Quiz 2: An Introduction to Genes and Genomes


GENES: The genes are the sequences of DNA nucleotides and are generally 1000 to around 4000 nucleotides long. The sequence of the DNA nucleotides provides the instructions or code for the synthesis of the RNA (ribonucleic acid). Most of the genes produce messenger ribonucleic acid (mRNA) molecules that encode protein, but some genes produce RNAs that do not code for proteins. The genes control the proteins produced by a cell and influence how cells, tissues, and organs seem, both through the naked eye and a microscope. These inherited appearances are called traits. The genes influence the cell metabolism, and cognitive and behavioral abilities such as intelligence. The genes affect our susceptibility to certain types of the genetic disorder. Some traits are controlled by a single gene, and some are determined by multiple protein-producing genes. CHROMOSOMES: The genes are contained in chromosomes. The chromosomes are the tightly packed coils of the DNA and protein. During the cell division process, the chromosomes enable cells to separate the DNA content evenly in daughter cells. Multiple numbers of genes are contained in chromosomes, and the number of genes contained in a chromosome can vary depending on the size of the chromosome.

The cDNA or complementary DNA is DNA produced from a messenger RNA (mRNA) template in a reaction, which is catalyzed by the enzymes DNA polymerase and reverse transcriptase. To make clones of prokaryotes, the cDNA is regularly used. The sequence of the one strand of DNA molecule is: img . The complementary strand will be an antiparallel strand to the strand of DNA. The sequence of the antiparallel strand would be: img .

The method by which the information stored in genes is utilized to construct a functional gene product is known as gene expression. The functional gene products are generally proteins, but in genes which are non-protein coding, such as rRNA genes or tRNA genes, the functional RNA is the gene product. The procedure of gene expression is used by eukaryotes, viruses, and prokaryotes to produce the macromolecular machinery such as DNA for life. The steps involved in the procedure of gene expression can be modified, including the transcription, translation, post-translational modification, and RNA splicing of a protein. Gene regulation offers the cell control over function and structure, and is the source for cellular morphogenesis, differentiation, and the flexibility and versatility of any organism. Gene regulation may also support as a substrate for evolutionary change, since control of the timing, location, and amount of gene expression can have a superficial effect on the actions of the gene in a cell or in a multicellular organism.