6- Patterns On Inheritance

Front 1

What two factors cause variation in phenotypes?

Back 1

1.Genotype/genetics/alleles 2.Environment

Front 2

Height in humans is affected by both genetic and environmental factors. What is the main environmental factor that affects human height?

Back 2

Diet

Front 3

What is chlorosis in plants?

Back 3

When the plant cells do not produce enough chlorophyll so the leaves look pale and yellow.

Front 4

Which two environmental factors lead to a chlorosis in plants?

Back 4

Lack of light,Lack of iron ions and magnesium ions

Front 5

What is etiolation?

Back 5

When plants grow tall, weak stems, and have smaller, yellow leaves.

Front 6

Which environmental factor leads to etiolation in plants?

Back 6

Lack of light

Front 7

At which four points in sexual reproduction is variation introduced?

Back 7

1.Crossing over in prophase 1 of meiosis 2.Independent assortment of chromosomes in metaphase 1 of meiosis 3.Independent assortment of chromatids in metaphase 2 of meiosis 4.Fertilisation – fusion of random gametes

Front 8

What are the key features of both genetic and environmental variation for characteristics which show discontinuous variation?

Back 8

•Almost always caused by genes •Little or no environmental influence •Usually one (monogenic) or two genes involved, each with only a few alleles

Front 9

What are the key features of both genetic and environmental variation for characteristics which show continuous variation?

Back 9

•Characters controlled by many genes )polygenic) •The alleles may contribute a small amount to the phenotype, therefore have an additive effect•Continuous variation usually has a large environmental influences

Front 10

What does monogenic mean?

Back 10

Involving or controlled by one gene.

Front 11

How many sex chromosomes do humans have?

Back 11

Two (one pair)

Front 12

What are the chromosomes that are not sex chromosomes called?

Back 12

Autosomes

Front 13

What is sex linkage/a sex linked condition?

Back 13

When a gene is carried on the X or Y chromosome and so is inherited with the inheritance of the sex of the person.

Front 14

If a condition is X linked what does this mean?

Back 14

The genes for the condition are found on the X chromosome.

Front 15

Why are Y linked conditions rare?

Back 15

The Y chromosome is very small and carries very few genes.

Front 16

If there is an X linked condition which is recessive, how many phenotypes would there be for a female? And why?

Back 16

3-There are two X chromosomes in females so they can carry two alleles for the gene. The female could be either homozygous dominant, homozygous recessive or heterozygous.

Front 17

If there is an X linked condition which is recessive, how many phenotypes would there be for a male?

Back 17

2-There is only 1 X chromosome in males so they carry only one allele for the gene. The male could either have the condition (as he has one recessive allele) or not have the condition (as he has one dominant allele).

Front 18

When writing the genotypes for sex linked conditions, what ‘rules’ must be followed?

Back 18

- Always write the sex chromosomes e.g. XY or XX - Write the alleles for the condition as superscript on the sex chromosomes e.g. XHXh

Front 19

What is codominance?

Back 19

Where two different alleles are both expressed in the phenotype of the heterozygous individual.

Front 20

Flowers often show codominance in their colours. If one parent is homozygous for red flowers, and the other parent is homozygous for white flowers. What is the probability of the offspring being pink?

Back 20

100%

Front 21

What are the rules used when writing codominant alleles?

Back 21

- A normal sized capital letter is used to represent the characteristic e.g. C for colour - The allele for the characteristic is written superscript e.g. for a red colour CR - The alleles are all written as capital letters e.g CR and CW

Front 22

Draw the genetic cross when both parents are pink and have the genotype CR CW and show the ratio for the phenotypes of the offspring.

Back 22

1:2:1 Red:Pink:White

Front 23

What is meant by the term multiple alleles?

Back 23

When there are more than two alleles for one gene.

Front 24

The ABO blood grouping system is an example of multiple alleles. The alleles are written as I^A, I^B or I^O. I^A and I^B are codominant and I^O is recessive. What would be all the possible genotypes for a person with blood type B?

Back 24

I^B I^B and I^B I^O

Front 25

The ABO blood grouping system is an example of multiple alleles. The alleles are written as I^A, I^B or I^O. I^A and I^B are codominant and I^O is recessive. What would be all the possible genotypes for a person with blood type A?

Back 25

I^A I^A and I^A I^O

Front 26

The ABO blood grouping system is an example of multiple alleles. The alleles are written as I^A, I^B or I^O. I^A and I^B are codominant and IO is recessive. What would be all the possible genotypes for a person with blood type AB?

Back 26

I^A I^B

Front 27

The ABO blood grouping system is an example of multiple alleles. The alleles are written as I^A, I^B or I^O. I^A and IB are codominant and I^O is recessive. What would be all the possible genotypes for a person with blood type O?

Back 27

I^O I^O

Front 28

Draw a genetic cross to show the genotypes and phenotypes of the offspring of a couple with genotypes I^A I^O and I^B I^O and show the ratio of phenotypes for the offspring.

Back 28

1:1:1:1 AB : A : B : O

Front 29

What is dihybrid inheritance?

Back 29

Looking at the inheritance of two characteristics determined by two different genes on different homologous chromosomes.

Front 30

In a standard dihybrid genetic cross, how many different phenotypes would there be?

Back 30

4

Front 31

If the characteristics considered for tomatoes were whether they were red or yellow, and whether they were round or oval, what would the possible phenotypes be?

Back 31

Red round,Red oval,Yellow round,Yellow oval

Front 32

If red tomatoes are dominant (R) and yellow tomatoes are recessive, and if oval (O) is dominant to round (o). Write the genotype for a homozygous dominant red oval tomato.

Back 32

RROO

Front 33

If red tomatoes are dominant (R) and yellow tomatoes are recessive, and if oval (O) is dominant to round (o). Write the genotype for a homozygous recessive yellow round tomato.

Back 33

rroo

Front 34

If red tomatoes are dominant (R) and yellow tomatoes are recessive, and if oval (O) is dominant to round (o). Write the genotype for a double heterozygous tomato.

Back 34

RrOo

Front 35

If red tomatoes are dominant (R) and yellow tomatoes are recessive, and if oval (O) is dominant to round (o). What would be the phenotype of a double heterozygous tomato?

Back 35

Red oval

Front 36

What would be the gametes from a red oval double heterozygous tomato?

Back 36

RO Ro rO ro

Front 37

If double heterozygous parents are crossed in dihybrid inheritance, how many genotypes of offspring will be made?

Back 37

16

Front 38

If two double heterozygous parents are crossed in dihybrid inheritance, what is the expected ratio?

Back 38

9:3:3:1

Front 39

What is epistasis?

Back 39

The interaction of gene at different loci.

Front 40

What is a locus? (plural loci)

Back 40

The position of a gene on a chromosome.

Front 41

What is the effect of genes interacting?

Back 41

The genotype from one gene affects the expression of a separate gene.

Front 42

How does this affect the phenotypes?

Back 42

It reduces phenotypic variation and therefore affects phenotypic ratios.

Front 43

What do we call the gene that has an affect on another gene?

Back 43

The epistatic gene

Front 44

What do we call the gene that is affected by the other gene?

Back 44

The hypostatic gene

Front 45

What is recessive epistasis?

Back 45

Where the homozygous recessive masks the expression of the second gene.

Front 46

What is the expected ratio for recessive epistasis?

Back 46

9:3:4

Front 47

What is dominant epistasis?

Back 47

Where the dominant allele masks the expression of the second gene.

Front 48

What is the expected ration for dominant epistasis?

Back 48

12:3:1 or 13:3

Front 49

What is autosomal linkage?

Back 49

When genes are located close together on the same chromosome, they are likely to be inherited together.

Front 50

Why does linkage occur?

Back 50

The closer genes are together on a chromosome, the less likely it is that crossing over in prophase 1 will occur between those genes.

Front 51

What is the effect of autosomal linkage?

Back 51

There is less genetic variation, there may be less phenotypes and the expected ratios may not be met.

Front 52

What is the chi squared test used for?

Back 52

To test for a difference between expected and observed results.

Front 53

Why is the chi squared test used with genetics?

Back 53

It allows us to test our expected ratios of phenotypes against observations/data collected from sampling.

Front 54

In the formula below)LOOK AT CQ), what does O represent?

Back 54

An observed result

Front 55

In the formula below LOOK AT CQ, what does E represent?

Back 55

An expected value

Front 56

In the formula below LOOK AT CQ, what does ∑ mean?

Back 56

The sum of (add them all together)

Front 57

In the formula below LOOK AT CQ , what does X2 represent?

Back 57

Chi squared

Front 58

What type of variation must the data be in order for chi squared to be used?

Back 58

Discontinuous variation (discrete data)

Front 59

How do you calculate degrees of freedom?

Back 59

Minus 1 from how many categories/phenotypes you have.

Front 60

What probability level would you normally use when looking in the critical value table?

Back 60

5% probability (meaning 95% confidence level)

Front 61

What is a gene pool?

Back 61

The complete range of alleles in a population.

Front 62

What is the allele frequency?

Back 62

How often an allele occurs in a population e.g. 35% or 0.35.

Front 63

What affect does evolution have on allele frequency?

Back 63

Allele frequencies change as evolution takes place.

Front 64

How do new alleles occur?

Back 64

By mutation

Front 65

What is a selection pressure?

Back 65

A factor in the environment that means that the most adapted individuals will survive and the lesson adapted will not survive.

Front 66

What is stabilising selection?

Back 66

Where the most average individuals are favoured and selected for and extremes of the phenotype are selected against.

Front 67

What is directional selection?

Back 67

Where individuals towards one of the extremes of phenotype are selected for and over time these phenotypes become the most frequent.

Front 68

What is genetic drift?

Back 68

Variation in the frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.

Front 69

Why does genetic drift has less of an effect with larger populations?

Back 69

Chance variations in allele frequency even out with larger populations.

Front 70

What is a genetic bottleneck?

Back 70

When there are only a small number of individuals left in a population (maybe due to a natural disaster) and the gene pool is reduced so there is very little genetic variation in the population.

Front 71

What is the founder effect?

Back 71

When a small group of species are separated from a larger population. The few founding individuals of the new population have a small gene pool with very little genetic variation so all future individuals in that population will only have those alleles.

Front 72

What is the Hardy-Weinberg principle used for?

Back 72

To calculate allele frequencies.

Front 73

List 3 of the assumptions that are made when using the Hardy-Weinberg principle.

Back 73

•The population must be large •Random mating must occur •No mutations must occur •No gene flow can occur (i.e. immigration/emigration) •No selection can occur so that certain alleles are not selected for or against

Front 74

What does p represent in the equation?p+q = 1.

Back 74

The frequency of the dominant allele in the population.

Front 75

What does q represent in the equation? p+q = 1

Back 75

The frequency of the recessive allele in the population.

Front 76

What does p² represent in the equation? p² + 2pq + q² = 1

Back 76

The frequency of the homozygous dominant genotype.

Front 77

What does q² represent in the equation? p² + 2pq + q² = 1

Back 77

The frequency of the homozygous recessive genotype.

Front 78

What does 2pq represent in the equation? p² + 2pq + q² = 1

Back 78

The frequency of the heterozygous genotype.

Front 79

If brown is a dominant fur colour to grey in rabbits, and there are 20 grey rabbits in a population of 100, which part of the equations represents the 20 grey rabbits?

Back 79

q² (q² = 20% or 0.20)

Front 80

If brown is a dominant fur colour to grey in rabbits, and there are 80 brown rabbits in a population of 100, which part of the equations represents the 80 brown rabbits?

Back 80

p² + 2pq (all the homozygous dominant and heterozygous rabbits would be brown) (p² + 2pq = 80% or 0.80)

Front 81

What is speciation?

Back 81

The evolution of a new species from an existing one.

Front 82

How can it be proven that a new species has been formed?

Back 82

By attempting to breed individuals from the existing species and the new species, as members of new species will no longer be able to interbreed with the existing species to produce fertile offspring.

Front 83

What are the two types of speciation?

Back 83

Allopatric and sympatric speciation

Front 84

What is allopatric speciation?

Back 84

One population becomes split and the two newly separated populations are geographically isolated from one other – there is a physical barrier between two populations which prevents breeding.

Front 85

For allopatric speciation, what one factor must occur?

Back 85

There must be different selection pressures on each population e.g. a different climate/food/predator etc.

Front 86

Give one example of allopatric speciation.

Back 86

The finches on the Galapagos Islands (or any other applicable example)

Front 87

What is sympatric speciation?

Back 87

The population remains in the same habitat but becomes reproductively isolated so that some individuals cannot breed with others in the population.

Front 88

Give two examples of reproductive barriers.

Back 88

Behavioural = different courtship rituals Mechanical = different genitalia Seasonal = animals come into season (are fertile) at different times/season Gamete incompatibility = different numbers of chromosomes

Front 89

What is artificial selection?

Back 89

Selective breeding - where humans choose which individuals breed together based on desirable characteristics.

Front 90

Give two problems that arise due to artificial selection.

Back 90

Breeding of closely related individuals. Breeders select for aesthetic qualities not health.Genetic disorders often caused by recessive alleles – inbreeding increases the chance of homozygous recessive.It reduces the gene pool (smaller gene pool). Selecting for one trait often selects for another (unintentionally) where genes are on the same chromosome.

Front 91

Why are pedigree dogs an example of the problems caused by artificial selection?

Back 91

Pedigree dog breeds have been artificially selected over many generations to create extremes of phenotypes. This has involved inbreeding and resulted in health problems (e.g. breathing problems in pugs), less genetic variation and some undesirable traits unintentionally selected for (e.g. blindness in Dalmatians).