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BIOL 200 > KH8 > Flashcards

KH8 Flashcards

1
Q

What characteristic does the genome of each species of eukaryote consist of

A

A characteristic number of independent linear DNA molecules

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2
Q

What do chromosomes never exist as and what do they exist as instead

A

Never exist as naked DNA but always as a DNA/protein complex called chromatin

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3
Q

Hat is chromatin

A

DNA/protein complex

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4
Q

What is a key feature of chromatin organization

A

Condensation or compacting

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5
Q

When are chromosomes even more packed during mitosis and why

A

Metaphase to facilitate their equal distribution between the two daughter cells

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6
Q

What does a centromere do

A

Joins two sister chromatids together

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7
Q

What is the difference between condensation in metaphase vs interphase

A

Metaphase: highly condensed for transmission to daughter cells

Interphase: dynamic and controlled folding but not as condensed

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8
Q

Difference between metaphase and interphase in terms of replication and transcription

A

M: No DNA replication or transcription

I: Real functional chromosome undergoing replication and transcription

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9
Q

What happens to the chromosome in the transition from metaphase to interphase

A

Chromatin fibre of the chromosome unwinds to a degree

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10
Q

What is a nuecleosome

A

DNA wrapped around a histone (protein) octanes

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11
Q

What causes giant interphase chromosomes (polytene chromosomes of the fly salivary glands)

A

Driven by DNA: 10 cycles of DNA replication without cell division (1024 daughter chromatids)

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12
Q

How are regional differences in chromatin condensation in giant interphase chromosomes shown

A

Dark bands: topological domains (condensed chromatids)
Light bands: boundary elements

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13
Q

What do polytene chromosome puffs show

A

Chromatin decondensation with transcriptional activation, associated with active form of RNA polymerase II meaning active transcription

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14
Q

What does red and green mean in polytene chromosome puffs

A

Red = active for transcription
Green = inactive

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15
Q

What are the characteristics of the regulation of puffs

A

They are regions of active transcription done at different times in different regions

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16
Q

What are metaphase sister chromatids

A

Identical products of the previous semi conservative replication of a single chromosomal DNA molecule

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17
Q

What is a karyotype

A

The chromosomal complement of the species: the number, shape and size of the chromosomes are species specific

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18
Q

What are translocations

A

Chromosomes breaking and rejoining

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19
Q

When can translocation mutations happen and what can they cause

A

Can happen during a somatic cell division cycle and can cause disease

20
Q

Can chromosome rearrangement occur in the germ line

A

Yes

21
Q

What does chromosome rearrangement in the germ line do to gametes

A

Give them variant chromosomes

22
Q

Why is karyotype so consistent across a species

A

Germ line chromosome rearrangements are usually a dead end

23
Q

Is it possible for a chromosomal rearrangement variant to be successfully passed from one generation yo the next

A

Yes

24
Q

What are the elements required for replication and stable inheritance of linear chromosomes

A
  1. Origin of replication
  2. Centromere (gives equally to two daughters)
  3. 2 telomeres (ends)
25
Q

Where can the leu plasmid replicate and not replicate in

A

R: bacteria
NR: eukaryotes (bacterial origins of DNA replication do not work) plasmid cannot support leu- yeast growth in absence of leucine

26
Q

How can the plasmid leu- support yeast growth in absence of leucine in eukaryotes

A

If we insert a random piece of yeast in the plasmid that contained a yeast origin of replication

27
Q

What is ARS (autonomously replicating sequence)

A

Yeast origin on DNA replication

28
Q

What is the remaining issue even after yeast is added to plasmid

A

DNA not evenly partitioned between daughters, missing the centromere that drives mitosis segregation

29
Q

What is CEN

A

DNA sequence from a yeast chromosome centromere

30
Q

What is required for good segregation

A

Genomic fragment CEN (centromeric sequence)

31
Q

What is the kinetochore

A

Site where microtubule spindles attach to centromere

32
Q

What is CENP-A

A

A centromeric protein present on a nucleosome, it is a centromere-specific histone variant

33
Q

What does CENP-A do

A

Recruits the CBF3 complex which in turn recruits the Ndc80 complex which attaches to microtubles

34
Q

Does a plasmid with ARS and CEN that works well as an experimental circular chromosome in yeast also work well as a linear chromosome

A

No, they are made as circular and everything is lost when they are cut with a restriction endonuclease

35
Q

What are telomeres

A

Special sequences located at the end of eukaryotic chromosomes necessary for chromosome life

36
Q

How can linear plasmids containing ARS and CEN behave like normal chromosomes

A

If the genomic fragment telomerase (TEL) is added to both ends

37
Q

What is the function of telomeres

A
  1. Protect from exonuclease
  2. Prevent end-to-end fusion
  3. Solve a replication problem faced by linear DNA
38
Q

What is the telomere problem

A

Because the lagging strand cannot be completed, chromosomes should shorten at the ends in each replication

39
Q

Why is chromosome shortening unsustainable

A

Because at some point you will lose an essential gene

40
Q

What is the solution to chromosome shortening

A

Telomerase, a DNA polymerase that can extend telomeres, restoring chromosome length to overcome lagging strand end-shortening

41
Q

What do telomeres contain

A

Simple repeat DNA sequences

42
Q

What is a reverse transcriptase

A

A DNA polymerase that uses RNA as a template

43
Q

What is telomerase

A

A reverse transcriptase that carries its own template RNA complementary to the telomeres DNA repeat

44
Q

What does extending the template strand by telomerase allow

A

The primate more template DNA to prime on

45
Q

Where is telomerase primarily active

A

In germ cells and stem cells (somatic cells divide only a few times so existing telomeres repeats are long enough

BIOL 200 (13 decks)

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