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DNA

DNA. Chapter 11. What is DNA?. DNA = Deoxyribonucleic Acid DNA is the complete instructions for making all the proteins for an organism. The Structure of DNA. DNA is a polymer made of repeating subunits called nucleotides . Nucleotides have three parts: 1. simple sugar ( deoxyribose )

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DNA

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  1. DNA Chapter 11

  2. What is DNA? • DNA = Deoxyribonucleic Acid • DNA is the complete instructions for making all the proteins for an organism.

  3. The Structure of DNA • DNA is a polymer made of repeating subunits called nucleotides. • Nucleotides have three parts: 1. simple sugar (deoxyribose) 2. phosphate group 3. nitrogen base - Adenine (A) - Cytosine (C) - Guanine (G) - Thymine (T)

  4. DNA is like a ladder: - alternating deoxyribose and phosphate make up the sides - nitrogen bases make up the steps • DNA is two chains of nucleotides joined together by the nitrogen bases. • The nitrogen bases are held together by weak hydrogen bonds.

  5. DNA is shaped like a long twisting zipper and is called a DOUBLE HELIX

  6. Complimentary Base pairing • Adenine (A) always pairs with Thymine (T) • Cytosine (C) always pairs with Guanine (G) • The amount of Adenine (A) always equals the amount of Thymine (T) and the amount of Cytosine (C) always equals the amount of Guanine (G)

  7. The importance of the nucleotide sequence • The sequence of the nucleotides forms the unique genetic information of an organism. • A nucleotide sequence of A-T-T-G-A-C carries different information than the sequence T-C-C-A-A-A • The closer the relationship between two organisms, the greater the similarity in their order of DNA nucleotides

  8. DNA Replication • This is where the DNA in the chromosomes is copied. • Without DNA replication, new cells would have only half the DNA of their parents. • How DNA replicates: 1. The DNA molecule unzips - enzyme breaks bonds between nitrogen bases

  9. 2. Base Pairing - free nucleotide base pairs match with their compliment 3. Results in two exact copies of DNA

  10. Dnarna • Deoxyribose • Thymine (T  A) • Double-stranded • Longer • Ribose • Uracil (U  A) • Single-stranded • Shorter

  11. Three types of rna • Messenger RNA (mRNA) – takes info from the DNA in the nucleus to the cytoplasm and ribosomes • Ribosomal RNA (rRNA) – RNA that makes up ribosomes • Transfer RNA (tRNA) – transports amino acids to the ribosomes to be made into a protein.

  12. transcription • The process of converting the DNA in the nucleus into mRNA. • Steps of Transcription: 1. enzymes unzip the molecule of DNA 2. free RNA nucleotides pair with complimentary DNA nucleotides on one of the DNA strands 3. mRNA breaks away as the strands of DNA rejoin

  13. The genetic code • A code is needed to convert the language of mRNA into the language of proteins. • Each set of three nitrogen bases in mRNA represents an amino acid and is called a codon. • The order of nitrogen bases in the mRNA will determine the type and order of amino acids in a protein.

  14. Translation • The process of converting mRNA to protein • Translation happens at the ribosomes in the cytoplasm • tRNA brings the amino acids to the ribosomes • Long chains of amino acids are formed and become proteins when released from the ribosomes

  15. What is a mutation? • Any change in the DNA sequence is a mutation. • Mutations in reproductive cells get passed on to the next generation. • Mutations in body cells may cause problems in the individual, but will not get passed on to the next generation.

  16. Point mutations • A change in a single base pair in DNA THE DOG BIT THE CAT THE DOG BIT THE CAR • Just like a change in a letter changes the meaning of the above sentence, a change in one nitrogen base can change the entire structure of a protein.

  17. Frameshift mutations • A mutation where a single base is added or deleted from DNA. • It shifts the reading of codons by one base

  18. Chromosomal mutations • Parts of chromosomes are broken off and lost • Often, chromosomes break and then rejoin incorrectly • Sometimes the parts join backwards or even join the wrong chromosomes. • Four kinds of chromosomal mutations: -deletion, insertion, inversion, translocation

  19. Causes of mutations • Anything that causes a change in DNA is called a mutagen. • Forms of radiation such as X-rays, ultraviolet light, and nuclear radiation contain a lot of energy and can blast DNA apart • Chemical mutagens can interact with DNA and cause changes

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