More than a genome (Dr Curran) Flashcards
How do we obtain the sequence of all of
the DNA in an Organism’s
Genome?
Basically: through cloning
• Chromosomes are broken into small overlapping pieces and cloned
• Ends of clones (telomere) sequenced and reassembled into original chromosome strings
• Each piece (end of clone) is sequenced multiple times to reduce error rate
– 10-fold sequence coverage achieves a rate of
error > 1/10,000 (lots of sequences = less error)
How does genome size changed based on the organism?
-the more complex the organism= the larger the genome size (more information)
What can DNA sequencing tell us?
• The DNA sequence.
• The geography of the Genome.
– Relates structure to function e.g Relative position of genes and other sequences.
• The evolutionary history of the Genome.
– The roles played by genome/gene duplications.
• The potential functions of encoded sequences by:
– Comparisons to other sequences of known functions in other databases.
– Identification as unique using other databases.
And by advanced studies
– Microarray analysis.
– Deletion of reading frames.
What common characteristic do all organisms have?
-All living organisms had a single origin
• All living organisms have remarkably similar genetic components (universal code)
• Life evolved once and we are descendents of that event
• Analysis of appropriate biological systems in model organisms provides fundamental insight into corresponding human systems
What is the largest DNA sequencing effort that has been made to date?
The Human Genome project
-interdisciplinary and collaboration between many institutions
What are the insights we gained from the human genome project?
- Approximately 40,000 human genes
- Genes encode noncoding RNA or proteins
- Repeat sequences are > 50% of genome
- Distinct types of gene organization
How are genes organized?
• Gene families
– Closely related genes clustered or dispersed
• Gene-rich regions
– Functional or chance events? (referring to the regions)
• Gene deserts
– Span 144 Mb or 3% of genome
– Contain regions difficult to identify?
• e.g., big genes – nuclear transcript spans 500 kb or more with very large introns (exons < 1% of DNA)
What is lateral transfer of genes?
- > 200 human genes may arise by transfer from organisms such as bacteria
- Lateral transfer is direct transfer of genes from one species into the germ line of another
Are there significant variations in genes according to race?
-No:
• Genome sequence centers have sequenced significant portions of at least three races
• Range of polymorphisms within a race can be much greater than the range of differences between any two individuals of different race
• Very few genes are race specific
• Genetically, humans are a single race
What are some areas of study that havent been fully explored in the human genome?
- Small genes are hard to identify
- Some genes are rarely expressed and do not have normal codon usage patterns – thus hard to detect
- What are the RNA molecules doing?
What is DATA?
A representation of facts, concepts, or instructions in a formalized manner suitable for: • COMMUNICATION. • INTERPRETATION. or • PROCESSING. by humans or by automated means.
What is information?
Information is the result of: • PROCESSING. • MANIPULATING. and • ORGANISING Data.
How similar are mice and human genetics?
- overall gene sequence= the same
- how they are regulated is different
What is a natural occuring form of a clone?
- Twins!
- same exactly DNA sequence
- however unique individuals! - nature vs nurture
How are gene sequences expressed?
-EXPRESSING INHERITED DATA IS COMPLEX IN EUKARYOTES
• Chromatin affects expression
• There is a bewildering array of regulatory proteins
• RNA transcripts are frequently processed (spliced)
What are epigenetics?
- chromosomes are not just inherited DNA sequences
- epigenetics = inherited context (modified chromatin throughout lifetime)
- one type of epigenetics: histone modification
- another type: methylation
- epigenetics as important as DNA sequences (eg. worker bees and queen bees same sequence different epigenetics)
What does biological ambiguity essentially mean for DNA?
- DNA IS COILED UP INTO CHROMOSOMES BY PROTEINS.
- ALL SORTS OF FACTORS AFFECT HOW EASILY THE DNA CAN BE DECODED.
- THE SAME DATA IS DECODED INTO DIFFERENT BIOLOGICAL INFORMATION DEPENDING UPON THE ENVIRONMENT
- DNA DATA IS DECODED INTO BIOLOGICAL INFORMATION.
- THE SAME DATA IS DECODED INTO DIFFERENT BIOLOGICAL INFORMATION DEPENDING UPON WHICH CELL IT FINDS ITSELF IN.
What does splicing do?
- SPLICING CAN GENERATE AMBIGUITY IN THE ENCODED PROTEINS
- splicing is the process of removing parts of gene sequences and combining others
- not all of the data in the gene is found in the encoded protein
- because rna gets processed in the cells (splicing)
- one gene can generate many outcomes through processing
Give an example of RNA processing (splicing)
Dystrophin gene underlying Duchenne muscular dystrophy (DMD) is an extreme example of processing
Is the data in DNA absolute?
- NO
- one gene- many possible mRNAs
- released information is context sensitive (epigenetics)
- change the context and the information changes
What is an example where outside factors might affect a genetic condition?
Phenylketonuria (PKU)
- autosomal recessive
- yet with phenylalanine free diet can be perfectly healthy
