genetic variation

Question 1

meiosis definiton

Answer 1

Is a type of cell division division that produces sex cells/gametes with half the number of chromosomes as the somatic cell. Produces genetically unique daughter cells.

Question 2

3 sources of variation

Answer 2

independent assortment, segregation, crossing over

Question 3

independent assortment definiton

Answer 3

is where the homologous pairs line up randomly during meiosis.
Alleles are reshuffled and different / new combinations of chromosomes / alleles / genotype are created.

Question 4

segregation definition

Answer 4

is where homologous chromosomes separate / pull apart and migrate to the cell poles during meiosis.
Only one chromosome (gene / allele) from each homologous / pair is placed into the new cells / gametes made.

Question 5

crossing over definiton

Answer 5

is the exchange of alleles / segments of chromosomes / segments of DNA between homologous pair chromosomes. Crossing over can reshuffle / create new allele combinations of unlinked genes.

Question 6

genetic diversity definiton

Answer 6

variations in genetic make-up / genotype / total number of genetic characteristics in a species / population / genome / gene pool.

Question 7

gene pool definiton

Answer 7

is the total alleles available to a (breeding) population.

Question 8

allele

Answer 8

is a different version of a gene (alternate form of a gene)

Question 9

lethal allele

Answer 9

allele that causes death.

Question 10

allele frequency

Answer 10

number / amount / percentage of each allele in a population / gene pool.

Question 11

founders affect

Answer 11

is when a small group of individuals from an existing population moves to another area and establishes a new population, / are reproductively isolated from the original population.

Question 12

population bottleneck

Answer 12

a sudden / rapid / drastic reduction in population numbers that results in an under-representation of alleles in the gene pool (compared to original gene pool).

Question 13

genetic drift

Answer 13

chance / random change (removal) of alleles (individuals) in a population that results in loss of alleles or alleles becoming fixed

Question 14

migration

Answer 14

is the movement of individuals into / out of a population.

Question 15

mutation

Answer 15

is the (permanent) change in the gene sequence / nucleotide / gene / DNA.

Question 16

consequences for small populations

Answer 16

• Low genetic diversity: low number of differing alleles in a population / fixed allele.
• Small populations most likely have low genetic diversity because there are less individuals (less alleles) in the population and most likely allele frequency not representative of the original population / increased likelihood of inbreeding
• Small populations are also more likely to lead to fixed alleles / death has a larger proportional effect decreases genetic diversity / variation.

Question 17

natural selection

Answer 17

Is the process where individuals that possess the ‘best’ phenotype (genotype) in an environment survive and reproduce, therefore passing on favourable / desirable / advantageous alleles onto offspring / into the gene pool.
Within a population there is variation in alleles. Therefore, only individuals with alleles that are most suited to the environment will reproduce and pass favourable alleles on to the next generation. Non Favourable alleles will be lost from the population because individuals possessing them will have reduced reproduction and survival