Cell Growth, Division and Reproduction B1

B1. Basic Biological Principles Describe the events that occur during 3 stages of the cell cycle: interphase, nuclear division, cytokinesis. Compare and contrast processes and outcomes of mitosis and meiosis. Explain how genetic information is inherited. Explain the functional relationships between DNA, genes, alleles and chromosomes and their roles in inheritance.

B1. Vocabulary Allele genetics Allele frequency inheritance Cell cycle meiosis Chromosomes mitosis Crossing over nondisjunction Cytokinesis nucleus Deoxyribonucleic acid (DNA) DNA replication Gene gamete

ANALOGY: What would happen to a growing town if it continued to grow? Cell Size Limits to Cell Size Information Overload Large cells place more demands on the DNA to provide what the cell needs to live Information a cell needs to live is stored in DNA When a cell is small, its DNA can meet all of its needs If a cell gets too large, a cell’s DNA would not be able to keep up with the needs of the cell ANALOGY – a growing town ANALOGY: What would happen to a growing town if it continued to grow?

ANALOGY: Traffic Problems Cell Size Limits to Cell Size Exchanging Materials Cells rely on movement of material across the cell membrane Large cells have trouble moving enough nutrients in and wastes out ANALOGY: Traffic Problems

Limits to Cell Size Cell Size ANALOGY: Lots of Growth can mean lots of trouble both in a town and in a cell

Cell Division Cell Size A process by which a cell divides into two new cells Solves the problem of overloading DNA and not being able to get enough materials in or out

Model it… How does the surface area of a cube change as its volume increases? How does the relationship support the information learned today. Construct 3 different sized cubes. Ask students to determine the surface area (to represent the surface at which a “cell” can exchange material) and volume (significant of cell size). Volume increases at a much faster rate than the surface area.

The Process of Cell Division Chromosomes Cells store information in DNA DNA is packaged into chromosomes Prokaryotes = single circular chromosome Eukaryotes = many chromosomes Chromatin = all of the chromosomes in the nucleus

The Process of Cell Division Changes to the DNA during division DNA is copied before cell division (replication) When a cell is not dividing, DNA is uncoiled (chromatin) During division, DNA coils up (condenses) and individual chromosomes can be seen

Which is easier to separate? Chromosomes during cell division Chromosomes before cell division

The Process of Cell Division Changes to the DNA during division Once replicated, each chromosome consists of two identical sister chromatids held together at the centromere

The Process of Cell Division The Cell Cycle The series of events a cell goes through as it grows and divides growth DNA replication Cell division End Result = two new daughter cells genetically identical to the parent cell

The Process of Cell Division The Prokaryotic Cell Cycle happens quickly begins when the cell reaches a certain size is a form of asexual reproduction results in a new organism being formed called binary fission

The Process of Cell Division The Eukaryotic Cell Cycle Multiple stages with checkpoints Interphase G1: Cell Growth S: DNA Replication G2: Preparation for division Cell division (also called M phase) Mitosis: division of the nucleus Prophase Metaphase Anaphase Telophase Cytokinesis: division of the cytoplasm

The Process of Cell Division The Eukaryotic Cell Cycle

The Process of Cell Division Mitosis PROPHASE First phase of mitosis Chromosomes are visible Nucleus disintegrates Spindle fibers form Centrioles migrate

The Process of Cell Division Mitosis METAPHASE Second phase of mitosis Chromosomes line up across the center of the cell

The Process of Cell Division Mitosis ANAPHASE Third phase of mitosis Sister chromatids separate and move to opposite sides of the cell

The Process of Cell Division Mitosis TELOPHASE Final phase of mitosis Chromosomes unwind Nucleus reforms around each new set of chromosomes Spindles break down

Take a Break…QUICK CHECK Construct 3 different sized cubes. Ask students to determine the surface area (to represent the surface at which a “cell” can exchange material) and volume (significant of cell size). Volume increases at a much faster rate than the surface area. CLICK HERE

Cell Division and Reproduction Asexual Reproduction Cell division that results in a new organism Reproduction by a single parent Offspring are clones of parent Advantages: Quick - organisms well suited for an environment can reproduce very quickly Disadvantages: Lack of genetic diversity

Cell Division and Reproduction Sexual Reproduction Results from the joining of two different cells Offspring have a mix of DNA from both parents Advantages: Offspring are genetically different Disadvantages: Slow – takes time to mature and find a mate

Think about this… How many chromosomes do you have in your cells? How many of those chromosomes came from dad? How many of those chromosomes came from mom?

Cell Division and Reproduction Homologous Chromosomes Homologous chromosomes = chromosomes that carry the same types of genes An organism with two parents must receive a set of genes from both parent Reproductive cells therefore can only carry a half of the chromosomes When an organism produces reproductive cells (sperm and egg), homologous chromosomes must separate Meiosis is the process that ensures the separation of homologous chromosomes

Cell Division and Reproduction Homologous Chromosomes

Cell Division and Reproduction Meiosis Cell division that produces reproductive cells Begins with interphase (DNA replicated) Two rounds of division Meiosis I – homologous chromosomes Meiosis II – sister chromatids Each round of division consists of prophase, metaphase, anaphase and telophase

Cell Division and Reproduction Meiosis – End Result End result of meiosis is different from mitosis 4 cells produced Each cell contains half the # of chromosomes that are needed in the organism (haploid) Cells that form are genetically different

Cell Division and Reproduction The process of Meiosis Begins with interphase (DNA replicated) Two rounds of division Meiosis I – homologous chromosomes Meiosis II – sister chromatids Each round of division consists of prophase, metaphase, anaphase and telophase

Cell Division and Reproduction Meiosis and genetic diversity Prophase I Homologous chromosomes pair up Crossing over occurs between homologous chromosomes (exchange of genetic info) Produces new combinations of genes

Keystone Prep Questions Which statement best describes the phase of the cell cycle shown? The cell is in prophase of mitosis because the number of chromosomes has doubled. The cell is in prophase I of meiosis because the number of chromosomes has doubles. The cell is in telophase of mitosis because the cell is separating and contains two copies of each chromosome. The cell is in telophase of meiosis because the cell is separating and contains two copies of each chromosomes

Keystone Prep Questions 2. Mitosis and Meiosis are processes by which animal and plant cells divide. Which statement best describes a difference between mitosis and meiosis? Meiosis is a multi-step process. Mitosis occurs only in eukaryotic cells. Meiosis is used in the repair of an organism. Mitosis produces genetically identical daughter cells.