Inheritance and the Structure of DNA

Deoxyribonucleic Acid

DNA Discovery 1928-Frederick Griffith – transforming factor 1944-James Watson and Francis Crick – discovered that DNA was the transforming factor 1952-Rosalind Franklin and Maurice Wilkins – took x-ray photographs of the DNA molecule 1953-Watson and Crick – created a three-dimensional 3-D model of DNA 1962-Watson, Crick, and Wilkins – received the Nobel Prize in Medicine

What is DNA? Genetic material used to express traits Nucleotide units – Deoxyribose (sugar) – Phosphate – Base Purines (double ring) – Thymine ( T ) – Cytosine ( C ) Pyrimidine (one ring) – Adenine ( A ) – Guanine ( G )

Complementary Strands Order of bases on the nucleotides in one strand of DNA complements the order of bases on the opposite strand – base sequence

DNA Replication DNA stores and transmit information that tells cells which proteins to make and when to make them. DNA located in the nucleus and cannot leave. Duplication of DNA

DNA Helicase and DNA Polymerase 5”  3” refers to location of carbon on sugar, bases added to C with OH attached, work forward from there, refer to DNA handout. Bases attach to C #2, C#5 Phosphate

Deoxyribose vs Ribose sugars 2-Deoxy-Ribose in DNA is replaced by Ribose in RNA. The difference is a hydroxy group ( -OH ) in RNA versus a single proton ( -H ) in DNA. The extra -O- in the ribose backbone prevents formation of stable double-helices in RNA.

RNA (Ribonucleic Acid) RNA differs from DNA – Sugar is ribose – The nitrogen base THYMINE is replaced by URACIL – RNA is single-stranded There are three types of RNA – Messenger RNA (mRNA) – Transfer RNA (tRNA) – Ribosomal RNA (rRNA)

RNA Messenger RNA (mRNA) – copies the information from the DNA in the nucleus Transfer RNA (tRNA) – reads the information from mRNA – carries amino acids to the ribosome Ribosomal RNA (rRNA)

Transcription vs Translation Transcription – DNA to mRNA – in nucleus Translation – mRNA to tRNA and rRNA to make proteins – in cytoplasm

Transcription Reading the gene RNA polymerase (mRNA)

Translation RNA to proteins Cytoplasm – tRNA, rRNA, and mRNA – assemble proteins Genetic Code – Three letter word (codon) – Codon codes for amino acid – 64 mRNA

Translation Specific amino acid on one end of each tRNA. – anticodon on tRNA is complementary codon on mRNA. mRNA joins with a rRNA and tRNA – first tRNA is released from the ribosome – Amino acids bond creating a polypeptide chain – This process is repeated until one of three stop codons is reached