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

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 – 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