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Genetics > L2 DNA to Genes to Chromosomes > Flashcards

L2 DNA to Genes to Chromosomes Flashcards

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1
Q

what is the basis of heredity?

A

DNA

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2
Q

What does Chargaff’s rule say?

A

the content of purines (A and G) is = to the content of pyrimidines (C, U, T)

If the sequence of 1 is known, the other sequence can be predicted…

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3
Q

What is the sense strand?

A

same as coding strand = anti-template strand = mRNA

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4
Q

the sequence of the ____ is complementary to the gene sequence

A

probe

5’—TAAGCCAATTGG—3’
3’—ATTCGGTTAACC—5’
flip
5’—CCAATTGGCTTA–3’

in an mRNA - U would replace T!

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5
Q

what three regions make up eukaryotic genes?

A

coding region - exon
non-coding region - intron
regulatory sequences - promoters, enhancers, silencers

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6
Q

what does the regulatory sequence do?

A

regulates the rate at which transcription of the gene occurs

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7
Q

what do epigenetic modifications do? - like methylation…

A

regulate the rate a which transcription occurs

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8
Q

where are genes found?

A

nucleus and mitochondria

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9
Q

what type of DNA sequence makes up 97-98% of the human genome

A

extragenic DNA

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10
Q

what are the 3 main types of DNA sequences?

A

nuclear
extragenic
mitochondrial

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11
Q

how many copies of unique genes are in the nuclear genome?

A

25,000-30,000

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12
Q

where is the highest gene density of nuclear genes?

A

subtelomeric region - between centromere and telomere

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13
Q

which regions of nuclear genes are non-coding

A
  • heterochromatic and centromeric regions = transcriptionally inactive
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14
Q

what is the largest nuclear gene?

A

dystrophin

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15
Q

what is a single copy gene?

A

unique sequence in the genome that code for one protein - receptors, enzymes, hormones, structural elements of the cell etc.

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16
Q

what is a multigene family and what are the types?

A

genes with similar functions that have arisen by gene duplication

  • classic gene families
  • gene superfamilies
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17
Q

what is a classic gene family?

A

multicopy genes that show a high degree of homology – HOX genes + genes for rRNA, tRNA

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18
Q

what is gene superfamilies?

A

multicopy genes with similar function but limited gene homology – HLA gene, T-cell receptors

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19
Q

how much of our DNA codes for protein?

A

less than 2%

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20
Q

what is extragenic DNA and what are the types?

A

apparently, “junk DNA’ that is not transcriptionally active and has no known function yet…may play a role in gene expression

tandem repeat - based on region and size

  • satellite
  • minsatellite
  • -telomeric
  • -hypervariable
  • microsatellite

Interspersed

  • short interspersed nuclear elements
  • long interspersed nuclear elements
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21
Q

how do tandem repeated DNA sequences work?

A

consist of blocks of tandem repeats of non-coding DNA

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22
Q

what are the types of tandem repeats? what is an important characteristic of them?

A

VNTR and STR

they are polymorphic and inherited in a co-dominant fashion

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23
Q

what are satellite DNA?

A

repeated sequences of DNA usually clustered around centromeres of chromosomes

less sense than other DNA sequences

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24
Q

what are telomeric mini satellite?

A

short (6 nt) repeats found at the end of chromosomes - tellers

added by telomerases after DNA replication and are necessary to prevent the shortening of chromosomes which occurs with age

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25
what is hypervariable minisatellites?
aka VNTR 15-100 nt repeat sequence a number of times found in/around genes and were previously used for genetic fingerprinting but now STR is used
26
what are microsatellites?
aka STR very short (2 nt) ex. CACACACAC but can be 3-4 - repeated 5-50X! highly variable in repeat number co-dominant
27
what repeat extensions are associated with a number of diseases?
trinucleotide repeat expansions
28
what are SINEs
<500 bp long - make up 10% of human genome appears to be normal RNAs that were converted to DNA by reverse transcriptase and were reinserted back into the genome
29
what is the most common SINE in humans
Alu elements
30
what are LINES?
>6000 bp long able to make RNA code for reverse transcriptase
31
why might LINEs and SINEs be responsible for many mutations during meiosis?
unequal crossover - there are deletions where exons are maybe..
32
what are pseudogenes?
sequences that look like real genes but are not functional - no mRNA or protein product..
33
how were pseudogenes probably made?
evolution - gene duplication and subsequent mutation - copying of RNA back to DNA (viral) and reinserted back into genome.
34
what is mitochondrial DNA?
non-nuclear DNA (similar to prokaryotic gene) - arisen by endosymbiosis - single circular DNA - codes for proteins in mito - maternally inherited in humans - from cytoplasm of oocyte - mito disorders are only passed through maternal line - more prone for mutation because the bacterial repair mech. is not as good as eukaryotic mech.
35
what is DNA wound around and what does that form
histones (proteins) | forms a chromosomes
36
what is the constricted region of the chromosomes?
centromere
37
what does the centromere divide the chromosomes into?
2 arms - p arm = short - q arm = long
38
where is DNA most condensed and best visualized - at what stage of mitosis?
metaphase
39
how many sister chromatids does 1 chromosome have
2
40
what phase does chromosomes only have 1 chromatid?
interphase - decondensed
41
microtubules attach to ____ during cell division
centromere kinetochores
42
what are metacentric chromosomes?
p and q arms are equal in length example - chromosome 1
43
what are submetacentric chromosomes?
p arm is shorter than q arm example - chromosome 4
44
what are acrocentric chromosomes?
p arm contains little genetic info example - chromosome 13,14,15,21,22 involved in Robertsonian translocation codes for rRNA and tRNA
45
what is karyotyping?
visualizing chromosomes during metaphase - max condensation
46
how many pairs of autosomes are there?
22 pairs
47
how many pairs of sex chromosomes?
1 pair
48
how are chromosomes ordered?
according to size chromosome 1 is largest chromosome 21 is smallest
49
typically where does each chromosome come from?
one from mother and one from father
50
what is uniparental disomy?
when both the chromosomes of the pair are derived from the same parent
51
how are karyotypes named?
46, XY male 46, XX female *normal
52
how does a Barr body form?
in ALL SOMATIC CELLs in FEMALEs on X chromosome becomes transcriptionally inactive and bundles up
53
when does x-inactivation (lionization) occur?
early stages of development of female embryos
54
is X-activation random?
yes, - father x chromosome active in 50% of cells and mother x chromosome active in 50% of cells like a mosaic
55
what does it mean when x-activation is fixed?
the same x chromosome is inactivated in all descendants of the cell
56
what region regulates the x-activation?
x-activation center (Xic) that has teh gene XIST gene XIST RNA coat one of the x chromosomes = transcriptional interference
57
what locus is huntington's disease on?
chromosome 4p
58
what locus is beta globin on?
chromosome 11
59
what locus is alpha globin gene on?
chromosome 16
60
what MIM number does autosomal dominant disorders start with?
1 | -marfan syndrome 15..
61
what MIM number does autosomal recessive disorders start with?
2 | -CF 219...
62
what MIM number does x-linked disorders start with?
3 | -Duchenne MD 310..
63
what MIM number does mitrochondrial disorders start with?
5 | - leber hereditary optic neuropathy 535...

Genetics (15 decks)

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