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Genetics and Evolution > Gene Expression > Flashcards

Gene Expression Flashcards

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1
Q

What is a genotype?

A

The combination of alleles that an organism possesses for a specific gene

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2
Q

What is a phenotype?

A

The set of observable characteristics resulting from a genotype and environmental interactions

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3
Q

What is gene expression?

A

Information from a gene is used to synthesise a functional gene product, such as a protein

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4
Q

What is the link between genotype and phenotype?

A

Proteins

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5
Q

Phenotypes (observable characteristics and traits? are influenced by two things. What are they?

A

The environment and epigenetics

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6
Q

What is the Central Dogma of molecular biology?

A
  1. DNA is transcribed into RNA
  2. RNA is translated into proteins
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7
Q

In 1902, Sir Archibald Garrod was the first to suggest that genes dictate phenotypes by coding for specific enzymes within a metabolic pathway, by recognising what?

A

The inborn errors of metabolism mechanism

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8
Q

Beedle and Tatum created an experiment using bread mould, concluding that one gene codes for one protein. Is this correct?

A

No, genes can code for more than one protein

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9
Q

How are genes able to code for more than one protein?

A

By alternative splicing. Genes can also code for RNA molecules

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10
Q

Haemoglobin is a tetrameric molecule. What polypeptide chains is it made up of?

A

2 alpha and 2 beta polypeptide chains

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11
Q

What is a tetrameric molecule?

A

A molecule that consists of four structural subunits (such as peptide chains)

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12
Q

What are the main differences between the structure of RNA and DNA?

A
  1. Deoxyribose sugar in DNA and ribose sugar in RNA
  2. DNA is double-stranded and RNA is single-stranded
  3. DNA is a right-handed helix, but RNA can be variable in shape
  4. Thymine base in DNA and uracil base in RNA
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13
Q

What is the function of mRNA?

A

Carries information from the DNA sequence in the nucleus to the cytoplasm to code for proteins

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14
Q

What is the function of rRNA?

A

Ribosomal RNA are the components that make up ribosomes

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15
Q

What is the function of tRNA?

A

An adapter molecule that is involved in decoding genetic information during protein synthesis - carries amino acids

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16
Q

What are introns?

A

Long non-coding stretches of mRNA that lie between exons

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17
Q

What are exons

A

Smaller regions of mRNA that can be coding or non-coding

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18
Q

Splicing removes the ___ from the gene during mRNA processing.

A

Introns

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19
Q

Bacterial genes have no introns or no exons?

A

Introns

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20
Q

Before the RNA polymerase can bind to the DNA and transcribe it, what must bind to the promoter region?

A

Transcription factors

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21
Q

What makes up a gene?

A

A promoter region, introns, exons, and a terminator region

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22
Q

What binds to the DNA at the promoter region to make up the transcription initiation complex?

A

Transcription factors and RNA polymerase II

23
Q

Where does transcription occur in the cell?

A

The nucleus

24
Q

What is transcription?

A

Taking the information encoded in the DNA gene, and encoding the same information in mRNA ready for translation

25
Q

RNA polymerase synthesises mRNA in what direction?

A

The 5’ to 3’ direction

26
Q

What strand of DNA does RNA polymerase transcribe from - the template or coding strand?

A

The template strand

27
Q

The fully transcribed mRNA contains the same information as what strand - the template or coding strand?

A

The coding strand

28
Q

What part of the DNA gene signals to the RNA polymerase to stop transcribing and synthesising mRNA?

A

The terminator

29
Q

What are the two types of terminators?

A
  1. Hairpin loops of mRNA
  2. Stop codons
30
Q

The promoter regions of the DNA gene establish which segments of the DNA will be transcribed. What is the most common promoter?

A

The TATA box

31
Q

What is alternative splicing?

A

Different exons are used within a gene to create different polypeptide isoforms

32
Q

In eukaryotic cells, pre-mRNA transcripts are made from transcription. Before translation, they must be processed to what?

A

Mature mRNA

33
Q

In eukaryotic cells, pre-mRNA transcripts are made from transcription. Before translation, they must be processed by what three processes?

A
  1. Capping
  2. Polyadenylation
  3. RNA splicing
34
Q

What is capping in mRNA processing?

A

Adding a ‘cap’ at the 5’ end of the RNA, which is a modified guanine

35
Q

What is polyadenylation in mRNA processing?

A

Adding a poly-A tail at the 3’ end of the RNA, which a group of adenine molecules

36
Q

What is RNA splicing in mRNA processing?

A

Removing the introns

37
Q

Why is capping in mRNA processing important?

A

A cap at the 5’ end facilitates ribosomal attachment

38
Q

Why is polyadenylation in mRNA processing important?

A

Helps to stabilise the mRNA and prevents degradation to the end of the sequence. Also helps to move the mRNA across the nuclear membrane

39
Q

Why is RNA splicing important in mRNA processing?

A

Removes any non-coding regions and produces a mature transcript ready for translation

40
Q

How many nucleotides make up a codon?

A

Three

41
Q

One codon codes for how many amino acids?

A

One

42
Q

How many amino acids are there?

A

20

43
Q

What is the start codon?

A

AUG

44
Q

What are the three stop codons?

A

UAG, UAA, UGA

45
Q

What type of RNA molecule translated the mRNA codon into an amino acid?

A

tRNA

46
Q

How many nucleotides long is tRNA?

A

80

47
Q

What are the three steps of translation?

A
  1. Initiation
  2. Elongation
  3. Termination
48
Q

How is it possible that one species can be programmed to produce proteins characteristic of a second species?

A

The genetic code is universal

49
Q

What is the name of the enzyme that catalyses the addition of the correct amino acid to a tRNA molecule?

A

Aminoacyl-tRNA synthetase

50
Q

Why isn’t there a tRNA molecule for every codon of the universal genetic code?

A

tRNA has the ability to ‘wobble’ at the third base of the codon

51
Q

What happens during the initiation phase of translation?

A

The small unit of the ribosome attaches to the cap at the 5’ end. This creates a P site and an A site. The first tRNA carries the amino acid Met to the P site. The second tRNA carrying the next amino acid attaches at the A site

52
Q

What happens during the elongation phase of translation?

A

The amino acid at the P site attaches to the amino acid at the A site, and the first tRNA at the P site leaves. The tRNA at the A site moves to the P site and a new tRNA comes in. This continues in the 5’ to 3’ direction along the mRNA strand, synthesising the polypeptide chain

53
Q

What happens during the termination phase of translation?

A

The ribosome stops synthesising the mRNA strand when the stop codon reaches the A site. Release factors enter the A site and the completed polypeptide chain leaves the ribosome, and the complex dissociates

Genetics and Evolution (14 decks)

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