Gene Expression 1.3 Flashcards
What does Gene Expression involve?
Gene expression involves the
transcription and translation of DNA sequences.
What is Gene Expression?
the process by which specific genes are activated to produce a required protein.
How many genes in a cell are expressed?
Only a fraction.
Transcription and translation involve how many types of RNA? List them.
Three types of RNA (mRNA, tRNA and rRNA).
What is RNA?
RNA is single-stranded and is composed of nucleotides containing ribose sugar, phosphate and one of four bases: cytosine, guanine, adenine and uracil.
What does messenger RNA (mRNA) do?
carries a copy of
the DNA code from the nucleus to the ribosome.
What happens to the mRNA?
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 happens to tRNA?
Transfer RNA (tRNA) folds due to
complementary base pairing. Each tRNA molecule carries its specific amino acid to the ribosome.
What happens to rRNA?
Ribosomal RNA (rRNA) and
proteins form the ribosome.
What does a tRNA molecule contain?
an anticodon (an exposed triplet of bases) at one end and
an attachment site for a specific amino acid at the other end.
What is the role of RNA polymerase in transcription of DNA into primary mRNA transcripts ?
RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between the bases. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing.
What is the genotype?
an organisms complete set of genes which is determined by the sequence of DNA bases in its genes.
What are alleles?
different forms of the same gene.
What is the difference between a dominant allele and a recessive allele?
The dominant allele will be expressed in the organisms phenotype and the recessive allele will only be expressed when both copies are present.
What is a cells phenotype determined by?
the proteins that are synthesised when the genes are expressed.
What is a codon?
A triplet of bases.
Describe transcription.
The DNA is used to produce an RNA molecule that is called a mRNA primary transcript. This RNA has the same sequence as the gene. Human genes can be divided into exons and introns but it is only the exons that carry the information needed for protein synthesis and the introns are removed by splicing resulting in the formation of a mature mRNA transcript.
Describe translation.
amino acids are joined together in a certain order at the ribosome, where they can form a polypeptide chain.
What happens in RNA splicing?
The introns of the primary transcript are
non-coding regions and are removed.
The exons are coding regions and are joined
together to form the mature transcript.
