Patterns of inheritance

Question 1

what is continuous variation

Answer 1

when individuals in a population vary within a range, no distinct categories examples include height, fur length

Question 2

what is discontinuous variation

Answer 2

two or more distinct categories, no intermediates, blood group

Question 3

what do you call inherited characteristics that show continuous variation and are usually controlled my by many genes

Answer 3

polygenic

Question 4

what do you call inherited characteristics that show discontinuous variation and are usually controlled by one gene

Answer 4

monogenic

Question 5

what causes genetic variation in phenotypes, give examples

Answer 5

genotype
environment- diet in animals, etiolation (plants grow abnormally long due to lack of light)

Question 6

how does sexual reproduction cause genetic variation

Answer 6

meiosis makes gametes with a unique assortment of alleles through crossing over and independent assortment

Question 7

what is a gene

Answer 7

a sequence of bases that codes for a protein

Question 8

what is an allele

Answer 8

different version of a gene

Question 9

what is a genotype

Answer 9

the alleles it has

Question 10

what is a phenotype

Answer 10

the characteristics alleles produce

Question 11

what does homozygous mean

Answer 11

two copies of the same allele

Question 12

what is meant by the term codominant allele

Answer 12

when alleles are both expressed in th phenotype because neither one is recessive, for example horses hair can be a mixture of white and coloured hairs

Question 13

what is a carrier

Answer 13

a person carrying an allele which is not expressed in the phenotype but can be passed onto offspring

Question 14

what is dihybrid inheritance

Answer 14

the the inheritance of two characteristics which are controlled by different genes

Question 15

what chromosomes do women have

Answer 15

XX

Question 16

what chromosomes do men have

Answer 16

XY

Question 17

what does characteristics being sex linked mean?

Answer 17

some characteristics are sex linked meaning that the alleles that code for them are on the sex chromosome

Question 18

what is an autosome

Answer 18

a gene that is not a sex gene

Question 19

what ratio do you expect in a dihybrid cross

Answer 19

9:3:3:1

Question 20

what is epistasis

Answer 20

when the allele of one gene masks the expression of the alleles of the other genes

Question 20

what ratio would you expect in a recessive epistatic cross

Answer 20

9:3:4

Question 21

what ratio would you expect in a dominant epistatic cross

Answer 21

12:3:1

Question 22

label the chi squared equation

Answer 22

O= observed result
E= expected result
£= the sum of

Question 23

define the term gene pool

Answer 23

the complete range of alleles in a population

Question 24

what is stabilising selection

Answer 24

when an environment is stable and individuals with characteristics towards the middle of the range are more likely o survive, reduced the range of phenotypes

Question 25

what is directional selection

Answer 25

when there is a change in the environment and individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce

Question 26

what is genetic drift

Answer 26

individuals in a species show variation in their genotype
by chance the allele for one genotype are passed onto the offspring more often than others
so frequency of that allele increases
it can then lead to evolution by chance

Question 27

does genetic drift affect larger or smaller population sizes and why

Answer 27

smaller as In smaller populations chance has more effect

Question 28

what is genetic bottleneck

Answer 28

when an event like a natural disaster causes a big reduction in a population size leading to a reduction in gene pool

Question 29

what is the founder effect

Answer 29

what happens when just a few organisms from a population start a new population and there are only a small number of alleles in the initial gene pool

Question 30

what is the Hardy-Weinberg principle and what assumptions must be made

Answer 30

mathematical model which reprints that the frequencies of alleles in a population won’t change from one generation to the next
has to be a large population
no immigration/emmigration
no mutations
random mating

Question 31

label the allele frequency equation

Answer 31

p= frequency of dominant allele
q= frequency of recessive allele

Question 32

label the genotype frequency equation

Answer 32

p2= frequency of homozygous dominant genotype
2pq= frequency of heterozygous genotype
q2= frequency of homozygous recessive genotype

Question 33

what are some examples of artificial selection

Answer 33

bread wheat- high wheat yield, higher tolerance of cols, uniform stalk heights, short stalks
dairy cattle- high milk yield, long lactation, large udders
resistance to mastitis
calm temperament

Question 35

what are the problems with artificial selection

Answer 35

reduces gene pool
less chance of resistance to new disease
health problems for certain organisms

Question 36

what is allopatric speciation

Answer 36

when populations become reproductively isolated through a combination of geographic isolation and natural selection

Question 37

define the term species

Answer 37

a group of organisms with similar characteristics tat can reproduce to give fertile offspring

Question 38

what is sympatric speciation

Answer 38

speciation without geographical isolation and from random mutation

Question 38

how dos reproductive isolation occur

Answer 38

seasonal chnages
mechanical changes like genitalia
behavioural changes- different courting rituals