1 / 13

Molecular Genetics

Molecular Genetics. DNA RNA Gene Expression. DNA and RNA. DNA deoxyribonucleic acid Deoxribose sugar 2 strands held together with H bonds ATGC are the nitrogen bases Double helix Found only inside the nucleus RNA ribonucleic acid Ribose sugar and AUGC nitrogen bases 1 strand

linore
Télécharger la présentation

Molecular Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Molecular Genetics DNA RNA Gene Expression

  2. DNA and RNA • DNA deoxyribonucleic acid • Deoxribose sugar • 2 strands held together with H bonds • ATGC are the nitrogen bases • Double helix • Found only inside the nucleus • RNA ribonucleic acid • Ribose sugar and AUGC nitrogen bases • 1 strand • 4 types, mRNA, tRNA, rRNA, and snRNA

  3. Compare RNA and DNA

  4. Replication • DNA replication • Replication is semi-conservative • Occurs during interphase when each chromosome makes an exact copy (sister chromatid)

  5. DNA Replication cont’d • Involves several enzymes • Helicase- unwinds the helix • DNA polymerase- adds new nucleotide units to the parent strand of DNA • Ligase- connects the new strand and zips the molecule together. http://www.dnai.org/a/index.html

  6. Problem with replication? • At the end of each DNA molecule is a section of noncoding nucleotides called a telomere

  7. Telomere cont’d • Each time a cell divides and replicates its DNA a small part of the telomere is lost • This loss of telomere limits the number of times a cell can divide. • This erosion of the telomere during cell division is linked to the aging process and cancer • The enzyme telomerase is inactive in somatic cells but is active in cancer tumors. Can you identify the function of telomerase????

  8. Chromatin • In each cell DNA molecules are organized and wrapped around small proteins called histones. • The density of this wrapping is directly related to the expression of the genes found on the chromosome. • Dense wrapped – no gene expression • Lose wrapped – open to gene expression

  9. Gene experssion • Genes are located on the chromosome at a particular loci • When the gene is signaled to be expressed a series of enzymes go to work • helicase, RNA polymerase, ligase • Transcription occurs when the template strand of DNA is exposed and mRNA is made http://www.dnai.org/a/index.html

  10. Transcription • Process of making a mRNA molecule from the DNA template. • DNA - A T A G C A T A C T A G G • mRNA- U A U C G U A U G A U C C Transcription occurs with in the nucleus, after the mRNA is made however it goes through a series of modifications call RNA processing. This process allows for one gene to express multiple proteins, and is considered to be an element of the evolution process.

  11. Protein Synthesis • mRNA leaves the nucleus of the cell and moves into the rough ER. • A ribosome attaches to the mRNA and starts to Translate the sequence of nucleotides into a protein. • Translation involves several players: rRNA, mRNA, tRNA, amino acids, and enzymes http://www.dnai.org/a/index.html

  12. Translation • Translation occurs at the ribosome, and reads the mRNA 3 nucleotides at a time • 3 nucleotides make up a codon, which codes for 1 amino acid. • There are 64 different codons and only 20 amino acids. So there is repetition in the code • AUG is the universal start codon and codes for the amino acid Met. • There are 3 stop codons that terminate translation: UGA, UAA, UAG

  13. Translation cont’d • Once the codon enters the ribosome the complementary, anticodon, of the tRNA attaches to the mRNA. • The tRNA carries with it a specific amino acid, the amino acids are then bonded to each other as each sequential codon is read by the ribosome http://www.dnai.org/a/index.html The end result is a very specific amino acid chain called a polypeptide or protein.

More Related