What is the Secret What is the Secret of Life?of Life?

Deoxyribonucleic Acid is the Deoxyribonucleic Acid is the AnswerAnswer

History Lesson on DNAHistory Lesson on DNA

18691869 Swiss scientist Friedrich Miescher collected Swiss scientist Friedrich Miescher collected

bloodied bandages at the local hospitalbloodied bandages at the local hospital Collected nuclei from cells found on the bandagesCollected nuclei from cells found on the bandages Isolated a substance called NUCLEIN - this is the first Isolated a substance called NUCLEIN - this is the first

time that DNA was isolated time that DNA was isolated Unfortunately, he didn’t know anything else about this Unfortunately, he didn’t know anything else about this

moleculemolecule

History Lesson on DNAHistory Lesson on DNA

19441944 Canadian Scientist Oswald Avery Canadian Scientist Oswald Avery

proposed that DNA was involved in proposed that DNA was involved in HEREDITY (the passing of traits down HEREDITY (the passing of traits down from parent to offspring)from parent to offspring)

History Lesson on DNAHistory Lesson on DNA

19531953 British Scientists James Watson and British Scientists James Watson and

Francis Crick reveal the structure of DNA Francis Crick reveal the structure of DNA Perhaps the most important scientific Perhaps the most important scientific

discovery of the centurydiscovery of the century

Structure of DNAStructure of DNA

Watson and Crick described the structure Watson and Crick described the structure of DNA as a “of DNA as a “double helixdouble helix” – in simple ” – in simple terms, it looks like a coiled ladderterms, it looks like a coiled ladder Sides of ladder – made of alternating sugars Sides of ladder – made of alternating sugars

and phosphatesand phosphates Rungs of ladder – made of four chemicals Rungs of ladder – made of four chemicals

called nitrogen basescalled nitrogen bases

Structure of DNAStructure of DNA

Nitrogen BasesNitrogen Bases

There are only four nitrogen bases that make up There are only four nitrogen bases that make up a molecule of DNAa molecule of DNA Adenine (abbreviated as A)Adenine (abbreviated as A) Cytosine (abbreviated as C)Cytosine (abbreviated as C) Guanine (abbreviated as G)Guanine (abbreviated as G) Thymine (abbreviated as T)Thymine (abbreviated as T)

The secret of life is contained in the order of The secret of life is contained in the order of these four nitrogen bases on a DNA molecule – these four nitrogen bases on a DNA molecule – GENETIC CODEGENETIC CODE This code instructs cells what structures every cell in This code instructs cells what structures every cell in

an organisms’ body should producean organisms’ body should produce

The Genetic CodeThe Genetic Code

The code is like a blueprint that controls the production The code is like a blueprint that controls the production of proteins in the cellof proteins in the cell

Proteins makes up a lot of structures in animals and Proteins makes up a lot of structures in animals and plantsplants

Airlines use three letter codes for airports around the Airlines use three letter codes for airports around the worldworld YYC – CalgaryYYC – Calgary YYZ – TorontoYYZ – Toronto YVR – VancouverYVR – Vancouver LAX – Los AngelesLAX – Los Angeles

Each section of DNA will code for a specific part of a Each section of DNA will code for a specific part of a protein – just like airlinesprotein – just like airlines

Nitrogen BasesNitrogen Bases

Remember that a DNA molecule is a Remember that a DNA molecule is a double helixdouble helix

Certain nitrogen bases are compatible Certain nitrogen bases are compatible only with each otheronly with each other Adenine (A) will only pair with Thymine (T)Adenine (A) will only pair with Thymine (T) Cytosine (C) will only pair with Guanine (G)Cytosine (C) will only pair with Guanine (G)

How does DNA fit into the nucleus How does DNA fit into the nucleus of a cell?of a cell?

There is a lot of DNA in a nucleus (about 2 There is a lot of DNA in a nucleus (about 2 meters of it)meters of it)

To make it fit, it is tightly coiled in little packages To make it fit, it is tightly coiled in little packages called called CHROMOSOMESCHROMOSOMES In human cells – 46 chromosomes In human cells – 46 chromosomes

Chromosomes are found in pairs (23 pairs in humans)Chromosomes are found in pairs (23 pairs in humans) Offspring get one set of chromosomes from their mother and Offspring get one set of chromosomes from their mother and

one set from their fatherone set from their father All cells (except for gametes) will have 46 All cells (except for gametes) will have 46

chromosomes in their nuclei (GAMETES will have chromosomes in their nuclei (GAMETES will have only half or 23 chromosomes)only half or 23 chromosomes)

Chromosomes of other OrganismsChromosomes of other Organisms

Humans have 46 chromosomes but not all Humans have 46 chromosomes but not all species have that numberspecies have that number Gorilla - 48 chromosomes (24 pairs)Gorilla - 48 chromosomes (24 pairs) Fruit Fly – 8 chromosomes (4 pairs)Fruit Fly – 8 chromosomes (4 pairs) Sheep – 54 chromosomes (27 pairs)Sheep – 54 chromosomes (27 pairs) Dog – 78 chromosomes (39 pairs)Dog – 78 chromosomes (39 pairs) Cat – 38 chromosomes (19 pairs)Cat – 38 chromosomes (19 pairs) Horse – 64 chromosomes (32 pairs)Horse – 64 chromosomes (32 pairs)

Even though all of these species have different Even though all of these species have different numbers of chromosomes – the DNA is still numbers of chromosomes – the DNA is still made up of A, C, G, and T – just in a different made up of A, C, G, and T – just in a different orderorder

What happens when there are a What happens when there are a different number of chromosomes different number of chromosomes

in a cell?in a cell? Normal human cells have 46 Normal human cells have 46

chromosomes, however during chromosomes, however during reproduction, problems can occur causing reproduction, problems can occur causing fewer or more chromosomes being fewer or more chromosomes being presentpresent

Down’s SyndromeDown’s Syndrome

47 chromosomes – 3 copies of 47 chromosomes – 3 copies of chromosome number 21 in humanschromosome number 21 in humans Mental retardationMental retardation Extra fold of skin on eyelidsExtra fold of skin on eyelids A flattened foreheadA flattened forehead Poor muscle developmentPoor muscle development

Down’s SyndromeDown’s Syndrome

www.einstein-syndrome.com/ house/evan_stories.htm

Turner’s SyndromeTurner’s Syndrome

45 chromosomes – only 1 X chromosome 45 chromosomes – only 1 X chromosome (normal females have 2 X chromosomes (normal females have 2 X chromosomes and normal males have 1 X and 1 Y and normal males have 1 X and 1 Y chromosome)chromosome) SterileSterile Short statureShort stature

Turner’s SyndromeTurner’s SyndromeKaryotypeKaryotype of a patient with the of a patient with the

syndromesyndrome

XYY “Super Male”XYY “Super Male”

47 chromosomes – males that have 2 Y 47 chromosomes – males that have 2 Y chromosomes (normal males only have 1 chromosomes (normal males only have 1 Y chromosome)Y chromosome) Used to be thought to be a cause of violent Used to be thought to be a cause of violent

behaviourbehaviour

Klinefelter’s SyndromeKlinefelter’s Syndrome

47 chromosomes – males have an extra X 47 chromosomes – males have an extra X chromosomeschromosomes Small testiclesSmall testicles SterileSterile Frequent mental retardationFrequent mental retardation

Genes are found on ChromosomesGenes are found on Chromosomes

Genes are segments of DNA containing Genes are segments of DNA containing coded instructions for the formation of coded instructions for the formation of structures structures

Humans have 30,000 genes on 23 pairs of Humans have 30,000 genes on 23 pairs of chromosomes within every cell’s nucleuschromosomes within every cell’s nucleus

Characteristics of GenesCharacteristics of Genes

Genes are located on chromosomes in nucleiGenes are located on chromosomes in nuclei Each chromosome has a number of genes Each chromosome has a number of genes

located on itlocated on it Genes, like chromosomes, come in pairsGenes, like chromosomes, come in pairs Both genes in a pair carry DNA instructions for Both genes in a pair carry DNA instructions for

the same thing, and they occupy matching the same thing, and they occupy matching locations on the two chromosomeslocations on the two chromosomes

Offspring inherit genes from both parents, Offspring inherit genes from both parents, however the genes may be in different forms however the genes may be in different forms (ALLELES)(ALLELES)

Chromosomes, Genes and AllelesChromosomes, Genes and Alleles