Studied by 69 people
DNA contains the information to _______?
Build proteins
Proteins are needed for __________?
Structure, function, and regulation of the body.
Steps of Central Dogma?
1. DNA Replication
2. Transcription: Converts the DNA into a mRNA (message)
3. Translation: Interprets an RNA message into a string of amino acids, called a polypeptide, which makes up a protein.
In transcription RNA (Ribonucleic acid) acts as a __________?
Middleman between DNA and protein synthesis.
What is RNA?
A chain of nucleotides, each made of a sugar, a phosphate group, and a nitrogen base.
RNA differs from DNA in three major ways?
RNA has a ribose sugar.
RNA has uracil instead of thymine. ( A pairs with U)
RNA is a single-stranded structure. (This single stranded structure allows some types of RNA to form complex 3D shapes, and as a result, some RNA molecules can catalyze reactions much as enzymes do.)
Additionally, DNA codes for proteins, while RNA makes proteins.
Transcription/where
Nucleus
Transcription/purpose
Copy a sequence of DNA to produce a complementary strand of RNA.
Transcription/definition
Process of copying a sequence of DNA to produce a complementary strand of RNA.
RNA polymerase/definition
Enzymes that bond nucleotides together in a chain to make a new RNA molecule.
RNA polymerase moves in a ____________?
5'-3' direction
RNA polymerase also unwinds and unbinds the __________?
DNA double helix
RNA polymerase adds nucleotides to a new strand of _________?
RNA
Transcription produces three major types of RNA molecules?
mRNA
rRNA
tRNA
mRNA?
Intermediate message that is translated to form a protein.
rRNA?
Forms part of ribosomes, a cell’s protein factories.
tRNA?
Brings amino acids from the cytoplasm to a ribosome to help make the growing protein.
Steps in transcription?
1. INITIATION
2. ELONGATION
3. TERMINATION
(Honors) Initiation: TATA Box -
Promoter Sequence
(Honors) RNA polymerase binds to a region of a gene called the_________?
Promoter
(Honors) Promoter/Definition?
A segment of DNA that allows a gene to be found and transcribed
(Honors) The promoter tells the RNA polymerase where on the DNA to begin______?
Transcribing
A TATAA box is?
A DNA sequence that indicates where a genetic sequence can be read and decoded. It is a type of promoter sequence, which specifies to other molecules where transcription begins.
Elongation?
Using the DNA strand as a template the RNA polymerase makes a complementary strand of RNA.
Elongation is the stage when the RNA strand gets longer, thanks to the addition of new nucleotides.
Termination?
After a gene has been transcribed, RNA polymerase will encounter a terminator sequence and the RNA strand will be released.
Termination/ End result
mRNA
Before the mRNA can leave the nucleus and be used it needs to be edited (mRNA splicing).
(Honors) Pre-mRNA Splicing?
RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns (non-coding regions of RNA) and splicing back together exons (coding regions).
mRNA must be processed before leaving the nucleus.
(Honors) mRNA Splicing process?
Exons are nucleotide segments that code for parts of the protein.
Introns are non-coding nucleotide segments that intervene, or occur, between exons.
5' cap tail is added which helps preserve the mRNA and helps ribosomes bind to it.
Poly-A tail is added to help the mRNA leave the nucleus.
(Honors) 1.3' poly-A tail protects _________?
Protects mRNA from degradation
Aids in exporting the mature mRNA to the cytoplasm.
Involved in binding proteins to initiate translation.
(Honors) The 5' cap protects the __________?
newly-synthesized mRNA from degradation.
It also assists in ribosome binding to help initiating translation.
Translation/Definition
The process which translates an mRNA message into a polypeptide chain (protein).
Translation/Where
Cytoplasm
Primary?
Amino acid sequence
Secondary structure?
Alpha helix, beta sheet and loops
Tertiary?
Phi-Psi angle
Quaternary?
Arrangement of several Polypeptide chains
The human genetic code only directly encodes _______?
20 amino acids
Codon/definition
A sequence of 3 nucleotides that codes for an amino acid
The genetic code matches each mRNA codon with its _________?
Amino acid or function
The first two letters are the most important in coding for ____________?
Amino acids
Stop codons/definition
Signal the end of an amino acid chain.
Stop codons?
UAA,UGA, and UAG
Start codons/definition
Signals the start of translation. AUG which codes for methionine is the start codon.
Reading frame
It's crucial that the mRNA is read correctly.
A misread mRNA could change the protein completely.
Could lead to mutations.
In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.
Where these triplets equate to amino acids or stop signals during translation, they are called codons.
Universal Language
The genetic code is shared by almost all living organisms.
Codons are said to be universal throughout all living organisms. This allows crossing species and genetic modification.
The genetic code is universal means the same codons code for the same amino acids in all forms of life that exists today.
How to read the mRNA?
The mRNA is read by a ribosomal subunit (rRNA) and a transfer RNA (tRNA).
The rRNA is composed of 2 subunits a large and small, together they pull the mRNA through reading one codon at a time.
The large subunit holds onto the growing protein chain, while the small subunit holds onto the mRNA.
tRNA carry free-floating amino acids from the cytoplasm to the ribosome.
It's L shaped, (tRNA) one side has an amino acid attached; the other has a code called the anticodon.
The anticodon is a set of three nucleotides complementary to the mRNA.
mRNA: GGG
tRNA: CCC (this is the anticodon for GGG)
Ribosome
Large Subunit
Binding sites
Small subunit binds to mRNA
tRNA
Amino acid
Anti-codon
What happens when proteins fail to work?
When dietary protein is in short supply, the body tends to take protein from skeletal muscles to preserve more important tissues and body functions. As a result, lack of protein leads to muscle wasting over time.
The skin might also be affected—proteins enable skin regeneration, and if they do not work adequately, the skin might become dry and cracked.
Mutation/definition
DNA change
Mutations can affect a __________?
single gene or an entire chromosome.
Mutations can be good, bad, or neither.
Proteopathy?
The condition when proteins fail to work.
Point mutations/ Definition
Substitute one nucleotide for another. This means that an incorrect nucleotide is put in the place of the correct nucleotide.
Sickle Cell anemia/ Definition
Instead of coding for Glutamic acids, Valine is coded for when making the hemoglobin protein.
Examples of Gene mutations?
Cystic Fibrosis Tay-Sachs Cancer
Silent Mutation:
Silent mutations are mutations in DNA that do not have an observable effect on the organism's phenotype.
Missense Mutation:
A missense mutation is a mistake in the DNA which results in the wrong amino acid being incorporated into a protein because of change, that single DNA sequence change, results in a different amino acid codon which the ribosome recognizes.
Nonsense Mutation
A nonsense mutation, or its synonym, a stop mutation, is a change in DNA that causes a protein to terminate or end its translation earlier than expected.
Frameshift mutations:
Delete/insert nucleotides that don't belong
Frameshift mutations/ examples
Ex. THE CAT ATE THE RAT, delete the first E
THC ATA TET HER AT
Ex. THE CAT ATE THE RAT
Insert an extra C
THE CCA TAT ETH ERA T
Insertion mutation examples:
Fragile X Syndrome
Huntington's disease
Deletion mutation examples:
Cri du Chat
Male infertility
Prader Willi syndrome
Chromosomal mutations:
Changes in structure or number of chromosomes.
a.Duplication:
One chromosome may have two copies of a gene(s).
b.Translocation:
A piece of one chromosome moves to a non-homologous chromosome
Duplications and Translocations occur in _________?
germ cells during Prophase I of meiosis.
Duplication/ examples
Klinefelter syndrome
XXY syndrome
Affects men only
Translocation/ example
Down syndrome
Edwards syndrome
Not all mutations have an effect on an _________?
Organisms phenotype
Mutations that do not affect a resulting protein are called ___________?
silent mutations
Mutations can occur in all types of cells, but ________?
to affect an offspring it has to occur in germ cells (gametes).
Mutagens/ defintion
Agents in the environment that can change DNA.
ndustrial chemicals
They can speed up replication rate or break DNA strands.
Some mutagens occur naturally. Ex. : UV rays from sunlight, pesticides, nicotine, bacteria, viruses, etc...
Note 
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