3: Genes and Genomes Flashcards
Describe the main differences between prokaryotic and eukaryotic genomes and genes
- Bacteria are known to have a relatively small genome
- Bacterial genome is full of protein coding genes (no introns)
- Bacterial genome is linear, whereas eukaryotic genome is circular
Know the structure of protein coding genes
Draw out structure
look throughs slides
Describe the properties of highly repetitive sequences
- Short regions of highly repetitive DNA -also known as short tandem repeats or satellite DNA
- The difference in how many of the repeats is present in the length of the region is the basis for DNA fingerprinting
- Makes up ~3% of the genome
What are moderately repetitive sequences?
The presence of many copies of sequences derived from transposons are responsible for much of the variation in genome sizes
Makes up ~45% of the human genome
How much of the genome encodes proteins?
Only ~1.2% of genome encodes protein
The human genome contains ~20,000 genes
draw the sequence of pre-mRNA –> mRNA: cap and polyA tail
slides
insert picture later
How much of the genome is transcribed?
~60% of the genome is transcribed and most of this does not encode proteins (called non-coding RNA)
What are some examples of non-coding RNA?
- tRNA
- ribosomal RNA
- microRNA
- Long non-coding RNA
Breifly describe alternative splicing
- Carried out by a protein complex called the spliceosome
- Alternative splicing is the major mechanism to increase protein diversity (i.e. one gene encodes more than one protein)
Why do we have chromosomes?
Cells have a lot of DNA that has to be fitted into a very small volume. But the cell needs access to it.
Solution:
Chromosomes=DNA + associated proteins
• Compacts DNA
• Protect DNA from damage
• Ensures replicated DNA is properly segregated
Provides an overall organisation to DNA which facilitates recombination, and gene expression
What does a nucleosome consist of?
DNA + histone protein
Describe how DNA is packaged
slides
