Transcript DNA - Ms. Cardoza's Biology Class

Bellwork
 What are the three parts of a DNA
nucleotide?
 What would the complementary strand
of DNA look like (nitrogen bases)?
A T G C C G T T A A C G
 What would the complementary
mRNA strand look like?
DNA Structure
 Double Helix.
 made up of millions of tiny subunits called
Nucleotides.
Phosphate group
2. Pentose sugar
1.
1.
Phosphate
Nitrogenous
Base
(deoxyribose)
3. Nitrogenous base
Pentose
Sugar
Nucleotides
 Phosphate and sugar backbone
 the nitrogen bases form the “rungs”.
 There are four types of nitrogenous bases.
Nucleotides
 Each base will only bond with one other
specific base (Chargaff’s Rule, or Base-Pair Rule).
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
Form a base pair.
Form a base pair.
 Complementary
base pairing:
 the order of the
bases in one
strand
determines the
order of the
bases in the
other strand.
A
T
C
G
T
A
C
G
A
T
G
C
T
A
Agenda 12/19- Protein Synthesis
 Bellwork
 Essential Question: How does DNA code for
proteins? How does DNA determine the
structure and function of an organism?
 New information: Protein synthesis
(transcription and translation)
 Activity: Protein Synthesis practice worksheet
in pairs
DNA
Gene
Trait
Protein
Protein Synthesis Overview
•DNA is the genetic material
within the nucleus.
DNA
• Transcription creates an
mRNA using DNA information.
Transcription
RNA
•Translation creates a
protein using RNA information.
Translation
Nucleus
Protein
Cytoplasm
Protein Synthesis Overview
•Sections of DNA that code for
proteins are called GENES.
A Gene
• GENES determine what
proteins are made and
therefore what traits an
organism has.
DNA
Transcription
RNA
• A gene does not build proteins
directly. It sends instructions in
the form of mRNA which directs
protein synthesis.
Nucleus
Translation
Protein
Cytoplasm
Two Types of Nucleic Acids
RNA
Number of
strands
Usually single-stranded Usually double-stranded
Nitrogen Bases URACIL (instead of T),
Pentose Sugar
Codes for…
DNA
A, C, and G
THYMINE (instead of U),
A, C, and G
Ribose
Deoxyribose
Codes for proteins
Codes for RNA
Two types of nucleic acids
# of strands
kind of sugar
bases used
Types of RNA
 mRNA = messenger RNA
 Made during transcription
 Carries a complementary copy of the DNA code out of
the nucleus for protein synthesis on a ribosome
Types of RNA
 mRNA = messenger RNA
 tRNA = transfer RNA
 Transfers amino acids to the ribosome for protein
synthesis
 Found in the cytoplasm
 rRNA = ribosomal RNA
Transcription
 First the DNA is “unzipped”.
 Complementary RNA nucleotides are added to the
template strand, forming the new RNA molecule.
DNA coding strand
5’
3’
DNA
G T C A T T C G G
3’
G U C A U U C G G
3’
C A G T A A G C C
5’
DNA template strand
5’
RNA
TRANSCRIPTION
 RNA polymerase attaches
mRNA nucleotides to the DNA template:
 Guanine
to
Cytosine
 Cytosine
to
Guanine
 Adenine
to
Thymine
 Uracil
to
Adenine
 RNA polymerase cannot attach Thymine
3’
GUCAUUCGG
C AG T A AG C C
5
’
What happens after transcription?
 The new mRNA molecule (and DNA) has more
information than is required for making the
protein.
 The parts that aren’t directly needed for
making the protein are called INTRONSthey stay IN the nucleus.
What happens after transcription?
 The new mRNA molecule (and DNA) has more
information than is required for making the
protein.
 The parts that are needed for making the
protein are called EXONS- they EXit the
nucleus after being spliced together.
Translation
 The process of reading the RNA sequence of an
mRNA and creating the amino acid sequence of a
protein.
DNA
Transcription
T
T
C
A
G
T
C
A
G
A
A
G
U
C
A
G
U
C
DNA
template
strand
Messenger
RNA
mRNA
Codon
Codon
Codon
Translation
Protein
Lysine
Serine
Valine
Polypeptide
(amino acid
sequence)
Transcription
Translation
Protein Synthesis Overview
• Transcription creates mRNA
from DNA information- happens
in nucleus.
•Translation creates protein
using RNA information; happens
at a ribosome (in cytoplasm or
on rough ER).
DNA
Transcription
RNA
Translation
Nucleus
Protein
Cytoplasm
5 Minute Writing
 If one DNA strand has the nitrogen base sequence
below, what will the complementary strand look like?
 What will the mRNA produced during transcription
look like?
 What happens during the process of translation?
 AAG GCT TAT GCC CAT
Protein Synthesis Overview
•DNA is the genetic material
within the nucleus.
DNA
• Transcription creates an
mRNA using DNA information.
•Translation creates a
protein using RNA information.
Transcription
RNA
Translation
Nucleus
Protein
Cytoplasm
mRNA codons and the Amino Acids for which they code
Gene Mutations
the fat cat sat
 Point mutations: a single nucleotide is changed
 Substitution: Ex. F in “fat” is changed to an “e”:
 the eat cat sat
 Ex. Of a triplet sequence:
Gene Mutations
the fat cat sat
 Point mutations: a single nucleotide is changed
 Deletion: Ex. F in fat is deleted:
 the atc ats at
 Ex. Of a triplet sequence:

Frameshift mutation: caused by insertion or deletion
of fewer (or more) than 3 nucleotides; usually results
in all codons after that point being altered.
Gene Mutations
When the code is changed due to a mutation,
the amino acid sequence may be altered,
resulting in changes in the protein (or no
protein at all).
 Ex. Of a triplet sequence:

Substitution: Ex. F in “fat” is changed to an “e”:


the fat cat sat
the eat cat sat
Deletion: Ex. F in fat is deleted:

the atc ats at (frameshift mutation)