FOM: molecular genetics Flashcards
1
Q
Genome:
A
- The genetic information of an organism
2
Q
Gene:
A
- Basic unit of inheritance, a region of DNA that encodes a function
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)
4
Q
Direction of DNA synthesis:
A
- From 5’ to 3’
- 3’ has a free OH group for a phosphodiester bond to form
5
Q
Nucleotide structure (DNA): (3)
A
- Phosphate group
- Sugar (deoxyribose)
- Nitrogenous base (T,A,C,G)
6
Q
RNA nucleotide structure:
A
- Phosphate group
- Sugar (ribose)
- Nitrogenous bases (A,C,G,U)
7
Q
DNA structure (big):
A
- Double helix consisting of two antiparallel complimentary strands
8
Q
RNA structure (big):
A
- Single strand, can form complex shapes due to stretches of complementary base pairing
9
Q
Exons in DNA:
A
- Required information for protein coding sequence
10
Q
Introns in DNA:
A
- Non-coding information
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)
12
Q
Tandom repeats:
A
- Found at centromeres, ends of chromosomes and throughout genome
13
Q
Interspersed genome wide repeats:
A
- Retroviruses (long dead)
- Derived from RNA sequences
14
Q
Reverse transcription:
A
- The enzyme reverse transcriptase copies RNA to double stranded DNA for genome insertion
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
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
17
Q
Types of mutation: (3)
A
- Point mutation
- Insertion
- Deletion
18
Q
Causes for DNA damage: (5)
A
- Cellular metabolism
- UV light exposure
- Ionizing radiation
- Chemical exposure
- Replication errors
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
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
