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• Cells can contain 6-96-9 feet of DNA. If all the DNA in your body was put end to end, it would reach to the sun and back over 600600 times.
• DNA in all humans is 99.9 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 2525 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 55,000,00055,000,000 cells or between 63,000 to 93,00063,000 to 93,000 miles of DNA.
• It would take a person typing 60 words per minute, eight hours a day, around 5050 years to type the human genome.
ANSWER THE FOLLOWING (HW) 1.What is DNA?2. What are nucleotides?3. What are the 4 bases of nucleotides? 4. How do bases pair in DNA strands?5. What are the consequences of erros when bases do not pair correctly? 6. What is the function of DNA?7. Illustrate the DNA double helix
1. Represent and explain DNA structure
DNA is composed of units called NUCLEOTIDESNUCLEOTIDES, which are composed of three sub-molecules:
1. Pentose SugarPentose Sugar (deoxyribose)2. PhosphatePhosphate3. Nitrogen BaseNitrogen Base (purine or pyrimidine)
DNA is composed of two complimentarycomplimentary strands of nucleotides joined by hydrogen bondshydrogen bonds::
Adenine Adenine with Thymine Thymine (A-T or T-A)They join with 22 hydrogen bonds
Cytosine Cytosine with Guanine Guanine (C-G or G-C)They join with 33 hydrogen bonds
DNA twists into a double helix double helix
1. DNA directs thedirects the machinery of a cell to make specific cell to make specific proteinsproteins, and, therefore, DNA indirectly controls all of the functioning of all living things.
2. DNA stores the hereditary informationstores the hereditary information of an individual
3. DNA has the ability to mutatehas the ability to mutate (change). This allows for new characteristics and abilities to appear which may help an individual to survive and reproduce (EVOLUTIONEVOLUTION).
4. Self replication: DNA has the ability to make copies of itselfmake copies of itself
1. DNA replication is called ‘semi-conservativesemi-conservative’.
2. Semi-conservative replication is the process in which the original strandsoriginal strands of DNA remain intactremain intact and act as templatestemplates for the synthesis of duplicate strands of DNA.
3. One copy of a DNA molecule will split apart to make two two complete copies of itself. Each new DNA molecule is made up of half of the oldhalf of the old molecule and half of a newhalf of a new molecule.
1.1. UNZIPPINGUNZIPPING: The DNA molecule ‘Unzips’ as the hydrogen bondshydrogen bonds between the base pairs are brokenbroken. The enzyme HELICASEHELICASE causes this unzipping to occur.
2. COMPLEMENTARY COMPLEMENTARY BASE PAIRINGBASE PAIRING: Complementary nucleotides move into nucleotides move into positionposition to bond with the complementary bases on the DNA chain.
3. FORM NEW SUGAR PHOSPHATE BACKBONENEW 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 POLYMERASEDNA POLYMERASE which also checks for mistakesmistakes as it goes.
4. This process continues along the primary chain until we have 2 IDENTICAL STRANDS2 IDENTICAL STRANDS of DNA molecules (assuming there have been no errors made).
1) Mutations can occur naturallynaturally or through environmental environmental factors.
Environmental mutagensmutagens include some chemicals chemicals (food additives, pesticides, plastics) and radiationsradiations (X-rays to UV light).
2) A gene mutationgene mutation is a change of one or more nucleotidesnucleotides in a single gene. There are 3 types.
GENE MUTATIONS DeletionDeletion: 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.
AdditionAddition: 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.
SubstitutionSubstitution: 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 seriousnot 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?)
3. Chromosomal mutationsChromosomal mutations: a mutation of all all or partor part of a chromosome. These affect many affect many genesgenes.Example #1: crossing crossing overover where one part of a chromosome changes places with another. This can cause extra pieces, missing pieces, or the exchange of pieces of chromosomes.
Charlotte has Cri du Chat syndrome.
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.
Cri du Chat causes a varied level of mental handicap. The majority of the children need more specialized education.
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.
Example #2: non-disjunctionnon-disjunction = extra chromosomes or missing chromosomes due to mistakes made during meiosis.
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.
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.
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.
Definition: combining the DNA of two species.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).
2. Gene modification: repairing a gene (as in gene
therapy). 3. 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).
Recombinant DNA refers to DNA which
has been alteredby joining genetic material from two different sources!
