4.2 DNA and protein synthesis Flashcards
where does protein synthesis occur?
on ribosomes of the RER
What are the 2 stages of protein synthesis?
transcription
translation
where does transcription occur?
in the nucleus
What is transcription?
where one gene on the DNA is copied into mRNA
What is translation?
where the mRNA joins with a ribosome and corresponding tRNA molecules bring the specific amnio acid the codon codes for
Why is a copy of DNA made (mRNA) in protein synthesis?
DNA is too large to leave the nucleus and mRNA is much shorter and can fit through the nuclear pores
Why dont we want the DNA to leave the nucleus?
in the cytoplasms there may be enzymes that could damage the DNA
What is the process of Transcription?
- DNA helix unwinds and unzipps which is catalysed by DNA helicase to expose bases as a template
- DNA helicase breaks the H bonds between bases - unzipps
- one DNA chain acts as a template
- free mRNA nucleotides in the nucleus align with complementary DNA base
- RNA polymerase moved along the strand of nucleotides forming single standed pre-mRNA
- mRNA carries complementary codons
- at the end of the sequence mRNA is detached and DNA rewinds
- mRNA leaves nucleus where it attaches to ribosomes
What does DNA helicase do?
unwinds and unzipps the DNA helix by breaking the H bonds between bases
What does RNA polymerase do?
bonds together the RNA nucleotides by phosphodiester bonds to create a new RNA polymer of the genes thats been copied
Why is the mRNA in transcription called pre-mRNA?
it has to be modified before it can leave the nucleus
What is splicing?
removing introns
What protein is responsible for Splicing?
a splicesome
how does a splicesome work?
attaches to DNA
it splices and breaks the phosphodiester bonds so therefore splices out the introns
What happens during translation?
the polypeptide chain is created using the mRNA base sequence and the tRNA
Where does translation occur?
in the cytoplasm
What is thr role of the ribosome in translation?
it holds the mRNA and tRNA in place
How many tRNA molecules can the ribosome hold at one time?
2
Why is ATP required in translation?
to make the peptide bond between amino acids
where does splicing occur?
in the nucleus
What is made after splicing?
mature-mRNA
In what type of cell does splicing occur in?
eukaryotes
What are the differences of DNA replication and transcription?
DNA polymerase in DNA rep, RNA polymerase in transcript
1 template strand in transcript, 2 template strands in DNA rep
free DNA nucleotides in rep, free RNA nucleotides in transcript
What is the process of translation?
- mRNA attaches to the ribosome
- tRNA brings its specific amino acid
- tRNA anticodon are complementary to mRNA codon
- another tRNA molecule brings its amino acid to the mRNA codon at the ribosome site
- amino acids join together by peptide bonds with the use of ATP
- ribosome moves along to the next codon and the process repeats until a stop codon is reached, forming a polypeptide chain,
Where is the amino acid attachmtn site on the tRNA?
at the opposite end to its anticodon
What indicates what direction the mRNA should be read?
a start codon
what is a proteome?
The number of different proteins the genome can code for
What occurs during post transcriptional modification?
- removal of methionine from the start of the primary structure
- RER buds off as transport vesibles containing the polypeptide to be transferred to the golgi body
What happens to the polypeptide in the golgi body?
- chemical modification - adding a functional group
- packages it into lysosomes or secretory vesicles
What do lysosomes do?
contain hydrollytic enzymes, lysosymes, that digest the bacterial cell wall made of murein
What is the chemical group on the end of the polypeptide chain?
the amine group
How are tRNA and mRNA similar?
single stranded
adenine and uracil base pair
made of ribose
unpaired bases
How are tRNA and mRNA different?
H bonds in tRNA, phosphodiester bonds in mRNA
clover structure in tRNA
amino acid attachment point in tRNA
What is meiosis also known as?
reduction divison
Why is meiosis referred to as reduction division?
the number of chromosomes halves
How are amino acids added to a polypeptide chain during translation?
TRNA brings specific amino acid to ribosome
Anticodon on tRNA binds to codon
Amino acids join by condensation reaction
What are 2 molecules ribosomes are made of?
nucleic cids and proteins
What is the role of a ribosome during in the formation of a poylypeptide?
- mRNA binds to ribosome
- codons at the binding site
- allows tRNA with anticodons to bind
- catalyses formation of peptide bond between amino acids
- moves along mRNA to next codon
Where are the non-coding regions multiple repeats positioned in the genome?
positioned between genes
