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DNA - PowerPoint PPT Presentation


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DNA. Humans share 50% of their DNA with bananas. Cells can contain 6-9 feet of DNA. If all the DNA in your body was put end to end, it would reach to the sun and back over 600 times.

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slide2

Humans share 50% of their DNA with bananas.

  • Cells can contain 6-9 feet of DNA. If all the DNA in your body was put end to end, it would reach to the sun and back over 600 times.
  • DNA in all humans is 99.9 percent identical. It is about one tenth of one percent that makes us all unique, or about 3 million nucleotides difference.
  • DNA can store 25 gigabytes of information per inch and is the most efficient storage system known to human. So, humans are better than computers!!
  • In an average meal, you eat approximately 55,000,000 cells or between 63,000 to 93,000 miles of DNA.
  • It would take a person typing 60 words per minute, eight hours a day, around 50 years to type the human genome.
slide3

P.L.O.'s: students WILL...

  • Name the four bases in DNA and describe the structure of DNA using the following terms: Nucleotide (sugar, phosphate, base), Complementary base pairing, Double Helix, and Hydrogen bonding
  • Describe DNA replication with reference to three basic steps: “Unzipping”, Complementary base pairing, and Joining of adjacent nucleotides.
  • Define recombinant DNA
  • Describe three uses for recombinant DNA
  • Compare and contrast the general structural composition of DNA and RNA
slide4

So What Do We Know?

DNA is composed of units called NUCLEOTIDES, which are composed of three sub-molecules:

1. Pentose Sugar (deoxyribose)

2. Phosphate

3. Nitrogen Base (purine or pyrimidine)

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So What Do We Know?

DNA is composed of two complimentarystrands of nucleotides joined by hydrogen bonds:

Adenine with Thymine (A-T or T-A)

They join with 2 hydrogen bonds

Cytosine with Guanine (C-G or G-C)

They join with 3 hydrogen bonds

DNA twists into a double helix

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DNA STRUCTURE

ANIMATION

Start at Part 1: http://207.207.4.198/pub/flash/24/24.html

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Functions of DNA

  • DNA directs themachinery of a cell to make specific proteins, and, therefore, DNA indirectly controls all of the functioning of all living things.
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Functions of DNA

2. DNA stores the hereditary information of an individual

slide13

Functions of DNA

3. DNA has the ability to mutate (change). This allows for new characteristics and abilities to appear which may help an individual to survive and reproduce (EVOLUTION).

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Functions of DNA

4. Self replication: DNA has the ability to make copies of itself

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DNA REPLICATION

  • DNA replication is called ‘semi-conservative’.
  • 2. Semi-conservative replication is the process in which the original strands of DNA remain intact and act as templates for the synthesis of duplicate strands of DNA.
slide16

DNA REPLICATION

3. One copy of a DNA molecule will split apart to make two complete copies of itself. Each new DNA molecule is made up of half of the old molecule and half of a new molecule.

ANIMATION: http://www.lewport.wnyric.org/jwanamaker/animations/DNA%20Replication%20-%20long%20.html

slide17

STEPS TO DNA REPLICATION

  • UNZIPPING: The DNA molecule ‘Unzips’ as the hydrogen bonds between the base pairs are broken. The enzyme HELICASE causes this unzipping to occur.
slide19

STEPS TO DNA REPLICATION

2. COMPLEMENTARY BASE PAIRING: Complementary nucleotides move into position to bond with the complementary bases on the DNA chain.

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STEPS TO DNA REPLICATION

3. FORM NEW SUGAR PHOSPHATE BACKBONE: The nucleotides join as the sugars and phosphates bond to form a new backbone. This process occurs due to the enzyme DNA POLYMERASE which also checks for mistakes as it goes.

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STEPS TO DNA REPLICATION

4. This process continues along the primary chain until we have 2 IDENTICAL STRANDS of DNA molecules (assuming there have been no errors made).

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The Entire Process of DNA Replication

Start at Part 2 and skip to Part 5 (end): http://207.207.4.198/pub/flash/24/24.html

slide24

ERRORS = MUTATION

  • Mutations can occur naturally or through environmental factors.
  • Environmental mutagens include some chemicals (food additives, pesticides, plastics) and radiations (X-rays to UV light).
slide29

ERRORS = MUTATION

  • 2) A gene mutation is a change of one or more nucleotides in a single gene. There are 3 types.
  • Addition
  • Deletion
  • Substitution
gene mutations
GENE MUTATIONS

Deletion:one nucleotide base is left out. All of the amino acids after a deletion will be wrong, so SHAPE and FUNCTION of protein are altered. Serious.

Addition:one extra nucleotide base is added. This will also change the entire amino acid sequence of the protein, so SHAPE and FUNCTION of protein are altered. Serious.

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Substitution:when single bases or short pieces are replaced with one another.

Example: Sickle-Cell Anemia, only one nucleotide base is switched. This causes only 1 amino acid to change, but it is an important one.

This type of mutation is usually not as serious as the 1st two. It just depends on which amino acid is affected (does it have an ‘R’ group with a +,-, or S group?)

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ERRORS = MUTATION

3. Chromosomal mutations: a mutation of all or partof a chromosome. These affect many genes.

Example #1: crossing over where one part of a chromosome changes places with another.

This can cause extra pieces, missing pieces, or the exchange of pieces of chromosomes.

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Cri du Chat Syndrome

("Cry of the cat" in French) is a genetic disorder caused by the loss or misplacement of genetic material from the 5th chromosome.

It was first identified in 1963 by Professor Lejeune. He described the syndrome after the sound that many of the babies and young children make when crying.

Charlotte has Cri du Chat syndrome.

Cri du Chat causes a varied level of mental handicap. The majority of the children need more specialized education.

slide40

Example #2:

non-disjunction= extra chromosomes or missing chromosomes due to mistakes made during meiosis.

slide42

Down Syndrome occurs in approx. 1 in 700 births in Canada. A person with Down Syndrome has 47 chromosomes in each cell instead of 46. The chance of having a baby with Down Syndrome increases significantly with age; for example, between 20 and 24 years of age, the chance of conceiving a child with Down syndrome is 1 in 1,450, while at age 45 this probability increases to 1 in 32.

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WHAT IS KLINEFELTER SYNDROME?Discovered in 1942 by Dr. Harry Klinefelter. He studied 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm.

By the late 1950s, it was discovered that men with Klinefelter syndrome, had an extra sex chromosome, XXY instead of the usual male arrangement, XY.

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WHAT IS TURNER’S SYNDROME?A disorder that results from a non-disjunction of the X chromosomes during meiosis = X0 instead of XX. Individuals are short and stocky; also sterile.

slide47

RECOMBINANT DNA

Definition:combining the DNA of two species.

1. Gene displacing:add an extra copy of a gene (cows with huge teats to make double the milk) or deleting genes (removing the rotting hormone from tomatoes).

  • Gene modification: repairing a gene (as in gene
  • therapy).
  • Gene transformation:inserting genes from a different
  • species to give a new function (as in making goats with
  • spider proteins in their milk or making bacteria that create
  • human insulin).
slide48

Recombinant DNA refers to DNA which has been alteredby joining genetic material from two different sources!

slide50

RECOMBINANT DNA

ANIMATION

http://www.sumanasinc.com/webcontent/anisamples/molecularbiology/plasmidcloning_fla.html

http://www.present.udel.edu/biotech/rDNA.html