1
Q
polydactyly
A
- the genetic condition polydactyly is caused by a dominant allele
- people with this allele have extra fingers or toes
2
Q
cystic fibrosis
A
- the genetic condition cystic fibrosis is caused by the recessive allele, f
- the condition affects chloride ion transport across membranes, resulting in thick, sticky mucus
3
Q
DNA
A
DNA is a polymer made up of a chain of monomers called nucleotides.
4
Q
when are chromosomes visible in the cell
A
when the cell is dividing (during mitosis)
5
Q
mutations and enzymes
A
- a mutation may change a DNA triplet in a gene which codes for an enzyme
- this mutation in the DNA could cause the triplet to code for a different amino acid, resulting in an enzyme with an active site which is no longer complementary to the substrate
- this could affect the enzyme’s ability to perform its normal function which could, in turn, affect the phenotype of an organism
6
Q
silent mutations
A
- mutations that have no affect on the phenotype of the organism
- this could be because of mutations that occur in DNA that does not code for proteins
- or when the mutation changes one of the bases in the triplet but the triplet still codes for the same amino acid.
7
Q
genetic engineering of bacteria process
A
- a useful gene is cut from the DNA of one organism using a restriction enzyme which breaks bonds between nucleotides
- restriction enzymes cut the DNA in a staggered way leaving short sections of single-stranded DNA at each end of the gene called sticky ends
- the bacterial plasmid DNA is cut open using the same restriction enzyme creating complementary sticky ends.
- the gene is inserted into the plasmid. Hydrogen bonds form between the complementary bases in the sticky ends of the plasmid and the useful gene.
- ligase is used to seal the useful gene into the plasmid.
- the recombinant plasmid is then inserted into a bacterial cell, acting as a vector
- the bacterial cell is now a GMO. It can reproduce rapidly to produce large amounts of the protein.
8
Q
Proteins that can be produced by genetically modified bacteria:
A
- hormones e.g. insulin
- antibiotics e.g. penicillin
- enzymes e.g. rennin used in cheese production
- blood clotting factors e.g.factor VIII used to treat haemophilia
9
Q
genetic engineering of plants process:
A
- because plant cells do not have plasmids, the bacteria Agrobacterium tumefaciens is commonly used as a vector as they have a Ti plasmid.
- a recombinant Ti plasmid is created which inserts into the bacterial cell creating a transgenic bacterial cell
- Plant cells grown in the lab are mixed with transgenic bacterial cells. The Ti plasmid carries the useful gene into the plant cell and inserts it into the plant cell’s chromosome
- the GM plants are able to produce the protein coded for by the useful gene
10
Q
benefits of using genetic engineering in medicine
A
- GMOs can be used to produce MEDICINES e.g. GM bacteria produce human insulin which is used to treat diabetes
- GMOs have been used in the development of VACCINES e.g. recombinant hepatitis B vaccine is produced by GM baker’s yeast
- GM pigs are being developed with human-like ORGANS which can help to reduce shortage of suitable organ donors (although this raises ethical concerns)
- Human cells can be genetically modified using gene therapy to provide possible CURES for genetic diseases such as cystic fibrosis
- GM insects have been created to reduce the SPREAD of certain diseases such as malaria
11
Q
risks of using genetic engineering in medicine
A
- if the therapeutic gene is not accurately inserted into a chromosome it can cause cancer
- cancer arises when the therapeutic gene is inserted too close to a cancer-causing gene and this gene is then switched on.
12
Q
Examples of how embryonic stem cells could be used:
A
- treating diabetes by replacing insulin-secreting cells in the pancreas
- treating burns by replacing damaged skin tissue
- replacing neurones damaged by spinal cord injury
- replacing cells in the heart damaged by a heart attack
13
Q
problems with using embryonic stem cells
A
- increased risk of cancer developing
- treatments carry the risk of immune rejection because the transplanted cells are identified as foreign
- use of embryonic stem cells is controversial because they involve destroying human embryos
14
Q
induced pluripotent stem cells advantages
A
- more ethical than using embryonic stem cells
- stem cells produced from a patient’s own body cells so should not be rejected as foreign
15
Q
stem cells definition
A
undifferentiated cells which can divide by mitosis and become differentiated to form a number of different cell types
16
Q
source of totipotent cells
A
- zygote
- cells produced by the first few divisions after an egg cell is fertilised
17
Q
difference between totipotent and pluripotent stem cells
A
totipotent cells can differentiate into placental cells, but pluripotent cells cannot
18
Q
selective breeding/artificial selection
A
- Animals with desirable characteristics are selected for breeding
- These animals are bred together
- The animals with the most desirable characteristics are selected from the offspring
- These offspring animals are then bred together
- This cycle is repeated over many generations
- Over time the desirable characteristic starts to increase in the population
19
Q
disadvantages of selective breeding
A
- results in inbreeding depression (an increase in the frequency of individuals that are homozygous for deleterious recessive alleles) which increases the likelihood of genetic conditions arising
- this reduces the genetic variability of a population which may reduce the population’s ability to adapt to a changing environment
20
Q
X linked disorders
A
- caused by mutations in genes on the X chromosome
- fathers cannot pass on X linked traits to their sons
- also called sex linked disorders
21
Q
X linked dominant traits
A
- sons expressing the trait must also have a mother expressing the trait
- daughters expressing the trait must have a mother or father expressing the trait
- e.g. rett syndrome (progressive loss of motor skills and speech)
22
Q
X linked recessive traits + examples
A
- more common in males than females because females have to have 2 altered copies of the gene, whereas males have to have only 1 altered gene which is more likely to happen.
- sons expressing the trait can be born to mothers not expressing the trait
- eg hemophilia, colour blindness
23
Q
Y linked disorders
A
- caused by mutations in genes on the Y chromosome
- only males affected
- passed from father to son
24
Q
autosomal dominant example
A
huntington’s disease
25
autosomal recessive example
- sickle cell anemia
| - cystic fibrosis
26
mitochondrial inheritance
- applies to genes in mitochondrial DNA
- only egg cells contribute mitochondria to the developing embryo so only females can pass on mitochondrial variants to their children (both boys and girls)
- e.g. Leber's hereditary optic neuropathy (acute loss of vision)
27
autosomal recessive trait pattern
-recessive traits usually skip generations (i.e carriers only)
28
mendelian inheritance
- separates traits into dominant or recessive
| - applies to all sexually reproducing organisms (e.g. plants, animals)
29
what can cause genetic mutations
- external factors: mutagens (e.g. tobacco smoke) or ionising radiation (e.g. UV/X-rays)
- internal factors: mistakes during dna replication
30
CIP (congenital insensitivity to pain)
- a rare autosomal recessive disease that causes affected individuals to be unable to feel pain
- without the body’s natural warning mechanism, many with CIP exhibit self-destructive behaviour such as biting off their own tongue
- it is most likely so rare because individuals with this disorder do not usually survive to adulthood
BMAT Biology
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