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Y2S2 - Adv. Molecular Biology > MolBio4 - 32 > Flashcards

MolBio4 - 32 Flashcards

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1
Q

What does the word chromosome actually mean?

A

Coloured body

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2
Q

Where is most eukaryotic DNA stored?

A

Chromosomes

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3
Q

Other than linear DNA, what does each chromosome also comprise?

A

Proteins: packaging and folding; controlling replication, repair and recombination; mainting integrity; regulating gene expression

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4
Q

During what phase of mitosis are chromosomes easily distinguished?

A

Metaphase

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5
Q

What is the term given to the organised represenation of all the chromosomes at metaphase?

A

Karyotype

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6
Q

What is the karyotype of an organism?

A

The organised representation of all the chromosomes in a eukaryotic cell at metaphase

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7
Q

Describe chromosome arrangement during interphase

A

Each occupies a distinct subdomain of the nucleus, and transcriptionally inactive DNA is in the periphery

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8
Q

Describe chromosome movement during transcription

A

Activation is accompanied by movement from the periphery to the centre, indicative of very high order controls

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9
Q

Describe the general structure of chromatin

A

Highly coiled - looks like beads on a string - beads are nucleosomes

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10
Q

What are nucleosomes?

A

Protein core around which DNA coils like cotton on a bobbin

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11
Q

What are the protein subunits of nucleosomes called?

A

Core histones

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12
Q

How many subunits form a nucleosome?

A

8

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13
Q

What is special about nucleosome subunits?

A

Tails that are free to interact with other proteins

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14
Q

What are linker histones?

A

Proteins that strap DNA onto the core histone octamers and limit movement of DNA relative to the nucleosome

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15
Q

What packaging effet do histone octamers induce?

A

DNA packaged into compact, flexible 30nm chromatin scaffold that can be remodelled to accommodate protein complexes for gene transcription/replication

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16
Q

What are the two specialised DNA sequences imperative for DNA function?

A

Telomeres and centromeres

17
Q

What are telomeres?

A

Specialist overhanding single stranded TTAGGG repeats at ends of chromosomes, protecting the length of the chromosome, that can be several hundred nucleotides long

18
Q

What are centromeres?

A

Location of attachment of the mitotic spindle during cell division, ensuring faithful segregation of sister chromatids

19
Q

Outline the structure of a centromere

A

Made up of tandem repeats of alpha-satellite DNA that convey affinity for the kinetochore inner plate proteins. Kineotchore outer plate proteins bind to the inner plate, and then the protein components of the mitotic spindle

20
Q

What is CENP-A?

A

Gene that encodes the specialist H3 histone that mediates the attachment of chromsome to kineotchore

21
Q

What percentage of DNA sequence encodes cellular proteins?

A

1.50%

22
Q

What percentage of the human genome is made up of repeated DNA?

A

50%

23
Q

What is 50% of human DNA?

A

Repeated copies of retrotransposons known as parasitic DNA

24
Q

What are transposons?

A

Mobile genetic elements that jump around the genome

25
Q

What are the three types of transposons?

A

DNA, retroviral and non-retroviral polyA

26
Q

Why are DNA transposons important?

A

They confer the ability to mass re-arrange DNA

27
Q

How do DNA transposons work?

A

Mover around by ‘cut-and-paste’ WITHOUT self-duplication

28
Q

How do retro-viral transposons work?

A

Replicate by RNA intermediates producing new DNA copies that integrate at new genomic locations using self-encoded reverse transcriptase

29
Q

Outline the process of retro-viral replication.

A

Entry into cell > loss of envelope > single RNA > RNA/DNA > DNA double helix > integration > transcription > translation > more virus to infect organism

30
Q

Where are polyA retrotransposons commonly found?

A

Verterbrate genomes

31
Q

How do polyA retrotransposons replicate?

A

Via RNA intermediate using retro-transposon-encoded reverse transcriptase

32
Q

Outline the polyA retrotransposon replication mechanism

A

Element transcribed and translated to produce reverse transcriptase which then binds back onto the element. This then cleaves the first strand of target DNA, and reverse transcribes the RNA into the genome. Multistep process produces second DNA strand with element copy at new position

Y2S2 - Adv. Molecular Biology (14 decks)

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