genomes

Question 1

genome

Answer 1

total DNA in any single cell of an organism

nuclear DNA + mitochondrial ( + chloroplast ) DNA

Question 2

endosymbiosis

Answer 2

the proposition that symbiosis between prokaryotes gave rise to eukaryotic cells

• ancestral prokaryote
• infolding of plama membrane
• endosymbiosis
• ancestoral eukaryote

Question 3

endosymbiont

Answer 3

any organism that lives within the body or cells of another organism

Question 4

measuring genomes

Answer 4

they are measured by the number of nucleotides the DNA of that organism is made up of

often measured in Kbs (thousand base pairs)

Question 5

C-value

Answer 5

the amount of DNA in the haploid genome of an organism

human 3 x 10^6 kb

Question 6

C-value paradox

Answer 6

the amount of DNA an organism has does not reflect its evolutionary history or any other obvious feature ( e.g size of organism or percieved complexity )

Question 7

introns

Answer 7

non-coding DNA

allow alternative splicing and may have other important regulatory function

Question 8

telomere

Answer 8

a region of repetitive DNA sequences at the end of a chromosome

long repetitive sequences afford important chromosome protection

Question 9

transposable elements ( TEs )

Answer 9

‘mobile elements’

sequences of DNA that incorporate themselves into different parts of the genome

may make up ~ 25% - 50% of the total DNA in mammalian genomes and a significantly loarger portion in plant and insect genomes

can be categorised into 2 classes:

• transposons
• retrotransposons

Question 10

Transposons ( transposable elements )

Answer 10

the DNA of the mobile element (‘donor DNA’) is excised from its location by an encoded enzyme, transposase, and then re-inserted back into a region of the genome by the same enzymes

Question 11

retrotransposons

Answer 11

an RNA intermediate is produced from the donor DNA and then reverse transcribed int cDNA ( complementary DNA ) which re-inserts into a different genomic location. this group of mobile DNA is what accumulates and expands the genome

Question 12

non-viral retrotransposons

Answer 12

1. LINES ( 6 - 7 kbp long )

2. SINES ( 300 bp ) ‘hyperparasites’

Question 13

viral retrotransposons

Answer 13

encode for a viral shell which allows the retrotransposon to leave the cell and infect other cells/organisms