Inheritance variation and Evolution

• Mutations occur which provide variation between organisms

  -if a mutation provides a survival advantage the organism is more likely to survive to breeding age

  -the mutation will be passes onto offspring

  -over many generations,the frequency of the mutation will increase within the population
• Stages of genetic engineering

  1)gene of inerest is removed using enzymes

  2)gene is inserted into a bacterial plasmid using enzymes

  3)modified plasmid is put into a bacteria

  4)bacteria multiply and produce gene of interset (eg insulin)

  5)purify the wanted characteristics
• Phenotype

  An organism’s observable characteristics. Due to interactions of the genotype and the environment.
• Variation (environment)Environment:

  -the conditions the organism grows and develops in also affects its appearnace-example include scars in animals or smaller and yellow leaves in plants
• Advantages of asexual reproduction

  -only 1 parent is needed

  -uses less energy and is faster as organisms do not need to find mate

  -in favourable condidtions lots of identical offspring can be produced
• Genetic engineering

  Genes can be transferred tp the cell of animals and plants at an early of thier development so they develop desired charcateristics.

  -Plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits.

  -Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes.
• What is asexual reproduction

  Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
• Problem with selective breeding

  It can lead to inbreeding

  -Breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals

  -this results in the reduction of the gene pool,as the numbers of different alleles reduce (as they mostly have the same allele)

  -this means if the environment changes or there is a new disease,the species could become extinct as they all have the same genetic makeup (so the chance of a few organisms having a survival advantage and not dying is reduced)
• What is DNA

  The genetic material in the nucleus of a cell is composed of a chemical called DNA. DNA is a polymer made up of two strands forming a double helix. The DNA is contained in structures called chromosomes
• Sexual reproduction produces variation in offspring, which can lead to an organism having a survival advantage in changing environments.
• Although some individuals may die due to variation, it decreases the chance of the whole species becoming extinct.
• Sexual reproduction allows us to use selective breeding.
• Sexual reproduction mixes the genetic information from two organisms, allowing organisms with different desirable characteristics to be bred to produce offspring with even more desirable characteristics.
• Sexual reproduction speeds up natural selection.
• An example of using sexual reproduction to increase food production is breeding two animals with a lot of meat.
• Heterozygous

  When someone has two different alleles of a gene e.g. Ff.
• What is a genome?


  The genome of an organism is the entire genetic material of that organism. The whole human genome has now been studied and this will have great importance for medicine in the future.
• mitosis

  -produces 2 daughter cells

  -cells are gentically identical

  -the chromosome number is 46-used for growth and repair and asexual reproduction
• Alleles

  : A version of a gene.
• Homozygous: having two identical alleles of a particular gene or genes
• Dominant allele

  Describes an allele that is always expressed. Represented by a capital letter.
• Inherited disorders

  Polydactyly (having extra fingers or toes) is caused by a dominant allele.

  • Cystic fibrosis (a disorder of cell membranes) is caused by a recessive allele.
• Selective breeding


  Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics. Humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals

  1. choose parents who have the desired charcateristics

  2)select the best offspring and breed these to make the next generation

  3)These offspring are then bred again and again over many generations until the desired result is achieved.
• Gamete 


  Sex cells (sperm and egg cells) with half the usual number of chromosomes.
• Genetically modified crops

  they are engineered to be resistant to insects and to herbicides-this will result in increases yields as less crops will die
• Chromosome


  A long, coiled molecule of DNA that carries genetic information in the form of genes.
• What is sexual reproduction

  Sexual reproduction involves the joining (fusion) of male and female gametes:

  • sperm and egg cells in animals

  • pollen and egg cells in flowering plants.

  In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis
• Fossils are the 'remains' of organisms from millions of years ago, which are found in rocks.
• Fossils may be formed from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.
• Fossils may be formed when parts of the organism are replaced by minerals as they decay.
• Fossils may be formed as preserved traces of organisms, such as footprints, burrows and rootlet traces.
• Many early forms of life were soft-bodied, which means that they have left few traces behind.
• The traces of these early forms of life have been mainly destroyed by geological activity, which is why scientists cannot be certain about how life began on Earth.
• Fossils can teach us how much or how little different organisms have changed as life developed on Earth.
• Recesiive allele


  Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter.
• Genetic engineering can be very useful in medicine to mass produce certain hormones in microorganisms such as bacteria and fungi.
• In agriculture, genetic engineering can be used to improve yields by improving growth rates, introducing modifications that allow crops to grow in different conditions, introducing modifications that allow plants to make their own pesticide or herbicide, producing crops with extra vitamins in areas where they are difficult to obtain, and increasing yields to help solve world hunger, which is becoming an increasingly bigger issue due to population growth.
• Sexual reproduction produces variation in offspring, which means that if the environment changes it is likely that an organism in the species will have a characteristic that allows them to survive, known as a survival advantage.
• Although some individuals may die, variation decreases the chance of the whole species becoming extinct.
• Sexual reproduction allows us to use selective breeding, which mixes the genetic information from two organisms.