Organisation of eukaryotic genomes

Question 1

How many orders of magnitude between the smallest and largest eukaryotic genome?

Answer 1

5

Question 2

How many base pairs in 23 pairs of chromosomes?

Answer 2

6 billion

Question 3

Approximate length of DNA

Answer 3

2 metres

Question 4

Approximate number of cells in the human body

Answer 4

10^13 (ten trillion)

Question 5

Tree of what DNA contains

Answer 5

transcribed

• protein coding genes
• non coding genes

not transcribed
non structural
- unique
-repetitive
structural

Question 6

What is the dark matter of the eukaryotic genome?

Answer 6

Not transcribed, non-structural, unique DNA

Question 7

What is the longest gene?

Answer 7

dystrophin 2.2 million bps and takes 16 hours to transcribe

Question 8

How long is an average coding sequence?

Answer 8

1000 bps

Question 9

How long is an average gene?

Answer 9

20 000 bps

Question 10

Most common length of an exon?

Answer 10

37 codons (11bps)

Question 11

Most common number of exons for a human gene to have?

Answer 11

4

Question 12

What percentage of human genes have 2 or more exons?

Answer 12

95%

Question 13

Which gene has the longest coding sequence?

Answer 13

Titin

Question 14

How many exons does titin have versus dystrophin (if titin has the longest coding sequence evn those dystrophin is the longest gene)?

Answer 14

363 exons - titin

79 exons - dystrophin

Question 15

Percentage of introns and exons in an average human gene?

Answer 15

95% introns (non-doing DNA)

5% exons (coding DNA)

Question 16

How are protein coding genes distributed on chromosomes?

Answer 16

Non-uniformly

Question 17

What percentage of DNA is transcribed into RNA?

Answer 17

4%

Question 18

What percentage of DNA is protein coding genes and non coding genes.

Answer 18

protein coding genes = 1%

Non-coding genes = 3%

Question 19

What types of structure DNA is there that is not transcribed?

Answer 19

Telomeres

Centromeres

Question 20

What is a centromere?

Answer 20

Region of chromosome that links pair of sister chromatids and where spindle fibres attach via kinetochores during mitosis.

Question 21

How many centromeres per chromosome?

Answer 21

1

Question 22

What percentage of the human genome is made up of centromeres?

Answer 22

10%

Question 23

How many base pairs long are centromeres?

Answer 23

5 million

Mostly composed of alpha-satellites (171 bp repeats)

Question 24

Do centromeric regions of the chromosome have genes in them?

Answer 24

few/no genes

Question 25

What percentage of the human genome is made up of telomeres?

Answer 25

1%

Question 26

Telomeres

How many bps long?
What kind of repeat?
What overhang?

Answer 26

10 000bps long
TTAGGG repeats
3’ single strand overhang which invades double helix to form a T-loop

Question 27

Describe the regions on a chromosome which are next to the telomeres

Answer 27

Higher gene density. Genes in these regions have a high chance of being exchanged during genetic recombination.

Question 28

Optimal place along the chromosome for a selfish gene to go?

Answer 28

Regions next to telomeres (sub-telomeric regions) because they have a higher chance of being exchanged during recombination.

Question 29

What is satellite DNA?

Answer 29

simple sequence repeats (SSRs) of 1-6bp tandem repeats.

Question 30

What percentage of the genome is satellite DNA?

Answer 30

3%

Question 31

What causes simple sequence repeats?

Answer 31

DNA replication errors

Question 32

What are retrotransposons?

Answer 32

a genetic component that converts RNA back into DNA in reverse transcription so that they can copy and paste themselves in difefrent genomic locations

Question 33

Three retrotransposons

Answer 33

LTRs
LINEs
SINEs

Question 34

What percentage of the average gene is transposons?

Answer 34

30% LINEs, SINEs and SSRs

Question 35

Percentages of eukaryotic genome DNA

Answer 35

4% genes are transcribed in RNA

11% are non transcribed structural DNA

75% are non transcribed non structural DNA