1.3 Gene Expression Flashcards
What are the three types of RNA?
mRNA (messenger), tRNA (transfer), rRNA (ribosomal).
True or false? All the genes in a cell are expressed.
False - only a fraction are expressed.
What is RNA?
RNA is single stranded and is composed of nucleotides containing a ribose sugar, phosphate and a base.
What are the four bases found in RNA?
Adenine, cytosine, guanine and uracil.
What is a genotype?
The genetic material an organism possesses.
What determines an organism’s genotype?
The sequence of DNA bases in it’s genes.
What is a phenotype?
The physical appearance of an organism.
What determines an organism’s phenotype?
A genotype is determined by the proteins that’s are produced as a result of gene expression.
What is the function of mRNA?
It carries a copy of the DNA code from the nucleus to the ribosome.
What is the function of tRNA?
Each tRNA molecule carries its specific amino acid to the ribosome.
What is the function of rRNA?
Forms the ribosomes alongside proteins.
What is transcription?
The synthesis of mRNA from a section of DNA.
What is each triplet of based on an mRNA molecule called?
A codon.
What does a codon do?
Codes for a specific amino acid.
What is an anticodon?
An exposed triplet of bases.
What is the structure of a tRNA molecule?
It has an attachment site for an amino acid on one end and and an anticodon on the other.
What is the role of RNA polymerase in transcription?
RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases. It then synthesises a primary transcript of mRNA from RNA nucleotides.
What direction are RNA nucleotides added in?
5’ to 3’.
What happens after a primary transcript of mRNA is formed?
The mRNA separates from the DNA and moves away. The weak hydrogen bonds then re-unite and the molecules winds up again to make the double helix of DNA.
What does RNA splicing do?
Forms a mature transcript of mRNA.
What are introns?
Non coding regions that are removed in RNA splicing.
What are exons
Coding regions that are joined together to form the mature transcript of mRNA.
What is mature transcript of mRNA?
A joined chain of exons.
True or false? The order of exons is unchanged in RNA splicing.
True.
How are different proteins expressed from one gene?
Alternative RNA splicing.
What is alternative RNA splicing?
Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.
What is tRNA involved in?
The translation of mRNA into a polypeptide at a ribosome.
How does translation begin?
It begins at a start codon.
How does translation end?
It ends with a stop codon.
How do anticodons bond to codons?
Through complementary base pairing.
What joins amino acids together?
Peptide bonds.
Where are amino acids found?
The cytoplasm.
What happens as an mRNA molecule is passed through a ribosome?
Each codon is translated into an amino acid.
Amino acids are linked by peptide bonds to form __________.
Polypeptides.
What do polypeptide chains form?
The folded, three-dimensional shape of a protein.
What holds polypeptides together?
Hydrogen bonds.
What determines a proteins function?
It’s shape.
