5627759
Description
Mind Map by Natalina Laria, updated more than 1 year ago
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Created by Natalina Laria
about 8 years ago
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Genomes and evolution
- Prokaryotic gene and genome structure
- Genome size is related to complexity
- More genes corresponds to bigger genomes
- Selection for small genomes seems to occur. This is because rapid growth and short generation times leads to a
selective advantage
- More genes corresponds to bigger genomes
- Genome size is related to complexity
- Eukaryotic gene and genome structure
- No relationship between gene number, genome size and complexity
- Functions of complex transcription units
- The different proteins encoded may have slight
functional differences allowing them to be
specialized for particular functions, eg different
regulatory protein domains could be included in
different tissues
- More specialisation and greater complexity is due to more combinations, not more genes
- The different proteins encoded may have slight
functional differences allowing them to be
specialized for particular functions, eg different
regulatory protein domains could be included in
different tissues
- Exons
- Exons often correspond to protein domains
- A protein domain is a region of a
protein with a specific structure or
function. This region often folds
independently of the rest of the
protein
- A protein domain is a region of a
protein with a specific structure or
function. This region often folds
independently of the rest of the
protein
- Exon shuffling
- New genes evolve by joining together new combinations of exons
- Occurs over evolutionary time
- New genes evolve by joining together new combinations of exons
- Exons often correspond to protein domains
- Multigene Families
- A multigene family consists of a set of genes that
arose by duplication of ancestral gene and
subsequent divergence due to small changes to
the nucleotide sequence
- May contain pseudogenes that
are homologous but do not
produce a functional protein
- Within a gene family, particular members may
show specialized functions, eg for tissue or
developmental stage specificity
- May contain pseudogenes that
are homologous but do not
produce a functional protein
- The globin gene family
- Haemoglobin carries oxygen in our blood and consists of four globin proteins, two copies each of α
and β and the cofactor haem
- Foetuses require haemoglobin with a higher affinity for oxygen and express the γ globin gene
- Foetuses require haemoglobin with a higher affinity for oxygen and express the γ globin gene
- Haemoglobin carries oxygen in our blood and consists of four globin proteins, two copies each of α
and β and the cofactor haem
- A multigene family consists of a set of genes that
arose by duplication of ancestral gene and
subsequent divergence due to small changes to
the nucleotide sequence
- No relationship between gene number, genome size and complexity
- Mechanisms of genome evolution
- Point
mutations
- Replication strand slippage
- Replication strand slippage can lead to misalignment of the
template and newly synthesised strand and results in
unequal daughter strands
- Replication slippage also causes insertions or deletions of several nucleotides
- Generation of simple sequence repeat
- Trinucleotide expansion
- Generation of simple sequence repeat
- Replication slippage also causes insertions or deletions of several nucleotides
- Replication strand slippage can lead to misalignment of the
template and newly synthesised strand and results in
unequal daughter strands
- Transposition (Transposons)
- Moderately-repeated, mobile DNA sequences are interspersed
throughout the genomes of prokaryotes, plants and animals
- These sequences appear to serve
no useful function: selfish DNA
General
- DNA transposons (Class 2)
- Move via a 'Cut and Paste' mechanism
- Short terminal inverted repeats, short flanking direct repeats at target site
- Transposase gene (and sometimes others)
- Transposition through DNA replicative or non replicative
- Move via a 'Cut and Paste' mechanism
- RNA transposons (Class 1)
- Move via a 'Copy and Paste' mechanism
- Reverse Transcriptase
- Reverse transcriptase produces a DNA/RNA hybrid
- This is converted to double stranded DNA by
degradation of the RNA and synthesis of a new DNA
strand
- This is converted to double stranded DNA by
degradation of the RNA and synthesis of a new DNA
strand
- Reverse transcriptase produces a DNA/RNA hybrid
- Transposition by an RNA intermediate
- Long terminal direct repeats, short flanking direct repeats at target site
- Move via a 'Copy and Paste' mechanism
- Moderately-repeated, mobile DNA sequences are interspersed
throughout the genomes of prokaryotes, plants and animals
- Recombination
- Repeated sequences allow misalignment and then recombination
- Gene duplication
- Deletion
- Inversion
- Gene duplication
- Repeated sequences allow misalignment and then recombination
- Point
mutations
- The human genome
- Copy Number Variation
(CNV)
- Difference among individual organisms in the number of copies of any large DNA sequence (larger
than 1000 bp)
- Individuals vary in the number of copies of particular DNA sequences (genes, repeated sequences,
any chunk of DNA)
- Repeated DNA
- Simple sequence repeats (highly repeated) accounts for 3%
of the human genome
- Tandem repeats
spanning 20-100 kb
- Repeat length 1-500 bp
- Concentrated in particular regions of chromosomes,
especially centromeres and telomeres
- Most has no known function, but can be used as the basis of DNA fingerprinting as the number of SSRs varies between individuals
- Tandem repeats
spanning 20-100 kb
- Different types of mobile DNA elements (moderately
repeated) accounts for 45% of the human genome
- Simple sequence repeats (highly repeated) accounts for 3%
of the human genome
- Repeated DNA
- Individuals vary in the number of copies of particular DNA sequences (genes, repeated sequences,
any chunk of DNA)
- Difference among individual organisms in the number of copies of any large DNA sequence (larger
than 1000 bp)
- Copy Number Variation
(CNV)
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