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Molecules > Molecular Biology 1+2 > Flashcards

Molecular Biology 1+2 Flashcards

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1
Q

What are the three processes of information replication and use?

A

Transcription

Translation

Replication

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2
Q

What are the two kinds of nucleic acids?

A

RNA

DNA

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3
Q

What are the five nucleic bases?

A 
1- Adenine
2- Thymine (DNA)
3- Cytosine
4- Guanine
5- Uracil (RNA)
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4
Q

What are the two types of nucleic bases?

A

1- Purine: G A

2- Pyrimidines: T C U

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5
Q

How do the nucleic bases bond?

A

1- Hydrogen bonds
2- A=T
3- A=U
4- C≡G

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6
Q

How many strands does DNA have?

A

Two

Double strand held together by H bonds

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7
Q

How is DNA organised?

A

Chromosomes

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8
Q

When do chromosomes condense?

A

When cells divide during prophase

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9
Q

What is a nucleosome?

A

147 pairs of DNA

Associated with histone proteins

1.7 left-handed turns

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10
Q

What are the five types of histone proteins?

A 
1- H1
2- H2A
3- H2B
4- H3
5- H4
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11
Q

What is the function of H1 protein?

A

1- Helps form 30nm fibre

2- Sits on top of nucleosome to maintain the DNA wrapping around other histone proteins

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12
Q

Describe the structure of a chromosome.

A

Centrosome- holds 2 chromatids together

Gene- segment of DNA that codes for a trait

Chromatids- identical copies

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13
Q

How id DNA packaged?

A

1- DNA wraps around histone proteins forming nucleosomes
2- Wraps in a ‘beads on a string’ fashion forming euchromatin
3- Further condensed into a more compact 30nm fibre forming heterochromatin

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14
Q

How is protein access in a chromosome allowed?

A

1- Chromosome is remodelled
2- Condensed chromatin to decondensed chromatin
3- Remodelling complex and enzymes
5- ATP is used

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15
Q

Why is post-translation modification of histone proteins important?

A

Controls the levels of active proteins, activates or represses

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16
Q

Describe the human genome.

A 
1- Mapping of all human genes
2- ~3 billion base pairs
3- Actual genes make up less than 5%
4- Rest is 'junk' DNA
5- Many parts are repetitive
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17
Q

How many base pairs have been mapped in the human genome?

A

~3 billion base pairs

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18
Q

How much of the genome consists of actual genes?

A

<5%

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19
Q

What are two examples of interspersed repeats?

A

1- SINE: short interspersed element

2- LINE: long interspersed element

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20
Q

Where are SINEs and LINEs derived from?

A

Retroviruses

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21
Q

What are telomeres?

A

1- Region of repeated DNA
2- End of each chromosome
3- TTAGGG
4- Protects chromosome from deterioration or fusion with other chromosomes

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22
Q

What are minisatellites?

A

1- Tandem repeats

2- Consist of 70-100 bases repeated up to 40,000 bases

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23
Q

What are microsatellites?

A

1- Tandem repeated

2- Consist of 1-6 bases repeated to more than 100 bases

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24
Q

What is myotonic dystrophy?

A

1- Genetic disease, autosomal-dominant
2- Muscle atrophy
3- Weakness

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25
Q

What is mtDNA?

A

1- Mitochondrial DNA
2- Maternally inherited
3- Circular

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26
Q

Semiconservative

A

Each daughter DNA helix produced by replication contains one newly synthesised strand and one parent strand

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27
Q

Multiple origin

A

Allows DNA replication to occur simultaneously and more efficiently

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28
Q

2

A

Number of replication forks from each origin of replication

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29
Q

Bubble

A

Forms along a DNA strand during replication as there are 2 replication forks

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30
Q

DNA polymerase

A

Enzyme that synthesises DNA strands from free nucleotides

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31
Q

5’ to 3’

A

Direction of DNA replication

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32
Q

3’

A

End of a DNA strand that DNA Polymerase can add nucleotides to

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33
Q

Template Strand

A

Dictates what base is added to the growing strand by DNA Polymerase as it must be complementary

34
Q

Leading

A

Strand that is replicated continuously in the 5’ to 3’ direction

35
Q

Lagging

A

Strand that is replicated in short okazaki fragments in the 3’ to 5’ direction

36
Q

Okazaki Fragment

A

Form the lagging strand and are eventually joined to create one continuous strand of DNA

37
Q

RNA Primer

A

Short sequence required by DNA Polymerase before it can synthesis a new strand of DNA

38
Q

DNA Ligase

A

Enzyme that seals okazaki fragments together on the lagging strand

39
Q

DNA Primase

A

Enzyme that synthesises the RNA primer

40
Q

Single Strand DNA Binding Protein

A

Prevents the 2 DNA sequences that are unwound from rebinding before they are replicated

41
Q

Loop

A

Formed by a newly synthesised okazaki fragment as the DNA is unwound but has to double back on itself to be synthesised in a 5’ to 3’ direction

42
Q

DNA Polymerase Dissociation

A

Allows straightening of the loop created by formation of an okazaki fragment

43
Q

Werner’s Syndrome

A

Genetic syndrome that results in premature aging as telomeres at the end of chromosomes are shortened

44
Q

Overhang

A

Can occur at the end of the template of the lagging strand during DNA replication as it is not long enough to fold back on itself

45
Q

Telomerase

A

Enzyme with an RNA template that allows extension of the template strand so there is enough room for it to fold back and form the final okazaki fragment

46
Q

Telomerase

A

Can become less active with age resulting in loss of sequences at the ends of DNA

47
Q

Mutation

A

Can occur if mistakes caused by DNA polymerase are not detected

48
Q

Proofreading

A

Second functionality of DNA polymerase that allows it to check the correct base has been added

49
Q

P Site

A

Region on DNA polymerase where the new DNA strand is synthesised

50
Q

E Site

A

Region on DNA polymerase where the double helix is checked for correct base pairing

51
Q

Mismatch Repair

A

Mechanisms that use proteins to remove incorrectly paired base after replication

52
Q

Mutation

A

Can occur in the DNA that codes for DNA mismatch proteins and makes individuals more susceptible to further mutations

53
Q

Exonuclease

A

Enzyme domain of DNA Polymerase that catalyses the removal of incorrectly paired bases in the 3’ to 5’ direction

54
Q

PCR

A

Technique used to amplify sections of DNA sequences

55
Q

Heat

A

Used in PCR to break hydrogen bonds between base pairs and separate DNA strands

56
Q

Primer

A

Bind to complementary sections of DNA strands when the solution is cooled during PCR

57
Q

Nucleotide

A

Are also present in solution during PCR and are added to primers using DNA polymerase to synthesise a new DNA strand

58
Q

Multiple Cycle

A

Allow large amounts of DNA to be produced from a small quantity of starting material

59
Q

Pathogen

A

Can be identified using PCR by mixing a sample of its genome with several known primers, positive result if a primer is used and replication occurs

60
Q

PCR

A

Can be used to amplify maternal and paternal tandem repeats to determine whether offspring have inherited a chromosome from their mother or father

61
Q

Tandem Repeat

A

Are present on chromosomes and can be amplified to determine inheritance patterns

62
Q

ddATP, ddCTP, ddGTP, ddTTP

A

4 nucleotides that terminate DNA replication as they don’t have a free hydroxyl group on carbon 3 that can be attacked by an incoming nucleotide

63
Q

DNA Sequencing

A
  1. 4 tubes of DNA synthesis set up containing a small amount of 1 of the hydroxyl lacking nucleotides
  2. DNA replication occurs in each tube but is terminated at different points depending on when the hydroxyl lacking nucleotide is reached
  3. Strands of varying lengths are then separated using gel electrophoresis and the last nucleotide on each strand can be used to determine the DNA sequence
64
Q

Base

A

Represented by a peak in automated DNA sequencing

65
Q

sequencing

DNA Sequencing

A

Can be used to analyse mutations and personalise treatments

66
Q

How are DNA strands copied?

A

1- Semi-conservative model
2- Each of first generation has one parental strand
3- Only 50% of second generation have a parental strand

67
Q

How was the semi-conservative model proven?

A

Matthew Meselson and Frank Stahl’s experiment

68
Q

Describe Meselson and Stahl’s experiment on the semi-conservative model.

A

1- Heavy 15N/15N DNA is grown normally in 15N containing medium
2- Heavy DNA is used to grow the first generation in light 14N medium, leading to heavy/light DNA hybrid
3- Hybrid DNA continues growing to make second generation, with 50% light DNA and 50% hybrid DNA
4- Fourth generation has 75% light DNA and 25% hybrid DNA

69
Q

How many base pairs does a eukaryotic chromosome have on average?

A

~10^8 base pairs long

70
Q

At what rate does replication take place?

A

1- 2 kb/min

2- One chromosome may takes ~35 days

71
Q

How is replication sped up?

A

DNA replication takes place at many different sites simultaneously

72
Q

In what direction is DNA replicated?

A

5’ to 3’

73
Q

Is the replication fork symmetrical or asymmetrical?

A

Asymmetrical

74
Q

What is the replication fork?

A

1- Structure formed in DNA replication
2- The two strands of DNA are pulled apart by helicases
3- Each strand serves as a template for its replication
4- Leading strand: DNA synthesised in the same direction as the growing replication fork, or 5’ to 3’
5- Lagging strand: DNA synthesised in the opposite direction, leading to the formation of Okazaki fragments which are joined by DNA ligase

75
Q

What happens at the lagging strand?

A

1- Synthesised in the opposite direction
2- DNA polymerase adds RNA primer to start new Okazaki fragment
3- DNA polymerase finishes DNA fragment
4- Old RNA fragment is erased and replaced by DNA
5- DNA ligase joins Okazaki fragments together

76
Q

What happens at the DNA end to complete the lagging strand?

A

1- Template strand has repetitive telomere sequences while the newly synthesised lagging strand is incomplete
2- Telomerase binds and adds additional repeats to the template strands
3- This allows for the completion of the lagging strand’s synthesis by DNA polymerase and ligase

77
Q

At what stages can mutation be adjusted?

A

1- During synthesis

2- Post-replication

78
Q

What is PCR?

A

1- Polymerase chain reaction
2- Technique which allows replication of DNA to make large amounts
3- DNA is heated to separate strands and primers and polymerases are added to synthesise new DNA
4- Can be used to identify presence of infectious agents
5- Can be used to identify inheritance patters

79
Q

How is the presence of infectious agents identified using PCR?

A

1- Blood sample is taken from infected person
2- Cells are removed by centrifugioun
3- Viral/Microbial DNA is extracted and undergoes PCR
4- Gel electrophoreis is used to compare blood of infected person and noninfected person

80
Q

Three ways in which strands can be copied

A
  1. The semiconservative strand
  2. The conservative model
  3. The dispersive model
81
Q

What strands is the DNA made of after Semiconservative replication

A

Each daughter molecule consists
of one old strand (template) and
one newly synthesized strand

Molecules (4 decks)

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