DNA

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DNA RNA The Nucleic Acids
Remember Each chromosome is a very long DNA
molecule that contains many genes. Gene A
segment of DNA that is part of a chromosome that
is responsible for inherited traits such as eye
color, hair color, skin color, etc. It directs
the protein production that controls the cell.
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DNA RNA The Nucleic Acids

• DNA (Deoxyribonucleic Acid)
• Is an organic molecule composed of nucleotides.
• Is a molecule that is common to all living
  things, from bacteria to humans.
• It is the blueprint of an organism, containing
  the genetic instructions for building proteins.
• A DNA molecule canNOT be viewed with a compound
  light microscope.
• The composition of DNA was first described
  correctly in 1953 by two scientists, Watson and
  Crick. They discovered that it was formed from
  two long chains of nucleotides shaped much like a
  spiraling ladder, and they called it a double
  helix.

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DNA RNA The Nucleic Acids
Structure of DNA (DNA is composed of
nucleotides.) Nucleotides of DNA have three
Parts 1. Deoxyribose (a five carbon
sugar) 2. Phosphate group (these two bond
together to make up the sides of the
ladder) 3. 1 of 4 Nitrogen Bases Adenine
(A) Guanine (G) Cytosine (C) Thymine (T)
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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids
The nitrogen bases adenine and guanine are called
purines which have a double ring of carbon and
nitrogen. The nitrogen bases cytosine and
thymine are called pyrmidines, which have a
single ring of carbon and nitrogen.
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DNA RNA The Nucleic Acids

• The 2 chains of nucleotides in a DNA molecule are
  held together by hydrogen bonds between the
  nitrogen bases.

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DNA RNA The Nucleic Acids

• The 2 chains of nucleotides in a DNA molecule are
  held together by hydrogen bonds between the
  nitrogen bases.
• The 2 bases on the same rung of the DNA ladder
  are referred to as a base pair.
• In DNA
• Cytosine always bonds with guanine, and
• Thymine always bonds with adenine!
• CG GC
• TA AT

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DNA RNA The Nucleic Acids

• Base Pairing Rules. The strictness of
  base-pairing results in 2 strands that are
  complementary, which means the sequence of bases
  on one strand determines the sequence of bases on
  the other strand.
• Example
• 1st strand of DNA has T C G A A T T
• The other strand must have A C T A

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DNA RNA The Nucleic Acids

• Base Pairing Rules. The strictness of
  base-pairing results in 2 strands that are
  complementary, which means the sequence of bases
  on one strand determines the sequence of bases on
  the other strand.
• Example
• 1st strand of DNA has T C G A A T T
• The other strand must have A G C T T A A

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DNA RNA The Nucleic Acids

• All organisms contain the same DNA (made up of
  nucleotides with adenine, thymine, guanine, and
  cytosine)
• The reason organisms can be different from each
  other is because the order of nucleotides in two
  different organisms are different (sequence of
  bases)

Example A squirrel differs from a rosebush
because the order of nucleotides in its DNA is
different.
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DNA RNA The Nucleic Acids

• Replication
• During mitosis and meiosis the cells divide.
  Each time a cell divides it must make a copy of
  its DNA.
• Replication is the process by which DNA is
  duplicated, forming two identical copies from one
  original.

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DNA RNA The Nucleic Acids
These are the steps of replication 1. The enzyme
DNA helicase breaks the hydrogen bonds between
the nitrogen bases that hold the two strands
together, unzipping the DNA molecule. 2. As the
DNA continues to unzip, free nucleotides from the
surroundings in the nucleus bond to the single
strands base pairing. 3. The enzyme DNA
polymerase forms the sugar-to-phosphate bonds
that connect nucleotides on each strand of
DNA.
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DNA RNA The Nucleic Acids
Replication of DNA doesnt begin at one end of
the molecule and end at the other, rather it
occurs simultaneously at many points on the
molecule, speeding up to process. Replication
is completed when the entire molecule has been
unzipped and replicated.
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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids
Each new DNA molecule has one nucleotide strand
from the original DNA molecule and one nucleotide
strand that has been newly synthesized from free
nucleotides in the cell.
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DNA RNA The Nucleic Acids
Gene Expression is the use of genetic information
in DNA to make proteins.
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DNA RNA The Nucleic Acids
Gene Expression is the use of genetic information
in DNA to make proteins. Gene Expression takes
place in 2 stages
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DNA RNA The Nucleic Acids
Gene Expression is the use of genetic information
in DNA to make proteins. Gene Expression takes
place in 2 stages 1. Transcription is when the
RNA copy of a gene is made.
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DNA RNA The Nucleic Acids
Gene Expression is the use of genetic information
in DNA to make proteins. Gene Expression takes
place in 2 stages 1. Transcription is when the
RNA copy of a gene is made.
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DNA RNA The Nucleic Acids

• Gene Expression is the use of genetic information
  in DNA to make proteins.
• Gene Expression takes place in 2 stages
• Transcription is when the RNA copy of a gene is
  made.
• Translation is the 2nd stage of gene expression
  where 3 different kinds of RNA work together to
  assemble amino acids into a protein molecule.

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DNA RNA The Nucleic Acids

• Gene Expression is the use of genetic information
  in DNA to make proteins.
• Gene Expression takes place in 2 stages
• Transcription is when the RNA copy of a gene is
  made.
• Translation is the 2nd stage of gene expression
  where 3 different kinds of RNA work together to
  assemble amino acids into a protein molecule.
• Those 3 different kinds of RNA that work together
  are mRNA, tRNA, rRNA.

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DNA RNA The Nucleic Acids
Transcription Transcription is the process of
producing RNA (Ribonucleic Acid) from DNA. RNA
is the form in which information moves from DNA
in the nucleus to the ribosomes in the
cytoplasm.
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DNA RNA The Nucleic Acids
Transcription The process of transcription is
similar to the process of replication, but RNA
differs from DNA in 3 ways 1. RNA is single
stranded (DNA is double stranded) 2. RNA has
ribose as the sugar (DNA has deoxyribose as the
sugar 3. RNA has four nitrogen bases, but
Thymine is replaced with Uracil
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DNA RNA The Nucleic Acids
There are 3 Types of RNA 1. mRNA-messenger
RNA It carries the information from DNA (in the
nucleus) out into the cytoplasm 2.
tRNA-transfer RNA It brings amino acids to the
ribosomes so they can be assembled into
proteins. 3. rRNA-ribosomal RNA It makes up
the ribosomes, the site of protein synthesis
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DNA RNA
Cytosine
Cytosine
Guanine
Guanine
Adenine
Adenine
Uracil
Thymine
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DNA RNA The Nucleic Acids
The Genetic Code Remember that DNAs purpose is
to provide a blueprint for making proteins.
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DNA RNA The Nucleic Acids
The Genetic Code Remember that DNAs purpose is
to provide a blueprint for making proteins.
Proteins are built from chains of smaller
molecules called amino acids, and there are 20 of
them.
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DNA RNA The Nucleic Acids
The Genetic Code Remember that DNAs purpose is
to provide a blueprint for making proteins.
Proteins are built from chains of smaller
molecules called amino acids, and there are 20 of
them. Recall that there are only four
nitrogen bases. So how can four bases code for
20 amino acids?
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DNA RNA The Nucleic Acids
The Genetic Code The answer is that each strand
of DNA is read in sets of three nitrogen bases,
called a codon.
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DNA RNA The Nucleic Acids
The Genetic Code The answer is that each strand
of DNA is read in sets of three nitrogen bases,
called a codon. By reading in groups of three
bases there are 64 combinations possible.
Of these 61 code for amino acids, and there is a
START codon (AUG) and 2 STOP codons (UAA
UAG)
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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids
Protein Synthesis Equation DNA
mRNA Protein

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DNA RNA The Nucleic Acids
Protein Synthesis Equation DNA
mRNA Protein
transcription translation

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DNA RNA The Nucleic Acids
Translation Translation (or protein synthesis,
gene expression) is the process of converting the
information in a sequence of nitrogen bases in
mRNA into a sequence of amino acids that make up
a protein.
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DNA RNA The Nucleic Acids
Translation The steps of translation are

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DNA RNA The Nucleic Acids

• Translation
• The steps of translation are
• The first codon of the mRNA strand attaches to a
  ribosome (rRNA).

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DNA RNA The Nucleic Acids
Translation The steps of translation are 1. The
first codon of the mRNA strand attaches to a
ribosome (rRNA). 2. Then a tRNA molecule has a
special section called an anti codon that is
complementary to the codon on the mRNA molecule.
The first codon is methionine. AUG signals the
start of protein synthesis.

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DNA RNA The Nucleic Acids
Translation The steps of translation are 3.
Next the ribosome slides down the mRNA strand to
the next codon. 4. When the first and second
amino acids are in place, an enzyme joins them by
a peptide bond.
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DNA RNA The Nucleic Acids
Translation The steps of translation
are 5. This process continues until it reaches
a stop codon. The chain of amino acids are now
considered a protein.
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DNA RNA The Nucleic Acids

• The order of events that leads to genetic
  expression
• Protein synthesis
• DNA to RNA to amino acids to protein

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DNA RNA The Nucleic Acids

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DNA RNA The Nucleic Acids
Mutations Mutation is any mistake or change in
the DNA sequence. Mutations in gametes can be
passed on to offspring of the affected
individual, but mutations in body cells affect
only the individual in which they occur.

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DNA RNA The Nucleic Acids
Mutations 1. Chromosome mutation involves a
change in the structure or number of
chromosomes. One example is nondisjunction (when
one or more pairs of homologous chromosomes fail
to separate during meiosis.) Down Syndrome in
humans is caused by the presence of an extra
21st chromosome. Other chromosome mutations may
be caused by deletion, translocation, inversion,
and duplication of parts of the whole
chromosome.
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DNA RNA The Nucleic Acids
Four Types of Mutations 1. Deletion mutation-
a piece of chromosome breaks off
completely. The new cell will lack a certain
set of genes. Often this is fatal
to the zygote. 2. Duplication mutation- a
chromosome fragment attaches to its homologous
chromosome, which then carry two copies of a
certain set of genes.

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Deletion Mutation
Duplication Mutation
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3. Inversion mutation- the chromosome piece
reattaches to the original chromosome but in a
reverse position. 4. If the piece reattaches to
a nonhomologous chromosome a translocation
mutation results.
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Inverse Mutation
Translocation Mutation
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DNA RNA The Nucleic Acids

• Mutations
• Gene mutationinvolves a change in the chemical
  makeup of the DNA. This is where one or more DNA
  nucleotides are deleted or substituted with
  others. These are called point mutations.
• Frame shiftare mutations that change one or
  just a few nucleotides in a gene on a chromosome.
• Example sickle cell anemia and cystic
  fibrosis

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• Occasionally random gene mutations produce
  changes that make the individual better adapted
  to the environment. Such mutated genes tend to
  increase in frequency with in a population.

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DNA RNA The Nucleic Acids
Mutations 3. Mutagens increase the incidence of
mutation.
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DNA RNA The Nucleic Acids

• Mutations
• Mutagen mutation increase the incidence of
  mutation.
• Examples of these
• Xrays
• Ultraviolet rays
• Radioactive substances
• Chemicals
• Nicotine
• Alcohol