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Medicine > FOM: molecular genetics > Flashcards

FOM: molecular genetics Flashcards

1
Q

Genome:

A
  • The genetic information of an organism
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2
Q

Gene:

A
  • Basic unit of inheritance, a region of DNA that encodes a function
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3
Q

Chromosomes:

A
  • The human genome is divided into 46 chromosomes in somatic cells (non-sex)
  • 22 pairs of autosomes and either:
  • 2 X chromosomes (females)
  • 1 X and 1Y chromosome (males)
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4
Q

Direction of DNA synthesis:

A
  • From 5’ to 3’

- 3’ has a free OH group for a phosphodiester bond to form

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5
Q

Nucleotide structure (DNA): (3)

A
  • Phosphate group
  • Sugar (deoxyribose)
  • Nitrogenous base (T,A,C,G)
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6
Q

RNA nucleotide structure:

A
  • Phosphate group
  • Sugar (ribose)
  • Nitrogenous bases (A,C,G,U)
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7
Q

DNA structure (big):

A
  • Double helix consisting of two antiparallel complimentary strands
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8
Q

RNA structure (big):

A
  • Single strand, can form complex shapes due to stretches of complementary base pairing
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9
Q

Exons in DNA:

A
  • Required information for protein coding sequence
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10
Q

Introns in DNA:

A
  • Non-coding information
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11
Q

Pseudo genes:

  • Conventional
  • processed
A
  • Conventional: non functional genes due to mutations which have accumulated over time
  • Processed: DNA copies of mRNAs produced by reverse transcription ( copying RNA to DNA)
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12
Q

Tandom repeats:

A
  • Found at centromeres, ends of chromosomes and throughout genome
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13
Q

Interspersed genome wide repeats:

A
  • Retroviruses (long dead)

- Derived from RNA sequences

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14
Q

Reverse transcription:

A
  • The enzyme reverse transcriptase copies RNA to double stranded DNA for genome insertion
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15
Q

Discontinuous DNA Replication:

  • Leading strand
  • Lagging strand
A
  • Leading strand: Synthesised in the direction of unwinding

- Lagging strand: synthesised away from direction of unwinding

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16
Q

Role of primes in DNA replication:

  • DNA polymerase limitation:
  • Primase role
  • NTP removal
A
  • DNA polymerase cannot synthesise de nova
  • Primase (a form of RNA polymerase) lays an RNA primer to start the daughter chain
  • DNA polymerase 1 removes the NTP and replaces them wit dNTP’s
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17
Q

Types of mutation: (3)

A
  1. Point mutation
  2. Insertion
  3. Deletion
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18
Q

Causes for DNA damage: (5)

A
  • Cellular metabolism
  • UV light exposure
  • Ionizing radiation
  • Chemical exposure
  • Replication errors
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19
Q

DNA repair pathways: (5)

  • B E R
  • N E R
  • M E R
  • D R
  • D S B R
A
  • Base excision repair
  • Nucleotide excision repair
  • Mismatch excision repair
  • Direct repair
  • Double strand break repair
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20
Q

Excision repair pathway action: (3)

A
  • Recognise offending bases
  • Remove offending bases/nucleotides
  • Repair resulting gap
21
Q

Defects in repair mechanisms: (6)

  • Increased C….
  • N
  • P A
  • P
  • G I
  • I
A
  • Increased cancer risk
  • Neurodegeneration
  • Premature aging
  • Photosensitivity
  • Growth insufficiency
  • Immunodeficiency
22
Q

Types of RNA molecule: (3)

A
  • mRNA: messenger RNA, copy of protein coding sequence
  • rRNA: ribosomal RNA, component of ribosome
  • tRNA: transfer RNA, carries amino acid to ribosome
23
Q

RNA polymerase, 3 types in eukaryotes

A

Eukaryotes:
I: synthesises rRNA’s
II: synthesises mRNA’s
III: synthesises tRNAS’s and 1rRNA

24
Q

RNA transcription:

  • Requirements
  • Direction
  • Primer???
A
  • DNA dependent enzymes (requires a DNA template)
  • Synthesis 5’-3’
  • No primer required
25
Q

Synthesis of mRNA by RNA polymerase II:

  • RNA polymerase binds…..
  • DNA unwinds and …..
  • Approx. 17…..
  • Elongation of …..
A
  • RNA polymerase binds to promoter site on DNA template
  • DNA unwinds and RNA synthesis is initiated
  • Approx. 17 base pairs unwound
  • Elongation of RNA chain as RNA polymerase moves along the DNA template
26
Q

Promoters in mRNA production:

  • Core promoter:
  • Other TF’s:
A
  • Core promoter region: many transcription factors bound to the TATA region
  • For specialised proteins that need mass producing, other TF’s are bound to other sections of DNA
27
Q

Mediator complex:

A
  • Protein complex that binds to the TF’s, stabilising the complex, allowing more RNNA polymerase to bind
28
Q

Nucleosome:

A
  • Negatively charged DNA packaged around positively charged histones
29
Q

Genetic code:

A
  • The relationship between the sequence of DNA bases and the amino acids in proteins
30
Q

Features of the genetic code:n

  • codons
  • Some AA’s are …
  • Number of termination codons
  • Code is ….
A
  • Codons: three nucleotides that encode an amino acid
  • Some AA’s are encoded by multiple codons
  • 3 termination codons
  • Code is non-overlapping
31
Q

tRNA: (2)

A
  • tRNAs ‘read’ the genetic code

- tRNA with an aa attached is called Aminoacyl tRNA

32
Q

Components of a eukaryotic ribosome:

- Subunits

A

80S ribosome:

  • 60S sub unit: 28S rRNA, 5S, 5.8S, 49 proteins
  • 40S sub unit: 18S rRNA, 33 proteins
33
Q

Protein synthesis: initiation

  • Formation of the…..
  • Aminoacyl tRNA initiator binds to ….., which binds to the ….., moving to the ….
  • 60S subunit now binds to …..
  • Sites
A
  • Formation of the 80S initiation complex
  • Aminoacyl tRNA initiator binds to the 40S subunit, which binds to the 5’cap, moving to the AUG codon.
  • 60S subunit now binds to the AUG codon, forming 80s initiation complex
  • AUG codon takes up the P site, A site empty
34
Q

Protein synthesis: elongation

  • Next aminoacyl tRNA enters the …., forming a…… with its corresponding anticodon
  • ……. bond forms between the two aa, catalysed by …….
  • tRNA leaves the ……, ribosome …… emptying the A site
A
  • Next aminoacyl tRNA enters the A site, forming a base pair with its corresponding anti-codon
  • Peptide bond forms between the two Amino acids, catalysed by peptidyl transferase
  • tRNA of the P site leaves ribosome, ribosome moves along one codon, emptying A site
35
Q

Protein synthesis: Termination

  • Ribosome reaches a ……
  • Release factor enters the ……
  • RF attaches to the ……, carrying …..
  • …… the bond between the …………
  • Releasing the ….. and dissociating the components
A
  • Ribosome reaches a stop codon
  • Release factor enters the A site
  • RF attatches to the stop codon, with water binded
  • Hydrolysing the bond between the protein and the ribosome, releasing the protein and dissociating the components
36
Q

Homozygote:
Heterozygote:

A
  • Homozygote two identical forms of a particular gene

- Heterozygote: two different forms of a particular gene

37
Q

Mutations within coding regions: substitution

  • missense
  • nonsense
  • silent mutation
A
  • Missense: aa substitution
  • Nonsense: STOP codon
  • Silent mutation: same aa produced, different codon
38
Q

Mutations within coding regions: Insertion/deletion

A
  • Frameshift mutations
39
Q

Mutations outside coding regions: B-thalassaemia disorders in. B-globin chain synthesis

  • Promotors
  • Splicing mutations
  • 5’-CAP site
  • Poly-A-tail signal
A
  • Promotors: alters level of transcription
  • Splicing mutations: low/no beta global
  • 5’-CAP site: reduced levels of translation
  • Poly-A-tail signal: reduced translation
40
Q

Cell cycle: (4)

  2. prep for 3
  4. prep for 1
A
  • Mitosis
  • Growth/DNA rep. preparation
  • DNA replication.
  • Prep for mitosis, growth
41
Q

Interphase: prep for cell division

  • Cell cycle time
  • Phases
    1. G1
    2. S
    3. G2
A
  • 90% of cell cycle time
  • 3 phases
    1. G1 phase: growth for S phase
    2. S: DNA replication
    3. G2: growth for mitosis
42
Q

Mitosis: prophase (3)

  • Chromosomes visibly ….. and centromeres migrate to …
  • Microtubule spindles form …..
  • ……. breaks down
A
  • Chromosomes visibly condense and centrosomes migrate to opposite poles
  • Microtubule spindle forms between centrosome and kinetochore on chromosome
  • Nuclear membrane breaks down
43
Q

Mitosis: Metaphase

A
  • Chromosomes align on spindle equator
44
Q

Mitosis: anaphase

A
  • Sister chromatids pulled apart to opposite poles, each daughter cell inherits one chromosome copy
45
Q

Mitosis: telophase

A
  • Chromosomes de-condense and nuclear membrane reforms
46
Q

Mitosis: Cytokinesis

A
  • Membrane cleavage to form 2 identical daughter cells
47
Q

Regulation of the cell cycle: (3)

A
  • Cyclins regulate cell cycle
  • Cyclins bind and activate Cyclin dependant kinases (Cdks)
  • Cdks regulate expression or function of key proteins required in the cycle
48
Q

Meisosis:

A
  • Meiosis is a specialised form of cell division for gametes (sex cells)
  • A diploid cell (2N) divides to form 4 haploid cells (1N)
49
Q

Meiosis process:

A
  • Parent cell containing homologous pair of chromosomes divides into two daughter cells
  • Daughter cells separate, splitting the two sister chromatids
  • 4 Daughter cells with one chromosome each are formed

Medicine (18 decks)

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