Protein synthesis Flashcards
what is a codon
Each amino acid codon by three bases in a gene.
How many possible codons are there
64
What are codons also know as
Base triplets
How are proteins made
By reading the code of DNA
Explain how a gene can code for a particular protein
The order of bases in a gene determines the order of amino acids
Each gene contains a different order of bases which can code for a particular protein
What are the two stages in which proteins are made
- Transcription
- Translation
What are the strands links with the paired bases for DNA
A=T
C=G
What are the pairs for RNA
A=U
C=G
no more thymine (t)
What is a DNA molecule
Two strands coiled form a double helix
Explain Transcription
- DNA helicase unravels double helix
- DNA bases exposed on template strand
- Free RNA nucleotides in nucleus
- Free RNA nucleotides align with complementary base template strand
5.RNA polymerase form sugar phosphate backbone
- DNA helix reforms and mRNA leaves nucleus to enter cytoplasm
Where are proteins made
cells cytoplasm by ribosomes
Where is DNA found
Nucleus
Why cant the DNA found in the nucleus move out of the cell
Because it is too big
What is the role of mRNA
Transfer the information form the DNA to ribosome in the cytoplasm
How does the cell get the information from the DNA to the ribosome in the cytoplasm
messenger RNA ( mRNA
What is the difference between mRNA and DNA
mRNA
- shorter
- Uses u ( uracil) instead of thymine (T)
- Sugar ribose not deoxyribose
What is the role of RNA polymerase
enzyme involved in joining together the base sequence of the mRNA
- form sugar phosphate back bone
What are the three types of RNA which take place in protein synthesis
- mRNA ( messenger which forms a copy of DNA code)
- tRNA( which carries amino acids to the ribosomes to make protein)
- Ribosomal( Where protein synthesis occurs)
What are the steps for Translation
- mRNA binds to rRNA at start codon
- Free tRNA molecules in cytoplasm
- First tRNA binds to ribosome, complementary anticodon to start codon
- 2nd tRNA molecules binds to rRNA as complementary anticodon to codon
- peptide bond formed between amino acid of 1st and 2nd tRNA molecule
- 1st tRNA leaves ribosome without amino acid
- ribosome moves along mRNA to next codon
- 3rd tRNA molecule enters ribosome as anticodon that is complementary to 3rd codon.
8.5 Peptide bond forms between amino acid
- 2nd tRNA molecules leaves ribosome and ribosome moves along to next codon to mRNA
- Process continues to repeat until the stop codon is reached on mRNA
- rRNA detaches, mRNA is released and polypeptide released (newly form protein)
Where does transcription and translation occur
Transcription- Nucleus
Translation- Cytoplasm
How can a change in DNA affect the phenotype
by altering the sequence of amino acids in protein
What effect doe genetic mutation have on phenotype
some have a small effect
and rarely do they have a significant effect
what can cause incidence of mutations
Exposure to ionising radiation
- gamma rays
- X-Rays
- Ultraviolet rays
chemicals in tobacco
What can the resistance to antibiotics cause
-increase in bacterial populations
- increase infections becoming difficult to control
