Unit 4 Mixed Flashcards
What is the advantage of preventing self-pollination
Increases genetic variation and so increases the chances of survival of the species as it can adapt to a changing environment
Why is an even number of chromosomes needed to make a species fertile
Homologous pairs and bivalents can form during prophase 1 of meiosis and so gametes can be produced
Intron
Non coding region of DNA
is spliced out and not translated
Exon
Coding regions which are translated for a polypeptide
What are the potential problems of using a virus in gene therapy
Can cause an immune response
May not reach the target cell
May become pathogenic
May affect other genes - oncogenes
What are the disadvantages of using a molecular patch to treat DMD
• it is not permanent and so repeated treatments are needed
• the change is not present after cell replication and so is not passed onto next generation
Ethical issues of germ line therapy
• unknown long term effects
• possible activation of oncogenes
• the modified genes are passed onto the next generation and so will effect later generations
Antigen
Innates an immune response and the production of antibodies
What is an antigen-antibody complex
When a specific antibody is bound to an antigen
How can the sperm enter the secondary oocyte
Acrosome reaction
The acrosome releases hydrolytic enzymes such as proteases which hydrolyse the corona radiata and zona pellucide
How is polyspermy prevented
Cortical reaction
The cortical granules rupture and the zona pellucida thickens and hardens to form the fertilisation membrane
Continuous variation
Polygenic
Imtermediates
Discontinuous variation
Monogenic
Distinct groups
How does natural selection work
• variation is caused due to mutations
• some mutations will confer a selective advantage
• individuals with selective advantage is more likely to survive and reproduce and pass on advantageous alleles to offspring
• this is repeated over several generations and the allele frequency of the advantageous allele will increase
Sympatric speciation
Non-geographical barriers
Allopatric speciation
Geographical barriers
How do isolation barriers work
• prevent the gene flow
• genetic differences will accumulate and so they can no longer produce fertile offspring
Umbilical artery
Carries blood away from foetus
Contains carbon dioxide, urea
Umbilical vein
Carries blood to the foetus
Contains oxygen, nutrients and antibodies
Ethics of prenatal diagnosis
• more selective abortions
• moral status of the foetus
• may cause harm to foetus
• may give a false negative
Conditions required for germination and why
• water - cause cotyledons to swell and to dissolve substances to act as a fluid medium for enzymes
• oxygen - for aerobic respiration to produce ATP for metabolism
• suitable temperature- to increase rate of diffusion and to increase enzyme activity
Germination of non-endospermic seeds
• endosperm has been absorbed into cotyledons
• amylase digest starch in the cotyledons to maltose
• proteins and fats are also broken down into amino acids, fatty acids and glycerol
• these move into the plumule and radicle and are used for cell division for growth
Germination of endospermic seed
• starch, proteins and fats are in the endosperm
• the embryo produces gibberellin which moves into the aleurone layer
• the GA causes enzymes to break down proteins into amino acids which are used to synthesise other proteins such as amylase which breaks down starch in the endosperm into maltose
What is gene therapy
The treatment of genetic disease by replacing defective alleles in a patient with copies of a new DNA sequence