Module 5 obj 11
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what makes up Genetic code?
- A way for the cell to match the mRNA code to Amino acids
- Translation matches the mRNA "words" (sequence of bases) to the protein "words" (primary sequence of protein)
- There are 4 bases in mRNA (A,C,G,U) but 20 amino acids
- -4 bases taken one at a time can code 4 amino acids
- -4 bases taken two at a time can code for 16(=4x4)amino acids
- -4 bases taken three ata time can code for 64(=4x4x4) amino acids.
Define genetic Code
The three base sequence representing each amino acid
Because each three-base sequence in mRNA exactly matches a three base sequence in ___________, the correct amino acid sis brought to the __________ and the correct primary protein sequence is created.
True or False: There are more possible codes than there are amino acids to encode.
What allows us to use multiple combinations to code for the same amino acid?
There are more possible codes than there are amino acids to encode.
What is the Rossetta Stone of Molecular Biology?
The genetic code, as represented in the codon table.
What is the Codon Table used for?
- This is the code used to convert mRNA message to amino acid sequence
- For examople, AUG means "start"(Methionine)
- UAA, UAG, UGA mean "stop", GGG means "glycine"
What is the start codon?
- Protein synthesis always starts with AUG (codes for metnionin)
- if the final protein does not need methionine in this position, then it is cleaved away after the protein chain is made.
What are Stop Codons?
- Protein Synthesis ends with either UAA, UAG, or UGA
- Each has its own name: UAA-ochre; UAG-umber; UGA-amber.
- These names are fruit fly eye colors becuaes fruit flys were fuit flys were andimportant part of genetic research for many years
What is a Gene Polymorphism ?
- A change in the sequence of DNA which then results in a chasnge in the sequenc4 of mRNA is a gene polymorphism
- Most are silent, that is, they don't change the primary protein sequence
- Some polymorphisms cause noticeable changes in the organism; these are called Mutations
when do Mutations occur?
If the change in DNA(and RNA) results in a change in the amino acid sequence, which then changes the functino of the resulting protein.
What is a reading frame?
- The Codons are read in three letter combinations
- -e.g. CAT CAT CAT CAT
What are the Types of Mutations?
- Point Mutaions do not change the reading frame
- -these change only a soinge base (CAA CAT CAT CAT)
- -sometimes these do not change the protein sequences (silent mutations)
- -sometimes these do change the protein sequence
- --missense mutations: change one amino acid to another
- --nonsense mutations: change codon that codes for an amino acid to stop codon, resulting in abnormally short protein
- Frame shift Mutations change the reading frame
What is a Frameshift mutation?
If we intoduce a mutation after the start codon, that either adds or sbtracts a base, the entire frame is shifted so that all amino acids down stream from the mutation are wrong.
What type of mutation produces the disease Sickle-cell anemia?
Point mutation-only one codon ois altered (GAG mutated to GTG in DNA, GUG in RNA
List two types of Framshift mutations
- Deletion mutation- one base removed
- (CAT C(A)TC ATC ATC)
- Insertion mutatin- one base added
- (CAT CCA TCA TCA)
Which is more stable DNA or RNA?
What is RNA polymerase ?
The enzyme that forms RNA polymers
_________ is unstable and only exists long enough to make __________, then it is destroyed.
What are the different forms of RNA and what roles do they play in protein synthesis?
- messenger RNA (mRNA)
- -very unstable, allows for transcriptional control of protein production
- -made from a DNA template inside the nucleus
- -made by RNA polymerase II
- ribosomal RNA (rRNA)
- -more stable (mostly) made by RNA polymerase I
- -made ina structure inside the nucleus called the nucleolus
- transfer RNA (tRNA)
- -also stable, made by RNA polymerase III
- Messages are destroyed immediately after they are used;
- this allows the cell to change its protein composition dynamically by changing how much message is made.
True or false: rRNA componenst of a ribosome are (rarely) made in a stucture within the nucleaus called a nucleolus
False, they are mostly made in the nucleolus
In th cytoplasm rRNA and proteins are assembled into ____________.
Ribosomes either exists as free ribosomes or as part of the ______ ________ _________.
What type of RNA acts as a fleet trucks bringing raw materiel to a factory?
What is packed into chromosomes during cell division?
What do chromosomes consist of ?
- Two idendtical halves called chromatids
- Each is a single, continuous DNA molecule
- chromosomes are only visible during mitosis
- but the DNA is always there
- DNA packaged with histone proteins
- -DNacid: negative charge
- -Histones: positive charge to neutralize elctrical charge of DNA, alows tighter packing
What is the difference between Chromatin, Chromosomes, and Chromatids?
- Chromatin: DNA strand
- Chromosomes: visible packaging of DNA and histoness into X-shaped structure
- Chromatids: two idendical halfs of the chromosome, joined at centromere
- -recall thtat the mitotic spindles attach at the centromere and tears the two chromatids apart
- each chromatid is one continuous DNA molecule
What is the Centromere?
the point inwhich the two chromatids of a chromosome are attached together.
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