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Structure + Function 1 > nucleic acids and chromatin > Flashcards

nucleic acids and chromatin Flashcards

1
Q

When are chromosomes visible in the cell cycle?

A

Metaphase

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2
Q

What is the ordered display of chromosomes called?

A

Karyotype

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3
Q

How do you count chromosomes and chromatids?

A

Chromosomes: number of centromeres

Chromatids: number of arms

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4
Q

What are telomeres?

A

Ends of a chromosome

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5
Q

what is the constricted region of a chromosome?

A

centromere

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6
Q

what is the role of the centromere?

A

act as the site of assembly of the kinetochore

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7
Q

What is the kinetochore?

A

Highly compex multiprotein structure that is responsible for the actual events of chromosome segregation

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8
Q

What is mitosis?

A

Cell division

Mother cell divides to produce 2 new daughter cells that are genetically identical itself

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9
Q

what is the 3 components of a nucleotide?

A
  • nitrogen-containing base
  • 5 carbon sugar
  • phosphate group
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10
Q

Nitrogen containing bases in DNA / RNA

A

Cytosine

Guanine

Thymine / Uracil

Adenine

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11
Q

Bonding between nitrogen containing bases?

A

Hydrogen bonds

C ≡ G

A = T/U

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12
Q

Molecular shape of double stranded DNA?

A

alpha helix

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13
Q

Describe the structure of a DNA molecule

A

2 linear strands

Held together by hydrogen bonds between base pairs

Run antiparallel to each other

5’ to 3’ and 3’ to 5’

Twist together

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14
Q

How are adjacent nucleotides of RNA and DNA linked?

What is formed?

A

Phosphodiester bonds

Sugar-phosphate backbone

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15
Q

Describe the positioning of the phosphodiester bond between 2 nucleotides

A

Phosphate group attached to 5’ C forms bond with OH group on 3’ of the adjacent nucelotide

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16
Q

In which direction does the sugar-phosphate backbone grow?

A

5’ to 3’ direction

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17
Q

How does the OH group on the ribose in RNA nucleotides affect it? (not present in DNA nucleotides)

A

Responsible for secondary structure

More susceptible to alkaline degredation

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18
Q

What is a histone?

A

Protein that associates with DNA in the nucleus

helps condense DNA into a smaller volume

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19
Q

What is chromatin?

A

Complex of DNA and proteins

Forms chromosomes within the nucleus of eukaryotic cells

20
Q

Describe 2 forms of chromatin

A
  • Euchromatin
    *less condensed
    *can be transcribed
  • Heterochromatin
    *more condensed
    *not usually transcribed
21
Q

Describe 2 forms of chromatin

A
  • Euchromatin
    *less condensed
    *can be transcribed
  • Heterochromatin
    *more condensed
    *not usually transcribed
22
Q

Most of the chromosome body is which type of chromatin?

A

euchromatin

23
Q

What are nucleosomes?

Approximate diameter?

A

Fundamental subunit of chromatin

Where chromatin has wrapped around a histone

bead on a string

11nm

24
Q

what is a histone octamer

A

8 proteins called histones

25
What charge do histone core proteins have?
Positive - binds tightly to the negatively charged DNA backbone
26
Each nucleosome has how many turns of DNA? What are they wrapped around?
1.65 turns 8 histones - histone octamer
27
What makes up the histone octamer?
2 copies of each histone proteins: H2A H2B H3 H4
28
Which histone is not part of the histone octamer? Where is it found?
H1 found in Nucleosome linker DNA linker DNA is between nucleosomes
29
Nucleosomes fold around each other to form...
Chromatin fibre
30
What does chromatin fibre formation require? What does it do?
H1 Binds linker DNA between nucleosome cores Forms a chromatosome
31
What does chromatin fibre formation require? What does it do?
H1 Binds linker DNA between nucleosome cores Forms a chromatosome
32
what is chromatin remodelling?
when DNA "opens" using remodellers for gene expression to take place Cell's chromatin 'opens' using remodellers Allows access to the DNA for transcription
33
Describe ATP-dependent chromatin remodelling
ATP-dependent chromatin remodelling complex Moves, ejects, or restructures nucleosome Exposes DNA to transcription proteins
34
Two ways of chromatin remodelling
Using ATP-dependent chromatin remodelling complexes Enzymes modify the histone proteins in the nucleosomes by adding / removing covalently bonded moieties
35
Describe covalent histone modifications
Add/remove covalently bonded moieties to histone Done by enzymes HATs (histone acetyltransferases) - adds acetyl group kinases - transfer phosphate groups deacetylases - remove acetyl group methyltransferases add methyl group
36
How does remodelling chromatin mediate the activation of genes?
Exposes gene promoter sequences Increases frequency of transcription
37
What are histones rich in? In which part?
Positively charged lysine residues N terminus tails extend out of nucleosome between DNA turns
38
How can histone tails be modified? Where does each modification occur?
Methylation of lysine and arginine *inactivates Acetylation of lysine *activates Phosphorylation of serine *activate / deactivate
39
What can modified histone tails act as?
Signals / Binding sites for regulatory proteins some proteins promote condensation some promote decondensation easier to access dna
40
What can modified histone tails act as?
Signals / Binding sites for regulatory proteins some proteins promote condensation some promote decondensation easier to access dna
41
Does methylation activate or deactivate chromatin?
deactivate
42
Where in the chromosome is methylation common?
Heterochromatin areas ( places unlikely to contain any genes ) telomeres centromere
43
Where in the chromosome is methylation common?
Heterochromatin areas ( places unlikely to contain any genes ) telomeres centromere
44
Chromatin remodelling, DNA modification and histone modification influences the ____ but does not alter the ____
Influences phenotype Not alter genotype
45
Chromatin remodelling, DNA modification and histone modification influences the ____ but does not alter the ____
Influences phenotype Not alter genotype
46
Can modifications to DNA and histones be replicated?
yes

Structure + Function 1 (18 decks)

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