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Reproduction and Genetics Flashcards

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1
Q

What is genetics?

A

A study of the functions of single genes

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2
Q

What is genomics?

A

A study of the complete genetic material of an organism, their genome.

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3
Q

What is the intended purpose of the Human Genome and 100K projects?

A

To improve knowledge and understanding of genetic disorders and improve their diagnosis and treatment.

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4
Q

What was the type of sequencing used and the aims of the Human Genome project?

A

Type of sequencing used: Sanger sequencing, which sequences relatively small sections of DNA at a time, which took a long time.
Aims: Identify all the genes in the human genome and identify which chromosome each is on, determine the base sequences of the 3 billion base pairs in human DNA and store the information in databases.

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5
Q

What was the type of sequencing used and the aims of the 100K Genome project?

A

Type of sequencing used: Next Generation sequencing, which can sequence an entire genome in hours.
Aims: Study variation in the human genome, create a new genomic medicine service for the NHS, enable new medical research to study the potential of new and more effective treatments, study how best to use genomics in healthcare and how best to interpret data to help patients and kick-start a UK genomics industry.

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6
Q

What are the ethical issues for the amount of data produced by both the Human Genome and 100K projects?

A

-Ownership of genetic information, potential discrimination, social stigmatisation and misuse of data
-Identification of allele sequences enabling scientists to scan a patients DNA sample for mutated sequences and also to compare the sequence of DNA bases in a patients gene to a normal version of the gene
-Screening of embryos to detect the presence of disorders
-Concerns regarding the possibility of routine screening for adult-onset disorders
-Screening of embryos has led to concerns over choosing alleles to ensure specific characteristics
-Use of genetic screening and the value of genetic counselling

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7
Q

What has completing genome projects for other species allowed scientists to do?

A

-Look at evolutionary relationships. This provides true phylogenetic classification and can be used to correct mistakes made using classification based on phenotypic characteristics.
-Consider how to conserve species in the future by targeting which species need particular protection.

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8
Q

How has genome sequencing improve the treatment of malaria?

A

-Sequencing of the mosquito, Anopheles gambiae, genome is allowing scientists to develop chemicals which could render the mosquito susceptible again to insecticides.
-Sequencing of the parasite, Plasmodium sp., genome is allowing for development of more effective drugs.

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9
Q

How does a DNA profile and a DNA sequence differ?

A

A DNA profile represents only non-coding portions of DNA whereas a DNA sequence represents all the sequence of bases in a genome.

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10
Q

What units does a human genome contain?

A

Exons, which code for proteins and introns, which are blocks of non-coding DNA.

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11
Q

What are Short Tandem Repeats (STR’s)?

A

Blocks of repeated nucleotides in introns, which produce variation in individuals depending on how many times they are repeated.

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12
Q

What is an example of a Short Tandem Repeat?

A

D75280, where ‘GATA’ bases are repeated on human chromosome 7. Different alleles of this locus will have from 6-15 tandem repeats of this sequence. The more times it repeats, the larger the fragment of DNA will be.

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13
Q

What are the two techniques producing a DNA profile relies on?

A

The polymerase chain reaction (PCR) and gel electrophoresis.

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14
Q

What is the function of PCR?

A

PCR rapidly produces many billions of molecules from a single DNA molecule, enabling tests to be carried out accurately and more rapidly regardless of the age of the sample.

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15
Q

What are the function of primers?

A

They are single-stranded DNA which is complimentary to the start of the sequence and act as signals to the DNA polymerase to start copying.

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16
Q

Describe the steps of PCR

A
  1. The original DNA is heated to 95C to denature and separate it into two single strands.
  2. The solution is cooled to 50-60C triggering the primers to join the complimentary base sequence on each of the single strands of DNA. This allows the primers to bind to the DNA strands, triggering DNA replication.
  3. The solution is heated to 70C and DNA polymerase catalyses the synthesis of a complimentary strand for each of the single strands of DNA by forming the phosphodiester bonds in the sugar-phosphate backbone, producing two identical double strands of DNA.
  4. Steps 1-3 are repeated many times to produce over a billion copies of the original sequence from just one piece of DNA.
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17
Q

What is the function of gel electrophoresis?

A

This is a method of separating DNA fragments according to size. The gel is made from agarose, which contains pores in its matrix.

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18
Q

Describe the steps of gel electrophoresis

A
  1. The DNA is extracted from the sample and cut into small fragments using restriction endonucleases.
  2. Fragments of DNA are loaded into wells at one end of a trough containing gel.
  3. The gel is exposed to an electric current.
  4. Since the fragments are negatively charged they move towards the positive terminal.
  5. Smaller fragments find it easier to diffuse through the pores in the gel and so travel further than larger fragments in the same time.
  6. The DNA becomes separated into bands according to the size of the fragments.
  7. Fragment size can be estimated running a DNA ladder alongside.
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19
Q

What is genetic engineering?

A

The transfer of a gene from one organism into another, so that the gene is expressed in its new host cell, with the new host cell being described as transgenic.

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20
Q

Outline the basic steps of genetic engineering

A
  1. Identify and obtain the gene.
  2. Insertion of the gene into a vector, producing recombinant DNA.
  3. Insertion of the vector into the host cell and identification of the transgenic organism.
  4. Production of protein by the host cell/separation and purification of the protein.
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21
Q

How can the gene be initially identified in genetic engineering?

A

Using a gene probe, a specific segment of single-stranded DNA that is complimentary to a section of the gene.

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22
Q

How can the gene be isolated after identification in genetic engineering?

A

-Using reverse transcriptase and DNA polymerase
or
-Using restriction endonuclease

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23
Q

Describe the use of reverse transcriptase to isolate the gene

A

Cells that produce a specific polypeptide will contain many copes of the functional mRNA transcribed from the target gene. The mRNA can be isolated and complimentary single strands of copy DNA can be produced from the mRNA template by using reverse transcriptase. DNA polymerase can then be used to make double stranded DNA molecule which will be an exact replica of the gene.

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24
Q

What are the advantages to using reverse transcriptase to isolate the gene?

A

-This method avoids the need to locate the gene
-The DNA produced doesn’t include introns as the cDNA is copied from the functional mRNA
-The DNA produced does not contain any non-functional fragments

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25
Describe the use of restriction endonuclease to isolate the gene
Restriction endonucleases are bacterial enzymes that cut DNA at specific nucleotide sequences. The enzyme will cut the DNA into many small fragments and individual genes can be isolated. Some restriction endonucleases cut straight across a DNA double strand, making a blunt cut. But many make a staggered cut, which leaves sticky ends.
26
What are sticky ends?
Unpaired bases on strands of DNA. These bases pair with complimentary sequences readily.
27
What are the disadvantages to using restriction endonuclease to isolate the gene?
-If the recognition site occurs within the gene of interest, the gene will be broken into fragments which have no function -Eukaryotic genes contain introns, unlike prokaryotes. If a eukaryotic gene was transferred into a bacterium it would not have the enzymes to process the pre-mRNA. The introns would not be removed after transcription, so proteins would have extra amino-acids and be non-functional
28
What can be used as vectors to carry the gene into the cell?
A virus or a bacterial plasmid.
29
What is a plasmid?
They are much smaller than the bacterial chromosome and contain only a few genes. They can move in and out of cells which makes them useful for introducing genes into bacteria.
30
Describe the steps in which recombinant plasmids are produced
1. Bacteria are treated to destabilise the cell walls and breakdown the cell membrane. 2. Plasmids are isolated from the cell debris. 3. The circular plasmid is cut open using the same restriction endonuclease as was used to isolate the gene. 4. DNA ligase joins the plasmid and the gene DNA by catalysing the formation of phosphodiester bonds between their sugar-phosphate backbones.
31
Why is the same restriction endonuclease used to cut the plasmid as was used to isolate the gene?
So the plasmid has the same nucleotide sequence in its sticky ends as the gene.
32
What must happen to obtain transgenic bacteria which contain the recombinant plasmids?
-The plasmid must successfully incorporate the gene. -The bacteria must successfully take up the recombinant plasmids.
33
What are the two possible outcomes when the special plasmids are mixed with gene fragments in the presence of restriction endonuclease and DNA ligase?
1. The gene is included in the plasmid, disrupting the tetracycline resistant gene or 2. The plasmid is reformed without the insertion of the gene
34
What are the special plasmids used in the use of antibiotic resistance genes in the selection of recombinant bacteria?
Plasmids which already have two inserted genes, an ampicillin resistant gene and a tetracycline resistant gene.
35
What are the three possible outcomes once the special plasmids are mixed up with the bacteria?
1. Bacteria that have not taken up the plasmids 2. Bacteria that have taken up unaltered plasmids 3. Bacteria that have taken up recombinant plasmids
36
How are transgenic bacteria identified?
Using a technique called replica plating. Bacteria are grown on agar in a petri dish and a 'stamp' is used to transfer a sample of each bacterial colony onto agar plater containing either ampicillin or tetracycline.
37
What plate should bacteria with recombinant plasmids show up in?
In the plate with the ampicillin, as they can survive in the presence of ampicillin but not tetracycline since the resistance gene has been disrupted.
38
What plates should bacteria with no plasmids show up in?
Neither, as since they have not taken up any plasmids, they have no antibiotic resistance.
39
What plates should bacteria with the unaltered plasmids show up in?
In the plate with tetracycline and ampicillin, as the resistance gene is still intact so it can survive in the presence of tetracycline.
40
How are bacterial cells with recombinant plasmids cultured after identification?
In fermenters, where they divide over and over to form clones, each one containing copies of the recombinant plasmid. The bacterial enzymes transcribe the inserted gene in the plasmid and translate the mRNA to produce the desired protein.
41
What are some concerns regarding genetic engineering?
- Plasmids are easily transferred between bacteria. There are concerns that plasmids containing antibiotic resistance genes could be passed onto other bacteria. If plasmids with antibiotic resistance genes are passed onto pathogens, this could lead to infections that cannot be treated with antibiotics. -There are concerns that using fragments of human DNA could possibly transfer or activate oncogenes.
42
What are the benefits of the development of GM crops?
-Superior keeping qualities -Higher yield -A substantial reduction in pesticide use on crops engineered for resistance to fungal pathogens and insect attack
43
What are the concerns of the development of GM crops?
-Dispersal of pollen from crops engineered for herbicide resistance to wild relatives -Unknown effect of eating new protein produced in the crop -A reduction in biodiversity
44
What is gene therapy?
A technique in which a defective allele is replaced with one cloned from a healthy individual, providing a treatment or cure.
45
What is the main challenge of gene therapy?
Developing a gene delivery system, so that is it inserted correctly into the genome and functions correctly when there.
46
What does gene therapy use to introduce the DNA into the target cells?
-A virus or plasmid as a vector or -An injection of naked plasmid DNA
47
What are the two main approaches for gene therapy?
Somatic cell therapy and Germ cell therapy.
48
Describe somatic cell therapy
This method may be therapeutic, but the genetic changes are not inherited in daughter cells of treated cells, and do not appear in future generations. The treatment will have to be repeated regularly as the treated cells become worn out and are replaced by the body with new cells that don't contain a working copy of the gene.
49
Describe germ cell therapy
Germ-line therapy introduces the corrective genes into germ-line cells so the genetic correction is inherited.
50
Why is germ cell therapy controversial?
As genes interact with each other as some are switches that control other genes. Changing one gene or a set of genes in the oocyte has the potential to cause unpredictable effects in future generations.
51
What is the type of treatment that drisapersen shows in treating DMD?
Exon skipping, where a 'molecular patch' is introduced over the exons with the mutation, making the gene readable again. A shorter form of dystrophin is produced, but one thought to be more functional that the untreatable version.
52
Outline the mode of action of drisapersen
1. Drisapersen is a 50-nucleotide sequence that is complimentary to the mutated sequence 2. It binds to the mRNA over the exon with the deletion 3. That portion of mRNA becomes double stranded 4. The ribosome is unable to translate that portion of mRNA 5. The ribosome skips the mutation, producing a shorter, partially functional dystrophin protein molecule
53
How does genomics enable healthcare to be improved?
-more accurate diagnosis -better prediction -improved design of drugs -introduction of new and improved treatments for disease
54
What does the introduction of Next Generation sequencing enable to be developed?
Tailoring therapies to individual patients where an individual could have a unique treatment for a common disease.
55
What is tissue culture?
The practice of growing cells in a lab.
56
What does tissue engineering involve?
Inducing living cells to grow on a framework of synthetic material to produce a tissue such as skin.
57
What is the aim of tissue engineering?
To repair, improve or replace biological functions by the replacement of tissues or organs.
58
What are some other applications of tissue engineering?
Blood vessel replacement, bone and cartlidge repair and the treatment of degenerative nerve disease.
59
What is a stem cell?
An undifferentiated cell capable of dividing to give rise to cells which can differentiate into different types of specialised cells.
60
What are the sources of stem cells?
-From 3-5 day old embryos, embryonic stem cells which are totipotent -Adults tissues, such as bone marrow which can be 'reprogrammed' to become induced pluripotent stem cells
61
What does totipotent mean?
Cells which have the ability to differentiate into all possible cell types for that organism.
62
What does pluripotent mean?
Cells which have the ability to differentiate into many different cell types for that organism. They are not as versatile as totipotent cells.
63
What are the advantages of using stem cells?
Large quantities of genetically identical cells can be produced quickly.
64
What are the disadvantages of using stem cells?
-In mammals, the technique is very expensive and unreliable -in plants, disease or entry of pathogens may cause problems -Inadvertent selection of disadvantageous alleles -Long term or unforeseen effects such as the premature aging of cells
65
What are the ethical concerns over using embryonic stem cells?
-Some believe that using a human embryo represents the destruction of a potential human life -Some also believe that embryonic stem cell technologies are the first step towards reproductive cloning -Research with human embryonic cells is banned in some countries
66
Where does the supply of embryos for embryonic stem cells come from?
The surplus of embryos which were not place into a females uterus during fertility treatment.

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