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Genetics Flashcards

1
Q

What did Frederick Meicher Discover?

A

Discovered the nuclein which is high in phosphorus and acidic in a patient’s bandage

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2
Q

Base pairs of DNA and RNA

A

AT-GC, AU-GC

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3
Q

Base pairs of RNA

A

AU-GC

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4
Q

What did friderich meischer discover?

A

He took pus samples from patient’s bandages and discovered an acidic substance which contained phosphorous
-Called it nuclein since it was from the nucleus
-thought proteins were hereditary material

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5
Q

What did scientists think genetics were?

A

Thought proteins were hereditary material and thought heredity involved mixing parents characteristics

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6
Q

What did griffith discover

A

The transforming principle, he took two strains of pnuenomia S-strain and R-strain
Smooth - had capsule
Rough - had no capusile, rough colonies

  1. When S-strain was injected into mice the mice died, the s-strain was pathogenic but when the R-strain was injeted, they survived
  2. Heated s-strain cells which destroys the capsule no longer caused infection, but heated S-strain + R-strain mixed together killed the mice
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7
Q

What is transformation

A

Discovered by griffith, it is change in genotype/phenotype caused by the uptake of genetic material of a cell

The factor responsible for the change in genotype/phenotype is the transforming principle which was thought to be either protein or DNA

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8
Q

Avery, McLead and McCarty

A

They grew different strains of strepcoccus bacteria with S and R strains
-wanted to know which part of S-strain made R virulent
-RNA, DNA, or proteins
-heat killed S-strain and added it in

In a tube, they added 1/3 enzymes to kill DNA RNA or protein and then the tube with no DNA the mice survived

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9
Q

Hershey and Chase

A

Wanted to determine if it was protein or DNA that was the transforming principle/hereditary material
-used Ecoli and a bacteriophage (virus that infects bacteria)
-bacteriophage had DNA and a protein coat

Labelled DNA with phosphorus and protein with sulfur and then let the bacteriophages and ecoli interact

The phosphorous labelled DNA bacteriophage found that the bacteria had radioactivity detected in the cell
The sulfur labelled protein coat bacteriophage found no radioactivity in the cell

This suggested that DNA is what is injected into cells and it is the hereditary material and protein coats are not inserted into the cell

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10
Q

Pheobus Levene and Chargaff

A

Levene discovered the components of DNA that DNA was made of deoxyribose sugar, nitrogenous bases, and phosphate groups and believe ATGC was in equal amounts

Chargaff determined the actually quantities of DNA and determined the AT and GC are pairs that are equal in similar amounts
A=T A 30% T 30%
G=C G 20% C 20%

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11
Q

What are the two kinds of DNA replication?

A

conservative and semi conservative

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12
Q

Meelson and stahl experiment

A

they proved that DNA is semiconservative
-grew E.coli in medium containing heavy (15N) for 17 generations until all nitrogen in DNA becomes 15N
-then transferred the bacteria into a medium with normal light 14N and did 2 rounds of replication
-the e-coli was centrifuged and saw that there was lighter nitrogen and an intermediate nitrogen
-Any new DNA had the lighter nitrogen incorporated into it making it less dense than parent DNA and proved it was semi-conservative

Semi-conservative: means that new DNA consists of a strand from the old strand and new strand to form a hybrid

-50% new -50% hybrid

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13
Q

Explain the entire process of DNA replication

A

1: Strand separation

-Begins at replication origins, eukaryotes have many replication origins so an enzyme helicase binds to the origins and unwinds the two strands of DNA by breaking the H-bonds and forms replication forks
-Any tension in the DNA is relieved by topoisomerases enzyme which cut and untangle then rejoin the strands
-single strand-binding proteins prevent H-bonds from reforming due to attraction by keep them separated
-helicase separate the enzyme in both directions from many replication origins and forms a replication bubble as new DNA is synthesized
-eventually these bubbles meet and collide to form two identical daughter strands of DNA

2: Building complementary strands
-Since DNA polymerase can only add nucleotides to existing strands of DNA, an RNA primase enzyme adds a short segment of RNA segment on the beginning of the fork
-then DNA polymerase III begins adding the nucleotides to the 3’ end and can only build from the 5’ to the 3’ end direction
-the strand of DNA that goes the opposite way of the replication fork is the lagging strand
-RNA primase continues to add fragments so that the lagging strand is able to catch up

-As the fragment extends, DNA polymerase I replaces RNA primers with DNA nucleotides
-DNA ligase joins okazaki fragments together

3: Correcting Errors in Replication
-As DNA polymerase enzymes synthesize DNA polymerase checks for base-pair errors since it cannot continue if they’re mismatched so they back up and replace with the correct base

If some errors remain
-Special DNA polymerase I and II complexes locate the distortions and removes a portion of the strand around the mismatch then fill the gap with DNA polymerase and attached by DNA ligase

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14
Q

What did Watson and Crick conclude about the structure of DNA? (5)

A

-contains a sugar phosphate bone on each strand of helix
-nitrogenous bases are attached to backbone and directed towards the centre
-the bases are H-bonded with each other
-strands run clockwise
-DNA is antiparallel

-Franklin contributed to these findings of the backbone and nitrogenous bases in the middle

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15
Q

What are bacteriophages

A

Viruses that infect bacteria

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16
Q

What are okazaki fragments

A

Short fragments of DNA formed on the lagging strand

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17
Q

One-gene-one-enzyme hypothesis

A

The hypothesis that each gene is unique and codes the synthesis of a single enzyme

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18
Q

One-gene-one-polypeptide hypothesis

A

The restated hypothesis that each gene is unique and codes for the synthesis of a single polypetide since not all proteins are enzymes

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19
Q

What is the central dogma

A

The principle that genetic information flows from DNA to RNA to proteins
Two major steps:
-transcription
-translation

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20
Q

Transcription and translation brief definition

A

Transcription: information encoded in DNA is transcribed into an RNA copy in the nucleus
-RNA is able to leave the nucleus and then carry the information to ribosomes

Translation: assembly of amino acids into polypeptide using information from the RNA
-takes place in the ribsosomes in cytosol
-information from bases
-bases are translated into amino acids

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21
Q

What is the name of DNA and RNA

A

deoxyribonucleic acid and ribonucleic acid

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22
Q

What is the diff between DNA and RNA
strand
pairs
sugar

A

DNA
-double helix
-AT GC
-deoxyribose sugar (no OH)

RNA
-single stranded
-AU GC
-ribose sugar (OH)

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23
Q

How is DNA transcribed into RNA?

A

Same pairing but the uracil is going to be substituted for thymine

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24
Q

Three types of RNA

A

-messenger RNA mRNA
-transfer RNA tRNA
-ribosomal RNA rRNA

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25
Q

What is mRNA

A

The intermediate between DNA and ribosomes
-translated into proteins by ribosomes
-RNA verysion of the gene encoded by DNA
-varies in length

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26
Q

What is tRNA

A

-the deliver system of amino acids to ribosomes as they synthesize proteins
-very short
-contains a 3’ end and a 5’ end, the amino acid binds onto the 3’ end

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27
Q

What is rRNA

A

-binds with proteins to form ribosomes
-varies in length

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28
Q

What is the template strand

A

The stand of DNA that is read by RNA polymerase and transcribed into pre-mRNA

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29
Q

What is pre-mRNA

A

The initial product of mRNA transcription which cannot be used yet to produce a protein until it is modified

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30
Q

Why is RNA used?

A

Because ribosomes are located outside of the nucleus and DNA cannot leave the nucleus so RNA is transcribed by DNA template strand into a strand of mRNA and that mRNA after going through modifications can leave the nucleus and go to ribosomes which synthesize proteins

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31
Q

Genetic code

A

The relationship between bases and the amino acids they specify

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32
Q

Codon + order

A

A group of three base pairs that code for an amino acid and read from the 5’ to 3’ end

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33
Q

If we have 3 letter combinations there are 64 possible combinations but why are there only 20 amino acids?

A

This is because genetic code is redundant and different codons are able to code for the same amino acid

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34
Q

Wobble hypothesis

A

redundancy in the genetic code allows for the third base of a codon to change and still make the same amino acid - this is important so that it lowers chances of errors to greatly affect polypeptide sequences
-genetic code is also universal and same in all organisms

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35
Q

How many combinations of codons can be generated using a 3,4,5 base codon?

A

4^3
4^4
4^5

36
Q

Stop vs start codon

A

Start codon initiates polypeptide synthesis and start codon initiates stop and causes termination of translation

37
Q

Which proteins adds the bases in DNA replication vs transcription

A

Replication
DNA polymerase

Transcription
RNA polymerase

38
Q

Explain all the steps of DNA Transcription

A

Initiation
-First DNA needs to be unwound
-RNA polymerase is going to attach to the promoter region TATA and unzip it

Elongation
-RNA polymerase begins to make complementary copy of DNA and opens up the DNA
-doesn’t need primer because it is made from the 5’ to 3’ direction using the 3’->5’ DNA as template strand
-other strand is called coding stand
-the mRNA elongates and nucleotides are added, and then the growing strand unwinds from DNA and extends out and DNA double helix reforms

Termination
The transcription of a protein-coding gene is terminated when RNA polymerase recognizes a termination sequence which is a protein binding to the polyuracil region to terminate

39
Q

What is a promoter, what is the region called and why is it created like that?

A

A nucleotide sequence lies just before a gene and allows for the binding of RNA polymerase
The promoter region in eukaryotes is called the TATA box and it contains a lot of thymine and adenine bases
-the reason these bases are used is because they only contain 2 hydrogen bonds whereas GA contain 3 and less energy is required to break the bonds and RNA polymerase expends less energy opening up the DNA helix

40
Q

What direction is mRNA synthesized

A

5’->3’ end

41
Q

Coding vs template strand

A

The template strand is the strand of DNA running from 3’ to 5’ which codes the mRNA in the 5’ to 3’ direction and the coding strand is the strand of DNA that is not being copied but contains the same sequence as the RNA molecule

42
Q

Explain the direction of DNA replication and draw out the diagram

A

Draw look at notes

43
Q

What direction does RNA polymerase and DNA polymease build in?

A

5’ to 3’ direction and adds to the 3’ end

44
Q

Why are post transcriptional modifications needed?

A

After termination, the pre-mRNA is vulnerable to enzymes in the cytosol

45
Q

What is every single step in protein synthesis for DNA (just steps not explanation)

A

Transcription
1. Initiation
2. Elongation
3. Termination

Post transcriptional modifications

Translation
Initiation
Elongation
Termination

46
Q

Explain post transcriptional modifications of mRNA in protein synthesis

A

to the 3’ end, add a poly(A) tail - this translates properly and protects from enzymes
5’ cap to the 5’ end which is a sequence of 7 G’s and is a recognition site for translation

-There are now introns and exons remaning
-introns are non coding so must be removed to avoid error in final protein

Spliceosome complex with SnRNPS removes introns from mRNA by recognizing, looping the exons, pinching out the intron and joins exons together

47
Q

Introns vs exons

A

Introns are non-coding sequences of DNA/RNA in eukaryotes and exons code

48
Q

What is alternative splicing

A

Produces different mRNAs by joining exons in different combinations

49
Q

Explain DNA translation

A

Initiation
First aminoacyl-tRNA bound to Met (initiator tRNA), the start codon, is going to form a complex with the small ribosomal unit and then it’s going to bind to the 5’ cap of the mRNA and scan along until it reaches the AUG start codon AT P-SITE and then the large subunit binds and completes

Elongation
1. Aminoacyl-tRNA binds to the A-site and a peptidyl transferase cleaves the amino acid from P-site onto the A-site polypeptide chain
2.Ribosome moves along mRNA to shift and continue the process
3. tRNA in the E-site leaves

Termination
1.Once the stop codon appear on the A site aminoacyl-tRNA its going to bind a protein release factor instead of tRNA
2.polypeptide chain is released and ribosomal units detach from mRNA

50
Q

Explain how to determine an anticodon sequence and how it links to tRNA

A

The tRNA is an RNA that carries amino acids to the growing polypeptide chain in the ribosomes. The codon is in a 3’-___-5’ way and it reads the code of the amino acid

For example if Ser is AGU then the anticodon would read 3’-UCA-5’

51
Q

Explain ribosome structure

A

Contains APE site, large ribosomal unit and small which are composed of rRNA
A site: the aminoacyl-tRNA binds and adds the next amino acid
P site: tRNA carrying growing chain
E site: tRNA leaves the ribosome

52
Q

If the mRNA codon is 5’-AGU-3’ what would be on the tRNA?

A

3’-UCA-5’

53
Q

Explain tRNAs flexibility

A

The first two bases are precise but the third is flexible
-wobble hypothesis
-so two diff anticodons with diff third bases can bind as long as they code for the same amino acid

54
Q

Aminacylation

A

Process of adding amino acid to RNA
-product called aminoacyl-tRNA
-catalyzed by aminoacyl-tRNA synthetase

55
Q

What direction is mRNA read in?

A

5’ -> 3’

56
Q

What are point mutations what do they include

A

Mutations that affect a single base pair
-substituion
-inversion
-insertion/deletion

57
Q

types of small-scale/point mutations + what happens

A

Missense
-a single base pair changes and codes for a different amino acid
Nonsense
-a change of a single base pair/group results in a premature stop codon
Silent mutation
-change in one or more bases does not change the amino acid sequence
Frameshift
-the insertion of one/two base pairs which completely alters the reading of a.a
(multiples of 3 do not cause frameshifts)

58
Q

Amplification

A

gene duplication, when a group of genes is copied to multiple regions of chromosomes

59
Q

Causes of mutations (2)

A

Induced and spontaneous
Induced -> envirnment agent
spontaneous -> caused by error in DNA replication

60
Q

Translocation

A

A large scale mutation that takes a section of chromosome and puts it into another

61
Q

How does tRNA bind?

A

It binds 5’->3’
with a 3’-5’ anticoon

62
Q

What is biotechnology

A

Technology that uses biological systems to develop/create processes

63
Q

What does it mean when restriction sites are palindromic

A

The sites at which restriction enzymes cut are read the same front and back

64
Q

What joins together sticky vs blunt ends

A

Sticky - DNA ligase
Blunt - T4 DNA ligase

65
Q

What is recombinant DNA

A

DNA strand that is created using pieces from two or more sources

66
Q

Why is bacteria good for genetic engineering?

A

-inexpensive
-reproduce quickly
-contains plasmids which replicate independently of bacteria’s chromsomes

67
Q

How are target genes isolated in genetic engineering”

A

Using restriction enzymes which locates the target gene at a specific sequence on DNA and then cuts it into restriction fragments of either sticky or blunt ends by cutting the phosphodiester bonds

68
Q

Explain briefly how insulin can be genetically engineered

A

Insulin used to be isolated from pancreas of animals like pigs and cows but it needed to be mass produced and it caused allergic reaction
We use recombinant DNA which is DNA from two or more sources and insert the human insulin gene into plasmid of bacteria which will transcribe and translate it into insulin
This is done with restriction enzymes which cuts DNA at a specific sequence isolates the gene at recognition sites and create restriction fragments which can

69
Q

Which end is preferred sticky or blunt? Why?

A

Sticky is the preferred end because they assist DNA ligase reforming ends together by their complementary base pairs forming H-bonds

70
Q

What are plasmids

A

Small circular pieces of DNA that are found in bacteria which:
-replicate independently of chromosomal DNA
-mutate very quickly
-the plasmids code for specific proteins

71
Q

What is a vector

A

The plasmid which carries the foreign DNA

72
Q

Why is it so hard to control bacterial diseases?

A

Because it’s usually the work of the plasmid where it replicates too quickly and is hard to control

73
Q

How are restriction enzymes important for plasmids and target gene cutting?

A

Restriction enzymes must be the same restriction enzymes used in both the plasmid and the cutting of the target DNA or else the “cuts” will not be compatible

74
Q

Plasmids used in cloning contain an antibiotic resistance gene.
How does this help scientists?

A

Only the bacteria that contains the plasmid with the insulin gene will grow on the medium because bacteria without the plasmid dies. This makes sure it is easier to extract the insulin.

75
Q

Explain the steps in plasmid recombinant DNA

A
  1. The target gene is cut from a piece of DNA using a restriction enzyme and forms restrictions fragments
  2. The same restriction enzyme is going to cut the plasmids which have multiple cloning sites and is antibiotic resistant to make it linear
  3. The target gene and plasmid join together to make recombinant DNA by DNA ligase
  4. Transformed recombinant DNA molecule/plasmid is put into a bacteria to divide and amplify DNA
76
Q

What is PCR?

A

Polymerase chain reaction that amplifies certain copies of DNA quickly without a host organisms
-not whole genome but a target sequence of DNA

77
Q

Steps of PCR

A
  1. Denaturation (94 to 96 C)

The DNA molecules are denatured or seperated into two single strands at a high temperature and causes H-bonds to break

  1. Annealing (50-65)

Facilitates the DNA primers to be added to the complementary 3’ end of the DNA and be built in the 5’ to 3’ direction (1 for each side)

  1. Elongation (72)
    Taq polymerase extends DNA primers and makes complementary copies of each strand
78
Q

Why is Taq polymerase used?

A

Because it can withstand high temperatures since its extracted from bacteria from hot springs
-it is not denatured from high temperatures like DNA polymerase would be

79
Q

How to calculate number of copies made per PCR cycle

A

2 copies are made per cycle so you would produce 2^n
n= number of cycles

80
Q

What is gel electrophoresis used for?

A

It is used to separate large molecules like RNA, DNA, and protein based on size
-usually used after PCR

81
Q

Which side do DNA primers attach to in PCR

A

The DNA primers always build from 5’ -> 3’ direction so it will bind to the 3’ end of a denatured target DNA

82
Q

Steps for preparing gel

A

Step 1: Preparing Gel

Prepare the gel and place it in a gel box between two electrodes
Have wells where sample can be placed

Step 2: Load the Wells & Apply current
-add molecular markers which allow comparison of lengths
-apply current and since DNA is negative the negative electrode is placed at the top to repel so it travels downward to the positive electrode
-the smaller fragments are going to travel quicker

Step 3: Stain gel
-Stain the gel so the DNA is visible with ethium bromide which resembels a base so it inserts itself into DNA
-Glows under UV light

83
Q

What is a molecular marker?

A

A set of standards used in gel electrophoresis used to determine the size of fragments of DNA - a comparison point

84
Q

The further a sample of DNA from the negative electrode

A

The smaller the DNA fragment, the further it is because since its lighter, it is able to travel faster through the porous agarose gel

85
Q

How would gel electrophoresis be used in a crime scene?

A

You would take DNA samples from the victim, and possible suspects and then amplify it through PCR, then you would use gel electrophoresis to compare the victim’s DNA and the suspects and see which ones are the most similair

Biology (8 decks)

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