4-A DNA RNA and protein synthesis Flashcards
how is DNA stored in eukaryotic cells?
DNA is long and coiled
wound around histones (protein to support DNA structure)
DNA is coiled tightly into chromosomes which are found in the nucleus
How is DNA stored in prokaryotic cells?
DNA molecules are shorter in circular and are not associated with histones
Condenses by supercoiling to fit into the cell
What is a gene?
Section of DNA that codes for a protein which results in a characteristic
What is a genome?
All the genetic material in an organism/cell
What is a proteome?
The full range of proteins and organism/cells able to produce
What are introns?
Non-coding sections of DNA
What are exons?
Coding parts of DNA
What is an allele?
One or more alternative versions of the same game
What is a homologous pair?
And pair of matching chromosomes which each contain the same gene but could have different alleles
What are the two stages of protein synthesis?
transcription
translation
what is mRNA?
messenger RNA make during transcription carries the genetic code from DNA to ribosomes Single polynucleotide strand 
What is tRNA?
transfer RNA
involved in translation
carries amino acids to ribosomes single polynucleotide strand folded into Clover shape
has an anti codon and amino acid binding site

What is a triplet?
Series of three bases which code for one amino acid in a protein
what is the codon?
A base triplet in DNA/mRNA that codes for an amino acid 
What is an anti codon?
sequence of three bases in tRNA
What is transcription?
The first stage of protein synthesis in which an mRNA copy of a gene is made from DNA
What is the first stage of transcription?
RNA polymerase attaches to the DNA
hydrogen bonds between DNA strands are broken by DNA Helicase exposing the bases
What is the second stage of transcription?
RNA polymerase lines up free complemtary nucleotides along the exposed bases on the template strand
RNA polymerase joins the RNA nuclear tides by phosphodiester bonds forming an mRNA strand

What is the third stage of transcription?
RNA polymerase moves along the DNA
hydrogen bonds reform between the DNA nucleotides
What is the fourth stage of transcription?
RNA polymerase reaches a stop codon so it detaches from the DNA
MRNA strand is complete and moves out the nucleus through nuclear pore ready for translation
What is translation?
The second stage of protein synthesis in which amino acids are joined together by ribosomes to make a polypeptide chain
What is the first stage of translation?
MRNA attaches to a ribosome and tRNA carries amino acids to it
What is the second stage of translation?
A tRNA molecule with complimentary anti codon to codon of mRNA attaches by complementary base pairing
A second tRNA molecule attaches to the next codon 
What is the third stage of translation?
The two amino acids are joined by peptide bond catalysed by the ribosome
The first tRNA molecule moves away leaving amino acid behind
What is the fourth stage of translation?
A 3rd tRNA molecule binds to the next code on mRNA
The amino acid binds to the first two and the second tRNA molecule moves away
The process continues until a stop codon is reached and the polypeptide chain moves away 
What is the genetic code?
The sequence of base triplets in the mRNA which codes for a specific amino acids
What are the three properties of the genetic code?
Nonoverlapping
degenerate
universal
What does non-overlapping mean?
Base triplets don’t share their bases
what does degenerate mean?
An amino acid can be coded for by more than one codon
What does Universal mean?
The same base triplet code for the same amino acids in all living things
