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::) Flashcards

1
Q

what is the difference in structure and function in

  • superficial fascia
  • deep fascia
A

superficial fascia:

  • loose CT
  • connects the skin to the underlying bones or deep fascia

deep fascia:

  • *- dense fibrous connective tissue​**
  • encircle compartments within the body, particulary limbs and muscle compartments grouping muscles together
  • means muscles share **same neurovascular supply
  • avascular
  • innervated**
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2
Q

describe structure of a DNA nucleotide [3]

how do nucleotides connect to make DNA stucutre? [2]

A

each nucleotide contains:

  • deoxyribose (a pentose (five sugar carbon))
  • *- nitrogenous bases**
  • a phosphate group

how do nucleotides connect to make DNA stucutre? [2]​

the nitrogenous bases in the helixes can interact with each other via H bonds: double structure [1]

these double strands of DNA twist around each other in anti-parralel direction: one runs (3’ -> 5’), the other runs (5’ -> 3’)

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3
Q

describe the differences between non-homologous end joining and homologous recombination for double stranded DNA repair

A

non-homologous end joining:‘quick and dirty.’ get scars on DNA (regions of altered segment due to missing nucleotides). occur in non-coding regions of DNA

homologous recombination: more accurate. sister chromsome is used as a template. complete sequence is restored by copying sister chromosome.

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4
Q
  • why are double strand repairs of DNA more dangerous for single strand repair? [1]
A

there are no intact template strands to copy

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5
Q
  1. when does base excision repair occur?
  2. explain how base excision repair mechanism works
A
  1. correction of single bases that do not sig. distort DNA helix structure
  2. -single base is excised out (using an enzyme, such as uracil DNA glycosylase)
    - DNA polymerase adds correct base and DNA ligase seals the deal
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6
Q

what is role of topoisomerase? (enzyme found in bacterial DNA replication pathway)

A

topoisomerase = prevents supercoiling of DNA. removes knots and tangles in bacterial chromosome.

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7
Q

describe how replication starts at the origins of replication for both:

  • leading strand
  • lagging strand
A

leading strand: synthesis occurs in 5’ to 3’ direction

lagging strand: synthesis cannot occur in direction continously (as would be in 3’ to 5’ direction). INSTEAD: synthesised in short segments (Okazaki fragments) of DNA in 5’ to 3’ direction. DNA ligase joins the okazaki fragments to form the second strand of DNA

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8
Q

which enzyme adds bases onto DNA to allow it synthesise?

A

DNA polymerase ! :)

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9
Q

describe and explain the structure of a chromosome

A

telomeres:

- at each end

  • protective DNA cap.
  • contains repetitive DNA

Centromere:

  • found in centre
  • keeps sister chromatids together and attaches them to microtubules
  • repetitive DNA
  • organised into short arm - p (petite) and long arm - q
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10
Q

what are the ways you can have abornmal chromsome structure?

A

​chromomes can under go:

​deletion

duplication

inversion

translocation (one part of a chr joins another part of a chr)

Robertsonian translocation (two long arms of acrocentric chr (13, 14, 15 21, 22) join at their centromeres

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11
Q

explain the three different patterns that can cause Down Syndrome

A

1. trisomy 21: 95% DS - three copies of chr 21

2. Robertsonian translocation (chrs 14 and 21): 4%. have an extra copy of chr. 21 due to aforementioned translocation

3. Mosiacism: 1%. have normal and trisomy 21 cell linearges. occurs postzygotically. milder features (some cells have normal genome, some cells have trisomy 21 genome)

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12
Q

describe 3 prenatal diagnoses that can be undertaken to test for aneuploidy

A

1. amniocentesis: genetic testing of amniotic fluid. using needle to extract transabdominal. 15-18 weeks of preg (risk to miscarriage: 1/100). ultrasound guidance used. t

2. chorionic villus sampling: genetic testing of tissue from placenta (choroinic villi), ultrasound guidance used transabdominal or transcervical. 12-14 weeks

3. non invasise technqiues: ultrasound imaging of back of neck of embryo at 11-14 weeks. if depth of fluid at back of neck is 3.5-4.4 mm = 70% chance of delivering baby with no major abnormalities.

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13
Q

what are point mutations?

what are the differnent mutations that are consequences of point mutations(4)?

A

point mutations: change in single base pair mutations. occur in DNA replication errors. most common mutation. substitution, insertion, deletion or inversion of base pairs.

consequences:

a) silent mutation - no change to a.a. sequence

b) missense mutation: changes one a.a. to another (conservative: swaps for a.a. with similar properties, non-conservative: swaps for a.a. with dissimilar properties)

c) Nonsense mutation: creates an early stop codon (creates shorter a.a. highly damaging)

d) frameshift: due to deletion or insertion shifts entire coding sequence by one or more bases due to deletion or insertion of bases

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14
Q

how can you classify types of mutations? explain each type (3)

A

at scale of mutation:

1. genomic change: whole chromosome gain / loss

2. chromosomal change: result from rearrangement of genetic material and give rise to visible structural changes in chr.

3. gene mutation: vast majority are single base pair changes / small number of base pair changes

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15
Q

what are the different types of chromosomal mutations?

name two diseaese / disorders from chromosomal mutations?

A

what are the different types of chromosomal mutations?
deletion, duplication (part of a chr breaks off and attaches to sister chromatid), inversions (part of a chr breaks off and reinserts backwards), insertions (part of one getes inserted to another chr), translocation (part of chr breaks off and attaches to different chr)

name two diseaese / disorders from chromosomal mutations?
1. Y - chromosome infert: deletetion part of Y-chromsome. called azoospermia factor (AZF) A, B or C

2. Charcot-Marie-Tooth disease (CMT1A): duplication of regions of chr 17. progressive loss of neurons

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16
Q

what are non-disjunction diseases?

A

Nondisjunction means that a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell.

lead to:

gain or loss of whole chromosomes. e.g. Down Syndrome: trisomy

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17
Q

how does UV radiation cause direct mutations?

how does UV radiation cause indirect mutations?

A
  • *direct damage**
  • cause DNA phoshpate backbone to break
  • break BP connections
  • alter bases
  • cause intra-/inter- stand cross links

indirect damage:
ionizing radiation creates free radicals that damage DNA by reacting with i

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18
Q

what is the effect of DNA damage by UV radiation to melanocytes?

what does smoking do to DNA strands?

A

in melanocytes: pyrimindine dimers -> formed when cyclobutane rings occur between adjacent, same strand pyrimidines in DNA

  • (disrupts p53 gene (tumour supressor))

/

smoking:

causes double stranded breaks and base pair transversions (more deletarious types)

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19
Q

what does the mode of inheritance in Mendelian traits depend on?

A
  1. whether the gene is on an autosomal or sex chromsome
  2. whether the trait is determined by a dominant or recessive genotypes
20
Q

describe difference between frequency found and how strong the effects are of monogenic, oligogenic and polygenic diseaseS?

A

can generally understand whether a trait is more likely to be

monogenic: v. rare but strong effects & env effect small,

oligogenic: still rare (>0.1 to <5%). moderate effects.

polygenic common variants (>5%). weak effects. dont produce disesae in isolation. env has bigger effect

21
Q

what does non-coding DNA do / make? (5)

A

regulatory regions

non-coding RNA genes

centromeres

telomeres

transposons

22
Q

where are most genetic differences located in the genome - where do you find regions of low and high genetic variation?

A

regions of low genetic variation tend to be in conserved regions -> have really important functions

regions of high genetic variation tend to be in areas of DNA replication errors occur (e.g. lots of repeat sequences)

23
Q

what are copy number variations?

A

A copy number variation (CNV) is when the number of copies of a particular gene varies from one individual to the next.

24
Q

what is genome and what is epigenome?

A

genome: complete set of genes / genetic material present in a cell or organism. 3 billion bp in human. static.

epigenome: bits of the genome that are switched on / off. flexible - can change with age and environment ( the epigenome describes modifications to the genome that do not affect the DNA sequence but determine whether genes are switched on or off where and when they are needed.)

25
Q

when is epigenetic life?

what is epigenetic drift?

A

when is epigenetic life?

  • changes in epigenome through: pre-conception -> embryo -> infancy -> childhood -> adolescence -> early adult -> adult -> maturity
  • cumulative effects makes epigenome difficult to predict what the final outcome will be. also is flexible - so changes

what is epigenetic drift?

  • environmental exposure to different epigenetical determines epigenetic drift. epigenetic drift gets bigger as we get older
  • as move through life, environment plays bigger role on epigenome.
  • means we have a biological age and chronological age
26
Q

explain how modifying epigenetic environment can increase / decrease liklihood to getting disease?

A
  • everyone has an individual epigenetic predispostion to disease. but acquired epigenetic mutations can make someone meet the threshold for onset of symptoms earlier / later than expected
27
Q

which part of epigenome is inherited?

A
  • DNA methylation is inheritable
28
Q

describe which progeny are mutltigenerationally and transgenerationally epigenetically affected from changes to male / female?

A

multigenerational (directly exposed) - female: = F1 and F2. male: F1

transgenerational (no direct exposure) - female: F3. male: F2

females: germ cells are produced in developing fetus -> affects F1 and F2 directly, F3 indirectly (grandmother can effect grandchildren epigeneticlly).

e.g. granny smokes when pregnent - effects mother. But within mother, she produces oocytes that produces grandchild. oocytes were already formed when she was in-utero in granny- affects granchild

29
Q

what is genomic imprinting?

A
  • differential DNA methylation and histone methylation and acetylation of paternal or maternal allele
  • growth factor igf2 from father. igf2 receptor - from mother. (father wants as many offspring as poss. mother wants not too big so shes safe and doesnt lack own nutrients). they cancel each other out
  • if lacking in igf2 receptor -> offspring v large OR if ifg2 gene not on -> too small
30
Q

name 4 epigenetic therapies

A

- HDAC inhibitors -> vorinosat for acute myeloid leukaemia (phase 3 trial).

- DNMT inhibitors (5-azacytidine. inhibits DNA methylation)

- Non-coding RNA (difficult to deliver into humans)

- Osteopathic manipulation (changes to diet / exercise)

31
Q

draw schematic diagram of ribosome

what are the three different sites on a ribosome?

A

three sites:

A site. (tRNA binding site)

P site - bind tRNA to ribsome

E site - tRNA goes before exiting

32
Q

two most important sites on tRNA?

A

2 areas of note:

  1. one end is a molecule attached to a amino acid group at one end. the a.a. is catalysed by aminoacyl tRNA synthase ( enzyme that attaches the appropriate amino acid onto its corresponding tRNA)

2. anti-codon region -> sequence here is the anti-codon / complementary sequence to the mRNA

33
Q

what is tRNA and wobble?

what is another way that can increase no. codons from tRNA

A
  • there are 64 possible codon comibations, but there are not 64 tRNAs
  • therefore get wobble at the 3rd position of codon, where can change the last bp on the anti-codon
  • allows a single tRNa to recognise more than one codon

ALSO

can use modified adenosine: Inosine. inosine can regcognise A, C or U

34
Q

explain mechansim of elongation process of translation

A
  • tRNA with complementary anti-codon binds to the mRNA, occupying the A site in the ribosome
  • a peptide bond forms between two amino acids (the first a.a. and the a.a. bought in by tRNA)
  • the bond between the amino acid and the first tRNA is cleaved
  • the ribosome moves one codon further along the mRNA in 5’-3’ direction
  • the empty tRNA moves from the P to the E site
  • the A site is empty and ready for anther tRNA
  • the first, now uncharged tRNA is released from E site.
35
Q

explain the process of termination of translation

A
  • ribosome reaches a stop codon (UAG, UAA or UGA)
  • polypeptide released from the ribosome
  • tRNA is release from ribosome
  • ribosomal subunits dissociate from the mRNA
36
Q

explain the mechanism of initiation of translation

A

(- recruitment of proteins to the 5’ cap binding region of mRNA occurs. this protein complex involves proteins called eukaryotic initiation factor (elF)4F. also includes the initiator methionine tRNA (first AUG in protein)

  • this complex is taken to the ribosome. the ribosome allows the recruitment of the initiator methionine and then the initiation of translation
  • 40S scans mRNA in 5’ to 3’ direction until an appropriate start codon is found )

- the small subunit of a ribosome binds to AUG start codon

  • a specific initiator transfter RNA (tRNAiMet) carrying methionine binds to the AUG start codon
  • the large 60S subunit of a ribosome binds to this complex such that the tRNA occupies the P site
37
Q

what are differences in transcription and translation between pro and eukaryotes?

A

different RNA pol

different ribosome strucutre

38
Q

where does transcription and translation occur?

  • what acts as template for RNA synthesis?
A

transcription: nucleus
translation: cytoplasm
- DNA acts as a template for RNA synthesis in the nucleus

39
Q

which enzymes synthesiss RNA?

RNA and DNA are synthesised in which directions?

which DNA stand can be used as template for RNA synthesis?

A

- RNA polymerases

- RNA is synthesised in 5’-3’ direction only (DNA synthesised in both directions)

  • DNA template is therefore read in 3’-5’ direction
40
Q

what are the 5 steps in mRNA synthesis?

A
  1. initiaition - RNA polymerase binds to the gene
  2. Elongation: (of mRNA). the RNA polymerase transcribes the gene

3. termination: RNA polymerase stops transcribing the gene

4. processing: pre mRNA -> mature mRNA is formed

5. export: mRNA leaves nucleu

41
Q

describe how initiation of transcription works

A
  • DNA unwinds close to a gene, RNA polymerase binds to a promoter sequence
  • the promoter sequence acts as a template for the assembly of the multi component complex of proteins, called the pre-initiation complex, which brings pol II to gene
  • once bound, the RNA polymerase II can then start trancribing the gene. (get transcription intition, elongation and termination)
  • transcription always starts at ATG ​on Exon 1
42
Q

name some upstream features of transcriptional start site that are important

A

proximal promoter region:

  • TATA box: allows RNA polymerase II to orientate correct position on the gene.
  • upstream and downstream elements (from the start site ) that have a positive and negavively effect the rate of transcription in a gene.
43
Q

explain elongation of RNA synthesis

A

Elongation:

  • RNA polymerase synthesises complementary RNA in the 5’ - 3’ direction. uses NTP (ribonucleoside triphosphates)
  • ’ DNA is transcribed from the antisense / template strand
44
Q

what are the differences between the structure of RNA and DNA?

A

differences:

DNA: 2’C on sugar ring: H

RNA: 2’C on sugar ring: OH

45
Q

explain the processes that are involved to ensure that primary mRNA is modified before the export into cytoplasm?

A
  1. capping: at 5’ end: 7-methly guanoside and triphosphate linkage (added onto the first transcribed nucleotide)
  2. splicing: introns are cut out of RNA transcript
  3. poly adenine tail: lots of A added at 3’ end to make a poly A tail
46
Q

explain RNA termination

A
  • RNA polymersae reaches terminator sequence, transcription stops.
  • poly-A tail added on
  • transcript is cleaved
47
Q

describe structure of mature RNA have

A
  • 5’ cap.
  • 3’ poly A tail
  • only coding sequences on

FunMed Random (19 decks)

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