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
Synthesis of mRNA by RNA polymerase II: - RNA polymerase binds..... - DNA unwinds and ..... - Approx. 17..... - Elongation of .....
- 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
Promoters in mRNA production: - Core promoter: - Other TF's:
- 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
Mediator complex:
- Protein complex that binds to the TF's, stabilising the complex, allowing more RNNA polymerase to bind
28
Nucleosome:
- Negatively charged DNA packaged around positively charged histones
29
Genetic code:
- The relationship between the sequence of DNA bases and the amino acids in proteins
30
Features of the genetic code:n - codons - Some AA's are ... - Number of termination codons - Code is ....
- Codons: three nucleotides that encode an amino acid - Some AA's are encoded by multiple codons - 3 termination codons - Code is non-overlapping
31
tRNA: (2)
- tRNAs 'read' the genetic code | - tRNA with an aa attached is called Aminoacyl tRNA
32
Components of a eukaryotic ribosome: | - Subunits
80S ribosome: - 60S sub unit: 28S rRNA, 5S, 5.8S, 49 proteins - 40S sub unit: 18S rRNA, 33 proteins
33
Protein synthesis: initiation - Formation of the..... - Aminoacyl tRNA initiator binds to ....., which binds to the ....., moving to the .... - 60S subunit now binds to ..... - Sites
- 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
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
- 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
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
- 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
Homozygote: Heterozygote:
- Homozygote two identical forms of a particular gene | - Heterozygote: two different forms of a particular gene
37
Mutations within coding regions: substitution - missense - nonsense - silent mutation
- Missense: aa substitution - Nonsense: STOP codon - Silent mutation: same aa produced, different codon
38
Mutations within coding regions: Insertion/deletion
- Frameshift mutations
39
Mutations outside coding regions: B-thalassaemia disorders in. B-globin chain synthesis - Promotors - Splicing mutations - 5'-CAP site - Poly-A-tail signal
- 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
Cell cycle: (4) 1. 2. prep for 3 3. 4. prep for 1
- Mitosis - Growth/DNA rep. preparation - DNA replication. - Prep for mitosis, growth
41
Interphase: prep for cell division - Cell cycle time - Phases 1. G1 2. S 3. G2
- 90% of cell cycle time - 3 phases 1. G1 phase: growth for S phase 2. S: DNA replication 3. G2: growth for mitosis
42
Mitosis: prophase (3) - Chromosomes visibly ..... and centromeres migrate to ... - Microtubule spindles form ..... - ....... breaks down
- Chromosomes visibly condense and centrosomes migrate to opposite poles - Microtubule spindle forms between centrosome and kinetochore on chromosome - Nuclear membrane breaks down
43
Mitosis: Metaphase
- Chromosomes align on spindle equator
44
Mitosis: anaphase
- Sister chromatids pulled apart to opposite poles, each daughter cell inherits one chromosome copy
45
Mitosis: telophase
- Chromosomes de-condense and nuclear membrane reforms
46
Mitosis: Cytokinesis
- Membrane cleavage to form 2 identical daughter cells
47
Regulation of the cell cycle: (3)
- 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
Meisosis:
- Meiosis is a specialised form of cell division for gametes (sex cells) - A diploid cell (2N) divides to form 4 haploid cells (1N)
49
Meiosis process:
- 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