2.1.3 Nucleotides + Nucleic acids Flashcards
What is RNA made up of?
Nucleotide
A Pentose sugar (ribose) attached to a phosphate group and a base.
Bases: Adenine, Guanine, Cytosine, Uracil
How do RNA nucleotides join together?
A condensation reaction forming a phosphodiester bond
What is the function of RNA
Responsible for taking the info from the DNA, out of the nucleus to the ribosomes.
To synthesise proteins
What is the function of mRNA
Copy of one gene from DNA
Much shorter than DNA + short-lived.
Carries info from the DNA and nucleus to the ribosomes for PS.
What does tRNA do?
Found in cytoplasm
Folded single strand to create cloverleaf shape held by H bonds.
Transfers amino acids to the polypeptide chain.
Made up of a single strand of RNA
Has one anticodon found at the bottom of the molecule.
What bond holds together base pairs
Hydrogen bonds
What is the process of transcription?
RNA polymerase breaks the hydrogen bonds between the bases.
Adds RNA nucleotides to the exposed complementary bases on template strand.
Once two nucleotides are joined to their bases, RNA polymerase joins them together via a condensation reaction = phosphodiester bond.
Continues to move down the DNA, joining nucleotides to bases.
Once reached the end of the strand, RNA polymerase and pre RNA strand detach.
What is the process of translation?
mRNA strand reaches ribosome and attaches to it.
Inside, there are tRNA molecules (anticodons carrying amino acids.)
A tRNA molecule complementary to the codon on the mRNA strand, binds to it and another tRNA does next to it.
The ribosome joins these two amino acids together via a condensation reaction, forming a peptide bond.
The ribosome moves along, releasing the anticodon from the AA and codon.
Another tRNA molecule binds next to it and another bond is formed= continues.
Once at the end, the ribosome reaches a stop codon then, all detach from each other + polypeptide chain is formed.
What do our genes contain?
Coding sequences: introns
Non-coding sequences: exons
What is the process of splicing?
Specific proteins cluster around the pre-mRNA and remove the introns, then attach the exons together.
= mRNA
What is a codon.
A set of three bases in mRNA that code for an amino acid.
3 key features of the genetic code on mRNA
The genetic code on mRNA is:
1. Degenerate - This means that multiple different codons can code for the same amino acid.
2. Non-overlapping - This means that there is no overlap between codons when they are read: each part of the triplet is only read once.
3. Universal - This means that all living organisms use the same genetic code; each triplet codes for the same thing in any organism.
What is an anticodon?
Carries an amino acid with 3 bases complimentary to a codon on mRNA
How polypeptides/proteins control physical development of an organism
Structural proteins - keratin, collagen
Hormones
Hox genes - homeobox genes
Transcription factors
Semi-Conservative DNA replication
One strand is conserved and one new strand is created.
Occurs in S-phase in interphase of the cell cycle
What is a mutation
Copying errors in DNA replication can occur randomly and spontaneously - resulting in a change to the DNA base sequence.
Describing the DNA double helix
The top + bottom of each strand are either the 3’ (prime) end or 5’ (prime) end.
Number refers to which carbon within the deoxyribose sugar of the nucleotide is closest to the top/bottom.
The enzyme that catalyses DNA replication is complementary in shape to the 3’ end, can only attach to the DNA at this location.
Stages of DNA replication
- DNA helicase breaks the H bonds between the complementary bases of the two DNA polymer causes the double helix to unwind and the two strands to separate.
- Both strands act as templates for DNA replication.
- Free-floating DNA nucleotides align opposite their complementary base on the template strand of DNA. H bonds will form between the base pairs.
- DNA polymerase joins adjacent DNA nucleotides together, forming a phosphodiester bond between these nucleotides to create a new polymer chain of DNA.
Start and Stop Codons
Start codon: Start of every gene - enables the ribosome to attach
Stop codon: End of every gene - 3 bases that do not code for an amino acid - causes ribosome to detach + end translation.
Purines
2 carbon ring structures
(Adenine + Guanine)
Pyrimidines
1 carbon ring structure
(Cytosine, Thymine + Uracil)
