You Your Genes B 1 Revision Notes Individual

You + Your Genes B 1 Revision Notes

Individual Characteristics n Features determined either owing to environment or inheritance. Examples? n n n Variation amongst individuals Organisms made of cells. Cells controlled by a nucleus containing chromosomes. Each chromosome is made of thousands of genes which control how you develop. Genes tell the cell how to make proteins (50, 000 types in human body).

Chromosomes n Put in correct order, largest 1 st n Chromosome, gene, cell, nucleus Each body cell contains 46 (23 pairs) chromosomes. 23 from each parent. n Only sex cells (gametes) contain only 23 chromosomes. n

Genes and Alleles n n n Chromosomes pair up and genes for the same feature align next to each other. Different versions of the same gene are called alleles, e. g. eye colour (brown and blue alleles, but gene for the same feature). One allele is always dominant and means this feature shows up. The other allele is recessive.

Genetic Crosses n Mum has 2 alleles, n A and a for hair colour. Dad has the same ones. n A is brown hair n a is blond hair. n n n Both parents have brown hair. What is chance of offspring having blond?

X and Y XX is female. n XY is male. n Y dominates. n n 50: 50 chance of either sex n Sex-linked diseases; Haemophilia n Colour-blindness n Muscular dystrophy n

Inherited Diseases n Cystic Fibrosis. Caused by recessive allele. n Mainly people are carriers. n Causes cells to produce sticky mucus. Results in lengthy physio and higher infections rates. n n Huntington’s Disease. Attacks the nervous system. Symptoms include loss of muscle control and memory loss and commence later in life. n Caused by dominant allele. n

Ethical Decisions Amniocentesis is a test on an unborn baby to detect if it has cystic fibrosis. n It is not 100% reliable with a 0. 5% miscarriage risk, small chance of infection, and results only between 15 -18 weeks. n Information could be used to decide on a termination (abortion). This is an ethical decision based on genetic testing n

Reliability of Genetic Tests n False-negative; n n Wrong result which says a person does not have a medical condition but they do. False-positive; n Wrong result which says a person has a medical condition but they do not (this could have been aborted so ethics again!)

Designer babies n Embryo selection (form of IVF); n n Gametes fertilised in labs, and then the embryo’s tested for genetic disease/s (checking the alleles). Healthy ones used for mothers womb. What about the others? ? Gene therapy; n n Curing an inherited disease by putting correctly working alleles into a person. Had limited success. Currently illegal for sex cells. People worried it could lead to control features like eye colour, etc.

Cloning n n n Clone is genetically identical to the organism it was made from. Happens naturally with identical twins and also asexual reproduction (one parents such as bacteria). Early embryos are made of stem cells which can develop into any specialised cell. Scientists want to clone using cloned embryos. Ethical decisions?

Arguments n In favour; n n n Scientific progress Organ transplants Legal up to 14 days Your relation/friend? Against; n n n Human rights Lowers value of life ‘Murder’ of embryos