DNA & CHROMOSOMES Mrs. Stewart Honors Biology Central Magnet School Standards • CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. • CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits. Objectives • Evaluate the structure of a chromosome • Differentiate between prokaryotic and eukaryotic chromosomes • Infer the complexity of an organism based on chromosome number • Identify gender based on chromosomes How big is the unseen world of cellular biology? • Cell Sizes – Scale • Scale of the universe What is DNA? • DNA – contains all the genetic (hereditary) information necessary to build and maintain an organism DNA and Genes • Genes – specific sections of DNA that code for a trait How much DNA is in most of the cells in a human body? • Approx. 2 meters in every diploid cell • 2 meters = ___6.5___ Feet • Approx 6 billion base pairs of DNA per cell • Each of us has enough DNA in our bodies to reach from here to the sun and back more than 300 times • How is all of that DNA packaged so tightly and squeezed into a tiny nucleus? Activity • Materials needed: – Yarn = DNA – Easter Egg = Nucleus • Question: What do the differently colored sections of yarn relate to in DNA? • Mission: Make all the DNA fit into the nucleus in a way that it would still be “organized” Chromatin Definition: DNA that is tightly wrapped around proteins found in the nucleus of Eukaryotic cells Histones: A sphere-shaped protein that DNA wraps around oNot found in Eubacteria Chromosome Vs. Chromatin • Chromosomes are only present during cell division. • In between cell divisions, chromosomes are unraveled and called Chromatin Chromosome Vs. Chromatin • Chromosome: Tightly coiled DNA & proteins during cell division; DNA cannot be “read” while in this form. • Chromatin: Loosely coiled DNA & proteins during the cell’s life other than cell division. DNA can be “read” to direct activities of the cell. Chromosomes • Definition: – Rod-shaped or X-shaped structures made of tightly coiled chromatin in preparation for the cell to divide CHROMOSOMES Chromosomes What do they look like? •They look like an “X” after the DNA has been duplicated (just before the cell divides) •They look like an “I” after they divide and between cell divisions • How many do humans have? 23 Pairs of chromosomes (23 from mom, 23 from dad) = 46 chromosomes What does a chromosome look like? Chromosomes Chromatids Centromere Chromosome Terminology • Centromere- Connecting point between two chromatids - holds the chromatids together • Chromatids- identical strands of a duplicated chromosome – become visible at the beginning of Mitosis or Meiosis – Contains same genetic information on both Prokaryotic vs. Eukaryotic Chromosomes Prokaryotic • Circular • Only one • No histones (except Archaebacteria) • Not in a nucleus Eukaryotic • Rod or X shaped • Many • Histones • In nucleus Chromosome Think – Pair – Share Which is more complex in terms of DNA? Think – Pair – Share Which is more complex in terms of DNA? Adders Tongue Fern Human OR Think – Pair – Share Which is more complex in terms of DNA? Sand Dollar Potato OR Chromosome Numbers Organism # of chromosome Fruit Fly 8 Carrots & Lettuce 18 Cat 32 Earthworm 36 Human 46 Gorilla / Chimpanzee 48 Potatoes / Plums 48 Sand Dollar 52 Horse 64 Adder’s Tongue Fern 1262 Two Types of Chromosomes • SEX – Determine the gender of the individual – Carry a few other traits – 2 out of our 46 chromosomes • AUTOSOMES – Carry most of the traits that we inherit – 44 of the 46 chromosomes SEX Chromosomes • XX = • XY = HOMOLOGOUS CHROMOSOMES • A pair of autosomes that are the same size and shape and code for the same genes Mom • One comes from ____________ Dad • One comes from ____________ • Humans have 44 autosomes, so they have 22 pairs of homologous autosomes KARYOTYPE • A picture taken from a microscope of all the chromosomes within a cell. The chromosomes are then arranged in homologous pairs and given a set of numbers Diploid vs Haploid Cells Diploid Haploid Description Both sets of homologous chromosomes present Only one of each homologous chromosome present Type of Cell All cells but sex cells (egg or sperm) 2n Only sex cellsEgg or Sperm Abbreviation 1n Standards • CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. • CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits. Objectives • Evaluate the structure of a chromosome • Differentiate between prokaryotic and eukaryotic chromosomes • Infer the complexity of an organism based on chromosome number • Identify gender based on chromosomes Exit Ticket • Socrative.com • Room Number: Stewart348