inheritance and the structure of dna. deoxyribonucleic acid
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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
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