Chapter 9 Flashcards
how many genes nuclear genome?
how many genes mitochondrial genome?
nuclear genome: 26.000
mitochondrial genome: 37
what is mtDNA?
how is it organized?
inherited from?
mtDNA: mitochondrial DNA
> circular double stranded DNA
> typically inherited maternally
what is difference in promoters between nucleic and mitochondrial DNA?
nucleic DNA: promoters are mostly dedicated to specific genes
mitochondrial DNA: transcription often starts from common promoters in the CR/D loop region
what is a difference in codons between nuclear genetic code and mitochondrial genetic code?
mitochondrial code uses 60 codons
nuclear code uses 61 codons
> the stop codons vary as well
what is a difference in intron/exon usage between nuclear and mitochondrial DNA?
in mitochondrial DNA, introns are absent
> densely packed with gene information
how big is the human genome?
3.1 GB
estimate of total amount of human genes?
how many protein coding genes?
how many RNA genes?
total: 26.000 genes
> previously much higher estimates
protein coding: 20.000
RNA genes: 6.000
how many % of the genome encodes for protein synthesis?
how many % of the genome are repeat sequences?
2% of genome encodes for protein synthesis
50% of genome are repeat sequences that do not code for proteins
gene-dense regions are predominantly composed of ?
gene-poor “deserts” are composed of?
gene-dense regions: G and C
gene-poor regions: A and T
what was the goal of the Hapmap project?
hapmap project:
> chart all SNPs among various ethnic groups
the longest human gene codes for?
> how long?
> absence causes?
longest human gene codes for dystrophin
> 2.4 megabases long
> absence of dystrophin leads to progressive muscle weakness and fatigability
what are the 2 smallest proteins?
> how long?
oxytocine and vasopressine
> both peptides of 9 amino acids
> very similar, only 2 acids differ
what is the role of oxytocine?
oxytocine:
> acts as NTM in the brain
> known for roles in female reproduction
> sometimes referred to as “love hormone”
participants infused with oxytocine did what?
participants infused with oxytocine were more generous than control participants
what are “families of genes”?
families of genes:
> set of very similar genes, formed by duplication of a single original gene, and generaly with similar biochemical functions
what are pseudogenes?
> why do they appear?
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
what is rRNA?
why do we not know the exact amount of rRNAs?
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
snRNA?
> how many genes?
> main function?
snRNA: small nuclear RNA
> ~200 genes
> main function: involved in RNA splicing
snoRNA?
> main function?
snoRNA: small nucleolar RNA
> involved in maturation of rRNA
miRNA?
> main function?
micro RNA
> multiple important roles in gene regulation, notably in development and implicated in some cancers
>>> CANCER
pi RNA?
main function?
piwi-binding RNA
> often derived from repeats, expressed only in germ line cells
what is consitutive heterochromatine?
> % of total human genome?
> found where?
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)
which chromosomes are the acrocentric chromosomes?
acrocentric chromosomes: 13,14,15,21,22
how does tandem gene duplication occur?
tandem gene duplication
> crossover between unequally aligned chromatids
> either on
1) homologuous chromosomes (unequal crossover)
2) the same cchromosome (unequal sister chromatid exchance)
how does duplicative transposition work?
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
how does large-scale subgenomic duplications work?
large-scale subgenomic duplication
> also called segmental duplications
> can arise as a result of chromosome translocations
what is a transposons?
transposons
> mobile DNA sequence that can migrate to different regions of the genome
what is a retrotransposon?
a cDNA sequence that can integrate in a genome location
what is a retrogene?
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
