DNA is a code There are 2 types of code. The first type is: a set of symbols used to communicate
The English alphabet Examples of codes:
Greek alphabet Russian (Cyrillic) alphabet
Chinese alphabet Arabic alphabet
Mathematics π 0 1 2 3 4 5 6 7 8 9
Codes can also be: telephone number password a set of instructions Pollard Code of Conduct computer code zip code 02492 locker combination dress code blueprints code of chivalry Lego instructions
DNAis both a set of symbols used to communicateAND a set of instructions
DNA Building Blocks DNA is a gigantic molecule made up of millions of these smaller molecules: Nitrogen bases Adenine (A) Thymine (T) (deoxyribose) Guanine (G) (C) Cytosine (C)
DNAis made up of millions of“building blocks” callednucleotides,which contain: • 1 sugar • 1 phosphate • 1 nitrogen base • (eitherAdenine, Cytosine, Guanineor Thymine) P nitrogen NB S The DNA molecule’s shape is atwisted ladder,or double helix.
Millions of nucleotides bond together to form a DNA molecule. P Nucleotide NB S Sugar phosphate backbone
DNA “Ladder” Thesugarand phosphate molecules form the sides or backbone of the ladder. Thenitrogen basesform the “rungs” of the ladder. C G P S S P T A P S S P G C P S S P The DNA molecule is held together in the middle by weakhydrogen bondsbetween the nitrogen base pairs. T A P S S P C G P S S P A T P S DNA structure S P
C G A T 4 different bases GUANINE CYTOSINE ADENINE THYMINE
4 different bases Hydrogen bonds GUANINE CYTOSINE Deoxyribose Deoxyribose Hydrogen bonds ADENINE THYMINE Deoxyribose Deoxyribose
Double helix Double helix The twisted-ladder shape of DNA is called adouble helix.
DNA Structure Guanineonly bonds withCytosine Adenineonly bonds withThymine
Winners of the Race to Learn DNA’s Structure --Watson and Crickin 1953 with their model of DNA Watson and Crick Bob Watson Francis Crick
Rosalind Franklin Rosalind Franklin was a young British scientist whose experiments inX-ray crystallographyat King’s College London were essential to the discovery of DNA’s double helix shape by James Watson and Francis Crick in 1953. Franklin was cheated of deserved recognition by her early death from cancer, at the age of 38, in 1958. Nobel prizes are never awarded posthumously; when Watson, Crick and Wilkins got their awards in 1962, she was therefore ineligible, even though Watson & Crick owed much of their success to her work.
DNA SONG We love DNA Made of nucleotides, Sugar, phosphate, and a base Bonded down the sides. Adenine and thymine Make a lovely pair. Cytosine without guanine Would feel very bare. Oh-h-h, de-ox-y-ri-bo Nu-u-cle-ic acid. RNA is ri-i-bo Nu-u-cle-ic acid.
DNA Replication The DNA unwinds and separates down the middle (“unzips”) 2) Nucleotides floating in the nucleus attach to the 2 open sides. A -- T, C -- G 3) There are now 2 identical DNA molecules.
DNA Replication Step 1 The DNA molecule “unzips” down the middle. Step 2 Unattached nucleotides, floating in the nucleus, attach themselves to the two “half-ladders”, making…. Step 3 2 identical DNA molecules
Protein Synthesis • The nitrogen bases (A, G, C, T) make up DNA’s code. The nitrogen bases are read in groups of 3. • Each group of 3 bases is called acodon. • Each codon stands for 1 of the 20 amino acids. • There are also codes for “Start” and “Stop”.
Amino Acids There are 20 different amino acids Two examples • Amino acids are the building blocks of proteins. • Aprotein is a chemical made up of many amino acids bonded together. • Proteins: • carry out all cell functions • give an organism its traits.
A picture is worth a 1000 words…. DNABase pairs Nitrogen bases G C A A G T A C C T G A T G codons G C A A G T A C C T G A codon codon codon codon amino acid amino acid amino acid amino acid Amino acids Amino acids amino acid amino acid amino acid amino acid protein
Some Genetics Numbers Some Genetics Numbers 3 billion base pairs 3 billion base pairs 1 billion codons 1 billion codons in onehuman cell there are… 25, 000 genes inonehuman cellthere are… 25, 000 genes 46 chromosomes 46 chromosomes 7 feet of DNA 7 feet of DNA Number of people on Earth: 6.6 billion Number of people on Earth: 7.05 billion Number of people with exactly your DNA ….1 Number of people with exactly your DNA ….1 YOU !!! YOU !!!
GENES BY THE NUMBERS Even though all the cells in the body contain the exact same genes, the genes that are “turned on” in each cell vary depending on the cell’s function. These are the numbers of working genes in different parts of the body. Brain 3195 White blood cell 2164 Liver 2091 Heart 1195 Pancreas 1094 Bone 904 Colon 879 Skeletal muscle 735 Kidney 712 Skin 629 Thyroid Gland 584 Eye 547 Small Intestine 297 Smooth muscle 127 Esophagus 76 Red blood cell 8
Some fascinating facts about DNA… a single DNA molecule is made of 240 billion atoms (a water molecule is made of 3 atoms). • Each chromosome is a single DNA molecule about 2 inches long. If you unraveled all the DNA is one cell, it would measure 7 to 8 feet. 99.9% of all human DNA is the same; only 0.1% is different in each person. There are 3 billion nitrogen base pairs in one DNA molecule.
Mutation Accidents Happen, With Some “Accidents” (Base Mismatches) Leading toMutation Amutationis achange in DNA sequence. Mutations due to replication errors only happenonce in every trillion replicated nucleotides.
There are 3 types of base-pair mutation: 1.A base pair isdropped(DELETION) Example:CCCTTTbecomes CC TTT
Base-pair mutations 2.A base pair isadded(INSERTION) Example:CCCTTTbecomes CCCGTTT
Base-pair mutations Base-pair mutations 3.A base pair isswitched(SUBSTITUTION) Example:CCCTTT becomes CCATTT
Hemoglobin mutation A substitution in one base causes a change in one amino acid, which changes the hemoglobin protein enough to cause sickle cell anemia.
Mutations • Mutations happen all the time, in every species. • Mutations are usuallyharmfulorneutral---mutations are rarelybeneficial. • Mutations can cause cancer & some diseases(bad). • Mutations are the only way to bring new alleles (traits) into a species(good for evolution). So, just like Goldilocks – not too hot, not too cold, just right – the optimal rate of new mutation is a balancing act.
Causes of Mutation • Environmental factors such as • ultraviolet light (sunshine) • nuclear radiation or • certain chemicals Biohazard (mutagenic chemicals) Nuclear radiation 2.Copying errors Mistakes that occur when a cell replicates (copies) its DNA in preparation for cell division
Chromosomal Alterations Sometimes mutations occur to an entire chromosome, affecting the structure of the chromosome.
Chromosomal Alterations Sometimes mutations affect the number of chromosomes (an entire chromosome is missing, or there is an extra chromosome). Down syndrome, or Trisomy 21 Patau syndrome, or Trisomy 13
Chromosomal Alterations Syndromes of missing chromosomes Turner syndrome (missing X chromosome) Webbed neck, short stature, infertility, heart defects
Mitochondrial DNA Did you know that, in addition to the DNA in the cell nucleus, your cells also have DNA in their mitochondria? • Mitochondrial DNA • has 37 genes • 13 of them give instructions for cellular respiration • the rest give instructions for making transfer RNA (tRNA) and ribosomal RNA (fRNA) • is inherited from your mother, since usually only the egg contains mitochondria (the sperm’s mitochondria are in its tail, which falls off after fertilization)