BIO 305 1st Edition Lecture 1 Outline of Current Lecture I. IntroductionA. “Intro to Genetics” and “What Exam 1 Will Cover”II. ChromosomesA. Basic StructuresB. Basic KaryotypingC. In Somatic vs. Germs Cells, among species of organismsIII. The Cell CycleA. Overview of CycleB. How fast is each stage?C. How is it regulated?IV. MitosisA. Quick ComparisonB. The Four Stages of MitosisV. MeiosisA. Comparison RevisitedB. Important Principles of MeiosisC. Stages of MeiosisD. Errors in MeiosisVI. Life CyclesVII. Vocabulary and Sample Question from LectureCurrent LectureI. What is genetics?A study that is fundamental to understanding ANY biological phenomenonYou should have a basic knowledge of biology as a prerequisite to BIO 305, review any terms in your text as needed. Genetics is cumulative! If you fail to understand one part of everything, you will lack the basis for understanding the material that follows.EXAM ONE covers: Chapters 2-6 of the Griffith’s Text:Single-Gene InheritanceIndependent AssortmentMapping in EukaryotesGene InteractionII. ChromosomesA. Chromosomal Structure:Know: Telomere, Centromere, and Kinetochore Contains two “sister chromatids” that are identical EXCEPT by mutationWhen a chromosome divides, the lengths are not always congruent! (See vocab)In this case, a sister chromatid will have a “P-arm”, shorter, and “Q-arm”, longBe able to distinguish chromosome vs. chromatid vs. chromatinB. Human KaryotypingWhat is the difference between male and female?Autosomes vs. sex chromosomesHomologous Chromosomes – chromosome pairs of same length, centromere position, and genes for the same characteristics at corresponding loci (location on a chromosome) but are two different copies that diploid organisms inherit from each parentThis is different to:Sister Chromatids – two identical copies of a chromatidC. Somatic Cells vs. Germ Cells, in species of Organisms Somatic cellsAll cells derived from members of the species contain an identical number of chromosomesNote: Red blood cells are a rare exception! They contain no DNAMost are diploidsEx: 2n = 46, two setsGerm cells (egg, sperm, spores, etc.) are haploidEx: n = 23, one setPolyploids are exceptions! See vocab.Among SpeciesThe number of chromosomes depends on the species, aka “haploid number: n”Note: During human evolution, two chromosomes fused. That’s why humans have 23 and chimps have 24.How did we know that? Research shows a fusion of telomeres into 1 chromosomeIII. The Cell CycleA. Basic Overview Interphase  (S)  (G2)  Mitosis (Prophase, Metaphase, Anaphase, Telophase)  (G1)Some cells undergo a special stage: (G0) – non-dividing cell phase after G1Some can be stimulated to reenter the Cell CycleUse PMAT to remember the 4 stages of mitosisB. Which stages take the most time?G1 - slow  S – slowest  G2 – fast  Mitosis – fastest:P (very slow)  M (fast) = A (fast)  T (slow)C. Regulation of the Cell CycleP53 – gene that encodes for apoptosis, aka tumor-suppressor3 Checkpoints for regulation:G1/S: DNA damageG2/M: Incomplete DNA synthesisM: Incomplete spindle formationIV. MitosisA. Mitosis vs. MeiosisKnow: How does genetic material change in mitosis vs. meiosis?How is genetic info used to make protein?Mitosis – no change in genetic material; produces two identical daughter cellsImportant for growth, developmentAlso for sex in asexual organismsMeiosis – the genes are halvedB. The 4 Stages of Mitosis:Interphase – Absence of chromosomes, only chromatin in nucleusProphase – Migration of 2 pairs of centrioles to cell ends, spindle fibers, nuclear envelop disappears, DNA replication occurs; thus have 2 sister chromatidsMetaphase – Chromosomes migrate to equatorial plateNote: Look at how the kinetochore structure helps to align spindle fibersAnaphase – chromatids disjoin and migrate to ends, called daughter chromosomesEx: How many chromosomal structures do we have at this point?ANS: double (n), so 92 for humans! We have 23, it doubles twiceTelophase – Cytokinesis occursKnow the difference between animal and plant cytokinesis – animal constricts, plants form a cellplate down the metaphase plateLate telophase – Nuclear envelop reforms and chromosomes uncoilV. MeiosisA. Comparison revisitedMitosis – sisters are pulled apart, 1 round of replication, 1 round of divisionMeiosis – genetic material is halved: 1 round of replication, 2 rounds of divisionInvolves synapsis pairing, separates chromosome from its homologous chromosomeB. Important Principles of Meiosis1) Leads to one half of a parent cellDuring sex reproduction, gametes then combine in fertilization to reconstitute diploid complement2) The basis for two methods for genetic diversity:Independent Assortment - Reshuffles genetic material by generating gametes with many combinations among given haploid complement Crossing over results in further shuffling between members of each pair of homologous pair of chromosomesNote: For a diploid organism of 2n chromosomes, it is possible to generate 2n types of gametes with different combinations of chromosomesEx: In humans: n=23, 2^23 = 8.4 million possibilities due to independent assortment! Crossing over generates additional genetic diversity.C. Stages of MeiosisMeiotic Prophase I:The first division of Meiosis, also has four stages: 1) Chromatins condense  2) initial pairing to become bivalent  3) Synapsis occurs and sister chromatids become visible as tetrads  homologous chromosomes separate except at the chiasma  chromosomes further pull apart, centromeres are on the equatorial plate*Do not need to know the 5 names of stages in the Meiotic Prophase, just know what happens*Pairing of chromatid is according to sizeMeiotic Prophase II:There is no DNA replication between Meiosis I and II. Meiosis II is similar to Mitosis! What are the differences?D. Errors in MeiosisDisjunction – the separation of homologous chromosomes.Nondisjunction – an error where this separation is not achievedThere are two types of nondisjunction: 1st and 2nd division nondisjunction1st division nondisjunction: the error happened in the first meiotic division. After fertilized with sperm, results in “trisomic” and “monosomic” cell products. 4 daughter cells are: (|||) (|||) (|) (|)2nd division nondisjunction: the error happened in the second meiotic division. Sister chromatidswere pulled apart but ended up in only one cell, thus only two progenies are