chnages in the genetic makeup of a population

Question 1

gene pool

Answer 1

all the genetic information contained in a population over time

Question 2

where do new alleles come from

Answer 2

• mutations
  this is the random and unpredictable change in genetic information (base sequences)
  they occur from errors in DNA replication
• sexual reproduction
  recombination (crossing over and independent assortment) creates new combinations of existing alleles

Question 3

what are the two reasons for mutation and explain

Answer 3

induced: a mutation caused by the environment eg smoking / UV rays
spontaneous: a mutation due to an error in DNA replication with no known reason

Question 4

germline mutations

Answer 4

occurs in reproductive cells

can be passed onto offspring

Question 5

somatic mutation

Answer 5

occurs in body cells.

cannot be passes onto the offspring

Question 6

polyploidy

Answer 6

where an individual carries three or more SETS of chromosomes (eg 3n, 4n)`

Question 7

aneuploidy

Answer 7

individual posses an abnormal number of chromosomes (addition of one or missing one)

trisomy: extra homogulous pair
monosomy: missing one homogulous pait

Question 8

what are the type of point mutations

Answer 8

point mutation: a change in a single base within a gene
substitution
deletion
insertion

Question 9

substitution

Answer 9

one base is replaced by another in the sequence
can wither be missense, silent or nonsense
- missense: one amino acid alteration in polypeptide sequence. new base substitution codes for a different amino acid
- nonsense: base substitution codes for a STOP codon. has a serious effect on protein as it is shortened and may fold differently
- silent: base substitution codes for the same codon, no effect on polypeptide

Question 10

deletion

Answer 10

one base is removed from the sequence of bases in the gene

Question 11

base insertion

Answer 11

an extra base is added to the sequence of bases in a gene

Question 12

frame shift

Answer 12

a change in the reading frame caused by an insertion or deletion, not a substitution

Question 13

types of block mutation

Answer 13

block mutations are changes to sections of a chromosome inverse
translocation
duplication
block deletion

Question 14

inverse

Answer 14

segment is removed and then replaced in reverse order

Question 15

deletion

Answer 15

a portion of chromosome is removed

Question 16

insertion

Answer 16

part of one chromosome is removed and then added to a different chromosome

Question 17

duplication

Answer 17

a part of the chromosome is copied, resulting in a chromosome having two or more copies of that section

Question 18

tranlocation

Answer 18

parts of two chromosomes are swapped

Question 19

points for natural selection

Answer 19

1. there is variation within a population
2. a selection pressure means that some organisms have a better chance of reproducing than others
3. the organisms that can reproduce are likely to pass favourable characteristics (alleles) to the next generation
4. greater allele frequency of characteristic is present in the population

Question 20

gene flow

Answer 20

the movement of alleles between populations by migration of the individuals carrying them.
KP: there must be sexual reproduction for new alleles to be introduced into the population

Question 21

genetic drift

Answer 21

a chance event happening in the population that significantly changes the frequency of alleles in the population

• more prominent in small populations than in larger
• can make less suitable alleles more common in a population by chance

Question 22

bottle neck

Answer 22

example of genetic drift
there is a random drastic reduction in the population (due to a natural disaster) which affects the gene pool
gene pool is then limited to the alleles the survivors had.

Question 23

founder effect

Answer 23

example of genetic drift
members of a large population establish a new population in a new biologically isolated area
(for examples if beetles were blown into an island by a tornado with no other beetles they are the founder of new populations)

Question 24

monomorphic populations

Answer 24

all members of a population shows one form of a trait

Question 25

monomorphic populations

Answer 25

all members of a population shows one form of a trait

Question 26

speciation

Answer 26

when do naturally selected or selectively bred populations become their own species

Question 27

SPECIES

Answer 27

a population that has the potential to interbred.

defined in terms of reproductive isolation meaning that one group of genes becomes isolated from the other

Question 28

how can isolation of genes occur

Answer 28

allopatric speciation

sympatic speciation

Question 29

allopatric speciation

Answer 29

caused by geographical isolation (eg a seperate river, mountain range, oceans etc)
results in no gene flow between them and another population

Question 30

sympatic isolation

Answer 30

is gene isolation caused by behavioural differences, chromosome differences and seasonal behaviour including

• behavioural differences/isolation: reproductive behaviours change such that similar species do not recognise each other for mating purposes
• mechanical: structural differences in genitalia making it impossible to interbreed
• reproductive isolation: lizards example