CELLULAR PROCESSES; REPRODUCTION Unit 5
Cell Cycle Chromosomes and their make up Crossover Cytokines Diploid (haploid diploid and karyotypes) Mitosis Meiosis What is Cancer? Somatic Cells
THE CELL CYCLE Cell Cycle- series of events that take place in a eukaryotic cells leading to its division Interphase- Cell growths, accumulating nutrients for mitosis Replication of DNA- stage which the cell splits itself into 2 distinct cells
CELLULAR DIVISION Cellular division is a complicated process that cannot be done by simply pinching the cell in half Both prokaryotes and eukaryotes include distribution of genetic material known as DNA Into two identical daughter cells Gnome- is a cells genetic information Each Cell contains enough genetic material if all the DNA in the cell is stretched out from end to end it would be over 2 meters long or 250,000 times greater the cells length How then does the DNA fit in the cell?
CHROMOSOMES DNA is condensed and packaged into structures called Chromosomes A DNA strand can encode for several different proteins and consist of several hundred genes Chromatin- is the DNA and Protein used to pupils the chromosome
CHROMOSOMES Chromosomes are in the nucleus Every Eukaryotic species has a certain number of chromosomes in each cell Somatic Cells- body cells that aren't meant for reproduction Gamete- Sperm and Egg Cells Humans= 46 Chromosomes in Somatic Cells and 23 Chromosomes in Gamete Cells
DISTRIBUTION OF CHROMOSOMES DNA is in preparation for Cellular division all the time even when the cell is not in the act of division DNA is constantly being stretched out and replicated then condensed back down to chromatic fibers to make chromosomes Each duplicated chromosome has 2 sister chromosomes which are joined copies of the original chromosome Centromere- is the center region (protein) which the sister and original chromatin attach to
CELL CYCLE STAGES G1 phase (interphase) S phase (interphase) G2 phase (interphase) M phase (mitosis)
INTERPHASE G1, S, and G2 Phase S phase is the DNA Synthesis phase Takes up 90% of the time for the Cell Cycle
M PHASE Mitotic Phases when mitosis occurs Cytokinesis or cell splitting occurs at the end Result is 2 daughter cells Prophase, Metaphase, Anaphase, Telophase then Cytokinesis PMAT Cytokinesis
FROM G2 PHASE TO PROPHASE What needs to happen before mitosis can occur? 2 centromeres have formed from 1 Chromatin have not condensed to Chromosomes yet
PROPHASE Chromatin fibers become more condensed to form chromosomes The Nuclear Envelope starts to disappear Each chromosome has 2 identical Sister Chromatids Mitotic Spindle Fibers start to form Centromeres move away from each other
METAPHASE Centromeres are on opposite poles of the cell Chromosomes line up down the middle of the cell Spindle fibers attach to the center (kinetochore) of each chromosome
ANAPHASE Sister Chromatids are pulled apart to opposite ends and become full fledge chromosomes The new chromosomes start to move toward opposite ends of the cell The cell starts to elongate At the end of this phase each end of the cell has a equivalent and complete set of chromosomes
TELOPHASE A nuclear envelope started to form around each set of chromosomes Chromosomes start to deco dense The net result is 2 genetically identical nuclei
CYTOKINESIS Cleavage Furrow is made and the cell is pinched in half 2 new cells have been made and the process of cellular division can start over again
CONTROLLING THE CELL CYCLE Cell Cycle Control System- molecules in the cell that both triggers and coordinates key events in the cell cycle These molecules create checkpoints in the cycle to check and make sure everything is replicating properly Once the Checkpoint has been reached the molecules will "tell" the cell whether to go ahead with replication or just to sit and await further instructions
WHAT HAPPENS WHEN THE CHECKPOINTS DON'T WORK? Cells continue to replicate They will replicate the error that would normally have stopped the replication This error can lead to a whole number of problems Unregulated cellular replication can and most of the time does result in Cancer
CANCER Cancer cells do not stop when the cell cycle tries to regulate it (they go a wall) These cells can divide rapidly and invade other tissues damaging them or inhibiting functions of them They don't stop growing just because they outgrow their resources Benign tumor- is a group of abnormal (Cancer) cells that remain at its original site and do not have enough genetic changes to survive in other tissues Malignant tumor- a group of abnormal (Cancer) cells whose genetic and cellular changes enable it to invade other tissues and spread
SOME EXTRA VOCABULARY Karyotypes- display of chromosome pairs of a cell arranged by size and shape Crossing over-the exchange of genetic material between non sister chromatides during Prophase 1 of Meiosis Haploid- a cell containing only 1 set of chromosomes Diploid- a cell that contains 2 sets of chromosomes 1 from each parent
MORE VOCABULARY Epithelium- a membranous cellular tissue that covers the free surface or lines at tube or cavity of an animal body Ploidy- degree of repetition ion of a panic number of chromosomes Apoptosis- Programed cell death, a genetically directed process of cellular self destruction
WHY DO CELLS DIVIDE? If a cell didn't divide rapidly and just grew, it would quickly out grow its resources or it would be so big the organelles would not be able to keep up with the cell This would lead to an inability to keep cellular homeostasis and result in apoptosis By having a lot of smaller cells it is easier to keep cellular homeostasis. It is not that big of an issue if a cell dies. Also if there is a genetic issue with one cell it is a lot more disposable then if there were only a few large cells.
HEREDITY Genetics- is the Scientific study of heredity (the transmission of traits from one generation to the next) Asexual reproduction- reproduction where the offspring is an exact genetic copy of the parent Sexual reproduction- two parents give rise to offspring that have unique combination of genes inherited from the two parents.
VOCABULARY Homologous Chromosomes- a pair of chromosomes that are the same length and have the same centromere position Sex chromosomes- These are the homologous chromosomes that determine sex (X &Y) (Female = XX Male = XY) Zygote- Male and Female diploid sex cells (egg and sperm)
MEIOSIS Meiosis reduces the number of chromosome sets from diploid to haploid Meiosis closely resembles mitosis stepwise However after interphase meiosis unlike mitosis will go through 2 consecutive cell divisions (meiosis 1 and meiosis 2) This results in 4 daughter cells (instead of 2 with mitosis) that are haploid cells This only occurs in sex cells
MEIOSIS 1 Separates homologous Chromosomes Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokinesis (cell splits)
MEIOSIS 2 Separates sister chromatids Prophase. 2 Metaphase2 Anaphase 2 Telophase 2 Cytokinesis
PROPHASE 1& 2 Chromosomes begin to condense and prophase proceeds as it did in mitosis Crossing over occurs as homologous chromosomes start to connect to one another only occurs in prophase 1
METAPHASE 1 & 2 Just like in mitosis the chromosomes start to line up along the center of the cell Spindle fibers attach to the chromosomes Because of the crossing over in prophase 1 there are not genetically equal chromatids in metaphase 2
ANAPHASE 1 & 2 Just like in mitosis the chromatids are moved to opposite poles guided by the spindle fibers Anaphase 1 & 2 are exactly the same
TELOPHASE 1 & 2 AND CYTOKINESIS Both proceed as in mitosis but remember that after telophase 1 & cytokinesis there is no reproduction of existing chromosomes they go right into Meiosis 2 and Prophase 2 2 daughter cells after telophase 1 4 daughter cells after telophase 2
WHY DOES MEIOSIS MAKE SENSE? With Sex Cells we are only needing haploid cells so they don't need a full set of chromosomes Sex Cells are needed in vast quantities because of their rapid disposal rate Increases genetic diversity of each individual cell because of crossing over and having different sets of genes in each cell opposed to a replicate of the original
DNA DNA is also know as Deoxyribonuleic acid Double Stranded helix that contained the genetic information for cellular function growth and division Watson and Crick were the first scientist that provided a model for DNA
WATSON AND CRICKS MODEL 2 anti-parallel strands Nucleotides 5-carbon sugar (backbone of DNA) Nitrogen base pair A phosphate group
NUCLEIC ACID Nucleotides are the basic building blocks of nuclei can acids These consist of sugars phosphate groups and nitrogen bases
SUGAR AND PHOSPHATE PORTION
NITROGEN BASE PAIRS Think of theses as rungs in a ladder (2 come together to form the full rung) Adenine, Thymine, Cytosine, Guanine These base pair up to form the rungs in "the ladder" Adenine always pairs with Thymine & Cytosine Always pairs with Guanine We uses their first letters to shorten their names A-T and C- G
VOCABULARY Purine- 1 of 2 types of nitrogenous bases found in nucleotides characterized by a 6 member ring fused to a 5 member ring (Adenine and Guanine) Pyrimidine- 1 of 2 types of nitrogenous bases found in nucleotides characterized by 6 member ring ( Cytosine and Thymine) Complementary Strands- a strand of DNA that completes the DNA Helix by having a complementary set of nucleotides Nuclease- an enzyme that cuts damaged section of DNA and Replicants Telomeres- special nucleotide sequences at the end of DNA strands these act as a buffer between genes it acts as a stop signal
WHAT WOULD BE THE COMPLEMENTARY DNA STRAND TO THESE SINGLE STRANDS OF DNA TGCCAAATGTGCTAATC ATAAGAGCCTCGTCAAA TTCACCGAGCTTACCCT
DNA REPLICATION In order for DNA to replicate the double helix must be split to 2 separate templates Once the strands are separated a complementary strand is made on each template
WHERE DOES IT START? The Origins of Replication is a short set of nucleotides that cold for starting vise verse for when to stop On a strand of DNA the start code codes for replication going both ways on the strand this area where replication starts diverging is called a replication bubble
At each end of the replication bubble is a replication fork (a y shape region where the parental strands of DNA are being unwound) Helicases are enzymes that untwist the double helix at the replication forms separating the 2 parental strands making hem available for replication DNA Polymerase is an enzyme that catalyze so the synthesis of the new DNA by adding Nucleotides to the Preexisting chains
ANTIPARALLEL STRANDS The 2 ends of DNA strands are Different this gives each strand directionality (3' end and a 5' end) The 2 strands are opposite of on another Polymerase can only go from 3' - 5' Leading strand is the strand in which goes from 3' to 5' into the replication fork Lagging strand is the opposite from the leading strands where fragments are constantly being made to fill in the holes in the replicant
PROOF READING Errors happen one and every 1,000,000 nucleotides DNA Polymerase proof reads each nucleotide agains it's template as son as it is added to the growing of strands After all their other enzymes proofread the proofread and replace any mismatched nucleotides Permanent changed in the DNA are called Mutations