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.
DNA is composed of units called NUCLEOTIDES, which are composed of three sub-molecules:
1. Pentose Sugar (deoxyribose)
3. Nitrogen Base (purine or pyrimidine)
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
Start at Part 1: http://188.8.131.52/pub/flash/24/24.html
2. DNA stores the hereditary information of an individual
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).
4. Self replication: DNA has the ability to make copies of itself
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.
2. COMPLEMENTARY BASE PAIRING: Complementary nucleotides move into position to bond with the complementary bases on the DNA chain.
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.
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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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.
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?)
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.
("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.
non-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.
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).
Recombinant DNA refers to DNA which has been alteredby joining genetic material from two different sources!