5.1 10.1 The Cell Cell Growth Cycle KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.
5.1 10.1 The Cell Cell Growth Cycle Why must cells divide? Growth and Repair - increase number of cells - replace worn-out or damaged cells -via Mitosis Sexual Reproduction - formation of a new cell from union of two sex cells (fertilization of sperm and egg) -via Meiosis
5.1 10.1 The Cell Cell Growth Cycle Cells divide at different rates. The rate of cell division varies with the need for those types of cells. Some cells are unlikely to divide.
5.1 10.1 The Cell Cell Growth Cycle The cell cycle has four main stages. The cell cycle is a regular pattern of: -growth(g 1 & G 2 ) - DNA replication (S) - cell division (M) G 1 S G 2 make up the Interphase (before cell division)
5.1 10.1 The Cell Cell Growth Cycle The main stages of the cell cycle are G 1, S, G 2, and mitosis. Gap 1 (G 1 ): cell growth and normal functions DNA synthesis (S): copies DNA Gap 2 (G 2 ): additional growth Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) Mitosis occurs only if the cell is large enough and the DNA undamaged.
5.2 10.2 Mitosis Cell Division and KEY CONCEPT Cells divide during mitosis and cytokinesis.
5.2 10.2 Mitosis Cell Division and Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA
5.2 10.2 Mitosis Cell Division and DNA plus proteins is called chromatin. chromatid Chromatin condenses to form chromosomes. One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes. telomere centromere telomere Condensed, duplicated chromosome
5.2 10.2 Mitosis Cell Division and Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell Interphase prepares the cell to divide. During interphase, the DNA is duplicated. centrioles spindle fibers centrosome nucleus with DNA Interphase = Grow and Copy DNA!!
5.2 10.2 Mitosis Cell Division and Mitosis divides the cell s nucleus in four phases. Stage 1: Prophase 1) centrioles move to opposite sides of the cell 2) nuclear membrane breaks down 3) chromatin condense to form chromosomes 4) spindle fibers form 3 2 1 4 Prophase = Wind Up!!
5.2 10.2 Mitosis Cell Division and Mitosis divides the cell s nucleus in four phases. Stage 2: Metaphase Chromosomes line up in the middle of the cell at the metaphase plate (or equator). metaphase plate Metaphase = Line Up!!
5.2 10.2 Mitosis Cell Division and Mitosis divides the cell s nucleus in four phases. Stage 3: Anaphase Centromere divides and sister chromatids separate to opposite sides of the cell. centromere sister chromatids Anaphase = Split Up!!
5.2 10.2 Mitosis Cell Division and Mitosis divides the cell s nucleus in four phases. Stage 4: Telophase (opposite of Prophase) 1) cleavage furrow forms 2) spindle fibers break down 3) nuclear membrane reforms 4) chromosomes uncoil back to chromatin 4 3 2 cleavage furrow 1 Telophase = Ready? Set
5.2 10.2 Mitosis Cell Division and = division of the cytoplasm differs in animal and plant cells. In animal cells, the membrane pinches closed to form 2 separate cells. = Divide!!
5.2 10.2 Mitosis Cell Division and differs in animal and plant cells. - In plant cells, plant cells do not have centrioles to separate the cells a new cell plate is laid down between the cells to separate them
5.2 10.2 Mitosis Cell Division and
KEY CONCEPT Gametes have half the number of chromosomes that body cells have.
You have body cells and gametes. Body cells are also called somatic cells. Germ cells develop into gamete. Gametes are sex cells: egg and sperm. Gametes are located in the ovaries and testes. Gametes have DNA that can be passed to offspring. body cells sex cells (sperm) sex cells (egg)
Your cells have autosomes and sex chromosomes. Your body cells have 23 pairs of homologous chromosomes. Homologous chromosomes - same chromosomes, but one chromosome comes from each parent (Homo = same) - have same structures but carry different genes Pairs 1-22 = autosomes Pair 23 = sex chromosomes (X/Y), determine gender in mammals.
Body cells are diploid; gametes are haploid. Diploid (2n) cells have two copies of every chromosome. Body cells are diploid. (23 pairs = 46 chromosomes) Half the chromosomes come from each parent. Haploid (n) cells have one copy of every chromosome. Gametes are haploid. (23 chromosomes) Gametes have 22 autosomes and 1 sex chromosome.
Mitosis and meiosis are types of nuclear division that make different types of cells. Mitosis makes diploid cells. (2n 2n) occurs in body cells produces identical cells (46 46) Meiosis makes haploid cells. (2n 1n) occurs in sex cells produces gametes (46 23)
Asexual Reproduction produces identical cells through mitosis. Single-celled eukaryotes ex: yeast, paramecium, and amoeba Simple multicellular eukaryotes ex: hydra
Sexual reproduction produces genetically different cells by joining gametes through fertilization. Fertilization is the process when sperm and egg join to form a zygote. Complex multicellular organisms (like us) cannot produce gametes by mitosis because the chromosomes will DOUBLE after fertilization. What if we did, then. Doesn t work! 46 + 46 92 fertilization egg sperm zygote
Meiosis makes sperms and eggs 46 chromosomes to 23 chromosomes half the number of chromosomes 46 23 meiosis egg 46 23 diploid sperm haploid
When gametes are reduced to 23 chromosomes, they can combine through fertilization The new zygote will have 46 chromosomes again! 46 23 23 zygote meiosis egg 23 46 46 23 sperm fertilization
Putting it all together meiosis fertilization mitosis + development 46 23 meiosis egg 46 23 sperm 23 23 fertilization 46 46 46 46 46 46 46 46 46 zygote mitosis mitosis & development
Identical vs. Fraternal twins
KEY CONCEPT During meiosis, diploid cells undergo two cell divisions that result in haploid cells.
Cells go through two rounds of division in meiosis. Meiosis I (first division) and Meiosis II (second division) occurs in gametes (sperm and egg) diploid haploid (2n 1n) creates genetic diversity (variations) Meiosis I Meiosis II Diploid Haploid
Meiosis I and meiosis II each have four phases, similar to those in mitosis Interphase Meiosis 1 (P1-M1-A1-T1-) Meiosis 2 (P2-M2-A2-T2-Cytoknesis) Pairs of homologous chromosomes separate in meiosis I. Sister chromatids divide in meiosis II. homologous chromosomes sister chromatids sister chromatids
Meiosis I occurs after DNA has been replicated (interphase). Meiosis I divides homologous chromosomes in four phases.
Prophase I - similar to Prophase in mitosis except homologous chromosomes pair up (one from Dad and one from Mom)
Prophase I - When homologous chromosomes pair up, crossing over may occur. - Crossing over is the exchange of DNA between two homologous chromosome. - Crossing over results in genetic variations. (this is why siblings may look similar, but still different)
How does meiosis explain family resemblance and differences. Let s look at some Celebrity Brothers and Sisters!!
Metaphase 1, Anaphase 1, Telophase 1, - homologous chromosomes line up, split up, divide into two cells, and ready to proceed to Meiosis 2
Meiosis II divides sister chromatids in four phases. DNA is not replicated between Meiosis I and Meiosis II. Two cells divide into four haploid cells.
Haploid cells develop into mature gametes. Gametogenesis is the production of gametes. Gametogenesis differs between females and males. Spermatogenesis = sperm production 1 germ cell 4 sperm cells Oogenesis = egg production 1 germ cell 1 egg cell + 3 polar bodies
Meiosis differs from mitosis in significant ways.
Comparing Mitosis and Meiosis Mitosis Meiosis # of divisions 1 2 # of daughter cells Genetically identical? 2 4 Yes No Chromosome # Same as parent (2n) Half of parent (n) Where Somatic cells Sex cells When Throughout life At sexual maturity Role Growth and repair Sexual reproduction