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Medicine yr1 > FOUNDATION-GENETICS > Flashcards

FOUNDATION-GENETICS Flashcards

1
Q

how is DNA read?

A

3’ to 5’

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2
Q

how is DNA synthesised?

A

5’ to 3’

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3
Q

what are chromosomes 1-22 called?

A

AUTOSOMES

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4
Q

what does chromosome 23 determine?

A

sex

XX or XY

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5
Q

what are the main enzymes involved in DNA synthesis?

A

1-topoisomerase enzyme unwinds supercoiled helix DNA

2-Helicase enzyme breaks hydrogen bonds between the base pairs of DNA, creating a replication fork

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6
Q

what happens to the leading strand after DNA strands are separated?

A
  • DNA primase adds an RNA primer to the template to begin the 5’ end of the new strand
  • DNA polymerase iii binds to the RNA primer and continues to make the leading strand by adding DNA bases
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7
Q

what happens to the lagging strand after DNA strands have been separated?

A

-DNA primase adds an RNA primer to the template to begin the 5’ end of the new strand

  • DNA Polymerase iii binds to these RNA primers and adds DNA on in chunks
  • —>forms Okazaki fragments-which are joined by DNA ligase
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8
Q

what is the job of an exonuclease and how is it involved in the final stage of DNA synthesis?

A
  • an exonuclease will go back to cut out the RNA primers

- DNA will be filled in using DNA polymerase i (particularly on the lagging strand)

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9
Q

what is a telomere?

A

-repetitive nucleotide sequence at the end of every chromosome

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10
Q

what is the role of a telomere?

A
  • prevent the shortening of chromosomes during replication and maintains stability
  • prevents the ends of chromosomes being damaged
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11
Q

what is telomerase?

A

enzyme that extends the telomere of a chromosome by copying a short template sequence within the RNA component onto chromosome ends

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12
Q

describe the steps of transcription.

A
  • DNA Helicase unzips DNA to expose the template DNA
  • RNA polymerase binds to a promoter region
  • RNA polymerase adds complimentary RNA nucleotides (U instead of T)
  • DNA reads 3’—->5’-therefore pre-mRNA is made 5’—–>3’
  • pre-mRNA has its introns cut out using a splicesosome
  • mRNA moves from nucelus to ribosome for translation
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13
Q

describe the steps of translation.

A
  • ribosomes are found on the RER
  • mRNA is read in triplet codons by the ribosome and tRNA molecules
  • AUG is start codon
  • small ribsosome sub-unit-matches tRNA anti-codons to mRNA codons
  • large sub-units-forms peptide bonds between the newly attached amino acids-condensation reaction
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14
Q

what are post-translational modifications?

A

-a variety of reactions that changes the structure and therefore function of the proteins made in transcription and translation

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15
Q

what do post-translational modifications increase?

A

functional diversity of the proteome by the addition of functional groups or proteins, proteolytic cleavage of regulatory subunits, or degradation of entire proteins

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16
Q

what are examples of post-translational modifications?

A

-acetylation, glycosylation, phosphorylation and proteolytic cleavage

  • specific examples
  • pre-protein is cleaved to form a mature protein
  • pro-insulin is cleaved into active insulin + protein C
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17
Q

what is gene expression?

A

the process by which genes are made available (on) and unavailable (off) for protein synthesis

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18
Q

what can inhibit transcription?

A

-methylation of DNA-methyl groups bind to cytosine and is a chemical example of epigenetic modification

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19
Q

what promotes transcription?

A
  • acetylation of histones-acetyl groups unwind chromatin from histones and is a structural example of epigenetic modification
  • ubiqitination of histones (less condensed)-makes it easier for enzymes to bind and begin transcription
20
Q

What does pcr stand for?

A

polymerase chain reaction

21
Q

what is pcr and what is it used for?

A

technique used to make copies of a specific DNA region in vitro (in a test tube rather than organism)
-used for-DNA cloning, medical diagnostics and forensic analysis of DNA

22
Q

what is the goal of pcr?

A

to make enough of the target DNA region so that it can be analysed

23
Q

what does pcr require?

A

a DNA polymerase enzyme that makes new strands of DNA using existing strands as templates

24
Q

which DNA polymerase is used for pcr and what does it require?

A

Taq polymerase

-but can only make DNA if its given a primer

25
Q

what is sanger gene sequencing?

A

the average of many long molecules with little to no prior knowledge of DNA sequence

Sanger sequencing is a method of DNA sequencing that involves electrophoresis and is based on the random incorporation of chain-terminating dideoxynucleotides by DNA polymerase during in vitro DNA replication

26
Q

what is NeXT Gen DNA?

A

individual short molecules, prior knowledge of DNA sequence

a type of DNA sequencing technology that uses parallel sequencing of multiple small fragments of DNA to determine sequence

27
Q

What are some examples of numerical chromosomal abnormalities (4)?

A
  • aneuploidy
  • monosomy
  • trisomy
  • polyploidy
28
Q

describe what is meant by aneuploidy.

A

-a numerical chromosomal abnormality that affects one pair of chromosomes

29
Q

describe what is meant by monosomy.

A

loss of one chromosome

30
Q

describe what is meant by trisomy and give an example of a disorder caused by this.

A

gain of 1 chromosome eg downs syndrome-Trisomy 21

31
Q

describe what is meant by polyploidy.

A 
a numerical chromosomal abnormality in which an entire set of chromosomes has been added
eg.
-triploidy
-tetraploidy
(fatal)
32
Q

what are some examples of structural chromosomal abnormalities?

A
  • depletion-section of DNA is deleted
  • duplication-section of DNA is duplicated
  • inversion-section of DNA is copied the wrong way around
  • substitution-section of DNA moves from one chromosome to another
  • translocation-2 separate sections of DNA from different chromosomes swap places with each other
33
Q

what are mendelian genetics?

A

the manner by which genes and traits are passed from parents to their children

34
Q

what is autosomal dominance? Give an example of a disorder showing this.

A

only one copy of an allele is required for expression of gene
Huntingtons

35
Q

what is autosomal recessive? give an example of a disorder showing this.

A

2 copies of same allele are required for gene expression of the phenotype
-sickle cell anaemia

36
Q

what is x-linked recessive and who does it tend to affect?

A

allele on the X chromosome

tends to affect males predominantly

37
Q

what is x-linked dominant?
who does it affect?
Is it common or rare?

A

only 1 copy of allele on X chromosome needed for susceptibility

  • affects both males and female but males carry 1 copy of X chromosome-so have higher incidence and severity
  • RARE
38
Q

what is co dominance and what is an example?

A

alleles are equally expressed, leading to both phenotypes being present
eg-maternal blood type A, paternal B
offspring blood type AB

39
Q

what is penetrance?

A

the proportion of people with a particular genetic change who exhibit signs and symptoms of a genetic disorder

40
Q

what is incomplete penetrance?

Give an example.

A

genotype or mutation is present but the phenotype may not be
eg. BCRA1 or BCRA2 gene mutation may not necessarily cause cancer

41
Q

what is lyonisation?

A

females inherit 2 X chromosomes of which one X chromosome is inactivated randomly and permanently-this is to prevent over expression of genes

42
Q

what is mitochondrial DNA?

A

DNA plasmids exist in the mitochondria and this always comes from the mothers ovum

43
Q

what are features of autosomal dominant pedigree diagrams?

A

-doesn’t skip a generation
-proportion seen in males equal to proportion seen in females
-typically associated in conditions where there is an overproduction of protein
eg huntingtons

44
Q

what are features of autosomal recessive pedigree diagrams?

A

-affects males and females proportionally
-tends to skip a generation
-lack of function of an enzyme is likely to be autosomal recessive
eg sickle cell anaemia

45
Q

what are the features of x-linked recessive pedigree diagrams?

A
  • predominantly present in males passed over from the mother who is a carrier
  • this is because only 1 X chromosome is present in a male and this will only come from the mother
  • daughters are less likely to get it as they would require 2 defective alleles from mother and father
46
Q

outline the steps of PCR

A

1-denaturation
–>addition of heat (94-98 degrees) to separate DNA stands

2-annealing

  • ->cooling strands (45-60 degrees)
  • ->primers join to strands at specific segment of DNA you want amplified

3-dna synthesis

  • ->dna polymerase works on the 2 strands adding DNA nucleotides
  • ->increased temp to 70-75 for taq polymerase to work optimally

Medicine yr1 (55 decks)

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