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Genetik og Personlig Medicin > Modul 1 > Flashcards

Modul 1 Flashcards

1
Q

somatisk celle

A

kropsceller, er de der udgør langt størstedelen af mennesket. Bortset fra kønsceller, (også kaldet gameter eller spermatozoer og aegceller) er alle celler pr definition somatiske celler.

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2
Q

den totale maengede DNA i en somatisk celle =

A

cellens genom

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3
Q

cellekerne (nuckleus) DNA

A

inde i cellekernen findes hovedparten af det DNA en celle indeholder i form af kromosomer. Kopier af hvad der er arvet fra far (P) og mor (M). Hos et individ vil cellekerne genomet i alle de somatiske celler principield vaere det samme.

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4
Q

mitokondrie DNA (mtDNA)

A

inde i mirokondrierne (cellernes energifabrikker) findes et stykke DNA i mange kopier. Mitokondrie DNA kopier af hvad der er arvet fra mor (M). Antal mitokondrier varierer fra celle til celle.

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5
Q

somatisk celle kerne indeholder

A

22 autosomale kromosompar (homologe kromosomer, idet det er to meget ens men normalvis ikke identiske kromosomer)

Et kønskromosompar (XX hos kvinde, XY hos maend)

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6
Q

Karyotype, normal kvinde

A

46XX

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7
Q

Karyotype, normal mand

A

46XY

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8
Q

en celles karyotype beskriver …

A

de kromosomer der er i cellen

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9
Q

hvilken process sikrer at hver somatisk celle indeholder 46 kromosomer?

A

mitose

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10
Q

hvilken process sikrer at kønsceller/gameter indeholder 23 kromosomer?

A

Meiose

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11
Q

Hvilken fase foregår DNA replikation i?

A

S-fasen

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12
Q

DNA polymerase

A

replikerer DNA ud fra “replication origins”

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13
Q

DNA polymerase afleaser template streng

A

3’-5’

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14
Q

DNA polymerase synteserer i

A

5’ - 3’, nyt DNA som er komplimentaert of antiparrallelt i forhold til template DNA

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15
Q

Telomer

A

reperteret DNA sekv ens involveret i DNA replikation ved kromosome enderne. Telomere bliver kortere efter hver DNA replikation. Enzymet telomerase sørger for at der i kønsceller og tidligere embryo sker den nødvendige forlaengelse af telomere som vil tillade mange celledelinger.
- 2 telomere per kromosom

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16
Q

Centromer

A

Repeteret DNA sekvens først involveret i en sammenholdning af replikeret kromosomalt DNA og derefter den korrekte deling af replikeret kromosomalt DNA i anafasen. Dette sker ved at centromeret binder til proteiner.

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17
Q

søsterkromatider

A

har identisk DNA sekvens

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18
Q

homologe kromosomer har..

A

ikke identisk DNA sekvens

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19
Q

mitose resulterer i

A

kan danne 2 nye celler (datter celler), som er genetisk identiske både indbyrdes og med den oprindelige (parantele) celle.

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20
Q

hvad er et gen

A

et afgraenset stykke dobbeltstrenget genomisk DNA der indeholder al den nødvendige information til at der igennem transskription kan dannes RNA der er komplementaere til den ene DNA streng som transkriberes.

Det dannede RNA kan have en funktion i sig selv eller efterfølgende bliver translateret til protein med en funktion, hvis RNA translateres til protein bruges betegnelsen “protein kodende” om genet

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21
Q

arts genom

A

minimum af genomisk DNA, som
kendetegner arten. Så måske lidt forvirrende bruges betegnelsen ”det humane
genom” til at beskrive at ca 3.200.000.000 bp kan beskrive de basale genetiske
byggesten hos mennesket (22 autosomer, et X-kromosom, et Y-kromosom og
et mitokondrie genom). Men dette er uden at tage højde for antal gange hver
af disse genetiske byggesten faktisk er brugt i en somatisk celle

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22
Q

kvinde DNA bp i en somatisk celle

A

6.4 milliarder

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23
Q

mand DNA bp i en somatisk celle

A

6.2 millarder bp

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24
Q

transkriptionfaktorer

A

er proteiner der binder til promoter DNA sekvens afhængigt (feks TATA-box) og definerer
transskriptions start sted og hvilken retning der transskriberes (aflæses).

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25
Q

nogle gener har mere end en promoter

A

alternative promotorer. Der kan således være mulighed for at lave forskellige RNA ud fra et gen.

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26
Q

første exon begynder

A

pr definition praecis der hvor transkription starter

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27
Q

RNA pol aflaeser template DNA i 3-5’ direktion,

A

men transskriberer et nyt RNA 5’-3’ direktion.

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28
Q

Ikke transkriberede DNA strand

A
  • sense strand
  • kodende
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29
Q

navne for det transkriberede DNA strand

A
  • anti sense
  • template
  • ikke kodende
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30
Q

poly A signal

A

RNA bliver klippet over i 3’ ende efter Poly A signal, og så påsat PolyA tale (ca 200x A)

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31
Q

5’ cap RNA

A

m7G

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32
Q

imellem exons og introns

A

donor splice sites (GT) mellem exon - intron sekvenser

Acceptor splice site (AG) mellem intron - exon sekevenser

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33
Q

RNA splejses

A

co-transskriptionelt vha ‘splice-factors’ der binder RNA ‘splice sites’ hvorefter intron sekvenser bliver fjernet vha ”klippe og klistre” mekanisme.

34
Q

hvad splejser man ud af RNA sekvens

A

introns

35
Q

slutprodukt indeholder

A

exons og kaldes mRNA

36
Q

silencer og enhancer

A

kan også findes i introns, der kan vaere flere af dem og raekkefølgen kan også variere.

37
Q

TF binding til promoter, enhancer og silencer i en DNA sekvens regulerer

A

sammen med transskription, og derved mRNA ekspression niveauet i forhold til maengede, sted og tid.

nogle TF er udtrykt i alle vaev, og andre er vaev-specifikke.

38
Q

Hvad er kromatin

A

Histoner er proteiner med den egenskab at de (8 stk) kan danne en ”kugleformet” struktur hvor omkring ca
140-150 bp dobbeltstrenget DNA kan vikles rundt. En sådan DNA/protein pakningsenhed kaldes et
nukleosom. Genomisk DNA er i en cellekerne pakket i form af nukleosomer, og denne pakning kaldes
kromatin.

39
Q

eukromatin

A

åben kromatin

40
Q

heterochromatin

A

lukket kromatin

41
Q

epigenetik: X crom inactivation hos kvinder

A

Kvinder, 46XX, men store dele af det ene X kromosom er transskriptionelt inaktivt pga pakning som heterokromatin.
(inaktiv X kromosom kan ses som Barr-Bodies under et mikroskop).

42
Q

translation sker i

A

cytoplasm (inde i ribosomer)

43
Q

translation i ribosomer retning

A

5’-3’ direktion

44
Q

miRNA

A

17-27 nukleotider (baser) lange RNA. Der findes mange miRNA gener.

antiparallel og komplementaer binding af miRNA (oftest i mRNA 3’ UTR), kan haemme translation samt stabilitet af mRNA.

45
Q

seed sekvens i mRNA

A

vigtigst for mRNA binding, så hele miRNA sekvens behøves IKKE vaere komplementaer til mRNA.

46
Q

funktion of miRNA

A

fin tuning af gen-ekpression. miRNA regulering betyder at maengden af mRNA ikke nødvendigvis er direkte proportionel med maengden af det korresponderende protein.

47
Q

hvordan foregår translation

A

aflaesning af kodons i mRNA, som bliver genkendt af anti-kodons i tRNA igennem antiparallel komplementaer baseparring og hvor en tRNA med en given anti-kodon altid er bundet til en specifik type aminosyre.

48
Q

start af translation

A

AUG som binder til tRNA med aminosyre Methionine (MET, M) og hvorefter læserammen er fastlagt (læseramme = opdelingen af RNA sekvens i triplets svarende til kodons).

49
Q

Hvorfor eksisterer NMD mekanismen?

A

en teori er at der er ingen mRNA repair i forbindelse med RNA transskription og mRNA splejsning hvilket kan resultere i mRNA med nonsense codons pga fejl og derfor potenielt dannelse af for korte proteiner. Sådanne korte proteiner kan vaere skadelige for cellen og derfor fordel for cellen at hindre de bliver lavet.

50
Q

NMD

A

normalt er stop codon placeret i det sidste eller naestsidste exon af 3’ enden, men i NMD er stop codon fundet tidligere i proteinet, og dermed kan mRNA blive nedbrudt og som konsekvens mindre protein maengde.

51
Q

DNA basic components

A
  • sugar (deoxyribose)
  • phosphate
  • nitrogenous base
52
Q

pyrimidines

A

cysteine and thymine

single carbon ring

53
Q

purines

A

adenine and guanine

double ringed carbon structure

54
Q

watson and crick proposed

A

the double helix structure of DNA

55
Q

DNA structure

A

backbone composed of sugar and phosphate, while the nitrogenous bases are pointed inward, making DNA basic.
^held together by phosophodiester bonds

56
Q

DNA coiling

A
  1. DNA packed arund histones (140-150bp)
  2. forms a nucleosome
  3. nucleosomes turn to form solenoid structure (includes about 6 nucleosomes)
  4. solenoid organized into chrom. loops
57
Q

BASIC DNA replicatio

A

Hydrogen bonds break b/w bases
- produces ssDNA

complementary base pairing

template strand

DNA polymerase - adds nucleotides to 3’ end of the new strand.
- Also performs proofreading

58
Q

DNA replication synthesis direction

A

5’-3’ direction

59
Q

multiple replication origins

A

human DNA replication is slow, to speed it up, there are multiple replication origins, which results in multiple seperations of the DNA strands called replication bubbles.

60
Q

5’ cap

A

added to RNA 5’ end during synthesis to prevent degradation. Also helps to indicate the starting position for translation of the mRNA.

61
Q

transcription occurs till

A

termination sequence is reached.

62
Q

poly A tail

A

adeninde bases are added to the 3’ end of the RNA molecule.
- this structure is involved in stabilizing the mRNA molecule so that it is not degraded when it reaches the cytoplasm

63
Q

euchromatin characteristics

A

Acetylation
- acetyl group attached to lysine in histones.

Acetylation of histones decreases the histones ability to tightly bind to DNA.

Allowing more transcription activity

63
Q

euchromatin characteristics

A

Acetylation
- acetyl group attached to lysine in histones.

Acetylation of histones decreases the histones ability to tightly bind to DNA.

Allowing more transcription activity

64
Q

heterochromatin characteristics

A

Less transcriptionally active DNA, more condensed, less acetylated,

65
Q

Transciptional silencing associated with

A
  • methylation of promoter regions
  • miRNA - 17-27 small RNA molecules that are not translated, but bind to RNA and downregulate it and cause destabilization.
66
Q

helix turn helix

A

two alpha helices are connected by a short chain of amino acids which constitute the turn. the carboxyl terminal helix is a recognition helix that binds the DNA major groove.

67
Q

helix loop helix

A

two alpha helices (one short and onr long) are connected by a flexible loop. The loop allows the two helices to fold back and interact with one another. The helices can bind to DNA or to other helix-loop-helix structure

68
Q

zinc finger

A

zinc molecules are used to stabilize an amino acid structure (helices, beta sheets,( with binding of the alpha helix to the DNA major groove

69
Q

leucine zipper

A

two leucine rich alpha helixes are held together by an amino acid side chains. the alpha helices form a Y shaped structure whose side chains bind to the DNA major groove.

70
Q

beta chains

A

side chains extend from the two stranded beta sheets to form contacts with the DNA helix

71
Q

siRNA

A

a type of short RNA sequence bind single specific targets and are used in cancer therapy and some forms of gene therapy

72
Q

lncRNA

A

long coding RNA
length greater than 200 nucleotides. some are involved in gene regulation.

ex: lncRNA encoded by the XIST gene, which inactivates one X chromosome in the genomes of female embryoes.

73
Q

consensus sequences in splicing

A

splicing enzymes are directed to appropriate locations by DNA sequences known as consensus sequences. These are situated adjacent to the exon.

74
Q

types of repeptitive DNA

A

Satellite DNA
- clustered together in certain chromosome locations, where they can occur as tandem repeats (beginning of one repeat occurs immediately adjacent to the end of another repeat)

Dispersed Repetitive DNA
- scattered singly throughout the genome; they do not occur in tandem

75
Q

minisatelite and microsatelite DNA

A

mini:
- blocks of tandem repeats whose totalt length is much smaller, usually a few thousands bp

micro: evens smaller

both are useful in forensics

76
Q

diploid cell division

A

mitosis - nuclear division
cytokinesis - cytoplasmic division

before a cell can divide, it must duplicate its DNA in the interphase of the cell cycle.

77
Q

CDK (cyclin depndent kinases)

A

a family of kianses that phosphorylate other regulatory proteins at key stages of the cell cycle.

Faulty regulation can lead to cancer.

78
Q

mitosis phase

A

Prophase
- chromosomes become visible
- nuclear membrane disappears
- spindle fibers form (radiating from to centrioels, located on opposite sides of the cell)

Metaphase
- chromosomes are most highly condensed
- chromosomes located in the equatorial plane, and very easy to see through a microscope

Anaphase
- centromere of each chromosome splits, allowing sister chromatids to seperate.
- Spindle fibers attach to centromere and is pulled to the opposite sides of the cell
- now the cell contains 92 seperate chromosomes

Telophase
- new nuclear membrane around each set of 46 chromosomes.
- spindle fibers disappear
- chromsomes decondense
- cytokinesis - division of cytoplasm

completion of telophase = 2 diploid daughter cells, both identical to the original cell.

79
Q

haploid meiosis I

A

Prophase I
- chromatin strands coil and condense, causing them to become visible chromosomes
- synapsis: homologous chromosomes pair up side by side
- chromatids of two chromosomes intertwine (bivalent or tetrad)
- chiasmata : cross shaped strucutres that mark attachments between the homologous chromosomes. Each chiasma indicates a point at which the homologous chromosomes. Crossing over: produces chromosomes that consist of combinations of parts of the original chromsomes.
- spindle forms
- nuclear membrane disappears

Metaphase I
- completion of spundle formation and alignment of the bicalents which are still attatched at chiasmata in the equatorial plane

Anaphase I
- chiasmata disappear
- homologous chromosomes are pulled by the spindle fibers towards opposite sides of the cell
- centromeres do NOT duplicate and divide so that only half of the original number of chromosomes migrate toward each pole
- chrom. migrating toward each pole thus consists of each pair of autosome and one pair of sex chromosomes

Telophase I
- chrom. reach opposite sides of the cells
- new nuclear membrane forms
- two daughter cells contain haploid number of chrom and each chrom. has two sister chromatids
- cytokinesis ( in females, all cytoplasm goes into one of the daughter cell, while the other becomes a polar body)

80
Q

meiosis I vs meiosis II

A

meiosis I
- reduction division stage
- two haploid cells are formed from a diploid cell.
- these haploid cells are oogonia in females and spermatogonia in men

Meiosis II
- Equational division
- each haploid cell is replicated

81
Q

haploid meiosis II

A

Interphase II - no replication

Prophase II
- chromosomes thicken
- nuclear membrane disappears
- spindle fibers form

Metaphase II
- spindle fibers pull the chromosomes into alignment at the equatorial plane

Anaphase II
- centromere split and each carries a single chromatid toward a pole of the cell. Chromatids have now seperated but because of chiasma formation and crossing over, the newly seperated sister chromatids may not be identical

Telophase II
- chrom. reach opposite sides of the cell an begin to uncoil.
- new nulcear membranes are formed
- cytokinesis - females: unequal division again of cytplasm leading to one egg cell and another polar body.
- the polar body formed in meiosis I may have undergone division leading to sometimes on egg cell and three polar bodies.

Genetik og Personlig Medicin (1 decks)

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