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Molecular Genetics Flashcards

(54 cards)

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1
Q

What holds genetic material?

A
  • Chromosomes
  • Proteins and nucleic acids in cells
  • Bacteria
  • Eukaryotes (i.e. humans)

*Basically anything living

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2
Q

Building Blocks of DNA

A

DNA is made up of :
- Sugars (5’ 3’ is based on the carbon placement and numbers)
- Base (will be different in different DNA),
Phosphate group = same

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3
Q

Base pairs are linked by hydrogen bonds, hydrogen bonds are:

A
  • Weak bonds
  • Important in structures of biological molecules
  • Occur between an electronegative atom (often oxygen or nitrogen) and a hydrogen
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4
Q

Complementary base pairing (which are purine and which are pyrimidines)

A

Purine: Adenine and Guanine

Pyrimidine: Thymine and Cytosine

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5
Q

Chargaff’s rule in which bases can pair together?

A

Cytosine and Guanine (Car in Garage)

Adenine and Thymine (Apple in Tree)
- however, the thymine goes into a Uracil when it is RNA :)

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6
Q

Are DNA strands parallel or anti-parallel?

A

Antiparallel

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7
Q

What are the DNA strands linked together with (bond wise)

A

Hydrogen bonds

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8
Q

What is a polymer and monomers

A

Polymers are chains made up of repeats of a monomer unit (they are building blocks)

  • Monomers are what polymers are made up of. They are bonded covalently
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9
Q

What was Beadle and Tatum’s experiment

A
  • they broke the assumption that one gene is one DNA and is responsible for one trait
  • They realised that mutations of genes affect the enzymes of organisms (basically that genes create enzymes)
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10
Q

What is the link between genotype and phenotype?

A

Proteins!

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11
Q

What do proteins do? (In terms of DNA)

A
  • Proteins are the molecules that are visible in the phenotype (for example tyrosinase -> albinism)
  • They can be the signals to make visible changes in phenotype
  • Different alleles produce different proteins (i.e. SRY gene)
  • Different proteins produce different phenotypes
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12
Q

What is the genotype determined by?

A

DNA

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13
Q

What is the phenotype determined by?

A

Proteins

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14
Q

Structure of RNA (similarities and differences)

A

Similarities to DNA
- Sugar phosphate backbone, linked by phosphodiester bonds
- Bases vary

Differences to DNA:
- Single stranded
- Different sugar (ribose instead of deoxyribose)
- Different base: Uracil instead of Thymine
- Extra OH - more reactive, less compact

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15
Q

Structure of RNA (more specific structure names)

A

Lollipop structure (big end), hairpin structure (thinner end) - look up photo haha

Single stranded but can have double helices or even triple helix

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16
Q

What is mRNA

A

Messenger RNA

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17
Q

Transcription (RNA synthesis) - key steps (3) and key info

A
  • Requires a DNA template
  • Occurs in only one direction (5’ 3’)
  • Catalysed by an enzyme: RNA polymerase II
  • Requires energy that is provided by monomers

The three key steps:
1. Initiation
2. Elongation
3. Termination

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18
Q

Initiation (Transcription)

A

RNA polymerase binds to a promoter

  • A promoter is what starts transcription, it controls the attachment of RNA polymerase to the DNA
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19
Q

Elongation (Transcription)

A
  • RNA strand gets longer due to the addition of new nucleotides
  • RNA polymerase ‘walks’ along one strand of DNA (template strand) in the 3’ to 5’ direction
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20
Q

Termination (transcription)

A
  • Release of RNA polymerase and completed RNA from the DNA template at the terminator
  • RNA polymerase starts and stops transcription at specific sequences

-Transcription is initiated when RNA polymerase binds to a specific DNA sequence called a promoter

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21
Q

Promoter

A

Where is starts

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22
Q

Terminator

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A

Where it ends

23
Q

The genetic code

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A

The rules used to convert RNA information into protein information

24
Q

Features of the genetic code

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A
  • Universal (almost)
  • Redundant (degenerate), but unambiguous
  • Non- overlapping
  • Start and Stop codons
25
Start codon
AUG- methionine
26
Stop codons
UAA, UAG, UGA
27
What is a reading frame?
The three bases that create the amino acids in the codon chart, they are called codons. There are three possible reading frames- going from the DNA template strand to the mRNA strand
28
What is needed for translation?
mRNA: the template tRNA: adaptor molecules that convert a sequence of codons to a sequence of amino acids rRNA: a component of the ribosome that makes proteins Energy: in the form of GTP Ribosomal proteins: To make use of GTP GTP= nucleotide with guanine in it, releases energy
29
tRNA
Transfer RNA
30
rRNA
Ribosomal RNA
31
The ribosomes tRNA binding sites
- The A (amino acyl) site - the P (peptidyl) site - the E (exit) site
32
the A site
Accepts an incoming tRNA bound to an amino acid
33
the P site
The second binding site for a tRNA carrying a polypeptide (growing polypeptide chain)
34
the E site
Once the stop codon is added the E site releases the Amino acid chain into the body
35
Protein synthesis (steps)
Initiation - assembly of the ribosome on the mRNA at the start codon (AUG (methionine)) Elongation- 3 step catalytic cycle involving addition of amino acids Termination- release of the completed protein at a stop codon (releases amino acid chain)
36
Initiation of protein synthesis
- Identification of the AUG start codon - Insertion of the tRNA - Assembly of ribosome - the ribosome interacts with mRNA and tRNA
37
The 3 step cycle of elongation
- Entry of tRNA into the A site - Formation of peptide bond - Translocation (movement of the ribosome by 1 codon) *The mRNA is translated 5' to 3'
38
Termination
The protein synthesis is terminated when a stop codon is encountered
39
DNA replication in vivo
G1 = period of cell growth before DNA is duplicated S = period when DNA is duplicated (when things happen) G2= period after DNA is duplicated and cell prepared for division Mitosis
40
Semiconservative replication
Where DNA molecules in daughter cells have one strand of DNA from the parent and one that was newly synthesised Each DNA molecule is made of an old strand and a new strand
41
Initiation of DNA replication
- DNA helicase unzips DNA from replication origins - Primase produces and RNA primer - DNA polymerase II can continue from this
42
Lagging strand
DNA strand where DNA helicase and DNA polymerase III travel in opposite directions is called the lagging strand
43
Okazaki Fragments
allows polymerase to synthesise lagging strand fragments they are small fragments that get 'filled in'
44
Enzymes involved in DNA replication
Initiation: - Helicase - Primase (RNA polymerase) Extension: - DNA polymerase III Fixing the lagging strand - DNA polymerase I - DNA Ligase Termination- when all DNA has been replicated
45
Mutation rate balance (too many, too few)
Too many: Most offspring are at a selective disadvantage (or dead) Too few: Species are not able to adapt to change and might become extinct (not enough variation)
46
Point mutations (the three types)
Silent mutations Missense mutations Nonsense mutations
47
Silent mutations
The base change does not result in a protein change and overall does not affect anything
48
Missense muations
A single amino acid is changed, can affect phenotype
49
Nonsense mutation
An amino acid codon is changed to a stop codon. (prematurely stops the sequence)
50
Common missense mutation
Sickle cell anaemia - mutation at position 6 from glutamic acid to valine (Glu6Val)
51
Insertion/deletion mutation
Can cause frameshift - Where a base is added or deleted in and leads to the reading frame being shifted so different amino acids are being read
52
Insertion/Deletion mutation example
Belgian blue cattle have an 11bp deletion in the myostatin gene. This causes a frameshift and leads to a premature stop codon which causes the cattle to be extra 'muscly'
53
Phylogeny based DNA sequence
Using a phylogenetic tree to determine genetic distance A matrix is also used to determine the difference between each other
54
FOXP2 example
- Genetic speech disorder - difficulty with writing, grammar, comprehension, facial movements, bipedal movement Gene mapping revealed that all patients have a missense mutation in the FOXP2 gene

Biology (3 decks)

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