Chapter 9

Question 1

how many genes nuclear genome?

how many genes mitochondrial genome?

Answer 1

nuclear genome: 26.000

mitochondrial genome: 37

Question 2

what is mtDNA?

how is it organized?

inherited from?

Answer 2

mtDNA: mitochondrial DNA

> circular double stranded DNA

> typically inherited maternally

Question 3

what is difference in promoters between nucleic and mitochondrial DNA?

Answer 3

nucleic DNA: promoters are mostly dedicated to specific genes

mitochondrial DNA: transcription often starts from common promoters in the CR/D loop region

Question 4

what is a difference in codons between nuclear genetic code and mitochondrial genetic code?

Answer 4

mitochondrial code uses 60 codons

nuclear code uses 61 codons

> the stop codons vary as well

Question 5

what is a difference in intron/exon usage between nuclear and mitochondrial DNA?

Answer 5

in mitochondrial DNA, introns are absent

> densely packed with gene information

Question 6

how big is the human genome?

Answer 6

3.1 GB

Question 7

estimate of total amount of human genes?

how many protein coding genes?

how many RNA genes?

Answer 7

total: 26.000 genes

> previously much higher estimates

protein coding: 20.000

RNA genes: 6.000

Question 8

how many % of the genome encodes for protein synthesis?

how many % of the genome are repeat sequences?

Answer 8

2% of genome encodes for protein synthesis

50% of genome are repeat sequences that do not code for proteins

Question 9

gene-dense regions are predominantly composed of ?

gene-poor “deserts” are composed of?

Answer 9

gene-dense regions: G and C

gene-poor regions: A and T

Question 10

what was the goal of the Hapmap project?

Answer 10

hapmap project:

> chart all SNPs among various ethnic groups

Question 11

the longest human gene codes for?

> how long?

> absence causes?

Answer 11

longest human gene codes for dystrophin

> 2.4 megabases long

> absence of dystrophin leads to progressive muscle weakness and fatigability

Question 12

what are the 2 smallest proteins?

> how long?

Answer 12

oxytocine and vasopressine

> both peptides of 9 amino acids

> very similar, only 2 acids differ

Question 13

what is the role of oxytocine?

Answer 13

oxytocine:

> acts as NTM in the brain

> known for roles in female reproduction

> sometimes referred to as “love hormone”

Question 14

participants infused with oxytocine did what?

Answer 14

participants infused with oxytocine were more generous than control participants

Question 15

what are “families of genes”?

Answer 15

families of genes:

> set of very similar genes, formed by duplication of a single original gene, and generaly with similar biochemical functions

Question 16

what are pseudogenes?

> why do they appear?

Answer 16

pseudogenes

> defective gene copy in a gene family

> gene duplication that creates many similar copies of one gene sometimes fails -> pseudogene

> dysfunctiona, do not code for protein or are not expressed

Question 17

what is rRNA?

why do we not know the exact amount of rRNAs?

Answer 17

ribosomal RNA

> ribosomal RNA arrays were excluded from the human genome project, as a result of technical difficulties in obtaining unambiguus ordering of overlapping DNA clones for long regions composed of very similar tandem repeats

Question 18

snRNA?

> how many genes?

> main function?

Answer 18

snRNA: small nuclear RNA

> ~200 genes

> main function: involved in RNA splicing

Question 19

snoRNA?

> main function?

Answer 19

snoRNA: small nucleolar RNA

> involved in maturation of rRNA

Question 20

miRNA?

> main function?

Answer 20

micro RNA

> multiple important roles in gene regulation, notably in development and implicated in some cancers

>>> CANCER

Question 21

pi RNA?

main function?

Answer 21

piwi-binding RNA

> often derived from repeats, expressed only in germ line cells

Question 22

what is consitutive heterochromatine?

> % of total human genome?

> found where?

Answer 22

consitutive heterochromatine

> accounts for 200mb (6.5%) of the human genome

> mostly consists of long arrays of high-copy-number tademly repeated DNA sequences

> mostly found around centromere, especially on chromosome 1,9,16,19 and Y chr ( and the accrocentric chr)

Question 23

which chromosomes are the acrocentric chromosomes?

Answer 23

acrocentric chromosomes: 13,14,15,21,22

Question 24

how does tandem gene duplication occur?

Answer 24

tandem gene duplication

> crossover between unequally aligned chromatids

> either on

1) homologuous chromosomes (unequal crossover)
2) the same cchromosome (unequal sister chromatid exchance)

Question 25

how does duplicative transposition work?

Answer 25

duplicative transposition

> a duplicated DNA copy integrates into a new subchromosomal location

> this typically involves retrotransposition: reverse transcriptase makes a cDNA copy of a RNA transcript -> copy integrates into chromosomal location

Question 26

how does large-scale subgenomic duplications work?

Answer 26

large-scale subgenomic duplication

> also called segmental duplications

> can arise as a result of chromosome translocations

Question 27

what is a transposons?

Answer 27

transposons

> mobile DNA sequence that can migrate to different regions of the genome

Question 28

what is a retrotransposon?

Answer 28

a cDNA sequence that can integrate in a genome location

Question 29

what is a retrogene?

Answer 29

when cDNA integrates in genomic location, by chance close to a promotor region suitable for this gene

> this creates a intronless retrogene that can be expressed