Flashcards in Nucleus Deck (28)
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1
Q

How much space does the nucleus occupy in the cell?

A

10%

2
Q

How many nuclear pore complexes does the nucleus have?

A

3000-4000

3
Q

What is the matrix in the nucleus called?

A

Nucleoplasm

4
Q

What is the nuclear material stored as in the nucleoplasm?

A

Chromatin

5
Q

How much DNA is in a human cell?

A

2m

6
Q

Why are chromosomes neutral ?

A

DNA charge is negative and histones are positive.

7
Q

What is euchromatin?

A

Most common type of DNA found in cells

Active chromatin which is involved in transcribing RNA to produce proteins.

8
Q

What is heterochromatin?

A

The genetically inactive DNA.

In a typical cell 10% of the genome is heterochromatin.

9
Q

Where is heterochromatin more concentrated?

A

Centromeres and telomeres

10
Q

How are genes in euchromatin silenced?

A

By moving them to the heterochromatin

11
Q

What do nucleoli do?

A

Manufacture the subunits that make up ribosomes

12
Q

What is the granular material in the nucleolus?

A

Ribsomal subunits that have already been formed

13
Q

What is the space between the outer and inner membranes of the nuclear envelope called?

A

Perinuclear space

14
Q

What signals are used to transport RNA and ribosomal subunits to the cytoplasm?

A

Nuclear export signals

15
Q

What is a chromosome?

A

Single linear molecule of dna which contains genes

16
Q

What do telomeres do?

A

Protect the end of the chromosome from degradation by forming G quadruplexes

17
Q

How big are chromosome territories?

A

2 um

18
Q

Where are euchromatin and heterochromatin found?

A

Euchromatin is in the interior of the nucleus and heterochromatin is in the periphery of the nucleus.

19
Q

What 3 key features to scientists use to identify chromosomes?

A

β†’SIZE
β†’BANDING PATTERN
β†’CENTROMERE POSITION

20
Q

List 6 nuclear compartments and their functions.

A

β†’CHROMOSOME TERRITORIES: they store DNA and control access to it

β†’REPLICATION FACTORIES: nascent DNA (lagging strand) production

β†’TRANSCRIPTION FACTORIES: nascent RNA (lagging strand) production

β†’SPLICEOSOME: irregular domains containing splicing factors

β†’NUCLEOLI: ribosome biogenesis

β†’PML NUCLEAR BODIES: possible nuclear depot.

21
Q

What are 3 functions of the nucleolus?

A

β†’ transcription of rRNA genes to produce a large 45S precursor

β†’cleavage/modification of rRNA into 18S, 5.8S and 28S rRNA

β†’assembly of ribosomal subunits (18S, 5.8S, 5S and 28S)

22
Q

What are the 3 distinct zones of the Nucleolus:

A

β†’Fibrillar Centre: Ribosomal RNA genes.
β†’Dense Fibrillar Component: rRNA transcripts
β†’Granular Component: Processing and Assembly

23
Q

What can move via Nuclear Pore Complexes:

A

β†’Nuclear Export: ribosomal subunits and mRNA, Proteins require a nuclear export signal.
β†’Nuclear Import: Histones, DNA/RNA polymerases and other nuclear proteins.”

24
Q

How does the position of centromere differ:

A
β†’Metacentric = Centromere in centre.
β†’Submetacentric = Centromere close to centre.
β†’Acrocentric = Centromere far away from centre.
25
Q

What are the main Functions of the Nucleus:

A
β†’Stores cells DNA.
β†’DNA replication.
β†’Transcription (making RNA).
β†’Ribosomal biogenesis.
β†’Controls communication between nucleoplasm and cytoplasm.
26
Q

Outline the basic Chromosome structure:

A
β†’Telomeres: protect chromosome ends.
β†’Centromeres (primary constriction): needed during cell division.
β†’Multiple origins of replication.  
β†’Q arm longer 
β†’P arm shorter
27
Q

How are Chromosomes identified in the lab:

A

β†’G banding: Chromosomes partially digested and stained with (giemsa).
β†’G dark: gene poor, heterochromatin rich.
β†’G light: gene rich, euchromatin rich.
β†’Forms a unique banding pattern (like barcode).”

28
Q

How is the Nucleus organised:

A

β†’Functional Nuclear Compartmentalisation:

Subnuclear compartments exist despite the absence of internal membranes.”