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Genetics

Genetics. 2/10/2014 to 2/14/2014. DNA structure. In 1952, scientist Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form. The actual model of DNA was made by James Watson and Francis Crick. DNA model. DNA looks like a twisted ladder.

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Genetics

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  1. Genetics 2/10/2014 to 2/14/2014

  2. DNA structure • In 1952, scientist Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form. The actual model of DNA was made by James Watson and Francis Crick.

  3. DNA model • DNA looks like a twisted ladder. • Each side of the ladder is made up of sugar-phosphate molecules. • Each molecule consists of the sugar called deoxyribose and a phosphate group.

  4. What is DNA? • A cell uses a code stored in its hereditary material. The code is a chemical known as DNA. • It contains information for an organism’s growth and function. • When a cell divides, the DNA code is copied and passed to the new cells.

  5. DNA model • The rungs of the ladder are made up of other molecules called nitrogen bases. • DNA has 4 kinds of bases: adenine, guanine, cytosine and thymine. • The nitrogen bases are represented by A G C T

  6. DNA model • Cytosine always pairs with Guanine • Adenine always pairs with Thymine • Like interlocking pieces of a puzzle each base bonds only with its correct partner

  7. Copying DNA • When _____________ are duplicated ________ mitosis and meiosis during _______, the amount of DNA in the nucleus is __________.

  8. Copying DNA • When chromosomes are duplicated before mitosis and meiosis, during interphase, the amount of DNA in the nucleus is doubled.

  9. Copying DNA • The two sides of DNA unwind and separate. • Each side then becomes a pattern on which a new side forms. • The new DNA has bases that are identical to those of the original DNA and are in the same order.

  10. Genes • Most of your characteristics, your hair color, height, and even how things taste to you depend on the kinds of proteins your cells make. • DNA in your cells stores the instructions for making these proteins. • The instructions for making a specific protein are found in a gene.

  11. Genes • Each chromosome contains hundreds of genes. • Proteins are made of chains of hundreds or thousands of amino acids. • The gene determines the order of amino acids in a protein.

  12. Making proteins • Genes are found in the nucleus but proteins are made on ribosomes in the cytoplasm. • The codes for making proteins are carried from the nucleus to ribosomes by another type of nucleic acid called ribonucleic acid or RNA

  13. RNA • RNA is made in the nucleus on a DNA pattern but is different from DNA • RNA is like a ladder that has all its rungs cut in half. • RNA has the nitrogen bases A, G and C like DNA but instead of thymine RNA has uracil U

  14. RNA • There are 3 main kinds of RNA: 1. messenger RNA (mRNA) 2. ribosomal RNA (rRNA) 3. transfer RNA (tRNA)

  15. Corresponding Sequence Activity • Write the sequence for this strand of DNA. • Write the corresponding strand of mRNA and tRNA

  16. Controlling Genes • Most cells in an organism have exactly the same chromosomes and the same genes but they do not make the same proteins. • Muscle proteins are made in muscle cells just like nerve proteins are made in nerve cells. • Cells must be able to control genes by turning some genes off and turning other genes on.

  17. Mutations • Sometimes mistakes happen when DNA is being copied. • If DNA is not copied exactly, the proteins made from the instructions may not be made correctly. These mistakes are called mutations. • Some mutations include cells that receive an entire extra chromosome or are missing a chromosome. Outside factors ex. Xrays, sunlight and chemicals have been known to cause mutations

  18. Results of a mutation • A change in a gene or chromosome can change the traits of an organism. • If the mutation occurs in a body cell it may or may not be life threatening. • If mutations occur in gametes then all the resulting cells will have the mutation.

  19. Results of a mutation • Mutations add variety to a species when the organism reproduces. • Many mutations are harmful to organisms often causing their death. • Some mutations do not appear to have any effect on the organism and some can even be beneficial.

  20. Check & Review • Describe how DNA makes a copy of itself?

  21. Answer • The 2 sides unwind and separate • A complementary strand is formed for each • The resulting double-stranded DNA has one original strand and one new strand.

  22. Explain • Explain how the codes for proteins are carried from the nucleus to the ribosomes.

  23. Answer • The codes are carried by mRNA from the nucleus to the ribosome.

  24. Apply • Apply: A strand of DNA has the bases AGTAAC. Using letters show a matching DNA strand.

  25. Answer • TCATTG

  26. Determine • Determine how tRNA is used when cells build proteins.

  27. Answer • The cytoplasm tRNA in the cytoplasm brings amino acids to the ribosomes. There, three nitrogen bases on the mRNA template match with 3 bases on the tRNA. The amino acids bond, and protein synthesis begins.

  28. Think critically • You begin as one cell. Compare the DNA in your brain cells to the DNA in your heart cells.

  29. Answer • The DNA is identical.

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