topic 3 - genetics

Question 1

what are gametes

Answer 1

the scientific name for a sex cell

Question 2

what is a polymer

Answer 2

a substance which is made up of many repeating units e.g DNA

Question 3

what is variation

Answer 3

the differences between members of the same species

Question 4

what are chromosomes

Answer 4

a long coiled up molecule of DNA

Question 5

what is an allele

Answer 5

a different version of the same gene

Question 6

what is a genome

Answer 6

all the genetic material within an organism

Question 7

what is a double helix

Answer 7

the characteristic shape of DNA - 2 strands coiled around each other

Question 8

what is a nucleotide

Answer 8

consists of sugar, a phosphate and a base. many of these join up to form a polymer of DNA

Question 9

what is meiosis

Answer 9

a type of cell division in which 4 genetically different gametes are produced. important for sexual reproduction

Question 10

what is a mutation

Answer 10

a change in the base sequence of DNA

Question 11

what is the human genome project

Answer 11

a project whose aim was to find every single gene in the human genome

Question 12

what is a dominant allele

Answer 12

an allele that is always expressed in the phenotype if the organism is heterozygous

Question 13

what is a recessive allele

Answer 13

an allele which is not expressed in the phenotype if the organism is heterozygous

Question 14

what is a carrier

Answer 14

the term for someone who has a disease causing recessive allele

Question 15

what is a gene

Answer 15

a sequence of DNA which codes for a particular protein

Question 16

what is a genotype

Answer 16

the term for the genes within an organism

Question 17

what is a phenotype

Answer 17

the term for the physical characteristic caused by a genotype

Question 18

how do bases pair

Answer 18

A-T C-G

Question 19

what is genetic variation

Answer 19

a type of variation which is caused by the environment which an organism is exposed to

Question 20

how do you extract DNA from onion cells
(each step and why)

Answer 20

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