Molecular Genetics Flashcards
What is DNA ELI?
DNA is deoxyribonucleic acid, that is found in the nucleus as genetic material, and is carrier of genetic information.
Why is deoxyribonucleic acid important?
It codes instructions to make a protein.
What is the structure of DNA (generalized)
DNA is a double helix composed of two chains of complementary nucleotides.
What are the monomers?
THE MONOMERS ARE NUCLEOTIDES! They are the building blocks of nucleic acids.
What is a nucleotide made up of?
- P-group or phosphate group
- Pentose sugar (deoxiribose)
- base.
What are two main types of bases in nucleotides?
Two types of nucleotides bases are the following:
Purine (R)- It is composed of two rings: Guanine and Adenine
Pyrimidine(Y)- It is composed of ONE ring: Thymine Cytosine
What is the DNA structure composed of (detailed/in depth)?
2 antiparallel strands of nucleotides,
1.The BACKBONE is made of alternating phosphates and sugars which are held together by strong covalent bonds.
- Rungs are made up of bases which are held together by weak hydrogen bonds.
What is Chargaff’s base pairing rule?
The percent of purines = the percent of pyrimidines
What is DNA replication and when does it occur?
It is a process by which the DNA copies itself and it occurs during the S phase of Interphase in Mitosis and Meiosis.
What are the origins of replication?
The specific starting point where DNA replication begins.
What is the first step to DNA replication?
The first step is unwinding or UNZIPPING. The original DNA acts as the template and an enzyme called HELICASE, which breaks the h-bonds between nucleotides which frees them and creates a REPLICATION FORK.
However it needs another enzyme to kick start this reaction, and that is PRIMASE.
What is the second step?
Complementary base pairing
Both antiparallel strands are replicated. The leading strand, gets replicated smoothly because the polymerase follows the helicase from 5 prime to 3 prime and the bases get copied.
HOWEVER! The lagging strand is antiparallel and the polymerase can’t just “slide” its way through lagging strand since it is going in an opposite direction from five prime to three prime. SO it must copy one section at a time as more template is made available. THIS IS CALLED OKAZAKI FRAGMENTS. Ligase will make sure that everything is connected in the end. Therefore a polynucleotide is created.
Conclusion…
Helicase unwinds the helix and separates the strands
Primase “kick starts” the reaction, polymerase III copies each strand (continuously on lagging and okazaki fragments on lagging)
What is editase?
PROOFREADER THAT CORRECTS POLYMERASE MISTAKES!
Tell me about the Central Dogma.
DNA molecules hold the genetic instructions for genes, and each gene consists of about 1000 DNA base pairs which are instructions to produce a single protein. HOWEVER…
And Eli what about however???
DNA is too large and complex to leave the nucleus so it gets converted into messenger RNA which is then interpreted by the ribosome into an amino acid sequence (protein) this is known as the Central Dogma
What is RNA?
RNA or, Ribonucleic Acid, is a nucleic acid that is generally single stranded and plays a role in transferring DNA to PROTEIN FORMING SYSTEMS of the cell.
What are the three types of RNA?
Messenger RNA- Takes coded instruction from DNA to ribosome
Transfer RNA- Carries specific AA to ribosome.
Ribosomal RNA- Makes up Ribosome which makes the protein.
What Transcription?
The process by which messenger RNA is synthesized from a template of DNA.
Steps of Transcription please.
- Helicase binds to a specific sequence of the gene and with the help of proteins called transcription factors it unzips the two strands apart and this is called elongation.
- The two strands made is called the template strand, which is used to make the mRNA, and the non-template strand which will do nothing except connect to make the DNA again.
- In the template strand, an enzyme called RNA polymerase, doesn’t need a primer, it simply initiates mRNA at the promoter or the start point and synthesizes it as it goes.
- Once RNA polymerase reaches the end of the gene termination occurs, and the enzyme detaches from the gene and the DNA is returned to its original state.
- The mRNA will leave the nucleus, it will find a ribosome. This is where translation occurs.
What is RNA made up of?
- Phosphate group
- Ribose
- Nitrogenous base
What is a triplet, codon and anticodon?
Triplet- 3 base letters of DNA
Codon- 3 letters on RNA complementary to DNA
Anticodon- 3 nucleotides on Trna
What is 5’ to 3’ in DNA?
5 prime end has a p-group attached to the 5th carbon in deoxyribose, and 3 prime end has hydroxyl group attached to 3rd carbon atom in deoxyribose.
What is DNA polyemerase III and I?
III adds nucleotides in pre-existing chain in replication, and I removes RNA primers in the end.
What are RNA primers?
They are synthesized by an enzyme called PRIMASE, and provides a starting point for DNA polymerase to add nucleotides, and it gets removed by polymerase I at the end of replication, and gets replaced by nucleotide.
What is RNA polymerase?
Catalyses addition of RNA nucleotides, and goes from 5 prime to 3 prime when synthesizing but goes through the template strand from 3 prime to 5 prime
What is translation?
A step in protein synthesis where in the genetic code carried by mRNA is decoded by the ribosome to produce the specific sequence of Amino acids in a polypeptide chain.
Three steps in translation
Initiation
Elongation
Termination
What happens in the first step, initiation?
The small ribosomal subunit (bottom) binds to the mRNA, and scans it for its start codon (AUG-MET) then the initiator tRNA binds to the start codon (p site) and the large ribosomal subunit binds to create a-site and p-site and E-site.
What is the A-site?
It is the first binding site of the tRNA, and it is where the new trna will be added and will move on to the p-site where the amino acids will add to the tRNA and so on.
What is the p-site?
2nd binding site on ribosome where initiator tRNA first resides and it removes AA from tRNA to bind with other AA in the A-site creating a growing polypeptide.
What is the E-site?
Where tRNA exits ribosome.
What is elongation step?
New tRNA binds to a site, AA binds with each other at p site tRNA leaves in e site forming a growing polypeptide. This process keeps happening as ribosome moves from the five prime to three prime of mRNA.
What is the termination step?
Located at end of mRNA, and it signals a release factor and last tRNA leaves and POLYPEPTIDE IS BORN BABY!
What is the release factor?
It is the codon that codes for the forming the protein to stop, essentially it is the STOP CODON.
Where is the growing poly chain located?
The p-site
Where is the new tRNAs located?
The a-site
What are chromosomal mutation effects?
Chromosome mutations can result in changes in the NUMBER OF CHROMOSOMES (nondisjunction) in a cell or changes in the structure of a chromosome
What are chromosomal mutations?
They are an unpredictable change that occurs in a chromosome, most often brought on by problems that occur during meiosis or by mutagens.
What is a gene mutation?
An alteration in the sequence of nucleotides. This change can affect a single nucleotide pair, or larger gene segments of a chromosome.
What are some examples of Chromosomal Mutations?
Deletion
Duplication
Inversion
Translocation
What is deletion?
Deletion is a mutation where a chromosomal segment is removed.
(Part of chromosome- cDe-deletion-ce
What is duplication?
Duplication is AA mutation where a chromosome repeats a segment (addition of a segment).
(part of DNA bc-duplication-bcbc)
What is inversion?
An inversion is a mutation where it reverses a segment within a chromosome.
(bcd-inversion-dcb)
What is translocation?
Translocation is a mutation where it moves a segment from one chromosome to another (non homologous)
What are point mutations?
Also called base-pair substition, this type of mutation changes a single nucleotide base pair.
What are examples of “base pair substitution”
Silent
Nonsense
Missense
What is silent mutation?
It is a point mutation where it has no effect on the amino acid, or in other words it just changes the third letter but it doesn’t change amino acid.
What is nonsense?
It codes for the stop protein to end the forming of the polypeptide chain.
What is missense?
Same as silent but it actually codes for diff amino acids, and therefore changes the protein.
What insertion/deletion mutations?
Type of gene mutation that adds or removes a nucleotide and that can completely change the grouping of codons, resulting in completely different amino acids hence the protein. THE EARLIER THE SEQUENCE THE MORE ALTERED THE PROTEIN!!!
