Unit 1- DNA And Protein Synthesis Flashcards
Is DNA and RNA a weak acid?
Yes
What elements are in nucleotides?
CHNOP
What components make up DNA?
- pentose sugar
- phosphate group
- nitrogenous base
What is a pyrimidine?
Single ring carbon/nitrogen structure
Thymine and cytosine and uracil
What is a purine?
A double ring carbon/nitrogen structure
Adenine and guanine
How is the sugar phosphate backbone of DNA made?
Nucleotide polymerisation
- covalent phosphodiester bonds form between phosphate and deoxyribose
- condensation reaction
Shape of DNA
- 2 polynucleotide strands run anti parallel forming a double helix
- hydrogen bonds form between the complementary base pairs
What is a gene?
A section of DNA that codes for a specific protein
Or
A sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain
What is gene expression?
The process by which the instructions in our DNA are converted into functional proteins (expressed)
What are the 2 stages of gene expression in order?
Transcription
Translation
What kind of cells have non-coding DNA?
Eukaryotes
What are the non-coding sections of DNA known as?
- introns (interruption sequences), they are found inbetween exons in a gene
- satellite DNA, which are regions of non-coding DNA found between genes
What is the purpose of non-coding DNA?
- structural (to help coil the DNA)
- some code for RNA but don’t code for a protein (not expressed)
- control functions (to regulate which genes are expressed)
- involved in DNA replication
- contains unused copies of genes
What is the purpose of DNA polymerase in DNA replication?
Catalyses the formation of phosphodiester bonds between adjacent nucleotides
What bonds are involved in DNA replication?
Covalent phosphodiester bonds
Hydrogen bonds
Describe the process of DNA replication
- DNA helical unwinds and separates the 2 strands of DNA, breaking the hydrogen bonds between base pairs
- the nucleotides present in the nucleoplasm attach themselves to the bases on the old strands by complementary base pairing
- DNA polymerase joins the new nucleotides together by strong covalent P bonds forming sugar back bone
- the 2 strands wind up into a double helix
- the DNA molecules are identical to each other and the old DNA, each new one containing an old and new strand
Where do the nucleotides that bind together to from the new polynucleotide strand come from?
Nucleoplasm
What are replication forks?
A replication fork is simply the site of DNA replication, and as DNA is so large it will have many forks at the same time
What are nicks in DNA strands?
Where a phosphodiester bond hasn’t formed between 2 adjacent nucleotides due to 2 forks meeting (2 DNA polymerase enzymes colliding and not finishing the job)
How are nicks in DNA strands joined?
DNA ligase
What is the purpose of DNA ligase in DNA replication?
- repairs nicks in DNA
- finds mismatched base pairs and replaces them with the correct base
Why is the known method of dna replication known as semi conservative replication?
Each new DNA molecule contains one new and one old strand
Differences between RNA and DNA? 4
RNA
- contains ribose sugar, instead of deoxyribose
- has base uracil instead of thymine
- single stranded
- shorter
What is mRNA?
- messenger RNA
- Carries the code for a particular protein into the cytoplasm
- just long enough to contain 1 gene (1000 nucleotides)
- degrades straight after use
Structure of tRNA:
Transfer RNA
- looped clover shape
- ends in the bases ACC, which bind to the amino acid
- contains a triplet nucleotide sequence (anticodon) which is complementary to a codon on the mRNA
What is rRNA?
Binds to proteins to form ribosomes, the site of translation
- 2 subunits and found in cytoplasm
What does degenerate mean?
There is often more than 1 codon for an amino acid
AUG is the codon for methionine, what is the significance of this amino acid?
This tends to be the start codon, so all proteins start with this amino acid
What amino acids to the stop codons code for?
None, when the rRNA reads the stop codon the whole process stops, no more amino acids are bonded
What does the term non-overlapping mean?
A sequence of six bases can only be read as 2 codons, eg AUGUAG only contains the codons AUG and UAG, not AUG,UGA…
Where are proteins synthesised? And why?
In the cytoplasm, as this is where the ribosomes are
What is another word for post transcriptional modification of mRNA?
Splicing
What is splicing?
When non coding introns are removed from pre-mRNA
Where does splicing occur?
In the nucleus
