General Biology 1 Past Paper Fall 2024 PDF

General Biology 1 Fall 2024 Somatic Cell Division (Mitosis) Prof : Dr. Vincent Gagnon  Homework Reminder: The flash cards are due the of September 23rd, 2024, before class. Please upload them on Léa dropbox Book Raven, Biology...

General Biology 1 Fall 2024 Somatic Cell Division (Mitosis) Prof : Dr. Vincent Gagnon  Homework Reminder: The flash cards are due the of September 23rd, 2024, before class. Please upload them on Léa dropbox Book Raven, Biology, 13th edition  Somatic Cell Division Study guide: Topic References (13th Ed) Compare & contrast chromosome structure in prokaryotes and eukaryotes. Section 10.1 & 10.2 Distinguish the five phases (G1, S, G2, M, C, plus G0) of the eukaryotic cell Section 10.3 & 10.4 cycle. Draw and label a schematic diagram of the cell cycle. Describe the events Figure 10.8 and lab occurring in each phase. Draw, label and/or identify cells in each stage of mitosis. Describe the Figure 10.11 and lab events occurring in each phase. Compare and contrast mitosis in plant and animal cells. Pages 205-206 and lab  Somatic Cell Division Bacterial cell division Bacteria divide by binary fission: Asexual reproduction: No exchange on chromosomes. Reproduction is clonal (identical DNA). Binary fission steps: Single, circular bacterial chromosome is replicated. Replication begins at the origin of replication and proceeds in two directions to site of termination. New chromosomes are partitioned to opposite ends of the cell.  Somatic Cell Division Bacterial cell division Septum form a new plasma membrane to divide the cell into two cells. Cell grows and divide creating Septum clone of themselves. No systematic exchange of chromosomes!  Somatic Cell Division Bacterial cell division The circular bacterial chromosome need to be compacted to fit inside the bacterial cell. For example, E. Coli bacteria chromosome is 500 time longer than the cell! Formation of loop domain by DNA binding protein (10 fold compaction). Then supercoiling happen to compact the DNA even more. Bacteria do no have nucleus, but nucleoid region in the cytoplasm where the DNA reside.  Somatic Cell Division Eukaryote cell division Chromosomes In Eukaryotes, chromosomes are linear (not circular as in Prokaryotes). Different species of Eukaryotes have different number of chromosomes. Garden pea Diploid (2n) with Human Adders tongue fern 14 chromosomes Diploid (2n) with 96-ploid with 46 chromosomes 1262 chromosomes  Somatic Cell Division Eukaryote cell division Chromosomes In addition to the number of different n = 23 chromosomes, organisms can also have a number of copies of homologous chromosomes that contains the same genes. The number of homologous 2n = 46 chromosomes is called ploidy. Haploid cell as only one set (n =1) of chromosome (sperm and egg cells in Human are haploid). Diploid cell as two set (n = 2) of homologous chromosome (Human somatic cells are diploid). Polyploid are species with numerous set of homologous chromosome.  Somatic Cell Division Eukaryote cell division Somatic cell: All cells of a multicellular organism that is not a sperm or an egg. They do cell division by mitosis. Diploid cells, 2 set of chromosomes in humans (2n). Reproductive cell: Gametes are haploid cell, 1 set of chromosomes (n), in humans (spermatozoa or eggs) They do cell division by Meiosis. Meiosis create those gametes (n) from diploid cell (2n) Offspring is a unique combination of genes from both parents.  Somatic Cell Division Eukaryote cell division In most animals, diploid state dominates Zygote first undergoes mitosis to produce diploid cells. Later in the life cycle, some of these diploid cells (called germ-line cells) undergo meiosis to produce haploid gametes (sex cells). Both somatic cells and germ-line cells are diploid. The critical difference is that somatic cells undergo mitosis to form genetically identical, diploid daughter cells, but germ-line cells can undergo meiosis to produce haploid gametes  Somatic Cell Division Eukaryote cell division Human have pairs of homologous chromosomes (contain the same genes). You get 23 chromosomes from your mother and 23 chromosomes from your father. You (2n = 46) Mother Father N = 23 N = 23  Somatic Cell Division Eukaryote cell division The zygote is forms when the ovule get The cell start to An average adult have about fertilised by the spermatozoid. divide. 3.72 x 1013 cell (Bianconi et al. 2013) Somatic cell* division include: Duplication of the organelles Creation of more cytosol * Somatic cell are all the cell in the body Replication of DNA (very important) except the sex cells (sperm and egg)  Somatic Cell Division Eukaryote cell division First cell division of an embryo  Somatic Cell Division Eukaryote cell division Cell Library DNA First cell division of an embryo  Somatic Cell Division Eukaryote cell division Cell Library DNA First cell division of Replication an embryo  Somatic Cell Division Eukaryote cell division Cell Library DNA First cell division of Replication an embryo  Somatic Cell Division Eukaryote cell division Cell Library Cell 1 Library DNA Library First cell division of Replication an embryo Cell 2  Somatic Cell Division Eukaryote cell division First cell division of Identical twins results from the accidental split of the embryo at first an embryo stage of cell division.  Somatic Cell Division Eukaryote cell division If you were to put all the DNA of only one cell end to end it would be more 2 m in length. To fit in the cell the DNA is compacted. Chromosomes loosely Depending on the phase of cell condense (Interphase). division, the DNA is more or less compacted. Between cell division (interphase) DNA is loosely compacted to be readable. During cell division DNA compacted in chromosomes (DNA is unreadable, but easier to Chromosomes condense move to the daughter cell). (During cell division).  Somatic Cell Division Eukaryote cell division Chromosomes structure (Interphase) Chromatin: it’s a complex of DNA and proteins (40% DNA / 60% proteins). Nucleosome Made of histones protein that have positively charged amino acids which are strongly attracted to negatively charged phosphate groups of DNA. Amino acids in the histones tails can be modified, changing gene expression. Nucleosome Histones DNA duplex coiled around 8 histone proteins  Somatic Cell Division Eukaryote cell division Chromosomes structure (Interphase) Nucleosome Nucleosomes are located every 147 DNA base pair (nucleotides). This form a structure that look like beads on a string.  Somatic Cell Division Eukaryote cell division Chromosomes structure (Interphase) Chromatin spatial organization TADs: topologically associated domains. Compartment: part of a chromosome. Territory: region that contain individual chromosome. DNA loosely compacted Loosely compacted DNA is readable by the cell. (Interphase).  Somatic Cell Division Eukaryote cell division Chromosomes structure (during cell division): Copies of chromosomes need to be condense during cell division to enable their partition in the new divided cell, since it would be hard to partition loosely compacted chromosomes. During mitosis, chromatin arranged around scaffold of protein to achieve maximum compaction. Chromosomes loosely condense (Interphase). Radial looping aided by condensin proteins.  Somatic Cell Division Eukaryote cell division DNA replication Prior to replication, each homologous chromosome are composed of a single DNA molecule (blue from your father and red from your mother).  Somatic Cell Division Eukaryote cell division DNA replication Prior to replication, each homologous chromosome are composed of a single DNA molecule (blue from your father and red from your mother). After replication, each chromosome composed of 2 identical DNA molecules which are called sister chromatids. The sister chromatids are held together at the centromere by cohesin proteins. DNA replication is done during the interphase, thus the chromosome would not be condense as in the image!  Somatic Cell Division Pair of homologous chromosomes that are replicated Human karyotype centromere Sister chromatids  Somatic Cell Division Eukaryote DNA replication End 2 nucleus Start 1 nucleus  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase 2. Mitotic Phase (M) End Start 2 nucleus 1 nucleus  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase G1 (gap phase 1): - It’s the primary growth phase of the cell. DNA loosely compacted (Interphase). - The term gap phase refers to its filling the gap between cytokinesis and DNA synthesis. - Proteins are synthesized and cell organelles are being duplicated. - For most cells, this is the longest End phase. 2 nucleus  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase S (synthesis): - It’s the phase in which the cell synthesizes a replica of DNA loosely compacted the genome. (Interphase). - The homologous chromosomes are replicated in sister chromatids. Homologous chromosomes Sister chromatids  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase G2 (gap phase 2): - It’s the second growth phase, and preparation for separation of the newly replicated genome. DNA loosely compacted (Interphase). - This phase fills the gap between DNA synthesis and the beginning of mitosis. - During this phase microtubules begin to reorganize to form a spindle. - Proteins are synthesized and cell organelles are being duplicated.  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase The duration of the cell cycle varies depending on cell type Typically, a dividing mammalian cell completes its cell cycle in about 24 hours. Frequency of cell division varies according with the cell type. Some cells divide frequently, such as skin, others divide more slowly such as the liver, while some cells do not appear to divide after maturity, such as the neurons. End 2 nucleus  Somatic Cell Division Cell division occurs in 2 phases: 1. Interphase The duration of the cell cycle varies depending on cell type Most of the variation in the length of the cell cycle between organisms or cell types occurs in the G1 phase. Cells often pause in G1 before DNA replication and enter a resting state called the G0 phase; cells may remain in this phase for days to years before resuming cell division. At any given time, most of the cells in an animal's body are in G0 phase. G0 phase  Somatic Cell Division Mitotic Phase (M): Cell division occurs in 2 phases: Chromosomes condense 1. Interphase G1 (gap phase 1): S (synthesis): G2 (gap phase 2): 2. Mitotic Phase (M) Mitosis: Distribution of chromosomes in each of the daughter cells (5 steps). Cytokinesis: Division of the cell cytoplasm to create 2 new daughter cells.  Somatic Cell Division Prophase Chromosomes condense with 2 sister chromatids held together at the centrosomes. Two centrioles move to opposite poles forming spindle apparatus (no centrioles in plants). Asters: radial array of microtubules from centriole in animals (not in plants). Nuclear envelope start to breaks down. Interphase – G2 Prophase  Somatic Cell Division Prometaphase Transition occurs after disassembly of nuclear envelope. Microtubules attaches to centromere of chromosomes (kinetochores). Each sister chromatid connected to opposite poles. Polar microtubule Prophase Prometaphase  Somatic Cell Division Prometaphase  Somatic Cell Division Metaphase Centrosome at opposite ends of the cell. Alignment of chromosomes on the metaphase plate. Prometaphase Metaphase  Somatic Cell Division Metaphase  Somatic Cell Division Anaphase Begins when centromeres split by the removal of cohesion protein. Separation of sister chromatids and migration to the poles using the kinetochore microtubule. At the end of this phase each pole has a complete set of 46 chromosomes (Human). Shortest phase of mitosis. Centromeres Polar microtubule Kinetochore microtubule Metaphase Anaphase  Somatic Cell Division Telophase Spindle apparatus disassembles. 2 daughter nuclei form: - 2 nuclear envelopes form. - Chromosomes become less condensed. Anaphase Telophase  Somatic Cell Division Cytokinesis Formation of cleavage furrow that pinches the cell into two identical daughter cells. After cytokinesis cell enters interphase. Telophase Cytokinesis  Somatic Cell Division Cytokinesis Formation of cleavage furrow that pinches the cell into two identical daughter cells. After cytokinesis cell enters interphase. Somatic Cell Division Somatic Cell Division  Mitosis and Cell Division Actine Animal cell Plant cell  Mitosis and Cell Division Plant cell Plant cell walls are far too rigid to be squeezed in two by actin filaments. Plant cell assemble membrane using vesicle until a partition is made (cell plate) dividing the cell in two. Cellulose is then laid down on the new membranes, creating two new cell walls. Mitosis and Cell Division Mitosis and Cell Division Cell Division- Mitotic Phases