Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIO 202 > Defining Gene and Protein Relationships (Experiments) > Flashcards

Defining Gene and Protein Relationships (Experiments) Flashcards

1
Q

Gene

A

A segment of DNA that carries the information to produce a specific RNA molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Proteins derived from RNAs create the….

A

physical manifestation of the traits encoded by genes (phenotype)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Proteins are the link between…

A

genotype and phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Gene Expression

A

The process by which DNA directs the synthesis of proteins (or just RNAs in some cases)

–> Getting the info into a useable form: “expressing” the info

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Garrod (1902)

A

First to suggest that genes dictate phenotypes through enzymes and their controlled production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Garrod’s Study + Idea

A

Studied Alkaptonuria –> Hypothesized that the symptoms of the disease reflected an inability to make a particular enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What causes black urine in Alkaptonuria?

A

The lack of an enzyme prevents the break down of homogenistic acid (HA) causing HA to accumulate and be secreted in the urine which creates a black color

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

“Inborn Errors of Metabolism”

A

Idea that recessive mutations in humans could cause defects in proteins, specifically those controlling metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Garrod was the first to…

A

link genes with enzymes that carry out metabolic reactions

–> Got people thinking about DNA encoding enzymes!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Beadle and Tatum (1940)

A

Built off of Garrod’s work to find EVIDENCE that genes are connected to metabolic enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What model did Beadle and Tatum use?

A

Neurospora crassa (Bread mold)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why was neurospora a good model? (3)

A

1) Cheap/easy to grow

2) A HAPLOID species –> Made it easy to study genes as only 1 copy needed to be mutated to see a change in phenotype

3) Modest food requirements –> Can be grown in minimal medium (important for their experimentation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Beadle and Tatum Hypothesis

A

If there is a 1:1 relationship between genes and specific enzymes, it would be possible to create mutants that are unable to carry out specific enzymatic reactions

–> (If enzymes and DNA are connected then certain mutations would lead to the loss of enzymatic function/production)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What mutants did Beadle and Tatum study?

A

Nutritional Mutants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Nutritional Mutants

A

Mutations that cause defects in enzymatic pathways needed for growth under normal growing conditions (in minimal medium for neurospora)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Beadle and Tatum:

Finding the Nutritional Mutants Methodology

A

1) Collected spores of the neurospora

2) Bombarded the spores with x-rays = some spores with random mutations

3) Offspring of x-rayed spores put in test tubes with COMPLETE medium

4) Took some growth colonies from each tube and put them in tubes with MINIMAL medium

–> The samples that had NO GROWTH in the minimal medium were the nutritional mutants (used in part 2 of the experiment)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Beadle and Tatum:

Pinpointing the “Broken” Pathway Methodology

A

Took the nutritional mutants and put them into two different conditions:

1) Minimal medium + full set of VITAMINS

2) Minimal medium + full set of AMINO ACIDS

(Found growth in the amino acid tubes)

3) Put the mutants into tubes containing minimal medium and just ONE amino acid to pin point which A.A. was the problem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happened to the nutritional mutants in minimal medium?

A

They died

–> Couldn’t produce an essential molecule needed for growth (that the complete medium had previously covered with its contents)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How did Beadle and Tatum determine the issue with the mutants was with amino acids?

A

When placed in minimal medium with just amino acids added in the mutants was “rescued” –> The mutant GREW when it hadn’t in just regular minimal medium

–> Therefore, the mutation must block the synthesis of one or more amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How did Beadle and Tatum determine which AA was the problematic one?

A

Put the mutants into tubes with minimal medium + just ONE A.A

–> Found that the mutant was “rescued” by the addition of ARGININE

= Therefore, the mutation must have impacted Arginine biosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Beadle and Tatum conducted further experimentation:

What did it show?

A

Showed that the mutants lacked an enzyme needed for arginine synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Beadle and Tatum CONCLUSION

A

Proposed the “one gene—one enzyme” hypothesis

–> The function of a gene is to dictate the production of a specific enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Flaws in the “one gene—one enzyme” hypothesis (3)

A

1) Not all proteins are enzymes –> Many genes encode non-enzyme proteins (ex: keratin)

2) Some proteins are encoded by multiple genes –> Proteins that have multiple subunits are usually encoded by different genes

–> One polypeptide is encoded by one gene

3) Many genes encode RNA molecules –> Many RNAs encoded by genes have other functions and NEVER get translated to proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Revised version of the “one gene—one enzyme” hypothesis:

A

“one gene—one RNA”

–> Gene = a segment of DNA that encodes a functional RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

RNA is the bridge between…

A

DNA and protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

The different “languages” of nucleic acids and proteins:

A

1) Nucleic acids = nucleotides/nitrogenous bases

2) Proteins = amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Going from DNA –> Protein requires a change of…

A

“language”

28
Q

Crick and Brenner (1960s)

A

Demonstrated that the genetic code is “read” in triplets (codons)

29
Q

Crick and Brenner: Main question

A

How could 4 nitrogenous bases encode for 20 amino acids?

30
Q

Crick and Brenner: Mathematical reasoning

A

1 Base = 1 A.A. –> Would only produce 4 A.A.s (4^1)

2 Bases = 1 A.A. –> Would only produce 16 A.A.s (4^2)

3 Bases = 1 A.A. –> Would produce 64 A.A.s (4^3)

–> Therefore, it must be at least 3 bases!

31
Q

Crick and Brenner: Hypothesis

A

From their mathematical reasoning:

The genetic code is read in triplets of 3 nucleotides

32
Q

Crick and Brenner: Experiment

A

Created insertion mutations that caused insertions of 1, 2, and 3 nucleotides in a gene and then examined the consequences of the mutations:

1) Control (Normal)

2) 1-2 Base Insertions = All A.A.s downstream of the 1-2 insertions were altered (frame-shift)

3) 3 Base Insertions = Only 1 A.A. was altered in the sequence (non-frame shift)

–> THEREFORE, 3 bases must encode ONE A.A.

33
Q

Codon

A

Units of 3 nucleotides on mRNA molecules that encode for a specific amino acid

34
Q

the #of nucleotides =

A

3x the # of Amino Acids

–> DNA segment is 3x longer than the produced polypeptide

35
Q

Nirenberg + Matthei (1960s)

A

Determined the first sequence of a codon and what amino acid it encoded for

36
Q

Nirenberg + Matthei: Experiment

A

1) Created an artificial mRNA containing ONLY URACIL
–> “poly-U mRNA

2) Put into test tube with all components needed for protein synthesis (ribosomes, 20 A.A.s, etc.)

3) Analyzed the A.A.s in the proteins produced

37
Q

Nirenberg + Matthei: Results

A

Produced polypeptide only contained PHENYLALANINE

–> Therefore, UUU must encode for the A.A. phenylalanine

38
Q

Number of Codons that encode for amino acids

A

61 (out of 64 total)

39
Q

What are the functions of the other 3 codons that don’t encode for amino acids?

A

STOP Signals –> Mark the end of translation

REMEMBER: STOP CODONS DO NOT IMPACT TRANSCRIPTION (as codons are only produced once transcription is done; only found in the mRNA molecules)

40
Q

STOP signal codons

A

1) UAA
2) UAG
3) UGA

–> Do NOT encode amino acids!!

All start with U!!!! (and have no Cs)

41
Q

Codon with “dual function”

A

AUG

–> START signal (of translation)
–> Amino Acid (methionine; met-)

42
Q

START Codon

A

AUG

43
Q

During translation, almost all proteins will have what A.A. first?

A

Methionine

–> But this A.A. is usually later on cleaved after translation is done

44
Q

Redundant Genetic Code

A

Many codons encode for the same amino acid (redundant)

45
Q

The genetic code may be redundant but it is NOT…

A

Ambiguous

–> ONE codon encodes for only ONE amino acid

46
Q

The redundancy of codons is not entirely random…

A

Codons that encode for the same amino acid typically only differ in their 3rd nucleotide base

47
Q

Due to the redundancy of the genetic code:

We CAN determine _____________________

But we CANNOT determine _________________

A

1) We CAN determine: A.A. Sequence from the DNA sequence

2) We CANNOT determine: The DNA sequence from the A.A. sequence

–> Multiple possible codons for one amino acid

48
Q

Codons are typically written in the____________ direction of…

A

5’ –> 3’ direction of the mRNA molecule

49
Q

Our ability to extract the intended info from the sequence of codons depends on…

A

reading the code in the proper groupings

–> Having the correct READING FRAME!

50
Q

Reading Frame

A

A method of dividing the sequence of nucleotides in mRNA into a set of NON-OVERLAPPING consecutive triplets (codons)

51
Q

Each reading frame begins with ___________

A

the START signal (methionine: AUG)

52
Q

After the START codon…

A

The subsequent code following the START signal is read CONTINUOUSLY as groups of 3 nucleotides

53
Q

Frame Shift Mutations

A

Mutations that cause the insertion or deletion of a number of nucleotides NOT DIVISIBLE BY THREE

54
Q

Effects of a Frame Shift Mutation

A

All codons downstream from the insertion or deletion are altered due to a change in the frame of reading

–> Produces a polypeptide that is different from the intended polypeptide downstream of the point of mutation

55
Q

THE FAT CAT ATE THE RAT –> What happens if the C is deleted?

A

A frame shift:

THE FAT ATA TET HER AT

–> Sentence become unreadable past the point where the C was taken out

56
Q

Suppressor Mutation

A

A mutation that alleviates or reverts the effects of an already existing mutation

“Rescues” the sequence / restores the reading frame

57
Q

The genetic code for a protein encoding region is read with an:

A

Open Reading Frame

58
Q

Open Reading Frame (ORF)

A

ATG —- >= 33 codons —- STOP

–> A sequence of DNA that contains an ATG (methionine) START codon followed in frame by 33 or more codons BEFORE reaching a STOP codon

59
Q

When an ORF is found in the DNA sequence…

A

it is predicted to be a protein-encoding gene

60
Q

Universal nature of the genetic code

A

The genetic code is shared by organisms from the simplest bacteria to the most complex plants and animals

–> The same codons are assigned to the same amino acids AND the same codons are used for START and STOP signals

61
Q

What is the universal nature of the genetic code evidence of?

A

Evidence that the genetic code evolved very early in the history of life since it is the system utilized by almost all organisms

62
Q

Due to the universal nature of the genetic code…

A

Genes from one organism can be transferred to another organism and transcription/translation of the gene will occur

63
Q

Medical implications of the universal genetic code:

A

1) Allows bacteria/other model organisms to be used as hosts for human protein synthesis (Ex: Insulin)

2) Allows us to study human diseases and genes in ways that otherwise wouldn’t have been possible (Ex: Alzheimer’s mice)

64
Q

Rare Exceptions to the Universal Code (2)

A

1) Certain unicellular eukaryotes have 1-2 codons that differ from the standard “universal” ones

2) Mitochondria use UGA codon to encode Tryptophan (Trp-) rather than using it as a STOP codon (universal function)

65
Q

The Central Dogma

A

Details how information travels: a directional relationship between DNA, RNA, and proteins

DNA —> RNA —> Proteins

BIO 202 (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions