Mutations and Gene Pools

Question 1

mutation

Answer 1

a change in a gene or chromosome leading to a new characteristic in an organism

Question 2

mutagen

Answer 2

an environmental agent that increases the rate of mutation

Question 3

population

Answer 3

a group of organisms of the same species living together in a particular place and particular time

Question 4

lethal recessive

Answer 4

recessive alleles that, inherited in the homozygous condition, result int he death of the embryo, foetus or child

Question 5

monosomy

Answer 5

where an individual has only one copy of a chromosome instead of two

Question 6

trisomy

Answer 6

where an individual has three copies of a chromosome instead of two

Question 7

genome

Answer 7

the compelte set of genetic material in a cell; an organisms’ complete set of DNA

Question 8

random assortment

Answer 8

the random separation of maternal and paternal chromosomes during the first division of meiosis

Question 9

crossing over

Answer 9

the interchange of the parts of the chromatids of a homologus pair of chromosomes during the first stage of meiosis

Question 10

non-disjunction

Answer 10

when one or more chromosomes fails to separate during meiosis

Question 11

random fertilisation

Answer 11

the ability of any one sperm to fertilise any available egg

Question 12

natural selection

Answer 12

the process by which a species becomes better adapted to its environment; those individuals with favourable characteristics have survived an advantage and so pass on those characteristics on to subsequent generations

Question 13

random genetic drift

Answer 13

the occurrence of characteristics in a population as a result of chance rather than natural selection; occurs only in small populations aka Sewall Wright effect

Question 14

founder effect

Answer 14

the type of genetic drift that occurs when a new population is formed by a small number of individuals; the small size of the sample can cause marked deviations in allele frequencies from the original population

Question 15

gene flow

Answer 15

the transfer of alleles from one population to another through migration

Question 16

geographical barriers

Answer 16

a feature in the landscape that prevents populations from interbreeding; includes oceans, mountain ranges, large lake systems, deserts and expansive ice sheets

Question 17

sociocultural barriers

Answer 17

barriers to interbreeding that are due to social and cultural factors

Question 18

special creation

Answer 18

the belief that God created all species

Question 19

evolution

Answer 19

the gradual change in the characteristics of a species

Question 20

variation

Answer 20

the differences that exist between individuals or populations of a species

Question 21

survival of the fittest

Answer 21

the principle whereby organisms with favourable characteristics survive; but organisms with unfavourable characteristics die before they have a chance to reproduce

Question 22

speciation

Answer 22

the process of new species developing

Question 23

Tay-Sach’s disease

Answer 23

a genetic disorder caused by a missing enzyme that results in fatty substances accumulating in the nervous system

Question 24

thalassemia

Answer 24

an inherited disease caused by a recessive allele, in which anaemia results from defects in the formation of harmoglobin

Question 25

sickle-cell anaemia

Answer 25

an inherited disease causing early death; results from the inheritance of two alleles for sickle-cell anaemia

Question 26

what is the difference between a gene mutation and chromosomal mutation?

Answer 26

a gene mutation occurs within a small amount of contained base pairs, whereas a chromosome mutation involves all or part of a chromosome, and affects more than one gene

Question 27

give two examples of a chromosomal mutation

Answer 27

Down syndrome (trisomy 21) and cri-du-chat (missing part of chromosome 5)

Question 28

give two examples of a gene mutation

Answer 28

cystic fibrosis, albinism, Duchenne form of muscular dystrophy

Question 29

give 5 examples of a mutagen

Answer 29

mustard gas, high temperatures, x-rays, radiation from radioactive waste, UV light, cosmic rays

Question 30

what sorts of factors affect the gene pool?

Answer 30

chance events - mutation that alters the expression of a gene natural means - changes to environment natural selection (survival of the fittest) random genetic drift migration genetic diseases geographical barriers

Question 31

give an example of a place where the founder effect has occurred?

Answer 31

Finland: a small gruop of individuals settled there around 2000 years ago and the population has remained relatively isolated with very little immigration

Question 32

how does migration affect allele frequencies? Give an example

Answer 32

if migrants bring aleles that are not already in the population, the frequencies for the alleles of that gene would be altered. eg China --> majority of people aer Rh positive but Europeans introduced the Rh allele into the Chinese population

Question 33

how do geographical and sociocultural factors influence allele frequencies of a gene pool?

Answer 33

``` geographical barriers (mountain ranges, large lake systems, expansive ice sheets, deserts) prevent species on either side from interbreeding sociocultural barriers (different languages, cultures, religions, economic background, education, social position) --> people of different groups tended not to associate with each other ```

Question 34

what are the main principles of evolution?

Answer 34

1. there is variation of characteristics within an individual 2. more offspring are produced than can possibly survive to maturity 3. struggle for existence due to excessive birth rates and limited resources 4. survival of the fittest 5. favourable characteristics (have survival value) are passed on to other generations 6. the proportion of alleles that produce favourable characteristics gradually increases

Question 35

describe two examples of natural selection in humans

Answer 35

body stature: short-bodied, long-limbed Africans; long-bodied, short-limbed Inuit

Question 36

what is the difference between trisomy and monosomy?

Answer 36

trisomy: extra copy of a chromosome monosomy: one chromosome is missing

Question 37

how can mutations affect the proportion of certain alleles in gene pools?

Answer 37

the frequency of mutations would gradually decrease as the people with the mutation die before they reach reproductive age and pass on the genes to the next generation

Question 38

how do new variations occur in a population?

Answer 38

through fertilisation and meiosis

Question 39

what is a selectively advantageous mutation?

Answer 39

a mutation that enhances the species' chances of survival

Question 40

how could isolation lead to selection and speciation?

Answer 40

prevents the interbreeding of species in different areas. different alleles are favoured in different environments occurs when two populations are separated for long enough, and adapt to their environmental conditions, interbreeding would no longer be possible