Genetics Chapter 2: Chromosomes and Cellular reproduction
Genetics Chapter 2: Chromosomes and Cellular reproduction PCB 3063
Popular in Genetics
Popular in GENE - Genetics
This 11 page Class Notes was uploaded by Adam Reinstein on Saturday September 3, 2016. The Class Notes belongs to PCB 3063 at Florida Atlantic University taught by David M. Binninger in Fall 2016. Since its upload, it has received 11 views. For similar materials see Genetics in GENE - Genetics at Florida Atlantic University.
Reviews for Genetics Chapter 2: Chromosomes and Cellular reproduction
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/03/16
Genetics chapter 2 I. Prokaryotes and Eukaryotes A) Prokaryotes are unicellular organisms with a fairly simple cell structure i. There are two fundamentally distinct types of prokaryotes: 1) Eubacteria true bacteria 2) Archaea “Ancient bacteria” that are evolutionarily closer to eukaryotes the eubacteria B) Eukaryotic cells are compartmentalized by intracellular membranes (aka have a nucleus) i. May be unicellular or multicellular II. Nucleus A) The nucleus is a Eukaryotic organelle that separates a cell’s DNA from the rest of the cell i. Transcription (RNA synthesis) in Eukaryotes is physically separated from translation (protein synthesis) B) Prokaryotes do NOT have a nucleus i. As a result of this, transcription and translation occur in the same compartment C) These differences affect gene regulation D) The structure of how DNA is contained in these cells dictates its function III. Eukaryotic DNA A) Eukaryotic DNA uses a class of proteins called histones to form tightly packed chromosomes. B) Chromatin a complex of Histones and DNA C) Histones help to keep the DNA tightly packed within the nucleus Chromosomes D) Bacteria usually have a single circular chromosome E) Eukaryotes have multiple chromosomes that each have a single linear DNA molecule F) replicating and distributing chromosomes to a new cell during cell division is more complex in eukaryotes IV. Viruses A) Simple nonliving structures composed of an outer protein coat and DNA or RNA (but NOT both!) B) Viruses need a host cell to reproduce i. This implies that viruses evolved after cells because they cant reproduce without their host cell ii. The genes of viruses are more closely related to their host and not to each other V. Cell Reproduction A) Three critical steps i. Accurate replication if the DNA 9 1) Typical error rate is approximately 10 or 1 error per billion nucleotides ii. A complete copy of the genome must be separated to different regions of the cell iii. Cell must divide B) Prokaryotic Cell Reproduction is rapid i. Can possibly divide once every 20 mins, which can lead to 1 billion VI. Plasmids A) Common in bacteria; very rare in eukaryotes B) Circular selfreplicating DNA molecules C) Small compared to the main chromosome D) Contain bacterial genes i. Ffactor in E. coli is a plasmid required for conjugation (genetic exchange) E) Many plasmids carry genes for antibiotic resistance VII. Eukaryotic Cell Reproduction A) DNA is distributed among multiple chromosomes B) Chromosomes are separated from the cytoplasm by the nuclear envelope C) Nucleus has an extensive crisscrossing network of protein fibers called the nuclear matrix i. The nuclear matrix takes part in DNA replication, gene expression, and modification of gene products D) Eukaryotic Chromosomes i. Each species has a characteristic number of chromosomes per cell ii. Cannot predict the number of chromosomes based on complexity of the organism iii. All somatic cells have two sets of chromosomes: One maternal, the other paternal VIII. Ploidy A) The number of sets of genetic info is the cells ploidy B) Haploid a single set of chromosomes C) Diploid two sets of chromosomes i. Two nearly identical chromosomes form a homologous pair ii. Each diploid cell has two copies of each gene. iii. Different forms of the gene are called alleles D) Polyploid more than 2 sets of chromosomes IX. Chromosome Structure A) Each chromosome consists of a single DNA molecule that is extensively coiled B) During most of the cell cycle, the chromosomes are diffuse chromatin C) Just before cell division, condense further to form the distinctive characteristics of individual chromosomes X. Chromosomes have 3 essential parts to them: A) A centromere i. This is an attachment site for the spindle microtubules ii. Responsible for pulling chromosomes to the edges of the cell during cell division iii. Kinetochore forms on the centromere (specific DNA sequence) and is the attachment site of the spindle microtubules iv. Lack of a centromere leads to chromosome loss which is usally fatal v. The location of the centromere classifies chromosomes by 4 types 1) Submetacentric 2) Metacentric 3) Telocentric 4) Acrocentric B) A pair of telomeres i. Special structure on the end (terminus) of the chromosome ii. Required for chromosome stability iii. May play a role in controlling cell division and possibly aging and cancer C) Origins of Replication i. These are the sites where DNA synthesis begins ii. Each chromosome must be duplicated prior to cell division iii. After DNA Replication there are two identical copies—Called sister chromatids—held together at the centromere iv. Each chromatid contains a single DNA molecule XI. Cell Cycle and Mitosis A) Process that passes an exact copy of the genetic information from a parent cell to two new daughter cells B) Checkpoints occur at critical transition steps along the cell cycle XII. Interphase A) Majority of the cell cycle when growth, differentiation and preparation for cell division occurs B) Three subphases of interphase G , S, 1 2 i. G =1 ell growth and synthesis of proteins needed for cell division are made, this lasts several hours ii. G1/S checkpoint is critical, the cell waits in G 1ntil it has all the enzymes needed for DNA Replication iii. Cell may exit the cell cycle (G0) if conditions are not favorable iv. If cell continues past G1/S checkpoint, it is committed to cell division C) G P0 se This is a nondividing phase that can arise if the environment is unsuitable, the cell can remain here for long periods of time or in some cases indefinitely D) S Phase i. DNA Synthesis ii. Each chromosome is duplicated iii. Before S phase, each chromosome is one chromatid iv. After S phase, each chromosome is composed of two chromatids v. Blocking DNA synthesis (due to drugs or a mutation) stops further advancement in the cell cycle E) G P2 se i. Additional events occur in preparation for cell division ii. Critical G2/M checkpoint must be passed before entering mitosis (M phase), this check point ensures that the cell’s DNA is completely replicated and undamaged XIII. Six Stages of Mitosis A) Prophase i. Chromatin begins to condense ii. Chromosome structure becomes visible with the light microscope iii. Mitotic spindle develops from a pair of centrosomes in animal cells iv. Some plants do not have centrosomes or centrioles v. Centriole is a specialized organelle within the centrosome B) Prometaphase i. Nuclear membrane disintegrates ii. Spindle microtubules enter the nuclear region iii. Microtubules attach to the kinetochore of one of the sister chromatids iv. Microtubules from the opposite side of the cell attach to the kinetochore of the other sister chromatid C) Metaphase i. Chromosomes align in a single line called the metaphase plate ii. Spindleassembly checkpoint establishes that each chromosome has spindle fibers attached from opposite poles of the cell D) Anaphase i. Anaphase begins as the chromosomes start moving toward opposite poles of the cell ii. The centromere splits and the two sister chromatids become separate chromosomes E) Telophase i. Chromosomes reach the spindle poles ii. Nuclear membrane reforms around the chromosomes iii. Chromosomes decondense iv. Cytoplasm divides – cytokinesis F) Chromosome movement i. Microtubules are composed of subunits of tubulin ii. Microtubules have polarity iii. Special proteins function as molecular motors to disassemble tubulin subunits G) Changes in chromosome number and DNA during the cell cycle XIV. Summary of Mitosis A) Produces two genetically identical copies of a cell B) Each cell has the complete set of chromosomes C) Each cell has about half the cytoplasm and organelles D) Mitosis produces two cells with the same number of chromosomes E) Cytoplasmic content is divided unevenly therefore the two cells NOT exactly the same (in cytoplasmic content, otherwise genetically identical) XV. Meiosis A) Specialized form of cell division B) Meiosis reshuffles the parental genes among their progeny C) Driving force in evolution D) Meiosis produces cells with 50% of the normal number of chromosomes (haploid product) E) Fertilization restores the normal chromosome number F) Unlike Mitosis, meiosis has two nuclear divisions, not just one. i. Separated into meiosis I and meiosis II G) Meiosis produces four cells with half of the normal chromosome number H) Meiosis produces cells with genetic variability I) DNA replication (S phase) occurs before cell division J) During prophase I, synapsis occurs i. synapsis 2 pairs (4 chromatids) of homologous chromosomes form a bivalent or tetrad. (see image below) K) Crossing over occurs on the tetrad i. Genetic Recombination/crossing over: when homologous chromosomes exchange genetic info (see image below) ii. This is the main source of genetic variation L) Anaphase I is similar to anaphase in mitosis, except we are pulling apart the tetrad, NOT the sister chromatids M)Meiosis II is functionally equivalent to mitosis N) Centromeres divide and each cell receives one of the two sister chromatid O) Genetic Diversity arises from 2 sources: i. Crossing over ii. Random distribution of maternal and paternal chromosomes: During metaphase the way in which the chromosomes align in the center is random and can shuffle alleles on different chromosomes. synapsis
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'