Gene expression Flashcards
gene
region/s of DNA that are made up of nucleotides; the molecular unit of heredity
genome
all the genetic material in the chromosomes of an organism, including its genes and DNA sequences.
coding regions
known as exons, and are the part of the gene that codes for a protein
noncoding regions
sequences are components of an organism’s DNA that do not encode protein sequences
telomeres
caps on the end of DNA that prolong the life of chromosome
introns
non-coding parts of genes that are transcribed into mRNA, but then removed by RNA splicing before transcription
TRANSCRIPTION
- RNA polymerase links to DNA at the beginning of the sequence to be transcribed. Only one of the DNA strands is used as a template.
- As RNA polymerase moves along the strand it picks up appropriate free RNA nucleotides from the nucleoplasm (that have entered the nucleus from the cytoplasm). It joins guanine to cytosine, but joins uracil to the DNA’s adenine. This happens until it reaches a ‘stop’ signal.
- The pre-mRNA detaches from the template strand. It is therefore a copy of the base sequence on the coding strand of the length of DNA. The two DNA strands join together by complementary base pairing. The DNA molecules winds back up into a helix.
TRANSLATION
- mRNA attaches to a ribosome.
- tRNA has an anticodon on one end and an amino acid bonded to the other, which it carries to the ribosome.
- The tRNA anticodon binds itself to the first codon on the mRNA due to complementary base pairing
- Another tRNA molecule binds to the second codon of the mRNA.
- The amino acids join by a peptide bond and the tRNA molecules detach themselves.
- This process is repeated, leading to the formation of a polypeptide chain. This occurs until a stop codon is reached.
codon
the three nucleotides in mRNA. Each codon codes for a single amino acid
anticodon
the three nucleotides in tRNA that pair to a codon
purpose of gene expression
to synthesise a functional gene product (protein or functional RNA); that the process can be regulated and is used by all known life.
These products are mainly proteins, but in non-protein coding genes such as transfer RNA (tRNA) genes, the product would be functional RNA (MORE STUDY)
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