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Mr. Gust Zoology. Understanding DNA, Genes and Chromosomes. What is DNA?. DNA stands for DEOXYRIBONUCLEIC ACID The DNA molecule is important in the “blueprint” of all living organisms. What about genes?. Genes make up the “blueprint.” Genes tell the organism how to look and act.
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Mr. Gust Zoology Understanding DNA, Genes and Chromosomes
What is DNA? • DNA stands forDEOXYRIBONUCLEIC ACID • The DNA molecule is important in the “blueprint” of all living organisms.
What about genes? • Genes make up the “blueprint.” • Genes tell the organism how to look and act. • Genes are composed of DNA.
And some more terms … • The study of genes is called GENETICS. • The master blueprint for a living organism is called a GENOME. • Biological research with DNA combines biochemistry and genetics and is called MOLECULAR BIOLOGY.
Genetic engineering is possible because … • DNA is a fairly simple structure. • Scientists can alter the DNA of a gene and the information that DNA contains. • Genes are organized the same way in all organisms, so genes can be moved from one organism to another.
The DNA molecule … • Two strands wrapping around each other • Resembles a twisted ladder • Described as a double stranded helix, or spiral • The sides are sugar and phosphate molecules. • The rungs are nitrogen-containing chemicals called bases.
The rules are strict! • Base adeninepairs only with thymine(an A-T pair). • Cytosine pairs only with guanine(a C-G pair). • Each daughter cell receives one old and one new DNA strand.
So why do the rules matter? • Each new strand exactly copies an old strand. • This prevents errors in cells or offspring. • If the rules are broken it’s a MUTATION!
Genes are basic … • The physical and functional units of heredity for plants, animals and humans • Every living cell contains 2 genes – one from each parent • Many genes make up a DNA molecule.
So what about sequences? • A gene has a specific sequence of nucleotide bases. • The sequence provides information for constructing proteins. • Proteins make up cell structure, tissues, and enzymes. • The human genome contains about 30,000 genes.
There are still many mysteries … • Human genes vary in length. • Only about 10% code proteins – EXONS • Some gene sequences have nocoding properties – INTRONS • Some portions of the genomeare not understood.
The protein connection … • Genes control protein makeup. • All living organisms are largely protein. • Humans can synthesize at least 100,000 proteins.
What do proteins do, anyway? • Cells, tissues and organs need them for • Structure • Function • Regulation • Many unique functions like: • Hormones • Enzymes • Antibodies • Muscles
What are proteins like? • Large and complex • Contain long chains of subunits called AMINO ACIDS • 20 different amino acids • Genes determine which amino acids will be synthesized by an organism.
Call out the codons! • Specific sequences of three DNA bases • They call for which amino acidswill be added • The genetic code is a series ofCODONS that specify whichamino acids are required tomake up specific proteins.
Let’s get to work … • GENE EXPRESSION – the process by which coded information is converted to protein • And the workers are: • Messenger RNA (mRNA) – temporary carrier • Transfer RNA (tRNA) – bonds with amino acids • RIBOSOMES – small cellular components
It all hinges on translation … • Ribosomes read the genetic code from mRNA. • tRNA transports amino acids to the ribosomes. • Ribosomes attach to the growing protein.
Scientists are busy mapping • A chromosome map • For many plants, animals and for humans • Chromosomal location for genetic diseases • Cystic fibrosis • Sickle cell disease
So what are chromosomes? • Cellular structures made of DNA molecules and protein • Rod-like in shape • Can be seen under the microscope • Carriers for genes
What about the human genome? • Some 3 billion base pairs • Organized into 24 distinct chromosomes • Genes are arranged along the chromosomes.
The nucleus of most human cells contains … • A set of 23 chromosomes from each parent • 22 pairs are AUTOSOMES • They determine hereditary traits • Do not determine sex • One pair are the SEX CHROMOSOMES • XX = female • XY = male