Download DNA - Imagine School at Lakewood Ranch

“Building Blocks of
Life”
 DNA—a chemical
that contains
information that an
organism needs to
grow and function

Mid-1800’s: Scientist know
nuclei of cells contain large
molecules
 By 1950: Chemists identify
what DNA was made of
 1952: DNA is discovered to
exist in a spiral form
 1953: Watson and Crick
make a model of the DNA
molecule


Picture a twisted
ladder
› Sides of ladder:
Deoxyribose and
phosphate
› Rungs of ladder:
nitrogen base
pairs




A = Adenine
G = Guanine
C = Cytosine
T = Thymine
 Bases
always
come in pairs
 Adenine
always
 Guanine
always
matches
Thymine
matches
Cytosine

Before mitosis or meiosis, DNA gets
copied. How does this happen?
1. The bonds between the nitrogen
bases are broken by an enzyme
2. The two sides of the DNA unwind and
separate
3. New bases pair with bases on original
DNA
All of your characteristics are determined
by your DNA
 Gene – sections of DNA on a
chromosome

› Genes contain instructions for making specific
proteins
› But… genes are on chromosomes, which are
in the nucleus… proteins are made on the
ribosomes in the cytoplasm…
› How do the protein codes get to the
ribosomes?
Ribonucleic

Acid!
RNA carries the codes for making
proteins from the nucleus to the
ribosomes in the cytoplasm

RNA is similar to DNA
except:
1. has one strand instead
of two strands.
2. has uracil instead of
thymine
3. has ribose instead of
deoxyribose (sides of
ladder on DNA)
Protein production begins when
messenger RNA (mRNA) moves into the
cytoplasm
 mRNA carries the code for making
proteins


Ribosomal RNA (rRNA): makes up
ribosomes, where proteins are built.

Transfer RNA (tRNA) brings amino acids
to the ribosomes to build the protein.
All of your cells have the
same DNA
 Cells use the genes they
need to do their job
and ignore the other
genes
 Example: Cells in your
stomach produce the
proteins needed to
digest your food while
muscle cells produce
proteins to make your
muscles move.

Sometimes mistakes
happen when DNA is
being copied.
 Mutations—any
permanent change in
the DNA sequence of a
cell’s gene or
chromosome

 Can
be caused by outside factors
like X rays, sunlight, and some
chemicals
A
change in a gene or
chromosome can change the
traits of an organism. Can
sometimes be fatal.

What are the nitrogen base pairs in a
DNA molecule?

A strand of DNA has the bases AGTAAC.
Use letters to show what the matching
strand would be

Adenine, Guanine, Cytosine, Thymine

TCATTG


What are the nitrogen base pairs in an
RNA molecule?
A strand of DNA has the following order
of bases: CGTATCGA. The corresponding
order of bases in the matching RNA will
be?

Guanine, Cytosine, Adenine, Uracil

GCAUAGCU

You begin as one cell. Compare the
DNA in your brain cells to the DNA in your
heart cells.

Describe how DNA makes a copy of itself

DNA in all types of cells is identical

Two sides unwind and are separated by
an enzyme; a complementary strand is
formed for each; the resulting double
stranded DNA has one original strand
and one new strand

What are the 3 types of RNA?

What do they do?

mRNA – carries code from nucleus to
ribosomes

rRNA – makes up the ribosomes

tRNA – brings amino acids to ribosome to
build the proteins