Lecture RR5. Genes and genomes transposable elements Flashcards
what is a genome?
The entirety of an organism’s hereditary information
Usually DNA (some viruses = RNA)
Eukaryotes → composed of coding (islands) and non-coding DNA (open ocean)
what is the difference in genome size attributed to?
the amount of non-coding DNA
What is a gene?
Definition of a gene = the entire nucleic acid sequence that is necessary for the synthesis of a functional product (polypeptide [Protein] or RNA)
Genes are transcribed
what is an Open Reading Frame (ORF)
it defines the coding sequence, it starts with a start codon and ends with a termination codon
what is a control region?
typically present upstream of the gene, contains promoters (sequences that recruit RNA polymerase) and other regulatory factors that will control the activity of the RNA polymerase.
what are ORF and control regions needed for?
so that transcription can start in the chain
what is the role of introns ?
separate the exons and are spliced out during mRNA processing
another benefits of introns is that with a single gene we can generate different versions of a protein, with the process of splicing (the removal of introns) can vary
Alternative splicing !
what is a transcription unit?
A region in DNA, bounded by an initiation (start) site and termination site, that is transcribed into a single primary transcript
what is the effect of alternative splicing?
with a single gene we can generate different versions of a protein, with the process of splicing (the removal of introns)
what are solitary or single-copy genes?
with a single gene we can generate different versions of a protein, with the process of splicing (the removal of introns)
what is a gene family?
the remainder (75%) occur as duplicated or in multiple copies. A set of related genes formed by duplication of an original single-copy gene make up a gene family
T or F, Proteins with similar functions often contain similar amino acid sequences that encode functional domains
True, these similarities can be observed with BLAST (Basic Local Alignment Search Tool) and other techniques
what can happen to gene functions as they are copied? (2)
- New gene copies can either evolve a new function or
- alternatively, degenerate over time losing their function (pseudogenes, they look like genes but dont have function)
what are paralogs?
closely related proteins in the same species (a-tubulin and b-tubulin in humans) but that have different functions
Give 3 examples of Non-Coding DNA
- Intragenic Noncoding DNA
- Introns
- UTRs (UnTranslated Regions) will not be removed in the process of splicing
what are orthologs?
the same protein, serving the same function, in different species (a-tubulin in humans and flies)
what are the 2 types of simple sequence repeats (SSR)
sequences that are outside of genes,
there are 2 types:
Minisatellite DNA and Microsatellite DNA
what is Minisatellite DNA ?
- repeat units are =14 to 100bp in length
- 20-50 tandem repeat units
- arrays of 1 to 5 kbp in length
- often in centromeres and telomeres
some of them seem to have a function because they are positioned at particular places like important places of our genome
What is Microsatellite DNA?
- Repeat units are typically 1 to 4 bp in length
- Arrays of up to =600 bp in length and composed of tandem repeat units
- sometimes found in transcription units (this is what is important about them), they sometimes appear in coding sequences
- expansion underlie several neuromuscular diseases like myotonic dystrophy and spinocerebellar ataxia
DNA polymerase slips during the replication of repeats
how can SSRs be used for DNA fingerprinting protocols?
each of us has a different amount of repeats in our genomes,
so then we do PCR fragments
and the lengths will be different from person to person
what are transposable (mobile) DNA elements?
- transposable DNA elements move within genomes by different mechanisms
- Mobile DNA elements influenced evolution and can cause mutations leading to disease
- Originally identified by Barbara McClintock by studying the color pattern formation in maize caused by the production of the pigment anthocyanin
what are the 2 types of repeated DNA sequences?
- Simple Sequence repeats (SSR)
- Transposable elements (TE) (also called jumping genes)
what are the 2 major classes of Transposable elements (TE) ?
transposons and retrotransposons
what is the enzyme needed for DNA transposons
transposase
