 3 bases/nucleotides that code for a particular amino acid.

- gene

A "sentence" of codons that form a list of amino acids required to build a polypedtide (protein). Sequences of DNA that code for proteins.

- double helix

Hydrogen bonding of nitrogenous bases causes DNA to form this shape. The sugar-phosphate backbone has a 3' to 5' directionality. The two strands are complementary and antiparallel.

- RNA

A copy of the DNA sequence that can be carried out of the nucleus and into the ribosomes for the synthesizing of proteins. It is the only nucleic acid present in some organisms, such as some viruses. It is also vital in important cell functions, such as transcription, and translation. Contains a ribose sugar. Single-stranded. Has the nitrogenous base uracil instead of thymine. Molecules are smaller. 3 main kinds of this polymer.

- DNA replication

Extremely complex process involving 30 different enzymes. DNA polymerase enzymes are only able to join the phosphate group at the 5' carbon of a new nucleotide to the hydroxyl (OH) group of the 3' carbon of a nucleotide already in the chain. As a result, DNA can only be synthesized in a 5' to 3' direction while copying a parent strand running in a 3' to 5' direction. To start the synthesis of the leading strand and each DNA fragment of the lagging strand, a RNA polymerase complex called a primosome or primase is required. The primase, which is capable of joining RNA nucleotides without requiring a preexisting strand of nucleic acid, first adds several complementary RNA nucleotides opposite the DNA nucleotides on the parent strand. This forms what is called a RNA primer.

- leading strand

During DNA replication, one strand is synthesized in a continuous way.

- lagging strand

During DNA replication, one strand is synthesized in discontinuous segments, known as Okazaki fragments.

- ribosomal RNA

Exist outside the nucleus in the cytoplasm of a cell in organelles called ribosomes.

- messenger RNA

Are the nucleic acids that "record" information from the DNA in the cell nucleus and carry it to the ribosomes for protein synthesis.

- transfer RNA

Delivers amino acids one by one to protein chains growing at ribosomes.

- transcription

Takes place in the nucleus. The transmission of information from DNA to protein happens through an intermediate molecule, messenger RNA or mRNA. mRNA is synthesized in the nucleus using a DNA strand as a template, and then it goes to the cytoplasm through the nuclear pore. Synthesis of proteins is carried out on the ribosomes, using mRNA as a template. This process is much more complicated in eukaryotes than in prokaryotes. In eurkaryotes, part of the gene sequence is translated to protein (exons), while some other gene segments do not code for the protein (introns).

- translation

Takes place in the cytoplasm. Polypeptides (proteins) are synthesized in the ribosomes. This process is directed by the mRNA. Two other classes of RNA also participate in this process. tRNA (transfer RNA) carry activated amino acids (the building blocks of proteins) into the ribosome, where the polypeptide will be synthesized. rRNA (ribosomal RNA) is present in the ribosomes, and provides a mechanism for decoding mRNA into amino acids and for interaction with the tRNA during this process.

- protein synthesis

The most important function. RNA is translated into a specific order of amino acids forming a chain of amino acids or a polypeptide. Protein is made of one or more polypeptides. 20 amino acids each corresponds to a specific set of three bases on mRNA strand (a codon). 64 codons, but only 20 amino acids. Terminating triplets or stop codons: UUA UAG UGA signal where the polypeptide chain stops forming. Occurs in ribosomes.

#. Cellular and chromosomal changes during eukaryotic cells cycle and gamete formation