Genetics Unit –Cell Reproduction

1. Genetics Unit –Cell Reproduction • Asexual reproduction • Binary fission • Mitosis • Sexual reproduction • Meiosis • Meiosis I, meiosis II • gametes

2. Genetics Unit – Chpt. 9Punnett Squares • Probability • Punnett square • Monohybrid, dihybrid • Dominant, recessive, homozygous, heterozygous • Incomplete, Co-dominant and x-linked traits

3. Genetics Unit –Gregor Mendel • Father of modern genetics • 1st to apply mathematics of statistics to crosses, 1840’s, Austria, monastery gardens • Genetics  field of biology devoted to understanding HOW characteristics are transmitted from parents to offspring • Heredity  the transmission of characteristics from parents to offspring

4. Mendel’s Laws • Law of Segregation : pair of factors is separated during the formation of gametes • Law of Independent Assortment : factors for different traits are distributed to gametes independently

5. Molecular Genetics • Molecular genetics  is the study of the structure and the function of the chromosomes and the genes. • This would include mapping the genome, locating markers for diseases, making proteins and technology like cloning, genetic engineering and DNA fingerprinting.

6. Genetics Unit- Nucleic acids and protein synthesis • DNA – organic compound made of repeating subunits called nucleotides. • A DNA nucleotide has three parts • Sugar (deoxyribose) • Phosphate group (PO4) • Nitrogen containing base (A,T,C,G) Adenine, thymine, cytosine and guanine

7. Watson and Crick • James Watson and Francis Crick are the discoverers of the DNA double helix • 1953, Cambridge, England • Built a wooden model based on other research , including x-ray crystallography • Other scientists involved where; Rosalind Franklin, Linus Pauling, Maurice Wilkins

8. Complementary Base Pairing • Because of the exact shape and size of the DNA, the sugars and phosphates make the ‘sides of the ladder’ and the nitogenous bases make the ‘rungs. • A and G (purines) are larger than C and T (pyrimidines) • MUST PAIR UP with A-T and C-G so all rungs are the same length. • A-T and C-G are hydrogen bonds.

9. DNA Replication During the S portion of interphase All DNA is copied so there are 2 complete sets, one set for each new cell p.188 DNA helix is untwisted by helicase enzyme DNA polymerase enzymes add new bases Get two identical strands of double helix

10. Mutations • Change in the nucleotide sequence • 1 error per 100,000 bases, VERY accurate • Proof reading enzymes correct – allowing for 1 per billion nucleotide average • Changes can also be caused by ‘mutagens’ like chemicals and radiation

11. RNA • Single stranded • Copies of DNA • Can leave nucleus • Takes DNA code to the ribosomes so that proteins can be manufactured • Contains the sugar ribose, and the bases A, C, G and U (uracil). There is no T in RNA

12. RNA Transcription • DNA is opened, only at the gene/region of interest. • A “copy” is made by matching A-U and C-G • The mRNA (leaves) and the DNA reseals. Original DNA is intact, undiluted, unchanged and in the nucleus. • RNA strand is EDITTED to delete unnecessary regions called introns and the ‘good regions are spliced together (exons) and make the final mRNA

13. Types of RNA • mRNA – messenger, carries DNA info from the nucleus to the cytoplasm • tRNA – transfer (transport), short chain, highly folded, binds specific amino acids to the mRNA • rRNA – ribosomal, most abundant version, ribosomes are made of protein and rRNA.

14. Translation of RNA into protein • “protein synthesis” • mRNA is read by the ribosome in chunks • Each region of 3 bases on the mRNA is called a codon (p.194) • Each codon signals a specific amino acid • If you put the right amino acids in the right order you have ….. A protein.

15. Remember….. “Every thing, in every cell, is either made of a protein or run by a protein.” Functions of proteins include – muscle, structure, storage, immunity, identification, communication, and transport

16. Genetics Unit – Chpt 11Gene Expression • Gene expression – all genes are not ‘on’ all the time. The process of turning on the right genes at the right time is gene expression • Genome – complete set of genetic material for an individual

17. Operons • Found in bacteria cells – very different machinery from our cells • Jacob and Monad • Operon = structural genes + promoter + operater • Operons can • 1. repress protein production (repressor) • 2. activate protein production (inducer)

18. More Chpt. 11 vocabulary • Cell differentiation – the development of cells that have specialized functions ( muscle, nerve, skin, etc.) • Morphogenesis – the formation of an organism, getting the tissues and organs in the right places • Homeotic genes – regulatory genes that determine where anatomical features go

19. CANCER • Malignant tumors are usually called cancer. • Tumor – abnormal proliferation of cells, uncontrolled cell division • Benign tumor – mass of cells • Malignant tumor – uncontrolled cell division that invades and destroys healthy tissue • Metastasis – spread of cancer to new sites

20. Cancer continued • Oncogenes – genes that “cause” cancer, code for uncontrolled cell growth • Tumor suppressor genes – code for proteins that prevented uncontrolled cell division. • Mutation of tumor suppressor genes cause a predisposition to cancers • Some cancers are now directly linked to viruses as their “cause” .