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Understanding DNA Structure, Replication, and Protein Synthesis

DNA, or deoxyribonucleic acid, is a double-stranded helix of nucleotides that stores genetic information. It consists of four bases: adenine, thymine, cytosine, and guanine, which pair specifically—A with T and C with G. DNA replication occurs in the nucleus during the S phase of interphase, where enzymes unzip the DNA and form new strands. DNA's instructions are transcribed to mRNA and translated into proteins, which determine our traits. Mutations in the DNA sequence can alter protein formation and may lead to various effects.

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Understanding DNA Structure, Replication, and Protein Synthesis

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  1. Molecular Genetics

  2. DNA • Deoxyribonucleic acid • A double stranded helix that is made of nucleotides • Stores our genetic information • Can never leave the nucleus

  3. A DNA nucleotide • There are four different bases that make up DNA • DNA has four complementary bases • Cytosine – guanine • Adenine - thymine

  4. DNA – the double helix Strong covalent bonds • Theses nucleotides join together to make the double stranded DNA. • Watson and Crick were the two scientists who discovered the DNA molecule Weak hydrogen bonds

  5. DNA Replication • Making another copy of DNA • Happens before the cell divides • S phase of Interphase • Happens in the nucleus

  6. Steps of replication • Unzip DNA • DNA helicase enzyme 2. Add complementary nucleotides • DNA polymerase enzyme 3. Zip up the new strands of DNA • DNA ligase enzyme

  7. DNA replication is semi conservative - each new strand is half old/half new

  8. How does DNA give us our traits? • Gene • piece of DNA that codes for 1 protein • The types of proteins that are made give us our characteristics • But DNA cannot leave the nucleus, and proteins are made in ribosomes! • So…

  9. RNA saves the day! • Ribonucleic acid • Cytosine – guanine • Adenine – uracil • Single stranded • Can leave the nucleus and enter the ribosome

  10. Types of RNA ribosomal RNA rRNA messanger RNA mRNA Transfer RNA tRNA

  11. Protein synthesis happens in two steps • Transcription • Making messenger RNA (mRNA) • Happens in the nucleus • Translation • Using mRNA, tRNA, and rRNA to make proteins • Happens in the ribosome

  12. Transcription DNA unzips new complementary RNA bases create an mRNA strand

  13. TranslationtRNAs put the correct amino acid sequence together to build a protein

  14. Codons and protein • Three bases (triplet code)on mRNA are called a codon and code for one amino acid.

  15. Mutation • A change in the sequence of bases of DNA • A change in the base sequence could lead to the wrong protein being made • There are two types of mutations • Point mutation– a single base is changed • AAT CGG ATA GTA • ATT CGG ATA GTA • Frameshift mutation – a base is added or deleted • AAT CGG ATA GTA • AAT CGT GAT AGT A • Which type of mutation is the most harmful?

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