Unit 5: Cell Division Study Guide

Chromosomes and Karyotypes

Introduction

1. Humans have 46 chromosomes

   • Chromosomes are made out of DNA and Histone Proteins

Problems with DNA

1. DNA is difficult to move around without getting tangled

   • Need it long and stretched out to copy it or to make proteins: Chromatin

     • Chromatin = Everything except cell division

   • Need it bundled (condensed) to move it around: Chromosome

     • Chromosome = Cell Division

Karyotypes

1. Karyotype: A visual display of an organism’s chromosomes

   • Allows us to learn about chromosome abnormalities

     • Too few, too many, too short, too long

   • Allows us to determine biological sex

2. Making a karyotype

   • Take pictures of the chromosomes in a cell (when they’re in chromosome form) and arrange them by size

     • Largest pair is labeled chromosome #1

Variations in Sex Chromosomes

1. Some people have a chromosome pattern other than the usual XY or XX

   • Could have XO or XXY

     • Internal and external sex organs can be either male or female but they may not go through full physical development at puberty

Types of Intersex Variations

1. Klinefelter Syndrome

   • Individual assigned male at birth is born with an extra X chromosome (XXY)

     • Do not produce the typical level of testosterone (a hormone responsible for testes and body hair)

2. Turner Syndrome

   • Individual identified as female at birth is missing an X chromosome (XO)

     • Infertile and height is shorter than average

The Cell Cycle

Introduction

1. DNA replication has to happen because each new cell that is produced needs a complete and accurate copy of the DNA or it will likely die

2. DNA replication occurs any time when a cell or nucleus divides

Causes of Cell Division

1. Growth

2. Repair

3. Immune System

Binary Fission

1. Cell Division in Prokaryotes (Bacteria and Archaea)

   • Asexual Reproduction

   • Results in 2 genetically identical daughter cells

Eukaryotes

1. Mitosis: division of the nucleus

   • Growth and Repair

2. Meiosis: division of the cytoplasm

   • Make gametes (egg or sperm)

Mitosis

Interphase

• Cell grows

• Cell replicates its chromosomes

• Prepares for cell division

Prophase

• Chromosomes condense

• Spindle fibers form

• Nucleus and nucleolus disappear

Metaphase

• Chromosomes line up in the middle

• Spindle fibers attach to centromeres

Anaphase

• Centromeres split

• Sister chromatids separate to opposite sides of the cell

Telophase

• New nuclei form

• Chromosomes begin to uncoil

Cytokinesis

• Cytoplasm is split

• 2 genetically identical daughter cells (diploid)

Meiosis

Introduction

1. Meiosis is the process that produces egg and sperm (genetically unique)

2. Meiosis 2 is just like mitosis

Mitosis vs. Meiosis

1. Mitosis

   • Diploid

     • Each cell has 2 complete sets of chromosomes (46)

     • 2 identical diploid cells

2. Meiosis

   • Haploid

     • Each cell has 1 set of chromosomes (23)

     • 4 unique haploid cells

Homologous Chromosomes vs. Sister Chromatids

1. Homologous: Chromosomes are approximately the same size, and have the same types of genes in the same location

Interphase

• Cell grows

• Cell replicates its chromosomes

• Prepares for cell division

Prophase 1

• Synapsis (homologues pair up)

• Tetrads form

• Crossing Over

Metaphase 1

• Homologous pairs line up

• Each side of the equator has chromosomes from both parents

Anaphase 1

• Homologous pairs split and travel to poles

• Centromeres do NOT break

• Independent Assortment: Random alignment of homologous chromosome pairs at metaphase plate, which leads to genetive diversity

Telophase 1 and Cytokinesis

Meiosis in Male and Female

Cancer

Introduction

1. Checkpoints exist throughout the cell cycle

   • If a cell does not meet a certain standard at a checkpoint, it will die (apoptosis)

What is Cancer?

1. Cancer is uncontrolled cell division

   • Cancerous cells should stop dividing and/or undergo apoptosis

     • Mutations in genes that code for proteins that regulate the cell cycle prevent the proteins from functioning properly

   • Cells divide rapidly and uncontrollably, forming a mass called a tumor

Benign vs. Malignant Tumors

1. Benign Tumor

   • Tumor cells grow only locally and cannot spread by invasion or metastasis

2. Malignant Tumor

   • Cells invade neighboring tissues, enter blood vessels, and metastasize to different sites

Causes of Cancer

1. Genetics

2. Malnutrition

3. Environment

4. Lifestyle