DNA and Inheritance- Inherited/heritable disease – caused by an absent or defective gene or chromosomal aberration that can be passed to an offspringDNA Structure- A/T and G/C paired- Double helix- Sugar phosphate backbone- Pairs joined by hydrogen bonds- A/G are purines- C/T are pyrimidinesChromosomes- Human DNA is packaged in 46 chromosomes (23 pairs – 2n=46)- 22 autosomal and 1 sex chromosome- 1 chromosomal pair from mom and dadDNA  DNA (replication)- takes place in nucleusDNA  RNA (transcription)- in nucleus, mRNA exits into cytoplasm to rough ERRNA  protein (translation)- takes place in cytoplasm, mRNA template used to build proteins from amino acidsIf DNA is the same, why are cells different?- Different cells transcribe different parts of the DNA- RNA and proteins differ between cells, but the DNA is the sameTranslation (RNA  protein)- Takes place in cytoplasm- mRNA used to build protein from amino acids- transcribed mRNA is a template (has four nucleic acids A, U, C, G)- genetic code links mRNA to proteins  codon reading frame (3 nucleic acid bases)- used to bring and link amino acids and ribosomes Ratio of 3:1:1 for nucleotide: codon: amino acid then also a stop codonWhat is cancer?- Unregulated cell growth and division that is detrimental to an organismo Cell loses balance between division and deatho Tumor: abnormal mass of tissue- All organisms, even plants, can have unregulated cell growthWhat regulates growth and cell division?- Cell needs nutrients, oxygenUnicellular organisms: grow and divide w/ enough nutrients and oxygen - Nutrients are primary growth and division regulatorsMulticellular organisms require input from nutrients, oxygen, and growth factorsUnicellularOrganism + nutrients = growthMulticellularOrganism + nutrients = no growthOrganism + nutrients + growth factors = growthWhat limits cell size in multicellular organisms?- SA/V: cells are small due to limits in nutrition uptake and nuceleus location- Proportions of different cells must be correct for functioningCell Cycle: the sum of events from 1 cell division to the next- Interphase – between divisions- Mitosis – replication and division of genotype- Cytokinesis – cell division and physical separationInterphase: cell carries out its basic functions- G1: cell grows, sensitive- S (synthesis): DNA replication- G2: prepares to divideCheckpoints: ensure that a cell does not enter one stage until the previous stage is complete- G1 screens for DNA damage- S ensures DNA replication- G2 checks if it’s ready for mitosis?- Metaphase: chromosomes attachedMitosis (somatic cell division):- Chromosome – single molecule of DNA with many genes and associated proteins- Homologous chromosomes – same genes but different allelesGregor Mendel: famous for pollination of peas- Before Gregor, people thought:o Spontaneous generation and blending inheritance traits resulted in randomly determined traits from a listDominant alleles appear to mask recessive alleles- Dominant alleles – exerts its effects whenever present- Recessive alleles – effect is hidden unless no dominant alleles present- Homozygous (either dom/rec) – possessing identical alleles of one gene- Hererozygous – possessing different alleles in one gene- Self fertilization always produces identical offspring- Cross-ferilization produces either all dominant characteristics or a mixDiploid: 2 full sets of chromosomes- Autosomes – 22 pairs- Sex chromosomes – 23rd pair- Humans have 2n=46Replication (DNADNA)One diploid cell  two diploid cells (mitosis)Cancer affects cell cycle controls:- Cell loses control over balance between cell division and death- Tumor: abnormal mass of tissue- Cancer cells can divide forevero Look different o Divide in absence of growth factorso Do not exhibit contact inhibition- Inheritance and environment both can cause cancer:o Mutations play a key role in cancero Oncogenes – mutated variants of genes that normally stimulate cell divisiono Proto-oncogenes – normal versionSubstitutionsb: (point mutations) change one nucleotide to another, depending on codon positionDeletions: nucleotides are deleted  causes frame shiftsInsertions: nucleotides are inserted  causes frame shiftsA mutation in which of these molecules would have the most direct and adverse effect?DNA SEQUENCENot all mutations are passed on.Cell types- Germ cells: destined to become gametes (sperm or egg)o Only divide through meiosis (2n-n)o Mutations passed on to offspring- Somatic cells: all of body’s cells that don’t become sperm or eggo Divide by mitosiso Mutations here are not passed on to offspringMeiosis (germ cell divisions)Meiosis halves the chromosomes number and exchanges alleles between homologous pairs of chromosomes.- 2 outcomes of meiosiso halves chromosome # (2n – n)o increases genetic variability by processes of crossing over- 2 unique featureso 2 divisions create 4 cellso shuffles genetic information2n (one diploid) n (4 haploid cells)2 homologous chromosomes exchange genetic materialIMPORTANTMEIOSIS VS. MITOSISWhere they occur in the body:- meiosis: germ cells- mitosis: somatic cellsAlignment of chromosomes- meiosis: homologous chromosomes line up double file (independent assortment) and separate- mitosis: line up single fileDaughter cells identical?- Meiosis: genetically different (cross over)- Mitosis: genetically identicalDaughters haploid or diploid?- Meiosis: haploid (n)- Mitosis: diploid