Key Area 3: Gene Expression Flashcards
What are genes?
DNA sequences that code for particular proteins
What determines a cell’s phenotype?
The proteins which are synthesised when the genes are expressed.
What is translation?
Amino acids come together at the ribosome where they form a polypeptide chain.
What types of RNA are involved in transcription and translation?
mRNA, tRNA and rRNA
What is the transcription and translation of DNA sequences involved in?
Gene expression
How many strands are in RNA?
One.
What is RNA made from?
Nucleotides
What are the bases in RNA?
Adenine, Uracil, Cytosine, and Guanine.
What is mRNA?
Messenger RNA copies the code from the DNA and carries it to the ribosomes where they are joined together.
What is tRNA?
Transfer RNA is found in the cytoplasm and become attached to specific amino acids, bringing them to the ribosomes where they are joined together.
What is rRNA
Ribosomal RNA forms a complex with protein molecules to make the ribosome.
What is transcription?
The process which the DNA is used to produce an RNA moleule called a primary transcript.
What are introns and exons?
Human genes that have been divided into coding and non-coding elements. Introns are non coding and exons are coding.
Are introns or exons more useful?
exons
Why are exons more useful?
They are coding, so they carry the information needed for protein synthesis.
What is the first stage of transcription?
RNA polymerase moves along the DNA, unwinding the double helix
What is the second stage of transcription?
Hydrogen bonds between bases break, separating the two DNA strands.
What is the third stage of transcription?
Free RNA nucleotides bond with the complementary base pairs on the DNA
What is the fourth stage of transcription?
Hydrogen bonds form between complementary bases
What is the fifth stage of transcription?
Strong bonds form between the phosphate of one nucleotide and the ribose sugar of the adjacent nucleotides.
What is RNA polymerase?
An enzyme that moves along DNA unwinding the double helix and breaks the hydrogen bonds between bases.
What enzyme synthesises a primary mRNA transcript from RNA nucleotides?
RNA polymerase
What does non-coding mean?
A section of transcribed DNA which does not contain the information required to produce a protein
What happens to the introns?
They are removed from the primary mRNA transcript.
What is RNA splicing?
The removal of introns and splicing of exons.
Is the order of exons changed during RNA splicing?
No.
What is the name given to modified mRNA after splicing?
Mature mRNA Transcript.
What happens to the mature mRNA transcript?
It passes out of the uncleus via a pore in the nuclear membrane, into the cytoplasm.
What is translation?
The synthesis of a polypeptide chain using mRNA as the code for the amino acid sequence.
What is involved in the translation of mRNA into a polypeptide at a ribosome?
tRNA
Where does translation begin?
At a start codon.
Where does translation end?
At a stop codon.
What is the first stage of translation?
A ribosome binds to the 5’ end of the mRNA template at the mRNA’s start codon.
What is the second stage of translation?
A tRNA molecule picks up its appropriate amino acid from the cytoplasm.
What is the third stage of translation?
The tRNA carries the amino acid to the ribosome and becomes attached by hydrogen bonds between its anticodon and the start codon
What is the fourth stage of translation?
Another amino acid will then be brought to the ribosome by tRNA.
What is the fifth stage of translation?
When the first two amino acid molecules are next to each other they join by a peptide bond.
What is the sixth stage of translation?
The process is repeated many times, thus translating the mRNA into a complete polypeptide chain.
What is the seventh stage of translation?
When a stop codon is reached, the ribosome releases the polypeptide.
What provides the energy for translation?
ATP
Where is tRNA found?
The cytoplasm
What are the 2 significant sides of tRNA?
The anticodon and the attachment site
What is an anticodon?
A triplet of bases at one end of the tRNA.
What does an anticodon correspond to?
A particular amino acid, carried by the tRNA at its attachment site.
What does the anticodon form weak hydrogen bonds with?
the corresponding codon on the mRNA.
How do anticodons bond to codons?
By complimentary base pairing
What do anticodons do with codons when they have bonded?
Translate the genetic code into a sequence of amino acids.
What joins amino acids after anticodons bond to codons?
Peptide bonds
What happens after the polypeptide is formed?
Each tRNA leaves the ribosome.
Can different proteins be expressed from one gene?
Yes.
Can different mature mRNA transcripts be produced from the same primary transcript?
Yes, depending on which exons are retained.
What can be included or excluded from the mature mRNA transcript?
Different exons of a gene.
What links amino acids to form polypeptides?
Peptide bonds
How does a polypeptide chain form the 3-dimentional shape of a protein?
They fold.
What holds a protein together?
Hydrogen bonds and other interactions between other individual amino acids.
What determines the functions of proteins?
Their shape
What determines the phenotype?
the proteins produced as a result of gene expression. Also environmental factors.
Where can proteins be found?
Connective tissue, bone and muscle.
What are the roles of proteins?
To act as enzymes, structural proteins, hormones, and antibodies.
