topic 3 - genetics Flashcards
what are gametes
the scientific name for a sex cell
what is a polymer
a substance which is made up of many repeating units e.g DNA
what is variation
the differences between members of the same species
what are chromosomes
a long coiled up molecule of DNA
what is an allele
a different version of the same gene
what is a genome
all the genetic material within an organism
what is a double helix
the characteristic shape of DNA - 2 strands coiled around each other
what is a nucleotide
consists of sugar, a phosphate and a base. many of these join up to form a polymer of DNA
what is meiosis
a type of cell division in which 4 genetically different gametes are produced. important for sexual reproduction
what is a mutation
a change in the base sequence of DNA
what is the human genome project
a project whose aim was to find every single gene in the human genome
what is a dominant allele
an allele that is always expressed in the phenotype if the organism is heterozygous
what is a recessive allele
an allele which is not expressed in the phenotype if the organism is heterozygous
what is a carrier
the term for someone who has a disease causing recessive allele
what is a gene
a sequence of DNA which codes for a particular protein
what is a genotype
the term for the genes within an organism
what is a phenotype
the term for the physical characteristic caused by a genotype
how do bases pair
A-T C-G
what is genetic variation
a type of variation which is caused by the environment which an organism is exposed to
how do you extract DNA from onion cells
(each step and why)
1) put the chopped onion (can be anything) in a beaker of washing up liquid - to break down cell membranes
2) place the beaker in a waterbath for 15 mins - to speed up the break down of the membrane and denature any enzymes
3) stand the beaker in iced water and stir - to prevent the break down of DNA
4) blend the mixture - to help break open the cells
5) filter the mixture and keep the filtrate - to remove any solid debris
6) place 10cm of filtrate in boiling tube and addd 2-3 drops of protease enzyme and mix - to break down proteins so the DNA can precipitate
7) carefully pour down ice cold ethanol down the side of the tube - to precipitate the DNA (make it visible)
8) use a glass rod to gently lift out some of the DNA
