Gene Expression 1.3 Flashcards
(33 cards)
What are the two parts of gene expression
Transcription and translation
What is within an RNA nucleotide
Phosphate
Base (A U G C)
Ribose sugar
Is RNA single or double stranded
Single stranded
What are the three types of RNA
mRNA (messenger RNA)
tRNA (transfer RNA)
rRNA (ribosomal RNA)
What is mRNA
Messenger RNA (mRNA) carries a copy of the DNA code from the nucleus to the ribosome
How is mRNA used in transcription and translation
mRNA is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm. Each triplet of bases on the mRNA molecule is called a codon and codes for a specific amino acid
What is tRNA
tRNA is a single stranded molecule but folds due to complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome.
A tRNA molecule has an anticodon at one end and an attachment site for a specific amino acid at the other end
What is rRNA
Ribosomal RNA and proteins form the ribosome. The ribosome is the structure where protein synthesis takes place
What is transcription
When a gene is to be expressed the base sequence of DNA is copied or transcribed into mRNA
What is step 1 of transcription
RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases
What is step 2 of transcription
As RHA polymerase breaks the bonds, it synthesises a primary transcript of mRNA using RNA nucleotides. These form hydrogen bonds with the exposed DNA strand by complementary base pairing
What is step 3 of transcription
RNA splicing forms a mature mRNA transcript. Uracil in RNA is complementary to adenine
What does a primary transcript consist of
Introns and exons
Is it introns or exons that get removed
Introns
What are the two steps of splicing
Remove the introns
Join the remaining exons together
What is it called when different proteins can be expressed from one gene
Alternative splicing
What is alternative splicing
Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained
What is translation
Once mRNA is out of the nucleus, it travels to the ribosome where it can now be translated into a protein in the cytoplasm
What is step 1 of translation
tRNA molecules have a triplet of unpaired bases at one end (known as an anticodon) and a region where a specific amino acid cab attach
What is step 2 of translation
The mRNA molecule travels through the cytoplasm and attaches to the ribosome
What is step 3 of translation
tRNA molecules transport specific amino acids to the ribosomes
What is step 4 of translation
Each mRNA codon codes for a specific amino acid
What is step 5 of translation
The first codon of an mRNA molecule is a start codon. This signals the beginning od translation
What is step 6 of translation
The anticodons and codons match up and form complementary base pairs. So the genetic code is translated into a sequence of amino acids
