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Biology > Molecular Genetics > Flashcards

Molecular Genetics Flashcards

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

A

Where it ends

23
Q

The genetic code

A

The rules used to convert RNA information into protein information

24
Q

Features of the genetic code

A
  • Universal (almost)
  • Redundant (degenerate), but unambiguous
  • Non- overlapping
  • Start and Stop codons
25
Q

Start codon

A

AUG- methionine

26
Q

Stop codons

A

UAA, UAG, UGA

27
Q

What is a reading frame?

A

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
Q

What is needed for translation?

A

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
Q

tRNA

A

Transfer RNA

30
Q

rRNA

A

Ribosomal RNA

31
Q

The ribosomes tRNA binding sites

A
  • The A (amino acyl) site
  • the P (peptidyl) site
  • the E (exit) site
32
Q

the A site

A

Accepts an incoming tRNA bound to an amino acid

33
Q

the P site

A

The second binding site for a tRNA carrying a polypeptide (growing polypeptide chain)

34
Q

the E site

A

Once the stop codon is added the E site releases the Amino acid chain into the body

35
Q

Protein synthesis (steps)

A

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
Q

Initiation of protein synthesis

A
  • Identification of the AUG start codon
  • Insertion of the tRNA
  • Assembly of ribosome
  • the ribosome interacts with mRNA and tRNA
37
Q

The 3 step cycle of elongation

A
  • 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
Q

Termination

A

The protein synthesis is terminated when a stop codon is encountered

39
Q

DNA replication in vivo

A

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
Q

Semiconservative replication

A

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
Q

Initiation of DNA replication

A
  • DNA helicase unzips DNA from replication origins
  • Primase produces and RNA primer
  • DNA polymerase II can continue from this
42
Q

Lagging strand

A

DNA strand where DNA helicase and DNA polymerase III travel in opposite directions is called the lagging strand

43
Q

Okazaki Fragments

A

allows polymerase to synthesise lagging strand fragments

they are small fragments that get ‘filled in’

44
Q

Enzymes involved in DNA replication

A

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
Q

Mutation rate balance (too many, too few)

A

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
Q

Point mutations (the three types)

A

Silent mutations
Missense mutations
Nonsense mutations

47
Q

Silent mutations

A

The base change does not result in a protein change and overall does not affect anything

48
Q

Missense muations

A

A single amino acid is changed, can affect phenotype

49
Q

Nonsense mutation

A

An amino acid codon is changed to a stop codon. (prematurely stops the sequence)

50
Q

Common missense mutation

A

Sickle cell anaemia
- mutation at position 6 from glutamic acid to valine (Glu6Val)

51
Q

Insertion/deletion mutation

A

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
Q

Insertion/Deletion mutation example

A

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
Q

Phylogeny based DNA sequence

A

Using a phylogenetic tree to determine genetic distance

A matrix is also used to determine the difference between each other

54
Q

FOXP2 example

A
  • 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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