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BIOL 1000 > Gene Expression > Flashcards

Gene Expression Flashcards

1
Q

What is a genome?

A

Complete genetic information of an organism

Includes coding and non coding dna

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2
Q

What does haploid mean?

A

One copy of something

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3
Q

What is a gene?

A

Sequence of nucleotides on a chromosome that codes for one or more biological product

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4
Q

What do protein vs non-protein coding genes code for?

A

Polypeptides, tRNA and rRNA

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5
Q

What is gene expression?

A

Synthesizing product encoded by the gene

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6
Q

When a product is synthesized the gene is?

A

Expressed

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7
Q

What is a nucleosome?

A

Histone octamer that dna wraps around

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8
Q

What is a histone octamer?

A

Two molecules of histones (H2A, H2B, H3, H4)

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9
Q

What does Linker DNA do?

A

Connect adjacent nucleosomes

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10
Q

What does the binding of histone H1 cause?

A

nucleosomes to package into a coiled structure called a solenoid

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11
Q

What is a solenoid also called?

A

30 nm chromatin fibre

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12
Q

What happens after solenoid is made?

A

fold and packs tighter to form chromosomes during division

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13
Q

What is the information flow pathway?

A

DNA turns into RNA, RNA is turned into protein, and this protein is expressed through the phentype

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14
Q

What is genotype vs phenotype?

A

genotype is our genes and phenotype is what you can see

(genotype is heterozygous brown/blue eyes, phenotype is brown eyes)

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15
Q

At what stage in the information pathway is gene expression regulated?

A

every stage

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16
Q

What does transcriptional control? Example?

A

controls which genes are translated, chromatin remodelling and transcription initiation

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17
Q

What does posttranscriptional control? Example?

A

controls the availability of mRNAs to ribosomes, pre-mRNA processing and miRNA

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18
Q

What does translational control? Example?

A

controls rate of protein synthesis, regulating translation initiation

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19
Q

What does posttranslational control?

A

controls availability of newly synthesized proteins, removing masking segments, glycosylation, phosphorylation, controlling protein breakdown, folding

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20
Q

What is transcription?

A

when the information of a gene is turned into a complementary mRNA strand

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21
Q

In transcription what direction is DNA read and what direction is mRNA created?

A

DNA is read in the 3’-5’ direction and mRNA is created in the 5’-3’ direction

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22
Q

Is DNA turned directly into mRNA?

A

No its first turned into premRNA which is then modified and turned into mature mRNA

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23
Q

What are the 3 phases of transcription?

A

initiation, elongation, termination

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24
Q

What are some regions that are upstream of the gene that are important? Why are they important?

A

Enhancer: activators also bind here, activators need to interact with each other
Promoter Proximal Element: contains regulatory sequences, site where protein binds, activators bind here
Promoter site: contains TATA box

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25
Q

What is chromatin remodelling?

A

DNa associated with histones are loosened in order to expose the promoter sequence

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26
Q

What needs to happen before transcription can occur in terms of tightness of dna?

A

needs to be loosened in order to make genes, promoter, enhancer, and promoter proximal site availble

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27
Q

What happens after activators bind to the DNA?

A

Recruit chromatin remodelling complexes which include molecules called histone acetyltransferase, other activators will bind to other regions which recruits general transcription afctors and rna polymerase

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28
Q

What do histone acetyltransferases do?

A

add acetyl groups to histones which removes the positive charge of the histones, this makes the attraction of the DNA to the histone less

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29
Q

If you find an activator on a gene it is probably in which format?

A

euchromatin

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30
Q

What does the mediator do?

A

help loop the DNA so the activators from the enhancer and promoter proximal element can interact with eachother and the transcription factors at the promoter

31
Q

Is there only one kind of activator?

A

No there are many

32
Q

What plays a role in which genes are transcribed?

A

the specific combinations of activators

33
Q

What do repressor proteins do?

A

overcome the effects of the activator proteins, can reverse the process

34
Q

What is the elongation stage? How many bases are exposed at a time?

A

when RNA polymerase binds and starts unwinding the DNA and adding bases, 10-20 bases

35
Q

Is a primer required for RNA polymerase?

A

no

36
Q

What happens during the termination phase for eukaryotes?

A

RNA nucleotide sequence called polyadenylation signal sequence is transcribed by RNA polymerase and then mRNA is released from RNA polymerase

37
Q

What happens during the termination phase for bacteria?

A

stops when termination

37
Q

What happens during the termination phase for bacteria?

A

stops when termination sequence is reached, the mRNA then forms a hairpin structure which causes RNA polymerase to seperate

38
Q

What does the polyadenylation sequence do?

A

addition of poly A tail to mRNA strand

39
Q

Is further modification from pre-mRNA to mRNA required in bacteria?

A

no

40
Q

What is the function of the 5’ G cap

A

helps with attached mRNA to ribosome

41
Q

What is the function of the poly A tail?

A

Facilitates the export of the mRNA from the nucleus through a nuclear pore, protects from degradation once it reaches cytoplasm, and the length of the tail determines the rate of reaction

42
Q

What are UTRs? What are they used for?

A

nucleotide sequences at the 3’ and 5’ end that are not translated into the polypeptide

5’ end has a lot of regulatory elements and play a role in the stability of the mRNA, also contains switches that determine whether translation occurs

3’ end contains signal for the poly A tail which is important for nuclear export and stability

43
Q

What is the poly A tail made up of?

A

adenines

44
Q

Are introns or exons translated into protein?

A

exons are, introns are removed via splicing

45
Q

What do snRNPs do?

A

they are recruited to and bind to the beginning of the intron and a key A base, they then loop together to form a spliceosome, the intron is spliced and released and the exons are joined

46
Q

What is alternative splicing? How does this happen?

A

a process that turns a single strand of mRNA into several different variants of mature mRNA

some exons are removed along with the introns

47
Q

Why is alternative splicing advantageous?

A

one strand of pre-mRNA can be turned into several types of mature mRNA without more DNA, energetically efficient and favourable

48
Q

Why is alternative splicing advantageous?

A

one strand of pre-mRNA can be turned into several types of mature mRNA without more DNA, energetically efficient and favourable

49
Q

What is the start codon? What is the amino acid?

A

AUG, methionine

50
Q

What are the stop codons?

A

UAA UAG UGA

51
Q

What direction do you read mRNA strand when translating?

A

5’ to 3’

52
Q

Why is redundancy important?

A

helps protect against single base substitutions or mutations, polypeptide may not be altered by mutation

53
Q

Where on tRNA does the amino acid attach?

A

3’ end of tRNA

54
Q

What is the difference between codons and anticodons?

A

codons are on mRNA and anticodons are on tRNA, codon is read in 5’ to 3’ direction and anticodon is read in 3’ to 5’ direction

55
Q

What is aminoacyl-tRNA-synthetase? Is ATP requires?

A

enzyme used to attach amino acids to tRNA, yes

56
Q

How many types of aminoacyl-tRNA-synthetase are there? What about tRNAs?

A

20, one for each amino acid

one or more tRNA for each amino acid

57
Q

What are the three sites on a ribosome?

A

A site: aminoacyl site
P site: peptide site
E site: exit site

58
Q

What are the steps in the initiation of translation?

A
  1. tRNA with start codon binds to small ribosomal subunit (initiator tRNA)
  2. this then binds to mRNA, the start anticodon pairs with the start codon on the mRNA
  3. large ribosomal subunit binds and initiator tRNA binds to A site
59
Q

What are the steps in the elongation phase of translation?

A
  1. new tRNA enters A site and its anticodon binds with the codon
  2. amino acid of tRNA in P site attaches to amino acid in A site
  3. moves down the mRNA
  4. another tRNA enters A site
  5. process repeats
  6. tRNA is ejected from E site
60
Q

Is protein synthesis catabolic or anabolic? Does it require energy? What supplies it with energy?

A

anabolic, yes, GTP (not ATP)

61
Q

What are the steps in termination of translation?

A

elongation will continue until a stop codon enters the A site, release factor binds to stop codon and causes mRNA to be released and ribosomal complex to seperate

62
Q

What does peptidyl transferase do?

A

used to form peptide bonds between adjacent amino acids

63
Q

What is polyribosomes mean?

A

when multiple ribosomes translate a mRNA at the same time, many copies in minutes

64
Q

How are proteins distributed within cells? Where are these things?

A

sorting signals, they are coded in DNA and appear when the protein is made

65
Q

What is polypeptide processing?

A

processing reactions that turn polypeptides into their finished form

66
Q

What are some examples of polypeptide processing?

A

removal of one or more amino acids, addition of organic groups, folding

67
Q

What are silent mutations?

A

one base is changed but it stills codes for the same amino acid, has no effect on the final protein function

68
Q

What are missense mutations?

A

one base is changed and it causes a different amino acid to be encoded, may or may not have asignificant effect on final protein structure and function

69
Q

What are point mutations? Examples?

A

mutations that alter a single base pair, silent, missense and nonsense

70
Q

What are nonsense mutations?

A

one base is changed and this causes a premature stop codon, usually results in a non-functioning protein

71
Q

What are frameshift mutations? Examples?

A

mutations that change the reading fram of the codon, addition or removal of a base, all amino acids after this type of mutation can change

72
Q

What end are amino acids added to?

A

C terminus

BIOL 1000 (12 decks)

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