DNA

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DNA CHROMOSOMES
Mrs. Stewart Honors Biology Central Magnet School
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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.

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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

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How big is the unseen world of cellular biology?

• Cell Sizes Scale
• Scale of the universe

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What is DNA?

• DNA contains all the genetic (hereditary)
  information necessary to build and maintain an
  organism

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DNA and Genes

• Genes specific sections of DNA that code for a
  trait

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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

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• 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?

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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

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Chromatin

• Definition
• Histones

• DNA that is tightly wrapped around proteins
• found in the nucleus of Eukaryotic cells
• A sphere-shaped protein that DNA wraps around
• Not found in Eubacteria

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Chromosome Vs. Chromatin

• Chromosomes are only present during cell
  division.
• In between cell divisions, chromosomes are
  unraveled and called Chromatin

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Chromosome Vs. Chromatin

• Chromosome
• Chromatin

Tightly coiled DNA proteins during cell
division DNA cannot be read while in this form.
Loosely coiled DNA proteins during the cells
life other than cell division. DNA can be read
to direct activities of the cell.
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Chromosomes

• Definition
• Rod-shaped or X-shaped structures made of tightly
  coiled chromatin in preparation for the cell to
  divide

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• CHROMOSOMES

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Chromosomes

• What do they look like?
• How many do humans have?

• 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

23 Pairs of chromosomes (23 from mom, 23 from
dad) 46 chromosomes
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What does a chromosome look like?
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Chromosomes
Chromatids
Centromere
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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

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Prokaryotic vs. Eukaryotic Chromosomes

• Prokaryotic

• Eukaryotic

• Circular
• Only one
• No histones (except Archaebacteria)
• Not in a nucleus

• Rod or X shaped
• Many
• Histones
• In nucleus

Chromosome
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Think Pair ShareWhich is more complex in
terms of DNA?
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Think Pair ShareWhich is more complex in
terms of DNA?
Adders Tongue Fern
Human
OR
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Think Pair ShareWhich is more complex in
terms of DNA?
Sand Dollar
Potato
OR
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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
Adders Tongue Fern 1262
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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

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SEX Chromosomes

• XX
• XY

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HOMOLOGOUS CHROMOSOMES

• A pair of autosomes that are the same size and
  shape and code for the same genes
• One comes from ____________
• One comes from ____________
• Humans have 44 autosomes, so they have 22 pairs
  of homologous autosomes

Mom
Dad
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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

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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) Only sex cells- Egg or Sperm
Abbreviation 2n 1n
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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.

30
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

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Exit Ticket

• Socrative.com
• Room Number Stewart348