What is the structure of DNA?
Deoxyribonucleic acid is a double stranded, double helix molecule
Where in the cell is DNA found?
Deoxyribonucleic acid is found in the nucleus of a cell. It is arranged wound up in Chromosomes.
What is a gene?
A gene is a section of a Chromosome that codes for a particular trait/characteristic e.g. hair colour.
What is an allele?
An allele is an alternative form of a gene e.g. if the gene is eye colour an allele may be blue eyes, green eyes.
What can cause variation within a species?
Genetic and environmental factors
What is a dominant allele?
An allele that will always be expressed
What is a recessive allele?
An allele that will need to be in a homozygous pair to be expressed
How are recessive and dominant alleles written?
A dominant allele is always a capital letter while a recessive allele is always the corresponding smaller letter
What is the genotype?
The allele pair for each characteristic
What is the phenotype?
The physical expression of an allele pair
How many chromosomes do humans have?
Humans have 23 pairs of chromosomes in each cell
How many chromosomes does each gamete (sex cell) have?
The human egg and sperm cell contain 23 chromosomes each.
What is the name of the cell created after fertilisation?
A zygote
What is cystic fibrosis?
An inherited disease that affects the respiratory system and digestive system. Sufferers produce much more, thicker mucus which lines the respiratory system.
What is cystic fibrosis?
An inherited disease that affects the respiratory system and digestive system. Sufferers produce much more, thicker mucus which lines the respiratory system.
Is Cystic Fibrosis caused by a dominant or recessive allele?
Cystic Fibrosis is caused by a recessive allele
What is a clone?
A genetically identical organism
What (naturally) creates clones?
Asexual reproduction
How can plants be cloned?
By taking a cutting of the plant
How was Dolly the sheep cloned?
- Cell was taken from the udder of a Finn-Dorset sheep
- An egg was taken from a Scottish Blackface sheep and it’s nucleus was removed.
- the two cells were combined with an electric shock
- the combined cell now has a single nucleus from the nuclear donor (Finn Dorset)
- Egg divides normally to form a blastocyst
Blastocyst is placed in the uterus of a surrogate ewe - 5 months later a lamb is born - Dolly the sheep
How does selective breeding work?
- A farmer decides which characteristic is most important
- Parents that show high levels of this characteristic are selected and bred
- Best offspring is chosen and bred again from this generation
- process repeated over generations until all animals have high levels of the desired characteristic
How does genetic engineering work?
Genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms
How is insulin produced?
- Gene that codes for insulin is extracted from normal human cell using enzyme
- A plasmid is isolated from a bacterium and the human insulin gene is inserted
- plasmid vector is inserted into a bacterium
- Bacteria reproduces, producing new bacteria that all have the plasmid vector and produce insulin
- Insulin can be extracted and used to treat people with diabetes
Advantages of genetic engineering
Quicker than selective breeding, can produce medicinal drugs, produces crops with specific characteristics
