Inheritance and the Structure of DNA Deoxyribonucleic Acid

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 (m. RNA) – Transfer RNA (t. RNA) – Ribosomal RNA (r. RNA)

RNA • Messenger RNA (m. RNA) – copies the information from the DNA in the nucleus • Transfer RNA (t. RNA) – reads the information from m. RNA – carries amino acids to the ribosome • Ribosomal RNA (r. RNA)

Transcription vs Translation • Transcription – DNA to m. RNA – in nucleus • Translation – m. RNA to t. RNA and r. RNA to make proteins – in cytoplasm

Transcription • Reading the gene • RNA polymerase (m. RNA)

Translation • RNA to proteins • Cytoplasm – t. RNA, r. RNA, and m. RNA – assemble proteins • Genetic Code – Three letter word (codon) – Codon codes for amino acid – 64 m. RNA

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