Cell Reproduction OVERVIEW Cell cycle Chromosomes Mitosis Meiosis

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Cell Reproduction

Cell Reproduction

OVERVIEW • Cell cycle • Chromosomes • Mitosis • Meiosis

OVERVIEW • Cell cycle • Chromosomes • Mitosis • Meiosis

CELL THEORY 1. Cells are the smallest unit of life. 2. All life is

CELL THEORY 1. Cells are the smallest unit of life. 2. All life is composed of cells. 3. New cells come from existing cells. All cells divide. • growth • repair e R l l e C n o i t c u prod

CELL CYCLE IN YOU All humans start as a single cell. • That single

CELL CYCLE IN YOU All humans start as a single cell. • That single cell starts dividing immediately • Each new cell created also divides… and they divide… and so on • This is how GROWTH happens • By adulthood, humans are approximately 37 trillion cells • 37, 000, 000 Cells continue to divide until they die (autolysis). • In humans, 2 trillion cells divide every day. Sometimes cell division goes awry. • Cancer – unregulated cell growth

CELL CYCLE AS PART OF LIFE Which characteristics of life does the cell cycle

CELL CYCLE AS PART OF LIFE Which characteristics of life does the cell cycle apply to? GROWTH AND DEVELOPMENT – adding new cells REPRODUCTION – creating new organisms

TWO METHODS OF CELL DIVISION Binary Fission -- used by prokaryotes (bacteria) to create

TWO METHODS OF CELL DIVISION Binary Fission -- used by prokaryotes (bacteria) to create new organism -- asexual reproduction -- both new organisms exact copies of the original Bacteria have single, circular chromosome that replicates Cell grows to twice original size Cell splits in two, each containing a circular chromosome.

TWO METHODS OF CELL DIVISION Mitosis -- used by eukaryotes for growth, development, or

TWO METHODS OF CELL DIVISION Mitosis -- used by eukaryotes for growth, development, or repair -- used for asexual reproduction (unicellular eukaryotes) -- creates two cells identical to the original cell

EUKARYOTE CHROMOSOMES Vocab terms: • chromatin • chromosomes • histones • chromatid • centromere

EUKARYOTE CHROMOSOMES Vocab terms: • chromatin • chromosomes • histones • chromatid • centromere • chromosome number Recall: • What is the macromolecule that contains the information that tells the cell how to grow and develop? • DNA • Where is it located? • nucleus • What does it look like? • long strands (plate of spaghetti) • What is it called when in these long strands? • chromatin

CHROMOSOME STRUCTURE Before a cell can reproduce it must do two things: 1. Replicate

CHROMOSOME STRUCTURE Before a cell can reproduce it must do two things: 1. Replicate its DNA 2. Coil up the chromatin into manageable forms Special proteins called histones help the cell package its DNA into a manageable form. Each chromatin strand coils into a spring shape around histones. The result is a tightly compacted form of the DNA now called a chromosome.

CHROMOSOME COILING Each chromosome now appears in an “X” shape. Each side of the

CHROMOSOME COILING Each chromosome now appears in an “X” shape. Each side of the chromosome is called a chromatid. Where the chromatids join is called the centromere.

CHROMOSOME NUMBER Every organism has a chromosome number unique to its species. The chromosome

CHROMOSOME NUMBER Every organism has a chromosome number unique to its species. The chromosome number represents the total number of chromosomes that non-sex cells of that species contain. v Sex cells will have a different number. v Individuals with genetic abnormalities may also have a different number.

CHECK YOUR NOTES You should have all of the following: • Cell reproduction as

CHECK YOUR NOTES You should have all of the following: • Cell reproduction as related to Cell Theory • Cell reproduction as related to characteristics of life • Reasons for cell division (prokaryotes and eukaryotes) • How cell division relates to organism growth • Binary Fission with diagram and explanation (prokaryotes) • Eukaryotic chromosome condensation • Eukaryotic chromosome structure with diagram • Vocab: chromatin, chromosomes, histones, chromatid, centromere, chromosome number

CELL CYCLE Vocab terms: • cell cycle • interphase • cytokinesis • • The

CELL CYCLE Vocab terms: • cell cycle • interphase • cytokinesis • • The cell cycle is the repeating series of events in the life of a cell -- from creation to division. When cells divide (cell division), they make more cells (cell multiplication). cell division cell multiplication parent cell daughter cell

CELL CYCLE The time between cell divisions is termed interphase. Ø Think of this

CELL CYCLE The time between cell divisions is termed interphase. Ø Think of this as the “in”between time. Once the cell has reached maximum growth, it undergoes cell division. During this process, the chromosomes and cytoplasm are equally divided between two new, identical cells. The original cell is termed the parent cell. The two new cells are each termed daughter cells.

INTERPHASE Interphase makes up most of the cell’s life. • The cell is growing.

INTERPHASE Interphase makes up most of the cell’s life. • The cell is growing. • The DNA is being replicated (copied. ) • The cell is preparing to divide. • The cell is performing its job. Ø liver, heart, muscle, etc. • The amount of time spent in interphase varies. Ø skin cells = short Ø nerve cells = long

STAGES OF CELL DIVISION The rest of the cell cycle is related to cell

STAGES OF CELL DIVISION The rest of the cell cycle is related to cell division. Mitosis The cell completes the four stages of cell division. Cytokinesis The cell completes the division of the cytoplasm and its contents. One parent cell has now become two daughter cells.

CHECK YOUR NOTES You should have all of the following: • Cell cycle explanation

CHECK YOUR NOTES You should have all of the following: • Cell cycle explanation • Cell multiplication and division • Stages of the cell cycle • Interphase events • Stages of cell division • Vocab: cell cycle, cytokinesis, interphase, cell division, cell multiplication, parent cell, daughter cell

MITOSIS INQUIRY ACTIVITY

MITOSIS INQUIRY ACTIVITY

MITOSIS Vocab terms: • somatic cell • gamete • prophase • metaphase • •

MITOSIS Vocab terms: • somatic cell • gamete • prophase • metaphase • • • spindle fibers anaphase telophase Objective: ensure each somatic daughter cell has a complete set (not more, not less) of genetic material. Eukaryotic organisms that use sexual reproduction have two kinds of cells: 1. Somatic cells – any cell type with the full chromosome number unique to that organism 2. Gametes – also known as sex cells, are cells with half the chromosome number unique to that organism, intended to be combined with another gamete to produce a single cell with the full chromosome number

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT Prophase spindle fiber formation • chromosome coiling • nuclear membrane disappears • spindle fibers begin to form two sister chromatids

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT Metaphase metaphase plate spindle fibers: microtubules chromsomes line up along the middle (equator) • spindle fibers are fully formed • spindle fibers have attached to centromeres • spindle fibers have aligned chromosomes along the middle

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT Anaphase • chromatids separate • spindle fibers pull chromatids to opposite poles chromatids

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT

MITOSIS Mitosis consists of four phases that always occur in the same order: PMAT Telophase cleavage furrow • chromatids reach poles • spindle fibers disappear • nuclear membrane begins to reform • cytokinesis begins nuclear membrane reforming

CYTOKINESIS The DNA of the cell has been successfully separated, the cytoplasm and its

CYTOKINESIS The DNA of the cell has been successfully separated, the cytoplasm and its contents finish dividing Cytokinesis • the cell membrane indents in the center as it begins the process of forming new membrane that will divide the parent cell into daughter cells • upon completion, the cell has divided all cytoplasm and organelles amongst the two new daughter cells

CELL CYCLE BEGINS AGAIN Each daughter cell now starts the cell cycle at the

CELL CYCLE BEGINS AGAIN Each daughter cell now starts the cell cycle at the G 1 phase.

CHECK YOUR NOTES You should have all of the following: • Objective of mitosis

CHECK YOUR NOTES You should have all of the following: • Objective of mitosis • Purpose of replicating DNA • Definitions of somatic cells and gametes • PMAT: all four stages, diagrams, explanation of corresponding events • Cytokinesis explanation and events • Vocab: somatic cell, gamete, prophase, metaphase, anaphase, telophase, spindle fibers

CHROMOSOME NUMBER Vocab terms: • diploid • haploid • n number • 2 n

CHROMOSOME NUMBER Vocab terms: • diploid • haploid • n number • 2 n • n • • autosomal chromosomes sex chromosomes homologous chromosomes sexual reproduction Sexual reproduction is the process by which a new organism is created by combining the genetic material of two existing organisms; usually one male and one female. Each existing organism contributes half the genetic information of the new organism. This genetic information is carried in specialized cells termed gametes (sex cells, sperm, ova)

CHROMOSOME NUMBER Recall: each organism has a chromosome number unique to it. In sexually

CHROMOSOME NUMBER Recall: each organism has a chromosome number unique to it. In sexually reproducing, eukaryotic organisms, that number is always an even number because those chromosomes are in sets. For example, humans have 46 chromosomes that consists of two sets. There are 23 unique kinds of chromosomes and each (genetically normal) human has 2 of each different kind. One set is contributed from the male (dad) and the other from the female (mom. )

CHROMOSOME NUMBER Each different chromosome is identified by a number. Numbers 1 -22 are

CHROMOSOME NUMBER Each different chromosome is identified by a number. Numbers 1 -22 are called autosomal chromosomes. Number 23 is the sex chromosome – either X or Y – that contributes to the determination of male or female. Chromosomes of the same kind (or number) are called homologous chromosome.

CHROMOSOME NUMBER The n number is the number of chromosome sets a cell contains.

CHROMOSOME NUMBER The n number is the number of chromosome sets a cell contains. Cells that contain 2 sets of chromosomes are referred to as diploid. They are also known as 2 n. Cells that contain 1 set of chromosomes are referred to as haploid. They are also known as n. In humans: 2 n = 46 = diploid = somatic cell n = 23 = haploid = gamete

MEIOSIS Meiosis is the process of cell division that produces gametes. It’s objective it

MEIOSIS Meiosis is the process of cell division that produces gametes. It’s objective it to produce gametes that are haploid – that have one of each kind of chromosome. Both of these gametes are haploid. Activity: Meiosis Structure Worksheet

MEIOSIS Objective: to produce gametes that are haploid – that have one of each

MEIOSIS Objective: to produce gametes that are haploid – that have one of each kind of chromosome. Meiosis consists of two steps: meiosis I and meiosis II Both are broken down into phases, like mitosis. The phases of meiosis I are similar to mitosis, but have 3 very important differences. These differences will result in 2 things: haploid gametes and increased genetic variability.

MEIOSIS n=? Prophase I • Chromosome coiling • Alignment of homologous chromosomes • Crossing

MEIOSIS n=? Prophase I • Chromosome coiling • Alignment of homologous chromosomes • Crossing over occurs Crossing over is a process by which homologues exchange sections of their DNA. This increases genetic variability in offspring. Genetic variability is all the possible, unique combinations of genes that are present in a population.

MEIOSIS Metaphase I • Chromosome pairs align in the middle • Side by side

MEIOSIS Metaphase I • Chromosome pairs align in the middle • Side by side arrangement is random – increases genetic variability • Spindle attach to the centromeres of one homologue from either side

MEIOSIS Anaphase I • Homologous chromosomes are pulled to opposite poles • Chromatids remain

MEIOSIS Anaphase I • Homologous chromosomes are pulled to opposite poles • Chromatids remain attached at the centromeres

MEIOSIS Telophase I • Homologues are pulled to opposite poles • Chromatids remain attached

MEIOSIS Telophase I • Homologues are pulled to opposite poles • Chromatids remain attached at the centromeres • Cytokinesis begins Cytokinesis • Upon completion of cytokinesis following PMAT I, cells are haploid • Sister chromatids are still attached • PMAT II will separate sister chromatids following the same steps as mitosis

MEIOSIS II Meiosis II looks just like mitosis. The important difference is that it

MEIOSIS II Meiosis II looks just like mitosis. The important difference is that it ends in four haploid gametes.