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Medicine > Foundation > Flashcards

Foundation Flashcards

1
Q

What are the steps of Transcription?

A

Initiation
Elongation
Termination

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2
Q

Describe each step of Transcription

A

Initiation
- RNA Polymerase binds to promoter region in gene and unzips portion of DNA into coding and template strand.
Elongation
- RNA Polymerase reads template strand in 3’ to 5’ strand direction
-New pre-mRNA strand formed in 5’ to 3’ direction through complimentary base pairing (this is when Thymine exchanged for Uracil, and ribonucleotides instead of deoxyribose)
Termination
-New pre-mRNA displaces as it forms and DNA double helix reforms

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3
Q

What is the difference between RNA Polymerase and DNA polymerase?

A

RNA polymerase unzips a small portion

DNA polymerase unzips a large portion

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4
Q

What are Transcription factors and what do they do?

A

Large proteins, bind to promoter region of gene and recruit everything needed for transcription e.g. RNA polymerase binds to TF.
Act as serving platter

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5
Q

Where is the untranslated region?

A

In-between 5’ and 3’

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6
Q

What are the types of Transcription factors and what do they do?

A

Enhancer - enhance gene expression

Silencer - prevent gene expression

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7
Q

How do Transcription factors reach the promoter region?

A

DNA loops around, allowing interaction

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8
Q

Describe how pre-mRNA can be modified into mature mRNA

A

RNA splicing
-remove introns to leave exons (coding sequence)
5’ capping
-Cap of 5’ end to stop degradation and promote export from nucleus
Polyadenylation
-Poly A tail (200 nucleotides) added to 3’ end. Stops degradation, gives stability and promotes export from nucleus.
-Bigger Poly A tail = more stability = more protein made

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9
Q

How is gene expression controlled in the nucleus?

A

Transcription, when DNA becomes RNA
-Activators and repressors choose which genes are turned on or off
RNA transcript becoming mRNA
-Alternative splicing
-RNA cleavage (rRNA molecules cleaved from larger transcripts, may be methylated or enzymatically modified)

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10
Q

How is gene expression controlled when leaving the nucleus?

A

Export through nuclear pores can be regulated using nuclear pore proteins

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11
Q

How is gene expression controlled in the cytosol?

A

During mRNA translation
-Repressor protein binds to 5’ or 3’ UTR = makes mRNA inactive and stops protein being made
-Inactive mRNA degrades (Poly A tail acta as timer)
Post-translational protein modifications
-Protein is made
-Phosphorylation activates or inactivates protein

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12
Q

What is the plasma membrane of a eukaryote cell?

A

A selectively permeable layer that surrounds the cell and maintains the differences between the cytosol and extracellular environment.

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13
Q

Describe the structure of the plasma membrane

A

A phospholipid bilayer with proteins embedded into it

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14
Q

What are the major lipids in the plasma membrane?

A

Phospholipids (phosphoglycerides)
Spingolipids
Sterols (cholesterol)

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15
Q

Name all the proteins found in the plasma membrane and give their function

A
  • Transporters: moves materials
  • Anchors: grab onto the matrix and link to the cytoskeleton of the cell
  • Receptors: hormones bind here and stimulate a response
  • Enzymes: stimulated by substances to generate a cell reaction
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16
Q

How can proteins be embedded in the plasma membrane?

A

Integrated/integral protein - embedded in bilayer
Peripheral - associated but not embedded
Lipid anchored

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17
Q

What is a glycocalyx?

A

Protein is glycosylated (has carbohydrate added)

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18
Q

What is the function of a a glycocalyx?

A

Role in cell-cell recognition, plasma protein protection and immunological roles.

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19
Q

Describe features of organelles

A
  • Membrane bound (create own environment and have specialised functions)
  • Different proteins in them give them functions
  • Differentiate based on function
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20
Q

How do the features of the plasma membrane help them in their roles?

A
  • Encloses organelles = creates environment
  • Selectively permeable barrier and proteins = regulation of environment exchange
  • Chemical messengers interact with receptors = communication between cell and environment
  • Anchors cells to extracellular matrix = structural support
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21
Q

What are the basic components of a eukaryotic cell?

A
  • Nucleus
  • Membrane bound organelles
  • Plasma membrane
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22
Q

What is the role of the cytosol?

A

Site of translation

Contents of cytoplasm excluding organelles (fluid component of cell)

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23
Q

What is the role of the nucleus?

A

Contains DNA

Site of transcription

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24
Q

What is the role of the cytoplasm?

A

Contents of cell within plasma membrane excluding nucleus

25
Q

What is the role of the RER?

A

Ribosomes on surface for protein synthesis

26
Q

What is the role of the SER?

A

No ribosomes

Involved in lipid synthesis

27
Q

What is the role of the Golgi apparatus?

A

Sorting and modification of proteins

28
Q

What is the role of the mitochondria?

A

Site of oxidative phosphorylation - ATP produced

29
Q

What is the role of the peroxisome?

A

Molecular oxygen used to oxidise organic molecules

30
Q

What is the role of the endosome?

A

Processes internalised proteins

31
Q

What is the role of the lysosome?

A

Involved in degradation of macromolecules

32
Q

What is translation?

A

The process of mRNA to protein

33
Q

What is a codon?

A

3 bases (= 1 amino acid)

34
Q

What are the main steps of translation?

A

Initiation
Elongation
Termination

35
Q

Describe initiation of translation

A
  • mRNA leaves nucleus through pore
  • small and big ribosomal units join together on mRNA
  • Subunits scan strand in 5’ to 3’ direction until AUG is found (start codon)
36
Q

Describe elongate of translation

A

-Subunits move along mRNA
-tRNA enter large subunit through A site
-Amino acid on tRNA join to other amino acid on new tRNA that enters (peptide bond between amino acids)
= amino aid chain/polypeptide is forming
-empty tRNA leaves out E site

37
Q

Describe termination of translation

A
  • Release factors recognise the stop codon (tRNA does not)
  • Polypeptide is released
  • Translational complex dissociated and components are recycled
38
Q

Describe important features of tRNA

A

Anticodon that is complimentary to codon and specific to amino acid

39
Q

How do amino acids join together?

A

In condensation reaction (dehydration synthesis) to form proteins

40
Q

Describe the structure of amino acids

A
  • Are neutral and only differ in their R group

- Characteristics depend on interactions

41
Q

What is a silent mutation?

A

No overall change in amino acids

42
Q

What is misense mutation?

A

Change in nucleotide sequence leads to change in amino acid

  • Harmless if same amino acid is formed
  • Harmful if another amino acid is made
43
Q

What is a nonsense mutation?

A

Artificial stop codon cause sequence to stop prematurely

44
Q

What is a frameshift mutation?

A

Codons are deleted or inserted

45
Q

How many codon combination possibilities are there?

A

64

46
Q

What is the start codon?

A

AUG

47
Q

What does ‘redundancy’ mean in genes?

A

More than one codon for each amino acid

48
Q

What does ‘no ambiguity’ mean in genes?

A

No single codon gives more than one amino acid

49
Q

What is the function of DNA?

A

Store for genetic information (instructions for development and function of cells). Information stored in chromosomes

50
Q

How is genetic information organised?

A

Into genes

Genes encode proteins (provide functions for life)

51
Q

Describe (+ draw) the structure of DNA

Figure 1

A
  • Double helix (double stranded)
  • Strands run in opposite directions (anti parallel)
  • Sugar is Deoxyribose phosphate backbone
  • Bases are Adenine, Thymine, Cytosine, Guanine
  • 2 H bonds between A and T
  • 3 H bonds between G and C
  • Bases inside, phosphate backbone on outside
  • Major and minor grooves
52
Q

Where specifically does transcription take place on DNA?

A

Major groove

53
Q

What is the function of RNA?

A

Translate genetic information to proteins

54
Q

What types of RNA are there?

A

mRNA, tRNA, rRNA (Translation of DNA to proteins)

miRNA (Regulation of gene expression)

55
Q

Describe (+draw) the structure of RNA

Figure 2

A
  • Single strand
  • Phosphate backbone
  • Sugar is Ribose
  • Bases are Adenine, Cytosine, Guanine, Uracil
56
Q

Describe the process of DNA replication

A
  1. DNA unwound using DNA helicase = produces two strands, 1 lagging (3’ to 5’ direction) and 1 leading (5’ to 3’ direction)
  2. DNA polymerase catalyses synthesis of new DNA : leading strand is synthesised continuously.
    DNA Primase adds RNA primers on lagging strand to allow base pairing (lagging strand synthesised discontinuously in Okazaki fragments)
  3. RNA primers removed, DNA ligase seals gaps.
  4. DNA is proofread to make sure there are no errors (can be fixed at this stage)
57
Q

What is the genome?

A

Complete set of DNA, includes all the genes

58
Q

Describe (+draw) the structure of a chromosome

Figure 3

A
  • Centre is centromere, allows separation into sister chromatids
  • Telomere at ends of chromosome, stops damage
  • Allele on chromosomes

Medicine (11 decks)

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