pack 19 population genetics

Question 1

what is variation

Answer 1

describes the differences in characteristics or phenotypes that exist

Question 2

what is phenotype

Answer 2

an organisms physical appearance
constitution and behaviour

Question 3

what is genotype

Answer 3

an organisms genetic make up

Question 4

where does interspecific variation occur

Answer 4

between different species

Question 5

where does intraspecific variation occur and what can it cause

Answer 5

within a species, can lead to natural selection and eventually speciation

Question 6

causes of variation

Answer 6

environment- diet, disease, climate
genetic- meiosis, mutations and random fussion

Question 7

name two ways in which meiosis introduces genetic variation to gametes

Answer 7

• crossing over and independent segregation of chromosomes

Question 8

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

Answer 8

• a gene is the sequences of bases in DNA that codes for the production of a protein leading to a change in the base sequence of the mRNA that is transcribed
  -if the sequence of bases is altered then this might change the sequences of amino acids coded for in the protein
• this change in the primary structire of the protein causes in the teritary structure as h bonds , disulphide bonds form in different places
• this can lead to a loss or reduction in function of the protein

Question 9

what can increase mutation rates and examples

Answer 9

mutagenic agents
- x-ray, uv light
- nitrogen dioxide chemicals in tobacco tar

Question 10

what are the types of mutations

Answer 10

• addition or deletion,
• substitution,
• duplication of bases
• inversion of bases
• translocation of bases

Question 11

what is addition or deletion

Answer 11

an extra base is added or removed in the sequence
- this changes all the triplets after the mutation and therefore a completely different amino acid sequence is made
- this is a frame shift mutation, as the ‘reading frame’ of the gene changes. One added or deleted base at the very start of a sequence could alter every triplet in the sequence. A deleted base near the end of the sequence is likely to have a smaller impact but can still have consequences.

Question 12

what is substitution and the 3 types

Answer 12

one base is swapped for another
- mis-sense - one of the amino acids in the polypeptide could change. the impact of this could change the primary structure which could alter the tertiary structure of the final protein. the protein may be a different shape and so not function properly.

• nonsense - the base change could result in the formation of a stop codon that marks the end of translocation
• silent - it could cause no difference due to the degenerate nature of the genetic code: the same amino acid could still be coded for.

Question 13

what is duplication of bases

Answer 13

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

Question 14

what is inversion of bases

Answer 14

• a group of bases becomes separated from the DNA sequence and rejoins at the same position but in the inverse order. the base sequence of this portion is therefore reversed and effects the amino acid sequence coded for.

Question 18

what is a gene pool

Answer 18

• the sum total of all the alleles of all gene loci in a population at a particular time

Question 19

hardy- Weinberg

Answer 19

p+q= 1
p= frequency of the dominant allele
q= frequency of the recessive allele
p2 = frequency of the homozygous dominant genotype
q2 = the frequency of the homozygous genotype
p2+q2+2pq= 1