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BIOL1010/1011 > Genetics: Lecture 5 > Flashcards

Genetics: Lecture 5 Flashcards

1
Q

The Gene Idea?

A

The idea that we have packets of information that get passed along from one generation to the next (i.e. the idea of genes) is a very old one.

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2
Q

Progression of Gene Theory?

A
  • Chaldean Pedigree (4000 BC)
  • Mendel’s inheritable factor (1857)
  • Darwin Variation in traits (1859)
  • Chromosome theory (early 20th century)
  • Watson & Crick (and Avery, Hershey/Chase, Griffith, and Franklin) DNA structure (1953)
  • Genetic code (deciphered 1960’s)
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3
Q

Chaldean pedigree?

A

Early pedigree of horses (4000 BC):

  • look at what is passed along generations
  • be able to select certain genes by crossing horses
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4
Q

Mendel heritable factor (1857)?

A

He figured out that we have genes:

  • Wasn’t sure where they were encoded
  • move along generations and some are dominant/recessive
  • some can get masked in one generation and could be present in the next
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5
Q

Darwin variation in traits (1859)?

A

Theory of natural selection:

  • variation needs to be introduced in populations otherwise they are susceptible to getting wiped out
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6
Q

Whose ideas fit together really well?

A

Mendel’s and Darwin’s ideas fit together extremely well.

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7
Q

Chromosome theory (early 20th century)?

A

Scientists were able to observe chromosomes with microscopes

  • We already knew they existed, but were able to confirm ideas and definitively visualize them.
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8
Q

Watson & Crick DNA Structure (1953)?

A

DNA is the structure that carries the genetic information.

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9
Q

Genetic Code (deciphered 1960s)?

A

Idea involving transcription and translation - genetic code made of codons and etc.

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10
Q

One polypeptide vs. protein?

A

One polypeptide doesn’t necessarily have a specific function. They corresponds to one gene.

Proteins have a specific function. They are made up of polypeptides and therefore, several genes.

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11
Q

How are traits made possible?

A

Traits are made possible by the presence of several different proteins. A trait consists of many, many, different amino acids which then code for a certain function.

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12
Q

Who determined the central dogma?

A

Francis Crick determined the central dogma of molecular biology.

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13
Q

What does the central dogma consist of?

A

The central dogma includes several steps.

DNA - mRNA: transcription

mRNA - polypeptide: translation

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14
Q

Where does transcription occur?

A

In the nucleus.

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15
Q

Where does translation occur?

A

In the cytoplasm.

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16
Q

2 important principles of the central dogma of molecular biology?

A
  • Genetic information moves from DNA to RNA to protein
  • No information can get back through other way: protein to DNA. This is because protein doesn’t carry information to make DNA.
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17
Q

What is the main difference between mRNA and DNA?

A

DNA has thymine whereas mRNA has uracil.

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18
Q

Transcription?

A

DNA - RNA
(A,T,C,G) - (A,U,C,G)

template strand - mRNA

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19
Q

Translation?

A

RNA - Protein
(codons) - (amino acids)

mRNA - Protein (amino acids)

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20
Q

Structure of a Gene?

A

START - coding sequence - STOP

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21
Q

Sequences recognized by RNA polymerase?

A

START - Promoter
STOP - Terminator

22
Q

Before transcription starts?

A

The recognition of the promoter by RNA polymerase.

  • RNA polymerase is a molecule that runs along the DNA molecule, until it recognizes the promotor.
  • It runs along the molecule throughout the process of transcription until it detaches at the end.
23
Q

Transcription Initiation?

A
  • The RNA polymerase opens up a replication bubble of unwound DNA.
  • The RNA begins being transcribed and new nucleotides are added to the 3’ strand as in DNA replication.
  • The RNA is being transcribed from the template strand of DNA rather than the non-template strand.
24
Q

Transcription Elongation?

A
  • The DNA is transcribed going downstream.
  • The DNA is rewound once the RNA polymerase moves along from it.
  • The newly made RNA moves down below the template strand
25
Q

Transcription Termination?

A

At the end, there is a DNA sequence that tells the RNA polymerase that the gene has been finished and we have a completed transcript of RNA.

  • The RNA polymerase falls off at this point.
26
Q

Messenger RNA (mRNA)?

A
  • a polymer of nucleotides that contain information to be converted by translation into a polypeptide (protein).
27
Q

Transfer RNA (tRNA)?

A
  • transport specific amino acids to the ribosome, the protein synthesizing complex.
28
Q

Ribosomal RNA (rRNA)?

A
  • complexed with proteins to form a ribosome.
  • very important part of ribosomes which are mostly composed of rRNA
29
Q

The Genetic Code?

A

A table of codons:

  • Consists of nucleotide bases that are read linearly in the 5’ to 3’ direction of the messenger RNA molecule, three at a time. The sequence of each triplet (codon) specifies an amino acid.
30
Q

The genetic code is __________?

A

The genetic code is degenerate because there are many instances in which different codons specify the same amino acid.

  • AUG and UGG are the only ones that code for one amino acid.
31
Q

How are nucleotide codons read?

A

Nucleotide codons are read linearly, specifying amino acids in the polypeptide chain.

For example:
DNA: TAC-AGA-TTG-TTC-CCC-ATC
RNA: AUG-UCU-AAC-AAG-GGG-UAG
AA: Met-Ser-Asn-Lys–Gly (STOP)

32
Q

Transfer RNA?

A

Contains the anticodon and carries the corresponding amino acid.

  • attaches to the mRNA codon, which is attached to the small half of a ribosome.
33
Q

Base pairing between anticodon and codon?

A

Base pairing between anticodon and codon:

Codon (in mRNA): AUG-UCU-AAC
Anticodon (in tRNA): UAC-AGA-UUG
Amino Acid (on tRNA): Met-Ser-Asn

  • The UAC carries the Met and transfers it to the codon during translation
34
Q

Hairpin loops?

A

loops in the tRNA structure

35
Q

Amino acid attachment site?

A

The amino acid attachment site is at the 3’ end of the tRNA molecule.

36
Q

Function of the large subunit?

A

The large subunit of the ribosome removes amino aid and joins it to the protein chain.

37
Q

A site?

A

tRNA enters ribosome at the A site and tested for a codon/anticodon match with mRNA.

38
Q

P site?

A

The tRNA is shifted to the P site, and the amino acid it carries is added to the end of the amino acid chain.

39
Q

E site?

A

The exit site, where the tRNA molecule flies off.

40
Q

What is the ribosome?

A

The ribosome is the site of protein synthesis

41
Q

Direction of Ribosome?

A

The ribosome moves downstream, reading mRNA from 5’ to 3’

42
Q

How is a new amino acid added?

A

The existing amino acid chain is added to the new tRNA on the A site. Then the whole ribosome moves toward the 3’ end.

43
Q

Translation Initiation?

A
  1. A small ribosomal subunit binds to a molecule of mRNA

GTP hydrolysis to GDP is used to allow large subunit to snap into place

  1. The arrival of a large ribosomal subunit completes the initiation complex. It snaps into place.
44
Q

What is the A site?

A

Aminoacyl site

45
Q

What is the P site?

A

Peptidyl site

46
Q

What is the E site?

A

Exit site

47
Q

Elongation of Translation?

A
  1. Codon recognition
  • There is a cloud of tRNA all trial and error to see if they fit with the codon, which will leave the amino acid.
  • hydrolyzed GTP (GDP) is involved in the next step - where the pre-existing polypeptide is added to the new amino acid.
  1. A peptide bond is formed between amino acids, where an H2O molecule is lost
  • This is a condensation reaction meaning a water is lost in the rxn.
  1. Translocation: The ribosome moves downstream, the empty tRNA is recycled whilst the tRNA connected to the amino acid chain is moved to the P site.
48
Q

Termination of translation?

A
  1. When a ribosome reaches a stop codon on mRNA
  • the release factor takes the place of the tRNA molecule on the A site.
  • the release factor is a stop codon
  1. The release factor promotes hydrolysis
  • The final tRNA molecule falls off and the polypeptide is freed.
  • two GTP are hydrolyzed into two GDP to promote ribosomal dissociation.
  1. The two ribosomal subunits and the other components of the assembly dissociate.
49
Q

Protein synthesis requires?

A

Energy, in the forms of ATP and GTP.

The tRNA can be recycled by having a new amino acid added to it.

  1. The amino acid and the appropriate tRNA enter the active site of the specific synthetase.
  2. Using ATP, the synthetase catalyzes the covalent bonding of the amino acid to its specific tRNA.
50
Q

Gene Expression?

A

The creation of gene products

mRNA - polypeptides
DNA - rRNA

51
Q

Why is the expression of genes regulated?

A

The expression of genes is regulated to conserve energy. We only use it when needed.

52
Q

Example of necessary use of energy?

A

Required: Photoreceptor genes needed in eyes.

Not: Photoreceptor genes not needed in the liver

*** Different cells need different active genes.

BIOL1010/1011 (22 decks)

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