Inheritance, variation and evolution

• What 4 bases is DNA made up of?

  Adenine (A)Guanine (G)Cytosine (C)Thymine (T)
• A is complementary to...

  Adenine is complimentary to Thymine (T)
• G is complimentary to..

  Guanine is complimentary to Cytosine ( C )
• Gene


  A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
• What does DNA stand for

  deoxyribonucleic acid
• DNA is a polymer made of

  Two strands forming a double helix.
• What is a nucleotide?

  Single unit of DNA; made up of a sugar, phosphate and a base

  
• The shape of the protein


  Determines its function
• The specific order of amino acids

  Determines the shape of the protein
• Protein Synthesis

  stage 1, transcription, inside the nucleus, making a small copy of the gene into mRNA.And stage 2, translation, the copied code, the mRNA leaves the nucleus and goes to the ribosome where a protein is made.
• What is the genome of an organism?

  entire genetic material of that organism
• Studying the genome has what benefits

  • search for genes linked to different types'of disease• understanding and treatment of inherited disorders• use in tracing human migration patterns from the past.
• How are gametes produced?

  By meiosis in reproductive organs; •All chromosomes are copied • They then divide into two • these cells divide one more time forming the gametes

  
• How do gametes restore the normal number of chromosomes

  They fuse at fertilisation.
• What is sexual reproduction

  Fusion of male and female gametes
• Advantages of sexual reproduction

  • produces variation in the offspring• if the environment changes variation gives a survival advantage by natural selection• natural selection can be speeded up by humans in selective breeding to increase food production.
• What is asexual reproduction

  The production of genetically identical offspring from a single parent. No fusion of gametes.
• Advantages of asexual reproduction

  • only one parent needed• more time and energy efficient as do not need to find a mate• faster than sexual reproduction• many identical offspring can be produced when conditions are favourable.
• What organisms reproduce both ways depending on the circumstances

  • Malarial parasites reproduce asexually in the human host, but sexually in the mosquito.• Many fungi reproduce asexually by spores but also reproduce sexually to give variation.• Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.
• Allele


  different forms of the same gene
• Genotype


  genetic makeup of an individual for a particular characteristic
• Phenotype

  physical characteristics of an organism for a particular characteristic
• Dominant allele is


  always expressed even if one copy is present
• Recessive allele is

  Only expressed if two copies are present
• 22 pairs control characteristics only, how many pairs carries the gene that determines sex


  One• In females the sex chromosomes are the same (XX).• In males the chromosomes are different (XY).
• Polydactyly

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

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

  Differences in the characteristics of individuals in a population
• What causes variation

  • the genes they have inherited (genetic causes)• the conditions in which they have developed (environmental causes)• a combination of genes and the environment.
• What is genetic variation caused by

  Mutations
• How often are mutations taking place

  They occur continuously.Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.
• What is selective breeding

  Process in which humans breed plants and animals for useful characteristics Type of sexual reproduction
• Reasons to selectively breed

  • Disease resistance in food crops.• Animals which produce more meat or milk.• Domestic dogs with a gentle nature.• Large or unusual flowers.
• What can selective breeding lead to

  'inbreeding' where some breeds are particularly prone to disease or inherited defects.
• Selective breeding involves

  Selective breeding involves choosing parents with the desired characteristic from a mixed population. They are bred together. From the offspring those with the desired characteristic are bred together.This continues over many generations until all the offspring show the desired characteristic.
• Genetic engineering


  as a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
• Examples of genetic engineering

  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.
• benefits of genetic engineering

  Help fight disease Increase nutrients in food Can be used to make medicines
• Negatives of genetic engineering

  Can reduce biodiversity Cause harm to wildlife Lead to antibiotic resistance
• Process of genetic engineering

  In genetic engineering, genes from the chromosomes of humans and other organisms can be 'cut out' and transferred to cells of other organisms.