Review 4: Heredity & Molecular Genetics AP Biology

Heredity & Molecular Genetics Meiosis produces haploid gametes. Different versions of same gene are called alleles. Mendelian inheritance Non-Mendelian inheritance Chi-square analysis DNA & RNA Central Dogma Regulation of Genes Mutations Biotechnology

Meiosis Produces Haploid Gametes Meiosis 1 separates homologous pairs: reduction division Meiosis 2 separates sister chromatids: produces 4 sex cells

Different Versions of Same Gene are Called Alleles Dominant vs. Recessive Homozygous vs. Heterozygous Phenotype vs. Genotype

Mendelian Inheritance Monohybrid Crosses -Aa x Az = 3:1 ratio -Law of Segregation Alternative alleles of a character segregate and remain distinct. Dihybrid Crosses -AaBb x AaBb = 9:3:3:1 ratio -Law of Independent Assortment Genes that are located on different chromosomes assort independently during meiosis. Test Cross -Determine genotype of individual showing dominant phenotype. -Unknown (A_) x aa (homozygous recessive)

Non-Mendelian Inheritance Incomplete Dominance (pink flower color) Co-dominance (blood type) Sex linked (mainly X-linked: color blindness, hemophilia) Epistasis (coat color) Pleiotrophy (dwarfism, giantism) Polygenic (skin color)

Epistasis The effects of one gene are modified by one or several other genes

Pleiotropy & Polygenic A single gene influences multiple phenotypic traits Examples: Dwarfism, Gigantism Polygenic

Chi-square analysis Determining if observed results are significantly different from expected results Know how to use formula when given & how to interpret results -degrees freedom (1 less than number of classes of results) -less than p=.05, then difference can be due to random chance alone & null hypothesis is accepted

DNA & RNA DNA: ACTG nitrogen bases, double helix - A:T, C:G RNA: ACUG nitrogen bases, single helix

Central Dogma DNA -> RNA -> protein -> trait Transcription (DNA -> mRNA) Translation (mRNA -> protein)

Transcription Production of RNA copy of DNA sequence In nucleus RNA polymerase copies coding strand & produces mRNA

Translation mRNA -> protein In cytoplasm Codons on mRNA read by ribosome Matched to anticodons of tRNA tRNA carries amino acids to mRNA & ribosome assembles polypeptide chain Start codon (Met) & stop codons, redundancy in code Universal code (single common ancestor)

Regulation of Genes Operons -Prokaryotes -Cluster of genes for enzymes in a pathway -Controlled by repressor protein -Repressible operon (synthesis pathway = tryp operon) vs. inducible operon (digestive pathway = lac operon) Transcription Factors -Proteins which enable bonding of RNA polymerase to gene

Operons Functioning unit of genomic material containing a cluster of genes under the control of a single regulatory signal or promoter

Mutations Fuel for evolution = variation, genetic change Gene duplication, point mutation, insertions, deletion

Biotechnology Scientists can modify an organism’s genome by inserting foreign DNA. Techniques

Modify Organism’s Genome Bacterial Transformation (human insulin gene in E. coli) Possible because of universal genetic code

Techniques Restriction digest: Restriction enzymes, sticky ends Transformation: Restriction enzymes, sticky ends, ligase, amp selection, lacZ screening Gel electrophoresis: DNA moves in an electrical field (negative -> positive), small pieces move further PCR: DNA amplification RFLP: DNA fingerprinting Sanger sequencing: Human Genome Project