Biology 1010 1st EditionExam # 2 Study Guide Lectures: 6 - 13Pedigrees• Goals of Pedigree Analysis1. Determine the mode of inheritance; dominant, recessive, partial dominance, sex-linked, autosomal, mitochondrial, maternal effect2. Determine the probability of an affected offspring for a given cross • Basic symbols • Autosomes- 22 paired chromosomes present in both males and females• Sex chromosomes- paired chromosomes that differ between males and females• XX- female, XY- male• Y chromosome- triggers male’s developmental pathway during fetal development • Women have 2 X chromosomes, so women have 2 copies of each gene on the X chromosome • Therefore, in women, the patterns of gene expression for genes on the X chromosome are the same as for gees on other chromosomes • Problem: since men have only one X chromosome, if a gene on the X chromosome is defective, they have no ‘back-up’ to produce the protein• Diseases associated with genes on the X chromosome are much more common in men than in women-women need to inherit 2 defective alleles, men need only one • A person’s sex is only relevant when the defective gene is located on a sex chromosome -baldness-color blindness -hemophiliaHomozygous and Heterozygous • Homozygous- having two identical alleles -AA aa (two recessive or two dominant) • Heterozygous- having two different alleles -Aa-this is also considered being a carrier (carry both alleles)• How traits are inherited-dominant allele: an allele that can mask the presence of a recessive allele -recessive allele: an allele that reveals itself only if the organism has two copies of that alleleChromosomes• Somatic (normal) cells have 40 chromosomes-diploid: two copies of each chromosome; one from each parent-all normal cells are somatic: examples are liver, kidney, skin• Gametic-Haploid: one copy of each chromosome; half of the DNA-Sex cells are gametic: examples are sperm or eggs• Genome: one complete set of genetic instructions encoded in the DNA of an organism • One chromosome from each pair is inherited from the biological mother and father • The 23rd chromosome pair determines a person’s sex (XX female, XY male)Gene expression • Gene: a length of DNA that codes for the protein that make up our bodies • Genes are the unit of inheritance • Loss of gene expression control can result in cancer-mutations can lead to a mass of body cells growing out of control, a tumor-if a tumor spreads to other tissues, the person is said to have caner • Genes regulate the cell cycle-a cell cycle control system regulates the timing of cell duplication-a proto-oncogene codes for proteins that tell the cell when to duplicate • Mutations in regulator genes can lead to an overgrowth of cells-a mutated proto-oncogene fails to regulate cell division and is called oncogene*cancer is caused by out-of-control cell growth due to a breakdown of the cell cycle control system• Cancer can occur when proto-oncogenes are mutated to oncogenes -a mutation in a growth factor gene can produce a hyperactive protein that promotes unnecessary cell division-a mutation that deactivates a tumor suppressor gene may result in uncontrolled growth*mutations may result in proteins that either don’t stop the cell cycle or stimulate growthMitosis vs. Meiosis • Phases of Mitosis1. Interphase (before mitosis)-the chromosomes are loosely gathered in the nucleus-chromosomes replicate into two sister chromatids 2. Prophase -replicated chromosomes begin to coil up-nuclear membrane begins to disassemble-protein fibers of the mitotic spindle begins to form 3. Metaphase-spindle fibers from opposite ends of the cell pull on chromosomes-chromosomes align along the middle of the cell4. Anaphase-spindle fibers shorten ad pull sister chromatids to the opposite ends of the cell5. Telophase-identical set of chromosomes reaches each pole-spindle fibers dissemble-nuclear membrane forms around each set of chromosomes to form the daughter cell nuclei6. Cytokinesis (after mitosis) -cytoplasm divides into two cells, each containing a full complement of organelles and DNA-cell membrane pinches in to completely surround each new daughter cell• Meiosis is the production of gametes -gametes (sperm and egg) are formed by a special type of cell division, meiosis-cells produced from meiosis are haploid-like mitosis, meiosis occurs in stages • Meiosis occurs in stages-meiosis (like mitosis) starts with chromosome duplication before division-in meiosis, there are then two rounds of cell division -the result of meiosis is four haploid offspring cells, all with one-half the number of chromosomes Epigenetics • The winding and unwinding and how “tight” the molecules wind around histones (proteins) may influence function• DNA is unwound in order to be read• DNA is wound for cellular replication Transcription & Translation • Step 1: transcription-getting the information from the DNA to the ribosome, where proteins are made-during transcription, mRNA serves as the messenger who delivers the instructions to the ribosome-RNA is similar to DNA, except single stranded U instead of T (bases = CGAU)a) An enzyme unzips the double-stranded DNA of a geneb) One strand of the DNA serves as a template for making mRNA c) The strand of mRNA leaves the nucleus through a nuclear pore, and goes to a ribosome• Step 2: translation -turning the sequence of bases into a sequence of amino acids bound together a) The ribosome binds to the bases 3 at a time-each triplet of mRNA bases = a codon codes for 1 amino acid -e.g. AAG codes for lysine and AGU codes for serine b) Transfer RNA (tRNA) brings the correct amino acids to the ribosome -anti-codon= group of 3 bases on the RNA-each tRNA carries one type of amino acid, depending on its anti-codon -the tRNA whose anti-codon binds complimentarily to the codon brings its amino acid to the ribosome-complimentarily = according to the binding rules of bases • The genetic code- the correspondence between particular mRNA codons and amino acids-e.g. UCU = serine, CGU = arginine and GGG = glycineDNA • Double Helix-the two strands of nucleotides -paired strands twist around each other-form a spiral-shaped helix-double helix because there are two strands-the sugars and phosphates from the outside “backbone” of the helix-the bases form the internal “rungs” like steps on a twisting ladder• Complementary base pairing-each strand of DNA is held together by