BY5.6 - Applications of Reproduction and Genetics

Question 1

What are clones?

Answer 1

Organisms that have been produced asexually and are genetically identical to the “parent” organism

Question 2

What are stem cells?

Answer 2

Totipotent or Undifferentiated cells

From a blastocyst (3-5 day old embryo)

Capable of dividing into different types of specialised cells

Question 3

Name the 2 main methods of cloning:

Answer 3

1) Embryo Splitting
2) Nuclear Transfer

Question 4

Describe the method of embryo splitting:

Answer 4

1) A blastocyst produced sexually is split into separate cells
2) cells divide, forming embryos
3) Embryos are transplanted into surrogate’s uterus

Question 5

Give the Advantages of embryo splitting

Answer 5

1) Used to conserve rare breeds
2) Farmers can increase their stock more than they would through sexual reproduction

Question 6

Give the disadvantages of Embryo Splitting

Answer 6

No Guarantee the traits of parents will be present in the identical offspring, as they were produced sexually

Question 7

Describe briefly the Method for Nuclear Transfer Cloning

Answer 7

1) Take the nucleus from a somatic cell of individual to be cloned
2) Insert into enucleated ovum

Question 8

Describe in full the Method for Nuclear Transfer Cloning

Answer 8

1) A somatic cell is taken in a biopsy from the donor
2) An unfertilised ovum is taken from the recipient and enucleated
3) Donor and Recipient cells fuse
4) Cell divides by mitosis
5) Totipotent Blastocyst forms –> embryo
6) Embryo implanted into uterus of recipient
7) Offspring genetically identical to donor born

Question 9

What are the Advantages of Nuclear Transfer?

Answer 9

1) Useful for production of genetically identically cells in quantity
- cancer cells for medical research
- monoclonal antibodies
2) Maintains genetic stocks - produces single identical line of cells

Question 10

What are the disadvantages of nuclear transfer?

Answer 10

1) Expensive and Unreliable in Mammals
2) Can cause inadvertent selection of disadvantageous alleles
3) Progeny can cause long term unseen effects - premature ageing

Question 11

What are bulbs?

Answer 11

Have short stems with closely packed leaves

Leaves swollen with stored food

Terminal bud produces next year’s flowering shoot

Lateral bud produces new plants

Question 12

What are Corms?

Answer 12

1) Have short, swollen stem - stores food
2) Papery thin leaves
3) Terminal bud produces next years flowering shoot

Lateral bud produces new plants

Question 13

What are suckers?

Answer 13

New plant grows from meristem of root or lower stem

Question 14

What are the three different methods plants use for vegetive propagation?

Answer 14

Bulbs

Corms

Suckers

Question 15

What is the technique of micropropagation based off?

Answer 15

Plant cells are totipotent:

• The ability of undifferentiated plant cells to give rise to all the differentiated cells of an adult plant

Question 16

What parts of the plant are used in micropropagation and why are they used?

Answer 16

The meristems (tips of roots and shoots)

as their cells are dividing rapidly

Question 17

Describe the Method of micropropagation

Answer 17

1) A plant with the desired characteristics is selected
2) meristem is removed from shoot with scalpel
3) meristem is cut into explants
4) explants are placed onto sterile, aerated nutrient rich agar
5) cells divide - mitosis
6) mass of undifferentiated cells - Callus - produced
7) Callus is subdivided & pieces differentiate into Plantlets
8) Plantlets transferred to sterile soil once a suitable size is reached

Question 18

Define Donor DNA

Answer 18

A gene that is isolated for insertion

Question 19

Define Plasmids

Answer 19

Circular loops of DNA in bacteria which acts as a vector

Question 20

Define Restriction Endonucleases

Answer 20

Enzymes which cut DNA molecules between specific base sequences called restrictions sites

Question 21

Define DNA ligases

Answer 21

Enzymes which join sections of DNA together (splices)

Question 22

Define sticky ends

Answer 22

The two ends of the ‘cut’ DNA segment, which comprise of unpaired bases

Question 23

Define recombinant DNA

Answer 23

DNA which is formed when a piece of ‘foreign’ DNA is incorporated into the plasmid from a bacterium

Question 24

Define reverse transcriptase

Answer 24

Enzymes which use mRNA as a template for making a DNA molecule

Question 25

What is Genetic Engineering?

Answer 25

A technique used to **extract genes** from **one organism** (the **donor**) to another organism (the **recipient**) to produce a **genetically modified organism** with a **new genotype**

Question 26

Why would donor genes be inserted into the recipient organism?

Answer 26

so that the gene codes for the synthesis of useful **gene products** e.g. **bacteria producing insulin**

Question 27

How is a gene isolated from donor DNA in recombinant genetic technology? Use the example of human insulin as the donor gene

Answer 27

1) **human insulin** producing **genes are located** using a **gene probe** 2) the gene is **isolated** using **restriction endonuclease enzymes** 3) each **specific restriction endonuclease cuts** the DNA at a **specific base sequence** - the **restriction site** e.g AATT 4) the unpaired DNA bases are called **sticky ends**

Question 28

what is used to insert the donor gene into the recipient? give an example for the case of human insulin synthesis

Answer 28

- a **vector** - a plasmid from e.Coli

Question 29

what does the marker gene in the synthesis of human insulin code for?

Answer 29

**antibiotic resistance** to **ampicillin**

Question 30

Describe the process of inserting the gene into a vector for recombinant DNA technology

Answer 30

\*Plasmid DNA is cut using the **same restriction endonucleases**/ as the donor DNA **sticky ends** are produced in **plasmid DNA** \* **sticky ends** on donor insulin gene and plasmids are **complementary** - **base pairing** occurs **DNA ligase** enzymes **join** sections of DNA from donor and plasmid together **Recombinant DNA** is formed

Question 31

Why are marker genes used in recombinant DNA technology?

Answer 31

When bacteria and plasmids are mixed together only a **small number of bacteria take up the recombinant plasmids**. The bacteria which contain the recombinant plasmids are **identified** by their marker gene

Question 32

give an example of a marker gene

Answer 32

**antibiotic resistance** to **ampicillin**

Question 33

How does the ampicillin-resistance marker gene show which bacteria contain recombinant plasmids?

Answer 33

1) **all the bacteria are cultured** on an agar plate containing **ampicillin** 2) the **surviving bacteria** must contain the **ampicillin resistance gene** 3) therefore the **surviving bacteria must contain the recombinant plasmid**, and therefore the human insulin production gene

Question 34

Once the bacteria are shown to contain recombinant plasmids, what is done with them?

Answer 34

They are cultured in an **industrial fermenter** to divide and produce insulin-synthesising clones the human insulin is then extracted and **purified**

Question 35

Why is it difficult to locate the correct gene for synthesis?

Answer 35

There are only **2 copies of the gene in a cell**

Question 36

Why is using mRNA an alternative to locating the gene itself?

Answer 36

there are **many copies of mRNA** in a cell that has been **transcribed** from the gene, which are **complementary to the gene** itself.

Question 37

Give the method of synthesising recombinant DNA using mRNA

Answer 37

1) mRNA is **extracted** 2) mRNA is mixed with **reverse transcriptase** enzymes 3) This synthesises many copies of a **single stranded DNA polynucleotide** called **cDNA** 4) **DNA polymerase enzymes** are added to convert cDNA into a **double stranded DNA** molecule to be inserted into a **plasmid**

Question 38

What are the advantages of recombinant DNA technology?

Answer 38

1) produces **complex proteins** or peptides in quantity which cannot be produced by other methods 2) produces **higher yielding crops** with **superior keeping qualities** 3) can be used for treating **genetic diseases**

Question 39

What are disadvantages of Recombinant DNA technology?

Answer 39

1) **techinically complicated** - **very expensive on an industrial scale** 2) **difficulties in identifying the genes of value** in a huge genome - 3) synthesis of a required protein may require /**several genes** 4) treatment of human DNA with restriction enzymes produces **millions of fragments** of **no use** 5) not all **eukaryote genes** will **express themselves** in **prokaryote cells** 6) bacteria **readily exchange genetic material** - use of **antibiotic resistant genes** in E.coli means that genes could be **accidentally transferred to human pathogens** 7) Possibility of **transfer of DNA** with linked pathogen genes e.g. oncogenes - **increase cancer risk**

Question 40

What allele, when mutated, expresses the non-functioning protein (of the same name) that causes cystic fibrosis?

Answer 40

**Cystic Fibrosis Transmembrane Regulator**

Question 41

How does the non - functional Cystic Fibrosis transmembrane regulator protein cause cystic fibrosis?

Answer 41

The non functional protein **cannot actively transports Cl- ions out of epithelial cells** 2) Cl- and Na+ build up in the cells 3) **lowers water potential** in the cell 4) **water moves into the cell** by osmosis down the water potential gradient 5) causes the mucus to be **thick and sticky**

Question 42

what are the problems caused by the thick mucus cystic fibrosis suffers have?

Answer 42

1) **blocked pancreatic duct** - prevents **pancreatic enzymes** from being **secreted** into the **duodenum** - \> **food digestion incomplete** - \> **limited absorption of food** 2) **clogged bronchioles and alveoli** - \> congestion and **difficulty breathing** **hard to move mucus** = **trapped bacteria**/virus = **reoccurring infections** e.g. bronchitis/pneumonia frequent **daily chest physiotherapy** needed to keep bronchioles open

Question 43

What is the aim of gene therapy?

Answer 43

to treat genetic diseases by **replacing the defective alleles** in the patients cells with copies of the **normal allele**

Question 44

What are the 2 types of gene therapy?

Answer 44

1) Somatic cell therapy 2) Germ line therapy

Question 45

When in someones life would germ line therapy take place?

Answer 45

when they are a gamete e.g. sperm/ovum

Question 46

Why would the genetic changes from somatic cell therapy not be inherited by the patients offspring?

Answer 46

only somatic cells are treated - gametes are not altered

Question 47

Give the method for cystic fibrosis somatic cell therapy

Answer 47

1) **identify and clone the CFTR gene** by PCR 2) I**nsert the normal CFTR allele into liposomes** 3) **aerosol inhaler** adds the normal allele to the **lung epithelial cells** 4) **Liposomes fuse with phospholipid bilayer** of the cell membrane 5) **DNA enters the cells** 6) epithelial cells with normal CFTR allele **express the normal CFTR protein**/ 7) Symptoms are alleviated

Question 48

What is germ line therapy?

Answer 48

When **normal genes are inserted into germ line cells** - e.g. sperm/ovum - enabling **genetic corrections to be inherited**

Question 49

What biological techniques need PCR to work, and why?

Answer 49

**1) Gene therapy**: - **millions of alleles needed** to have an overall effect on the body **2) Genetic fingerprinting**: - needed if **little DNA** is found at crime scene

Question 50

What does PCR stand for?

Answer 50

Polymerase Chain Reaction

Question 51

What is PCR?

Answer 51

a process which can /**copy a single gene** etc. **many times** by **mimicing semi-conservative replication**

Question 52

What do you need for PCR?

Answer 52

1) **PCR machine** 2) **Gene/DNA fragment** to be copied 3) **buffer solution** 4) **Free DNA nucleotides** 5) **DNA Polymerase** 6) **Primer**

Question 53

Describe the method of PCR

Answer 53

1) heat to **95 degrees** 2) hydrogen bonds in the gene break (**denature**) 3) 2 **template strands** are formed 4) cool to **55 degrees** 5) the **primers attach to complementary bases on target DNA** 6) heat to **70 degrees** 7) **DNA polymerase** pairs the **free nucleotide** bases to the DNA 8) a identical **copy of the DNA is formed** 9) repeat 25 times, producing 1 million copies

Question 54

What is a persons genetic fingerprint?

Answer 54

their DNA profile, which is unique to then

Question 55

what are exons?

Answer 55

regions of DNA that code for proteins

Question 56

What are introns?

Answer 56

regions of **non-coding DNA** contain blocks of repeated nucleotides called /**short tandem repeats** (STR's) the number of repeats **produces variation** in induviduals

Question 57

How is Genetic Fingerprinting used to settle paternity disputes?

Answer 57

1) **white blood cells are taken** from the mother, child, and potential dad 2) DNA taken from the cells undergo **electrophoresis** 3) the **bands of the mother are subtracted** from the child's genetic fingerprint 4) if the man is the father, he **must possess all the remaining bands** in the childs fingerprint

Question 58

what is a genome?

Answer 58

All the DNA including genes, in an organism

Question 59

What are the main aims of the Human Genome Project?

Answer 59

1) determine the **sequence of bases** in all human DNA 2) **Identify all the genes** formed by the bases 3) **Find the locus of all genes** on all 23 chromosomes 4) Store this information on a **database** 5) consider the **social, ethical and legal issues** from obtaining and storing the information

Question 60

what is the main benefit of the human genome project?

Answer 60

the information identifies which genes on particular chromosomes are responsible for different inherited diseases

Question 61

What are the 2 types of genetic tests?

Answer 61

1) **Mutated base sequences** a) **DNA probes**, **complementary to the mutated sequence**, are added to the patients blood. b) If the mutated sequence is present, the **probe will bind to it**, labelling it. 2) **DNA sequence comparison** : the patients **DNA sequence of a gene** is **compared** to the DNA sequence of the **normal gene**

Question 62

Give 3 uses of genetic testing?

Answer 62

1) **Carrier screening** - **identifies unaffected parents** which carry a **recessive allele** for an inherited disease which requires a homozygous recessive genotype to be expressed (**cystic fibrosis**) 2) **pre-symptomatic testing** for **predicting** adult onset disorders (**huntington's) disease**) 3) **pre-symptomatic testing for estimating the risk** of developing adult onset diseases (**alzheimer's, breast cancer**)

Question 63

What factors is the advice in genetic counselling based on?

Answer 63

1) whether there is a **family history** of the disorder 2) whether the parents are **closely related** 3) The **frequency of the allele** in the general population

Question 64

What are the tests to determine whether an embryo is affected with a disorder before it is born?

Answer 64

1) **Blood test - cystic fibrosis** 2) **Amniocentesis**, which involves withdrawing some **amniotic fluid**, which contains **embryonic cells** which can be analysed using a microscope 3) **Chorionic villus sampling** - removing foetal tissue (**8-10 weeks**) where the **cells are cultured** and **examined** under the microscope

Question 65

What are the Social, Ethical, and Legal concerns with gene testing/therapy?

Answer 65

1) **Anxiety** 2) Concerns that the risks of **discrimination** and social stigmatization could outweigh the benefits of testing 3) some believe that if prenatal tests are carried out, finding defective alleles will lead to an increase in the number of **abortions** 4) who should have **access to personal genetic information** and how it should be used e.g **employers/health insurance**