DNA (deoxyribonucleic acid). All living things contain DNA. Source of genetic traits. DNA is a nucleic acid. Nucleic acids are made of nucleotides.
Nucleotides Made of three things: 1. Phosphate (PO4) 2. Sugar (deoxyribose). 3. Nitrogen base.
Nitrogen BasesFour nitrogen bases makes four different nucleotides: –Guanine –Cytosine –Adenine –Thymine
Chargaff’s Rule He measured amounts of each base in various organisms and found: amt of adenine (A) = thymine (T) amt of cytosine (C) = guanine (G) This meant that A bonds to T and C bonds to G If 20% of strand is A, what %T? %C?
Structure of DNA Discovered by Watson and Crick Double helix- “spiral staircase”, 2 strands of nucleotides Siderails-sugar and phosphate Rungs-nitrogen bases – A----T – C----GHydrogen bonds (glue)
What is DNA Replication? Replicate = make “exact” copies. All DNA must be replicated before a cell can divide. Why? Why do cells need to divide? 1.Growth. 2.Repair or replace damaged cells. 3.Regenerate body parts (not all things can do this).
Enzymes and Replication Helicase- unwinds DNA DNA polymerase-moves along each strand and brings in bases for new strand copy
DNA Replication Can be a mistake in replication Mutations-change in DNA Caused by mutagens, such as X-rays, toxins, drugs, UV light, etc. Can cause disease, such as cancer, cystic fibrosis, etc. Can be: – insertions of extra bases – deletions of bases – substitutions of the wrong bases.
How Much DNA Is In Our Cells? Chromosome-strands of DNA coiled tightly Human cell has 46 (23 pair 2 sets of 23) 23 from Mom 23 from Dad
If all body cells contain the same # of chromosomes, why are all cells so different? Different cells make different proteins. Different “active” segments of DNA. During early stages of development, cells become “specialized.”
The first few cells that develop from the zygote are called stem cells. Stem cells differentiate into other cells.
2 Types of Cells Body cells somatic diploidchromosomes are in pairs (23 pairs) Reproductive cellsgametes egg & sperm haploid no pairs (23)
What is the Purpose of DNA? The cell “factory” makes proteins. Gene- a segment of DNA that codes for a protein. DNA has 1000’s of genes to make many different types of proteins. – Fingernails, hair, enzymes, hemoglobin, etc. Protein - polymer of amino acids
Part 1of Protein Synthesis: Transcription Transcription: DNA RNA (messenger) Occurs in nucleus DNA complementary to mRNA DNA: ATA-CGG-AAT transcription in nucleus mRNA: UAU-GCC-UUA
Part 2 of Protein Synthesis: Translation: Translation: mRNA protein Occurs at ribosomes in cytoplasm Codon-Three bases on mRNA that code for an amino acid mRNA: UAU-GCC-UUA (3 codons) translation in cytoplasm protein: a.a.---a.a---a.a. mRNA needs the help of tRNA to bring in the amino acids
Whole Process DNA: ATA-CGG-AAT transcription in nucleus mRNA: UAU-GCC-UUA(3 codons) translation in cytoplasm protein: a.a.-a.a-a.a.How do we know what amino acid results? The Codon chart or wheel!!!