DNA replication and transcription

Jorge García Ian López Carlos Ugalde DNA replication and transcription

Dna & RNA • Nucleic acids consist of long chains (polymers) of chemical units called nucleotides. • Both consist of a nitrogenous base, a phosphate group and a sugar. • The main differences in structure are that DNA has deoxyribose sugar, while RNA has ribose sugar and that RNA substitutes the thymine (T) nitrogenous base of DNA to uracil (U).

The functional significance of the base-pairing rules suggests a possible copying mechanism for the genetic material. • Process of Replication • The two strands of parental DNA separate and each becomes a template for the assembly. • The nucleotides are copied from the original DNA strand. • Enzymes link the new copied nucleotides to form the new DNA strands. DNA replication

DNA Replication

Transcription is the transfer of genetic information from DNA into an RNA molecule. • Process of Transcription • The fist phase called initiation is the attachment of RNA Polymerase to the promoter DNA. • RNA Polymerase stretches the DNA in order to separate one strand from the other. Then the nucleotides can be copied from the DNA and RNA Polymerase links the RNA nucleotides together. • RNA Polymerase continues to move through the DNA strands until it reaches the terminator. Now the RNA transcription is complete. Transcription

Translation is the transfer of the information of the RNA into a protein. • To convert the codons of nucleic acids to the one letter amino acid words of proteins, a cell employs a molecular interpreter, a special type of RNA called transfer RNA (tRNA). • Functions of tRNA • Picking up the appropriate amino acids. • Recognizing the appropriate codons in the mRNA. Translation

GENetic code • Set of rules giving the correspondence between codons in RNA and amino acids and proteins.

http://youtube.com/watch?v=983lhh20rGY From DNA to Proteins

Before leaving the nucleus RNA is first processed. The kind of RNA that encodes Amino Acid sequences is called the messenger RNA (mRNA) because it conveys genetic information from DNA to the translation machinery of the cell. Most genes of plants and animals include internal noncoding regions called introns. The coding regions , the parts that are expressed as amino acids are called exons. The process of cutting and pasting is called RNA splicing. The introns are cut from the pre mRNA and are left in the nucleus. RNA Splicing

http://br.youtube.com/watch?v=NuNBEMtfSDg RNA SPlicing

Any change in the nucleotide sequence of the DNA is called a mutation. • They can involve large regions of a chromosome or just a single nucleotide pair. • Divided into two general categories: • Base substitutions→ replacement of one nucleotide with another. • Base insertions or deletions→ Adding or subtracting nucleotides may alter the reading frame of the message. Altering one codon may change all the other codons. This would cause a nonfunctional polypeptide. Mutations in genes

Campbell, N (2006). Biology: Concepts and Connections. San Francisco, CA: Pearson Education Inc. • Nobel Web, (2008). DNA-RNA-Protein. Retrieved April 28, 2008, from Nobelprize.org Web site: http://nobelprize.org/educational_games/medicine/dna/index.html • Photos • http://www.anselm.edu/homepage/jpitocch/genbio/nucleotidedna.JPG • http://www.mtrinstitute.com/images/DNA.jpg • http://www.educa.aragob.es/iescarin/depart/biogeo/varios/BiologiaCurtis/Seccion%203/14-25.jpg • http://www.biologycorner.com/resources/replication.gif • http://www.mun.ca/biology/scarr/MGA2-03-28.jpg • Videos • http://youtube.com/watch?v=983lhh20rGY • http://br.youtube.com/watch?v=NuNBEMtfSDg Bibliographies

DNA replication and transcription