2 minute read

Chromosome

Protein Synthesis And Chromosomes

DNA is bound up within chromatids, which serve as storage unit for the DNA. In order for an mRNA molecule to be transcribed from a DNA template, the DNA needs to be freed from its tightly bound and condensed conformation so that the RNA molecule can form on its exposed strands during transcription. Some evidence exists that transcription can take place through histones. However, most often the genes on the DNA that have been activated after DNA binding protein unwind the chromatid structure. This loosened, transcriptionally active regions of DNA is microscopically resembles puffs on the chromosomes. When RNA transcription concludes, the puffs receed and the chromosome is thought to resume its original conformation.

Resources

Books

Nussbaum, Robert L., Roderick R. McInnes, Huntington F. Willard. Genetics in Medicine. Philadelphia: Saunders, 2001.

Rimoin, David L. Emery and Rimoin's Principles and Practice of Medical Genetics. London; New York: Churchill Livingstone, 2002.

Other

United States Department of Energy Office of Science. "Human Genome Project Information." (October 28, 2002). <http://www.ornl.gov/Tech Resources/Human_Genome/home.html>.

Kathleen Scogna

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chromatin: —The material that comprises chromosomes; consists of DNA and proteins.
Chromatin fiber: —The fiber that is formed by the gathering of nucleosomes by H1 histones.
Chromosome puffs: —The regions of active DNA that are transcribing RNA; appear as puffed regions in a chromosome.
Deoxyribonucleic acid (DNA): —The genetic material of cells that are packed into chromosomes.
Eukaryote: —A cell whose genetic material is carried on chromosomes inside a nucleus encased in a membrane. Eukaryotic cells also have organelles that perform specific metabolic tasks and are supported by a cytoskeleton which runs through the cytoplasm, giving the cell form and shape.
Exons: —The regions of DNA that code for a protein or form tRNA or mRNA.
Genome: —The complete set of genes an organism carries.
Histone: —A structural protein that functions in packaging DNA in chromosomes.
Homologue: —The partner of a chromosome in a chromosome pair.
Introns: —The sections of DNA that do not code for proteins or RNAs.
Karyotype: —An arrangement of chromosomes according to number.
Linker DNA: —The sections of DNA between nucleosomes.
Meiosis: —The process of sex cell division; results in four haploid daughter cells.
Messenger RNA: —The RNA that is transcribed from DNA in the nucleus; functions in protein synthesis.
Mitosis: —The process of body cell division; results in two diploid daughter cells.
Nitrogen-containing base: —Part of a nucleotide; in DNA, the bases are adenine, guanine, thymine, and cytosine; in RNA, the bases are adenine, guanine, uracil, and cytosine.
Nucleic acid: —The chemical component of DNA and RNA.
Nucleosome: —DNA wrapped around a histone core.
Nucleotide: —The building blocks of nucleic acids.
Octomeric histone core: —The "spool" in a nucleosome; consists of four small histones.
Ribonucleic acid: —RNA; the molecule translated from DNA in the nucleus that directs protein synthesis in the cytoplasm; it is also the genetic material of many viruses.
Ribosomal RNA: —A type of RNA that functions in protein synthesis.
Sister chromatids: —Two copies of the same chromosome produced by DNA replication.
Transcription: —The process of synthesizing RNA from DNA.

Additional topics

Science EncyclopediaScience & Philosophy: Chimaeras to ClusterChromosome - Dna And Protein Synthesis, Genes, Chromosome Numbers, Chromosome Shape, The Role Of Proteins In Packaging Dna