Patterns of inheritance and Variation

Question 1

What are the types of variation?

Answer 1

continuous and discontinuous

Question 2

What are levels at which variation can be influenced?

Answer 2

genes, environment and both

Question 3

How is there variation at a genetic level?

Answer 3

crossing over in prophase 1, independant assortment of chromosomes in metaphase 1, independant assortment of chromatids in metaphase 2, random fusion of gametes, mutations

Question 4

How is continuous and discontinuous variation controlled?

Answer 4

continuous - many genes
discontinuous - one gene

Question 5

How does both genetic and environmental factors influence phenotype?

Answer 5

genetic factors determine genotype and the characteristics they are born with but then environmental factors influence how they develop

Question 6

What are the two types of alleles?

Answer 6

dominant and recessive

Question 7

What is codominance?

Answer 7

two different alleles occur for a gene and both are expressed in the phenotype as they are equally dominant

Question 8

What is a dihybrid cross?

Answer 8

inheritance of two different characteristics (YyRr)

Question 9

What is autosomal linkage?

Answer 9

genes on same chromosome are inherited together

Question 10

What is a recombinant offspring?

Answer 10

an offspring that has a different combination of alleles than either parent

Question 11

When is null hypothesis rejected in Chi squared test and what can you conclude from that?

Answer 11

if chi squared value is greater than critical value at p=0.05 then there is a sig. difference between expected and observed

Question 12

What is an epistatic gene?

Answer 12

a gene that masks the expression of another gene

Question 13

What is recessive and dominant epistasis?

Answer 13

recessive - presence of two recessive alleles masks the expression of another gene
dominant - presence of one allele masks another gene

Question 14

What is an example of epistasis?

Answer 14

in labradors one gene codes for whether pigment is deposited in skin or skin and fur. Another gene codes for the colour of pigment produced. The first gene is epistatic as if they have two recessive alleles then pigment is only deposited in skin and so pigment of fur will not be shown as there is no pigment deposited there so the second gene is masked

Question 15

What does the hardy wienburg principle assume?

Answer 15

population is large, random mating occurs (also that no immigration, emigration, mutations or natural selection occurs)

Question 16

What are the factors affecting rate of evolution?

Answer 16

mutation, sexual selection, gene flow, genetic drift, natural selection

Question 17

What is the impact of small populations?

Answer 17

small genetic diversity so little variation, population cannot easily adapt to changes in environment so more chance of becoming extinct

Question 18

What are the two types of limiting factors for a population?

Answer 18

density dependant and density independent

Question 19

What are some example of density dependant and independent factors affecting population?

Answer 19

dependant - competition, prey, predation, disease
independent - climate change, natural disasters, seasonal change, human activity

Question 20

What is the founder effect?

Answer 20

small population arises due to isolation, gene pool is tiny and very low genetic diversity, only the few alleles in new colony can be passed on to offspring

Question 21

Describe the process of natural selection?

Answer 21

there is variation within a population due to random mutation, a selection pressure creates a struggle for survival, some individuals are better adapted to the selection pressure due to variation, these individuals survive and can reproduce, a greater proportion of next generation have this advantageous allele, they are then more likely to survive and reproduce and over many generations this allele becomes more frequent in gene pool

Question 22

What is stabilising selection?

Answer 22

the norm is selected for and extremes are selected against

Question 23

What is directional selection?

Answer 23

most common phenotype is no longer advantageous and one extreme is selected for

Question 24

What is disruptive selection?

Answer 24

both extremes are selected for and norm is selected against

Question 25

What must happen in order for speciation?

Answer 25

members of population become isolated and no gene flow occurs. random mutation continues in both groups. Selection pressures differ for the groups. changes in allele frequency in both groups is different and after many generations the groups become reproductively isolated

Question 26

What is allopatric speciation?

Answer 26

members of population become separated by a physical barrier and condition for each populations vary and then so do selection pressures

Question 27

When does reproductive isolation occur?

Answer 27

different mating seasons developed, changes in genitalia, new courtship rituals different from main population

Question 28

What is the process of artificial selection?

Answer 28

individuals are selectively bred due to desirable characteristics, so the these alleles are ‘selected for’, same as natural selection but selection pressure is humans choosing desirable characteristics

Question 29

What are some issues with artificial selection?

Answer 29

small gene pool, helpful alleles could be lost, exaggerates certain traits, increased chance of disease, ethical issues