Nucleus

Question 1

How much space does the nucleus occupy in the cell?

Answer 1

10%

Question 2

How many nuclear pore complexes does the nucleus have?

Answer 2

3000-4000

Question 3

What is the matrix in the nucleus called?

Answer 3

Nucleoplasm

Question 4

What is the nuclear material stored as in the nucleoplasm?

Answer 4

Chromatin

Question 5

How much DNA is in a human cell?

Answer 5

2m

Question 6

Why are chromosomes neutral ?

Answer 6

DNA charge is negative and histones are positive.

Question 7

What is euchromatin?

Answer 7

Most common type of DNA found in cells

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

Question 8

What is heterochromatin?

Answer 8

The genetically inactive DNA.

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

Question 9

Where is heterochromatin more concentrated?

Answer 9

Centromeres and telomeres

Question 10

How are genes in euchromatin silenced?

Answer 10

By moving them to the heterochromatin

Question 11

What do nucleoli do?

Answer 11

Manufacture the subunits that make up ribosomes

Question 12

What is the granular material in the nucleolus?

Answer 12

Ribsomal subunits that have already been formed

Question 13

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

Answer 13

Perinuclear space

Question 14

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

Answer 14

Nuclear export signals

Question 15

What is a chromosome?

Answer 15

Single linear molecule of dna which contains genes

Question 16

What do telomeres do?

Answer 16

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

Question 17

How big are chromosome territories?

Answer 17

2 um

Question 18

Where are euchromatin and heterochromatin found?

Answer 18

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

Question 19

What 3 key features to scientists use to identify chromosomes?

Answer 19

→SIZE
→BANDING PATTERN
→CENTROMERE POSITION

Question 20

List 6 nuclear compartments and their functions.

Answer 20

→CHROMOSOME TERRITORIES: they store DNA and control access to it

→REPLICATION FACTORIES: nascent DNA (lagging strand) production

→TRANSCRIPTION FACTORIES: nascent RNA (lagging strand) production

→SPLICEOSOME: irregular domains containing splicing factors

→NUCLEOLI: ribosome biogenesis

→PML NUCLEAR BODIES: possible nuclear depot.

Question 21

What are 3 functions of the nucleolus?

Answer 21

→ transcription of rRNA genes to produce a large 45S precursor

→cleavage/modification of rRNA into 18S, 5.8S and 28S rRNA

→assembly of ribosomal subunits (18S, 5.8S, 5S and 28S)

Question 22

What are the 3 distinct zones of the Nucleolus:

Answer 22

→Fibrillar Centre: Ribosomal RNA genes.
→Dense Fibrillar Component: rRNA transcripts
→Granular Component: Processing and Assembly

Question 23

What can move via Nuclear Pore Complexes:

Answer 23

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

Question 24

How does the position of centromere differ:

Answer 24

→Metacentric = Centromere in centre.
→Submetacentric = Centromere close to centre.
→Acrocentric = Centromere far away from centre.

Question 25

What are the main Functions of the Nucleus:

Answer 25

``` →Stores cells DNA. →DNA replication. →Transcription (making RNA). →Ribosomal biogenesis. →Controls communication between nucleoplasm and cytoplasm. ```

Question 26

Outline the basic Chromosome structure:

Answer 26

``` →Telomeres: protect chromosome ends. →Centromeres (primary constriction): needed during cell division. →Multiple origins of replication. →Q arm longer →P arm shorter ```

Question 27

How are Chromosomes identified in the lab:

Answer 27

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

Question 28

How is the Nucleus organised:

Answer 28

→Functional Nuclear Compartmentalisation: Subnuclear compartments exist despite the absence of internal membranes."