3.8.3 using genome projects

Question 1

what is the genome?

Answer 1

all the genes within an organism.

Question 2

what is the proteome?

Answer 2

all the proteins in which an organism codes for.

Question 3

what is an advantage of genome sequencing?

Answer 3

can aid understanding of gene function and interaction.

Question 4

what was the human genome project?

Answer 4

an international project to sequence the human genome.

Question 5

what did the human genome project identify?

Answer 5

• the base sequence of DNA.
• the number of genes.
• the location of genes.

Question 6

the information gained from the human genome project can be used to:

Answer 6

• identify genes linked to disorders and diseases, enabling genetic screening and more targeted therapies/gene therapies.
• conservation/maintaining genetic variability in crops (reversing hybridisation).
• genetic modification.

Question 7

why is determining the proteome of simple organism such as bacteria easier than determining the proteome of a complex organism such as a human?

Answer 7

prokaryotes have small genomes with no introns and there is no post-transcriptional or post-translational modification therefor the genome = the proteome.

Question 8

in prokaryotes why is the proteome larger and more complex than the genome?

Answer 8

• as eukaryotes have large amounts of non-coding DNA, including introns and repeating sequences, so its very difficult to identify which DNA codes for proteins.
• in eukaryotes splicing can result in one gene producing multiple proteins.
• eukaryotes have post-translational modifications, which increases protein diversity.

Question 9

what nucleotides does DNA sequencing use?

Answer 9

dideoxyribose nucleotides.

Question 10

what is special about dideoxynucleotides?

Answer 10

it has a hydrogen on the 3rd carbon instead of an OH group, therefore it can’t form a phosphodiester bond.

Question 11

why is dideoxyribose nucleotides called the chain terminators?

Answer 11

as when they are added to replicating DNA strands no further nucleotides can bind due to the lack of a 3’ hydroxyl group, which results in dideoxynucleotides being unable to form a phosphodiester bond.

Question 12

what is dideoxyribose nucleotides use in genome sequencing?

Answer 12

• run PCR thousands of times.
• end up with chains that differ by one base length.
  = there is a dideoxynucleotide in each base position across all the different chains.

Question 13

what is the traditional Sanger method for DNA sequencing?

Answer 13

• a separate well is used for each type of dideoxynucleotides.
• the dideoxynucleotides are labelled using radioactivity.
• each type of dideoxynucleotide is added to separate wells in a gel and separated using gel electrophoresis.
• fragments are separated by size.
  = read from bottom to top and the base sequence is determined from the order of fragments across the 4 lanes.

Question 14

what is the new automated method for DNA sequencing?

Answer 14

• each dideoxynucleotide is labelled with a fluorescent dye.
• uses electrophoresis inside a capillary tube.
• laser beam illuminates the dideoxynucleotides and a detector then reads the colour and position of each fluorescence.

Question 15

what is the advantage of the new automatic DNA sequencing methods compared to the traditional Sanger method?

Answer 15

automated sequencing is faster and can sequence larger amounts of DNA.