DNA, RNA, and Protein Synthesis
http://www.3dscience.com/3D_Models/Biology/DNA/DNA_with_Phosphate.php
CHAPTER 10
DNA, RNA, and Protein Synthesis
Section 1 Vocabulary Pretest
1. Virulent
2. Transformation
3. Bacteriophage
A.
B.
C.
Viruses that infect bacteria
Transfer of DNA fragments from cell to cell
Virus capable of causing disease
Answer key
1. Virulent
2. Transformation
3. Bacteriophage
C
B
A
Discovery of DNA
Three experiments led to the discovery of DNA as the hereditary factor that Mendel described in his experiments with pea plants.
Griffith’s Experiment (1928)—showed that hereditary material can pass from one bacterial cell to another
(transformation)
Avery’s Experiment (1940s)—showed that DNA is the hereditary material that transfers information between bacterial cells.
Hershey and Chase’s Experiment (1952)– confirmed that DNA, and not protein, is the hereditary material in all cells.
Section 2 Vocabulary Pretest
3.
4.
1.
2.
5.
6.
7.
8.
Nucleotide
Deoxyribose
Nitrogenous base
Purine
Pyrimidine
Base-pairing rules
Complementary base pair
Base sequence
A.
B.
C.
D.
E.
F.
G.
H.
Sugar found in DNA
Consists of a sugar, phosphate and nitrogenous base
Single ring nitrogenous base pair
Double ring nitrogenous base pair
Rule stating: A always pairs w/ T and C always pairs w/ G
Order of bases on an DNA strand
Contains nitrogen and carbon atoms and is found on the rungs of a DNA ladder
A and T C and G
Answer Key
5.
6.
3.
4.
7.
8.
1.
2.
Nucleotide
Deoxyribose
Nitrogenous base
Purine
Pyrimidine
Base-pairing rules
Complementary base pair
Base sequence
E
H
F
G
D
B
A
C
DNA Structure
By 1950, we knew DNA was the hereditary molecule.
How did it work? How did it replicate, store and transmit hereditary information and direct cell function?
The answer is found in the unique structure of DNA.
http://www.med.unc.edu/pmbb/DNA_Day/mission.html
http://svhs.ucps.k12.nc.us/academics/science.php
The structure of DNA was discovered in 1953 by
James Watson and Francis Crick .
Deoxyribonucleic Acid
Described as a double helix
(twisted ladder).
Formed by two long strands of repeating subunits called nucleotides .
http://www.biologyjunction.com/nucleotide_model_preap.htm
http://www.biojobblog.com/tags/dna/
http://www.biologyjunction.com/nucleotide_model_preap.htm
Each nucleotide has three parts:
Five-carbon sugar called deoxyribose
Phosphate group
(phosphorous bonded to 4 oxygens)
Nitrogenous base
(either adenine, thymine, guanine or cytosine) http://asm.wku.edu/pix/pix.htm
The sides of the ladder are formed by covalently bonding the sugar of one nucleotide to the phosphate of another.
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/dna-structure.html
Sugar
Phosphate
Covalent bond
The nitrogenous bases form the rungs of the ladder .
There are four types of nitrogen bases:
Thymine
Cytosine
Adenine
Guanine http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg4.html
Adenine and Guanine have a double ring of carbon and nitrogen atoms and are called purines .
Thymine and Cytosine have a single ring of carbon atoms and nitrogen atoms. They are called pyrimidines http://blog.dearbornschools.org/biologyblog/2010/02/09/february-9-2010/
The bases pair together to form the rungs of the DNA ladder.
Hydrogen bonds hold them together.
They always pair according to the following basepairing rules discovered by Erwin Chargaff in 1949:
A – T
C – G
Note : since this pairing guarantees that a purine always pairs with a pyrimidine, the rungs are always the same length
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/molecular%20biology/dsDNA.jpg
The base pairs of A/T and C/G are called complementary base pairs .
The order of base pairs on a chain of DNA is called its base sequence .
Because of its base pairing pattern, one strand of DNA can serve as a template for making a new complementary strand.
This is how DNA replicates itself .
A strand of DNA has the following sequence:
C T G G A C
What is the sequence of the complementary strand?
G A C C T G http://www.fhcrc.org/education/courses/cancer_course/basic/img/dna.gif
Section 3 Vocabulary Pretest
3.
4.
5.
1.
2.
6.
DNA replication
Helicase
Replication fork
DNA polymerase
Semi-conservative replication
Mutation
E.
F.
A.
B.
C.
D.
A change in a nucleotide sequence of DNA
Enzyme that separates two strands of DNA
Enzyme that adds nucleotide bases to copying strands of DNA
Point where two DNA strands separate
Process of copying DNA
DNA replication that results in one old and one new strand in each copied molecule
Answer Key
1.
2.
3.
4.
5.
6.
DNA replication
Helicase
Replication fork
DNA polymerase
Semi-conservative replication F
Mutation A
E
B
D
C
DNA Replication
DNA replication is the process by which DNA is copied in a cell before a cell divides by mitosis, meiosis, or binary fission.
Steps:
Helicases (enzymes) separate the DNA strands by breaking hydrogen bonds between base pairs. This creates an open area of DNA called a replication fork .
http://www.nvo.com/jin/nss-folder/scrapbookcell/DNA%20Replication.jpg
DNA polymerases (more enzymes) add complementary nucleotides to each of the original sides. Notice that synthesis on each strand moves in opposite directions.
DNA polymerase enzymes fall off and the two new strands completely separate.
An enzyme called
DNA ligase must fill in gaps created on the strand being copied in the opposite direction.
The end result is two new identical strands of DNA.
This type of replication is called semi-conservative replication because each of the new DNA molecules has kept (or conserved) one of the two (or semi) original DNA strands.
http://jc-biology.blogspot.com/2011/02/replication-of-dna-summary.html
Speed of Replication
DNA adds nucleotides at a rate of 50 per second.
However, at this rate it would take 53 days to replicate a large human chromosome.
Therefore, replication must begin at several, usually thousands, of different points, or origins , at the same time.
Mutations
Any change in the nucleotide sequence of a DNA molecule is called a mutation .
DNA polymerase can check and correct mistakes made during replication.
However, mistakes do happen.
Mistakes can be spontaneous or caused by environmental factors (radiation, chemicals, etc.)
Mutations can be helpful, harmful or harmless.
Mistakes made in genes that control cell division can lead to tumors .
Section 4 Vocabulary Pretest
5.
6.
3.
4.
7.
1.
2.
Ribonucleic acid
Transcription
Translation
Protein synthesis
Ribose
Messenger RNA
Transfer RNA
B.
C.
A.
D.
E.
F.
G.
Nucleic acid important in protein synthesis
Sugar found in RNA
RNA that carries instructions from the nucleus to ribosomes
Process of making an RNA molecule from a DNA template
RNA that assembles an amino acid chain
Process of assembling a protein from a coded RNA message
DNA RNA protein
Pretest continued
11.
12.
13.
14.
8.
9.
10.
RNA polymerase
Promoter
Termination signal
Genetic code
Codon
Anticodon
Genome
H.
I.
J.
K.
L.
M.
N.
An organism’s entire gene sequence
Sequence of nucleotides at the end of a gene
Sequence of nucleotides that start transcription
3-nucleotide sequence on mRNA that encodes an amino acid
3-nucleotide sequence on tRNA that complements a codon
Specifies the amino acid sequence of a protein
Enzyme that catalyzes the formation of RNA
Answer Key
6.
7.
4.
5.
1.
2.
3.
Ribonucleic acid A
Transcription D
Translation F
Protein synthesis G
Ribose B
Messenger RNA C
Transfer RNA E
8.
9.
10.
11.
12.
13.
14.
RNA polymerase N
Promoter J
Termination signal I
Genetic code M
Codon
Anticodon
Genome
K
L
H
Protein Synthesis (Big Picture)
Cells make proteins .
The instructions to make a protein are on the DNA in the nucleus.
Ribosomes in the cytoplasm make the proteins
Cells MUST be able to get the instructions from the
DNA inside the nucleus out to the ribosomes.
RNA is the messenger !!!
http://www.sciencephoto.com/images/download_lo_res.html?id=670020523
RNA Structure and Function
RNA is different from
DNA in 4 ways
RNA sugar is ribose
Uracil replaces thymine as a base
RNA is single stranded
RNA is shorter than DNA
DNA vs. RNA
DNA RNA
Double Single
Deoxyribose Ribose
Thymine
Longer
Uracil
Shorter
Types of RNA
Three major types of RNA
Messenger RNA (mRNA ) —carries instructions for making a protein from a gene in the nucleus to a ribosome in the cytoplasm
Ribosomal RNA (rRNA) —part of a ribosome
Transfer RNA (tRNA) —transfers amino acids to the ribosome to make a protein.
mRNA is made from
DNA in the nucleus. It carries the message for making a protein out of the nucleus to a ribosome in the cytoplasm rRNA is part of the ribosome.
tRNA is folded with many nucleotide bases. However, we emphasize the three at the bottom.
Protein Synthesis
Forming proteins based on information in DNA and carried out by RNA is called protein synthesis .
DNA RNA protein
It involves two processes:
Transcription
Translation
Transcription
Transcription —the genetic code is copied or
“transcribed” onto a mRNA in the cell nucleus.
Three steps:
RNA polymerase (enzyme) binds to a specific site on a
DNA molecule called a promoter . This causes DNA to unwind.
RNA polymerase uses the base-pairing rules to add the
RNA nucleotides that match the DNA code ( A/U; C/G )
RNA polymerase stops at a termination signal that marks the end of a gene.
Transcription
http://meyerbio1b.wikispaces.com/Transcription+and+Translation
Reading the Code
The code on the mRNA must next be “read” during the process of translation.
This genetic code tells us how a sequence of bases on a DNA molecule (or its RNA messenger) corresponds to a particular amino acid .
The code is read three bases at a time . Each 3 base sequence that codes for an amino acid is called a codon .
Codons in mRNA
Notice AUG is the start codon
UAA , UAG , and UGA are the stop codons.
Amino Acids
The genetic code rules are the same for nearly all living things.
The same codons always code for the same amino acids.
There are 20 different amino acids .
A chain of amino acids makes up a polypeptide .
Polypeptides join and twist to make up proteins .
It is tRNA and the ribosomes that assemble the proteins during translation.
Three bases at one end of a tRNA are complementary to a codon on the mRNA.
They are called an anticodon .
The specific amino acid that the codon codes for is attached to the top of the tRNA
A U G G G A C C U http://www.personal.psu.edu/staff/d/r/drs18/bisciImages/index.html
Translation
Translation —the making of a protein
Steps:
Initiation —ribosomal subunits, mRNA and the tRNA carrying methionine (amino acid of the start signal
AUG) bind together.
Elongation —the tRNA carrying the amino acid specified by the next codon binds. Peptide bonds form between the amino acids beginning the chain. This continues until a termination signal is reached.
Termination —stop codon is reached
Disassembly – the ribosome complex falls apart and the peptide is released.
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookprotsyn.html
Recap: Protein Synthesis: Big Picture
The Human Genome
Genome —the complete genetic material contained in an individual.
The entire Human Genome consists of 3.2 billion base pairs . We now know the order of these base pairs and have discovered that humans have approximately 30,000 genes .
We now need to learn where and when human cells use each of the proteins coded for in the genome.
This can help diagnose, treat, and prevent many genetic disorders.
