BB 3 - Transcription and Splicing Flashcards
What is a gene?
A section of DNA that codes for an RNA molecule, protein, or polypeptide.
What are enzymes?
Highly specific globular proteins that are biological catalysts produced by living things.
How many genes and chromosomes do humans contain?
25,000 genes
23 pairs of homologous chromosomes
Where are genes located?
At specific sites (loci) on the DNA
How can chromosomes be identified?
By their pattern of genes
What sequences does DNA contain?
Coding sequences and non-coding sequences
What is the name of coding DNA?
Exons
What is the name of non-coding DNA?
Introns
What are exons?
Coding DNA
What are introns?
Non-coding DNA
What do genes have both of?
Exons (coding DNA) and introns (non-coding DNA)
What are the general three steps for a gene to form into a protein?
Step 1: Transcription (whole gene is copied)
Step 2: Splicing (introns removed) and mRNA exported to cytoplasm
Step 3: Translation (polypeptide produced)
Where does transcription occur?
In the nucleus of eukaryotic cells.
What single strand is copied?
The template strand
What RNA is produced after transcription?
Messenger RNA (mRNA), which takes a copy of the gene code to the cytoplasm.
Step 1 of transcription
DNA is separated at a specific gene
Step 2 of transcription
RNA polymerase uses free RNA nucleotides to synthesise an RNA copy of the specific gene
Step 3 of transcription
The whole gene is copied, including non-coding introns
Step 4 of transcription
After copying the DNA is joined back together.
What must happen to non-coding introns after a gene is transcribed (copied)?
The non-coding introns must be removed.
What is the name of an RNA enzyme complex?
A spliceosome
What is the purpose of a spliceosome?
bring exon ends together and cut out the intron.
What does the final mRNA only contain before translation in the cytoplasm?
coding sequences (exons)
What did non-coding DNA be referred as?
Junk DNA
What is the purpose of non-coding DNA?
Gene regulation
