DNA Flashcards
What is the start codon’s amino acid sequence?
AUG, and the protein is methionine
What is a codon-binding site in tRNA molecules?
Three exposed bases which are complementary to the codon they are supposed to bind to on the mRNA, allowing them to connect to each other
What is a pyrimidine structure and what bases is it found in?
A six membered ring, found in thymine and cytosine
What bases are complementary? (in both RNA and DNA)
Adenine and Thymine (uracil in RNA)
Cytosine and Guanine
What is the role of DNA?
Contains all genetic information for living creatures
What are the stages of DNA replication?
1) Gyrase enzymes unwind the DNA strands
2) Helicase enzymes break the hydrogen bonds between the strands, splitting them into two
3) Free nucleotides are attracted to their complementary bases
4) DNA polymerase joins the new nucleotides together by forming covalent bonds
5) DNA fragments are sealed up by ligase enzymes, resulting in two new DNA strands
What are the components of an RNA nucleotide?
Ribose sugar, phosphate group and an organic base
What are the three types of RNA?
Messenger RNA, Transfer RNA, Ribosomal RNA
What is the role of ribosomes?
Read mRNA and translates the genetic code into amino acids
What is the process of translation?
1) Ribosome attaches to start codon on mRNA
2) tRNA molecule with complementary anticodon binds to the mRNA and forms hydrogen bonds
3) Second tRNA molecule binds with the next codon on the mRNA
4) Peptide bond forms between the amino acids that have been produced
5) Third tRNA bonds with the complementary codon, and as the ribosome can only hold two tRNA molecules simultaneously, the first one is released
6) Process continues until ribosome reaches a stop codon on the mRNA chain and detaches
What is ATP?
Energy store for almost all the chemical and cellular reactions that occur
What are the main differences between the structure of RNA and DNA?
RNA is single stranded, DNA is double stranded
RNA has uracil, DNA has thymine
RNA carbon 2 has an OH group, DNA carbon 2 has a H group
RNA has a ribose, DNA has a deoxyribose
What is the structure of ATP?
Central ribose sugar with an attached adenine base and three inorganic phosphates
What is the bond that joins two nucleotides together across bases?
Hydrogen bond
Where is ATP made?
In the mitochondria
What is the structure of a ribosome?
- made of ribosomal RNA and proteins
- contains two subunits (50s and 30s), either side of an mRNA strand
- either found free in the cytoplasm or bound to the rough endoplasmic reticulum
Why is DNA replication ‘semi-conservative’?
One strand is from the original DNA, and one strand is new
What is the process of ATP releasing energy?
Breaks down through hydrolysis into ADP and an inorganic phosphate. The breaking of the bond releases large amounts of energy, which fuels the reactions
Why does pre-mRNA need to be spliced?
To remove all the introns, which are regions that do not code for proteins, and only leave exons
How did Stahl and Meselson prove that DNA replication was semi-conservative?
1) Used E.coli bacteria, which has the base N14
2) Replicated lots of the E.coli bacteria with a base of N15, a much heavier isotope of nitrogen
3) Added this altered E.coli back into the original sample
4) Placed it into an ultracentrifuge, which could separate out the two samples due to their different densities
5) Repeated ultracentrifugation every 20 mins (E.coli’s rate of mitosis) and measured the results
What is a purine structure and what bases is it found in?
Double ringed structure with a six-membered ring attached to a pentose, found in Adenine and Guanine
What is the function of mRNA?
Transfers the genetic code from the DNA and moves it out of the nucleus
What is the process of transcription?
1) DNA helicase breaks the hydrogen bonds on the desired section of DNA to prepare it for transcription
2) RNA polymerase moves along the DNA template strand, beginning at a start codon
3) Polymerase joins complementary nucleotides onto the exposed strand, forming the pre-mRNA strand
4) DNA bases rejoin as RNA polymerase moves along, restoring the double helix structure
5) Pre-mRNA can then be spliced
Why is genetic code described as degenerate?
Multiple different codons code for the same amino acid - 20 amino acids but 64 codon combinations
