Biology Chapter 13
What happens to the tRNA that was attached to the first amino acid? (this question may be worded weirdly and not actually be helpful to find the answer at all)
That tRNA then moves into a third binding site, from which it exits the ribosome.
How do the locations of DNA and RNA differ?
The DNA molecule stays safely in the cell's nucleus, while RNA molecules go to the protein-building sites in the cytoplasm ((aka the RIBOSOMES.))
What serves as the start codon for protein synthesis?
The METHIONINE codon AUG serves as the start codon for protein synthesis.
What are introns and what is another name for them?
-Portions cut out of mRNA -aka intervening sequences
What is rRNA? (2)
-Proteins are assembled on ribosomes, small organelles composed of two subunits. -These ribosome subunits are made up of several ribosomal RNA molecules and proteins.
What are promoters? (2)
-Regions of DNA that have specific base sequences. -Promoters are signals in the DNA molecule that show RNA polymerase exactly where to begin making mRNA.
How does RNA structure differ from DNA structure? (3)
1. The sugar in RNA is ribose instead of deoxyribose. 2. RNA is generally single-stranded and not double-stranded 3. RNA contains uracil in place of thymine.
What do rRNA molecules help do? (2)
-They help hold ribosomal proteins in place and help locate the beginning of the mRNA message. -They may even carry out the chemical reaction that joins amino acids together.
What are the two basic types/categories of mutations? (2)
-Those that produce changes in a single gene are known as gene mutations, specifically called point mutations. -Those that produce changes in whole chromosomes are known as chromosomal mutations.
Despite their enormous diversity in form and function, ...
...living organisms display remarkable unity at life's most basic level, the molecular biology of the gene.
If a gene in one cell is altered...
...the alteration can be passed on to every other cell that develops from the original one.
Although some organisms show slight variations in the amino acids assigned to particular codons,
...the code is always read three bases at a time and in the same direction.
A gene that codes for an enzyme to produce pigment can control...
...the color of a flower.
Another gene produces proteins that regulate patterns of...
...tissue growth in a leaf.
How many different amino acids are commonly found in polypeptides?
20
What does a codon consist of?
A codon consists of three consecutive bases that specify a single amino acid to be added to the polypeptide chain.
What is each three-letter "word" in mRNA known as?
A codon.
If the next codon is UUC, a tRNA molecule with an ___ anticodon brings the amino acid phenylalanine into the ribosome.
AAG
The tRNA molecule for methionine has the anticodon UAC, which pairs with the methionine codon, which is...
AUG
At the same time as the ribosomes forming a peptide bond, what is happening?
At the same time, the bond holding the first tRNA molecule to its amino acid is broken.
DNA carries information for what?
DNA carries information for specifying the traits of an organism.
What are examples of chromosomal mutations? (4)
Deletion Duplication Inversion Translocation
What may mRNA molecules require?
EDITING
What does each tRNA molecule carry?
Each tRNA molecule carries just one kind of amino acid.
Each tRNA molecule has three unpaired bases, which is collectively called what?
Each tRNA molecule has three unpaired bases, collectively called the anticodon, which is complementary to one mRNA codon.
What are the remaining pieces called?
Exons, or expressing sequences
What happens after the start codon?
Following the start codon, mRNA is read, three bases at a time, until it reaches one of three different stop codons, which ends translation.
What is an example of a beneficial effect of mutations?
For example, mutations have helped many insects resist chemical pesticides.
What can frameshift mutations change?
Frameshift mutations can change every amino acid that follows the point of the mutation and can alter a protein so much that it is unable to perform its normal functions.
What is gene expression?
Gene expression is the way in which DNA, RNA, and proteins are involved in putting genetic information into action in living cells.
What do genes contain?
Genes contain coded DNA instructions that tell cells how to build proteins.
What is one of the most interesting discoveries of molecular biology?
One of the most interesting discoveries of molecular biology is the near-universal nature of the genetic code.
RNA polymerase only binds to _________.
Promoters
Where does transcription and translation take place in prokaryotes?
In prokaryotes, both transcription and translation take place in the cytoplasm.
How does the cell make mRNA?
In transcription, segments of DNA serve as a template to produce complementary mRNA molecules.
What is another name for insertions and deletions?
Insertions and deletions are also called FRAMESHIFT MUTATIONS because they shift the "reading frame" of the genetic message.
What happens in insertions and deletions?
Insertions and deletions are point mutations in which one base is inserted or removed from the DNA sequence.
What may introns and exons have a role in?
Introns and exons may also place a role in evolution, making it possible for very small changes in DNA sequences to have dramatic effects on how genes affect cellular function.
Where are introns when they are taken out of pre-mRNA?
Introns are taken out of pre-mRNA when they are still in the nucleus.
What happens as the ribosome reads each codon of mRNA?
It directs tRNA to bring the specified amino acid into the ribosome.
After mRNA is transcribed in the nucleus, where does it go?
It enters the cytoplasm for translation.
What may some pre-mRNA molecules be able to do?
Some pre-mRNA molecules may be cut and spliced in different ways in different tissues, making it possible for a single gene to produce several different forms of mRNA.
What are examples of gene/point mutations? (3)
Substitution insertion deletion
What do substitutions affect?
Substitutions usually affect no more than a single amino acid, and sometimes they have no effect at all.
Many proteins are ENZYMES, which do what?
Many proteins are enzymes, which catalyze and regulate chemical reactions.
What does mRNA stand for?
Messenger RNA
What do most genes contain?
Most genes contain instructions for assembling proteins.
What are mutations?
Mutations are heritable changes in genetic information.
Why are mutations often thought of as harmful?
Mutations are often thought of as harmful because they disrupt the normal function of genes.
What do mutations often produce?
Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.
Why are point mutations called this?
Mutations that involve changes in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence occurring during replication.
How are amino acids attached to the growing chain?
One at a time, the ribosome attaches each amino acid to the growing chain.
What happens in substitution?
One base is changed to a different base.
How are proteins made?
Proteins are made by joining amino acids together into long chains, called POLYPEPTIDES.
What are proteins specifically designed to do?
Proteins are microscopic tools, each especially designed to build or operate a component of a living cell.
What do proteins play a role in?
Proteins, in turn, play a key role in producing an organism's traits.
What does the genetic code have?
Punctuation marks
What does RNA control?
RNA controls the assembly of amino acids in proteins.
What is RNA in relation to DNA?
RNA is a disposable copy of a segment of DNA, a working copy of a single gene.
What enzyme does transcription require?
RNA polymerase
What does RNA polymerase do?
RNA polymerase binds to DNA during transcription and separates the DNA strands.
What does RNA polymerase do after it separates the DNA strands?
RNA polymerase then uses one strand of DNA as a template to assemble nucleotides into a complementary strand of mRNA.
What does RNA use the base sequence copied from DNA to do?
RNA uses the base sequence copied from DNA to direct the production of proteins.
How is the structure of RNA similar to DNA?
RNA, like DNA, is a nucleic acid that consists of a long chain of nucleotides.
What does rRNA stand for?
Ribosomal RNA
What role does the ribosome play in assembling proteins?
Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.
What is sickle cell disease?
Sickle cell disease changes the shape of red blood cells. Normal red blood cells are round. Sickle cells appear long and pointed.
What is sickle cell disease cased by?
Sickle cell disease is caused by a point mutation in one of the polypeptides found in hemoglobin, the blood's principle oxygen-carrying protein.
What are signals similar to promoters in DNA do?
Similar signals in DNA cause transcription to stop when a new mRNA molecule is completed.
What does the cell use as a template for making RNA?
The cell uses the sequences of bases in DNA as a template for making mRNA.
What is the "central dogma" of molecular biology?
The central dogma of molecular biology is that information is transferred from DNA TO RNA TO PROTEIN.
What do the codons of mRNA specify for?
The codons of mRNA specify the sequence of amino acids in a protein.
What is translation?
The decoding of an mRNA message into a protein.
How do mutations affect genes?
The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene function.
What happen to the exons after the introns are removed?
The exons are then spliced back together to form the final mRNA.
What is the first step in decoding genetic messages?
The first step in decoding genetic messages is to transcribe a nucleotide base sequence from DNA to mRNA. This is called transcription.
What is the first step in decoding these genetic instructions?
The first step in decoding these genetic instructions is to copy part of the base sequence from DNA into RNA.
How is the genetic code read?
The genetic code is read as three "letters" at a time, so that each "word" is three bases long and corresponds to a single amino acid.
How does this process of translation continue?
The polypeptide chain continues to grow until the ribosome reaches a "stop" codon on the mRNA molecule.
What does the ribosome help form?
The ribosome helps form a peptide bond between the first and second amino acids.
When the ribosome moves to the third codon, what happens?
The ribosome then moves to the third codon, where tRNA brings it the amino acid specified by the third codon.
What determines the function of the amino acids?
The sequence of amino acids influences the SHAPE OF THE PROTEIN, which in turn determines its function.
What determines the properties of different proteins?
The specific amino acids in a polypeptide, and the order in which they are joined, determine the properties of different proteins.
How many binding sites are in a ribosome for a tRNA molecule?
There are two binding sites in a ribosome, meaning that 2 codons, aka 6 nucleotides, can fit in one ribosome.
What does this transcribed information contain?
This transcribed information contains a code for making proteins.
What is mRNA's job?
To carry DNA information to ribosomes.
Where does transcription and translation take place in eukaryotes?
Transcription: Nucleus Translation: Cytoplasm
What is another name for transcription and translation?
Transcription: mRNA synthesis Translation: protein synthesis
What does tRNA stand for?
Transfer RNA
When does translation begin?
Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm.
What is tRNA's job?
When a protein is built, a tRNA molecule transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA.
What happens when the ribosome reaches a stop codon?
When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation.
What depends on whether a mutation is helpful or harmful?
Whether a mutation is helpful or harmful depends on how its DNA changes relative to the organism's situation.
Without mutations, what couldn't organisms do and what?
Without mutations, organisms cannot evolve, because mutations are the source of genetic variability in a species.
Use chapter 11 notes as a reference for chromosomal mutations.
Yo
point mutations on p. 373
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