variation

Question 1

define the term phenotype

Answer 1

the expression of the genotype and its interaction with the environment

Question 2

define the term genotype

Answer 2

an organisms genetic makeup

Question 3

define the term variation

Answer 3

the differences in characteristics or phentoypes that exist

Question 4

define the term mode

Answer 4

the most frequently occurring value

Question 5

define the term mean

Answer 5

a measure of central tendency of the data sometimes refferred to as the arethmetic mean

Question 6

define the term median

Answer 6

the middle value in the data when arranged in rank order

Question 7

state the two causes of variation

Answer 7

environmental

-genetic

Question 8

give examples of envionmental factors that can lead to variation

Answer 8

• temperature
• light intensisty
• diet

Question 9

give examples of genetic factors that can lead to variation

Answer 9

• meosis
• mutations
• random fusion of gametes

Question 10

name two ways in which meiosis introduces genetic variation into gametes

Answer 10

• crossing over

- independent segregation

Question 11

describe how random fertilisation of gametes causes genetic variation

Answer 11

gametes fusing is a random process and this produces new combinations of alleles and the offspring are therefore genetically different

Question 12

describe how mutations causes genetic variation

Answer 12

a chgnage in number or sequence of bases

Question 13

explain how gene mutations can lead to the production of non functioning proteins

Answer 13

the sequemce of bases in DNA is altered
the sequnece of bases in mRNA will change
the sequnece of amino acids in the protien may change
this change in the primary structire causes a change in tertiary structure as bonds form in different places
this can lead to a non functioning protein

Question 14

give examples of high energy ionising radiation that can disrupt the structure of DNA

Answer 14

• xrays
• beta rays
• gamma rays

Question 15

give examples of chemicals that can disrupt the structure of DNA

Answer 15

• nicotine

- benzoyl peroxide

Question 16

name the types of mutation

Answer 16

• addition
• deletion
• substitution

Question 17

describe the mutation of addition and deletion

Answer 17

an extra base is added or removed

Question 18

describe the mutation of substitution

Answer 18

one bases is swapped for another

Question 19

what happens after a bases has been added or deleted ?

Answer 19

it changes all the subsequent triplets after the mutation
so a completely different amino acid chain is made
ie frame shift

Question 20

describe the 3 consequences of a base substitution

Answer 20

• one of the amino acids in the polypeptide could change
• the base change could result in a stop codon that marks the end of translation
• it could cause no difference due to the degenerate nature of the genetic code

Question 21

name two other types of mutation

Answer 21

• duplication of bases

- inversion of bases

Question 22

describe the mutation duplication of bases

Answer 22

one or more bases are repeated producing a frame shift to the right

Question 23

describe the mutation inversion of bases

Answer 23

a group of bases become separated from the DNA sequence and rejoin at the same place nut in the inverse order

Question 24

Why is the genetic code describe as being universal ?

Answer 24

Same triplet codes for same amino acid

Question 25

Name the process that removes base sequences from pre-mRNA to form mRNA

Answer 25

Splicing