Understanding DNA, Genes and Chromosomes

1. Mr. Gust Zoology Understanding DNA, Genes and Chromosomes

2. What is DNA? • DNA stands forDEOXYRIBONUCLEIC ACID • The DNA molecule is important in the “blueprint” of all living organisms.

3. What about genes? • Genes make up the “blueprint.” • Genes tell the organism how to look and act. • Genes are composed of DNA.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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!

9. 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.

10. 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.

11. 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.

12. The protein connection … • Genes control protein makeup. • All living organisms are largely protein. • Humans can synthesize at least 100,000 proteins.

13. What do proteins do, anyway? • Cells, tissues and organs need them for • Structure • Function • Regulation • Many unique functions like: • Hormones • Enzymes • Antibodies • Muscles

14. 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.

15. 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.

16. 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

17. 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.

18. Scientists are busy mapping • A chromosome map • For many plants, animals and for humans • Chromosomal location for genetic diseases • Cystic fibrosis • Sickle cell disease

19. 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

20. What about the human genome? • Some 3 billion base pairs • Organized into 24 distinct chromosomes • Genes are arranged along the chromosomes.

21. 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