The cell’s control centre: nucleus and chromatin

Question 1

what are the main components of a eukaryotic cell + nucleus

Answer 1

surrounding outer membrane
cytoplasm
cytoskeleton
organelles
nucleus bound by membrane

Question 2

describe the cytoplasm

Answer 2

contains the cell contents in thick fluid

Question 3

describe the function of the nucleus

Answer 3

control centre within DNA

Question 4

the surrounding outer membrane has a ….. layer membrane

Answer 4

double

Question 5

what does the double layer membrane do

Answer 5

separates the cell from the env and communicates the interior of the cell with outside

Question 6

function of the cytoskeleton

Answer 6

keeps the shape

Question 7

describe the nucleus structure

Answer 7

bordered by porous double membrane = nuclear envelope

thin fibres of DNA

protein = chromatin

nucleolus

Question 8

what does the nucelous produce

Answer 8

rRNA to make ribosomes

Question 9

what type of substance is chromtain

Answer 9

protein

Question 10

what shape + size is the nucelolus

Answer 10

small + round

Question 11

describe the structure of DNA

Answer 11

nucleic acid
macromolecule
2 polynucleotide chain
poly made from nucelotides
nucleotide - dexoy, base, phosphate
two strands
held together by H bonds
double helix
bases on the inside of helix
comp bases
each strand serves as a template for the other

Question 12

describe the polarity of dna synthesis

Answer 12

the way the nucleotides are linked = dna chemical polarity
strands - anti-parallel
during dna synthesis - new nucleotide only added in 3’ end
dna synthesis in the 5’ to 3’ end - on other strand
uses dna polymerase

Question 13

describe dna replication

Answer 13

strands separate
h bond broken - helicase + uses ATP
new strand made using old strand as template
join via base pairing rule
dna polymerase
two identical double helixes form
old and new strand in each

Question 14

what are telomeres

Answer 14

special sequences at ends of chromosomes
protect dna
allow for replication - despite problems with lagging strand

Question 15

what is the enzyme that allows for replication to occur

Answer 15

telomerase

Question 16

what do centromeres allow for

Answer 16

allows duplicated chromosomes to be separated during cell division

Question 17

what does dna polymerase monitor

Answer 17

accuracy of base paring before completing the reaction

Question 18

what does proof reading involve

Answer 18

dna polymerase corrects the mistakes that have been made before going further

Question 19

what does removing damaged dna involve

Answer 19

recognise unusual dna structures
unusual structures removed

Question 20

damage to one strand can be repair using the ………. ……. as a …..

Answer 20

complimentary
strand
template

Question 21

what happens when dna is not repaired

Answer 21

cell cycle stops
cell death activated
mutation : genetic diseases/cancer

Question 22

why does dna combine with proteins

Answer 22

allow for:
packaging
access of replication + repair machinery
for controlling how dna is used

Question 23

what does controlling how dna is used involve

Answer 23

which genes are active and which are inactive

Question 24

dna + proteins =

Answer 24

chromatin

Question 25

what type of proteins form chromatin

Answer 25

histones and non histone proteins

Question 26

histones are the most common ….. ……

Answer 26

nuclear protein

Question 27

the main building block of chromatin is …….

Answer 27

nucleosome

Question 28

what do histones account for

Answer 28

akmost half of the proteins isolated from nuclei

Question 29

interphase vs mitotic chromosomes

Answer 29

interphase :
long thin threads of dna
can’t be distinguished under light microscope
chromosome territory

mitotic:
dna highly compacted
visible when cell prepares to divide

Question 30

what does chromosome territory mean

Answer 30

each chromosome occupies certain space inn nucleus

Question 31

human genome features

Answer 31

23 pairs of chromosomes
22 pairs of somatic chromosome
1 pair of sex chromosome
XX- female XY - male

Question 32

heterochromatin vs euchromatin

Answer 32

H = very condense, often no genes , if genes - inactive
E = less condensed, contain both active + inactive genes

Question 33

what does chromatin regulate

Answer 33

structure of chromatin regulates the access to dna

Question 34

what does dna methylation involve

Answer 34

methyl marks added to certain dna bases - repress gene activity

Question 35

chromatin regulation = ….. ……

Answer 35

epigenetic regulation

Question 36

what does histone modification involve

Answer 36

different molecules - acetyl, methyl
attach to sticking out histone tails

alters affinity of histones to dna + activity of dna wrapped around
form docking sites - for other regulatory proteins

Question 37

what does epigenetic modifications control

Answer 37

nucelosome arrangements
chromatin state
therefore gene activity

Question 38

what creates a higher predisposition for cancer

Answer 38

individuals who have a less efficient repair machinery

Question 39

what is xerodeerman

Answer 39

can’t repair dna following uv radiation
caused damage leading to skin lesions + skin cancer

Question 40

what can lead to the chromosome breaking

Answer 40

dna double strand breaks
- chromosome breaks into smaller parts

Question 41

describe the 2 mechanisms to repair broken chromosomes

Answer 41

1. broken ends put together quickly - nonhomologous joining - ERRORS
2. other chromosomes can be used as template to amend broken - homologous recombination - ERROR FREE