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