3.4 + 10.2 inheritance

Question 1

what are the mendelian laws?

Answer 1

1. law of segregation
2. law of independent assortment
3. law of dominance

Question 2

how many alleles for a gene does one organism have?

Answer 2

2

Question 3

gametes are [haploid/diploid]

Answer 3

haploid

Question 4

since gametes are haploid, how many alleles for a gene does a gamete have?

Answer 4

1

Question 5

what is the law of segregation?

Answer 5

each organism has two alleles for each gene, so each gamete carries only one allele

Question 6

in what scenarios is the law of segregation not followed? (think out of the box, but in syllabus)

Answer 6

• non-disjunction
• leads to gametes w abnormal no. of chromosomes –> abnormal no. of alleles

Question 7

if genes are on different chromosomes, do they affect each other?

Answer 7

no

Question 8

what is the law of independent assortment?

Answer 8

the separation of alleles for one gene occurs independently of other genes if the alleles are on different chromosomes

Question 9

in what cases is the law of independent assortment not followed?

Answer 9

• linked genes
• sex linked genes

Question 10

what is the law of dominance

Answer 10

recessive alleles will be masked by dominant alleles

Question 11

how many alleles are there for each sex gene for males?

Answer 11

1

Question 12

homozygous D and heterozygous forms ____________ cannot be distinguished

Answer 12

phenotypically

Question 13

why does co-dominance occur?

Answer 13

pairs of alleles are both expressed equally in the phenotype of a heterozygous individual

Question 14

give an example where there are codominant alleles

Answer 14

• ABO blood groups
• where allele A and B are equally expressed –> co-dominant

Question 15

what is the genotype of blood type O (differs from O levels)

Answer 15

ii

Question 16

what are the possible gametes in the inheritance of blood groups?

Answer 16

IA, IB, i

Question 17

what happens when A blood is transfused to B blood?

Answer 17

agglutination and then haemolysis

Question 18

who is the universal donor for blood?

Answer 18

O

Question 19

who is the universal recipient for blood?

Answer 19

AB

Question 20

cystic fibrosis is an [autosomal/sex-linked disease]

Answer 20

autosomal

Question 21

why are carriers usually heterozygous?

Answer 21

• they have one copy of the faulty, usually recessive allele but do not develop disease symptoms
• they may pass on this allele to offspring

Question 22

cystic fibrosis is a _________ genetic disease

Answer 22

recessive

Question 23

huntington’s disease is a __________ genetic disease

Answer 23

dominant

Question 24

what systems does cystic fibrosis affect?

Answer 24

it affects respiratory, digestive and reproductive systems

Question 25

how does cystic fibrosis arise?

Answer 25

- arises from mutation to the gene coding for a chloride channel - results in production of abnormally thick and sticky mucus

Question 26

what is the main symptom of cystic fibrosis

Answer 26

clogged airways and secretory ducts

Question 27

what type of disease is huntington's disease

Answer 27

autosomal

Question 28

how does huntington's disease arise?

Answer 28

- it arises from a mutation of the gene coding for huntingtin protein - results in neurodegeneration

Question 29

why is huntington's disease passed down although there are no carriers of the disease?

Answer 29

- in affected individuals, symptoms only show in adulthood - they might have already passed the faulty allele to their children

Question 30

why are genetic diseases rare?

Answer 30

any allele that affects survival and thus the capacity to reproduce is unlikely to passed down to offspring!

Question 31

females have _ and _ chromosomes males have _ and _ chromosomes

Answer 31

XX, XY

Question 32

why are more males than females affected by recessive sex-linked genes?

Answer 32

- females have 3 possible genotypes - thus 33.3% chance of getting the recessive condition - males have 2 possible genotypes - thus 50% chance of getting the recessive condition

Question 33

do males have allele masking for alleles on sex chromosomes?

Answer 33

nope

Question 34

what are two sex-linked recessive conditions?

Answer 34

1. red-green colour blindness 2. haemophilia

Question 35

how does red-green colour blindness arise?

Answer 35

- it arises from a mutation to the gene coding for red or green photoreceptors - this results in the inability to discriminate between red and green colours

Question 36

how does hemophilia arise?

Answer 36

- arises from a mutation in any gene encoding for clotting factors - results in persistent bleeding

Question 37

which chromosome is red-green colour blindness and hemophilia on?

Answer 37

X chromosome

Question 38

what factors increase the rate of mutations?

Answer 38

exposure to radiation and mutagenic chemicals

Question 39

what are two examples of the mutations caused by radiation?

Answer 39

bombing of Hiroshima and accident at Chernobyl

Question 40

what were the effects of radiation exposure after the accident at Chernobyl?

Answer 40

- increased incidence in thyroid cancer due to radioactive iodine - increase in birth defects

Question 41

what were the effects of radiation exposure after the bombing of Hiroshima?

Answer 41

- increased incidence in cancer development - altered immune functions –> higher rates of infection

Question 42

how is genetic variation ensured?

Answer 42

through independent assortment and crossing over

Question 43

which mendelian law does linked genes defy?

Answer 43

the law of independent assortment

Question 44

what are linked genes?

Answer 44

genes on the same chromosome

Question 45

how are linked genes represented?

Answer 45

AB –> same chromosome ======= ab –> same chromosome

Question 46

what does the notation represent? (understanding)

Answer 46

on one side of the double line are alleles found on one of the homologous chromosomes

Question 47

who discovered non-mendelian ratios

Answer 47

morgan

Question 48

what organism did morgan use in his experiments? (scientific name)

Answer 48

drosophila

Question 49

what did morgan's experiments show about inheritance?

Answer 49

it showed that linked genes were not independently assorted

Question 50

what did morgan discover

Answer 50

1. sex linked genes 2. and the fact that they were not independently assorted 3. non-mendelian ratios

Question 51

how can recombinants be detected?

Answer 51

- by observing the phenotypes - if the offspring has a new combination of traits it is recombinant

Question 52

what is the chi squared formula?

Answer 52

-

Question 53

how do you find degree of freedom

Answer 53

(n-1) where n is no. of phenotypes

Question 54

what is the p value when are results statistically significant?

Answer 54

when p<0.05

Question 55

what are the two types of variation?

Answer 55

discontinuous, continuous

Question 56

what is polygenic traits

Answer 56

traits that are controlled by more than two genes

Question 57

what are examples of non mendelian inheritance (summary) (5)

Answer 57

1. polygenic traits –> doesn't follow mendelian ratios for phenotypes 2. linked genes –> breaks law of indep assortment 3. sex linked inheritance –> same as above 4. codominance –> breaks law of dominance 5. recombinant phenotypes –> doesn't follow mendelian ratios for phenotypes

Question 58

is discontinuous variation mendelian inheritance?

Answer 58

yassss

Question 59

what is an example of polygenic traits

Answer 59

height, skin tone

Question 60

what are the characteristics of polygenic traits (3)

Answer 60

1. they are influenced by environmental factors 2. controlled by multiple genes - each gene has an additive effect to the trait 3. has a range of phenotypes - phenotypes follow a bell curve

Question 61

what are the mendelian ratios in monohybrid cross of homoD homoR

Answer 61

1

Question 62

what are the mendelian ratios in monohybrid cross of hetero hetero

Answer 62

3:1

Question 63

what are the mendelian ratios in monohybrid cross of hetero homoR

Answer 63

1:1

Question 64

what cross results in 1:1 mendelian ratio

Answer 64

monohybrid cross of hetero homoR

Question 65

what cross results in 9:3:3:1 mendelian ratio

Answer 65

dihybrid cross hetero hetero

Question 66

what are the mendelian ratios in dihybrid cross hetero hetero

Answer 66

9:3:3:1

Question 67

what genotype is used for test crosses?

Answer 67

homoR

Question 68

what cross results in 1:1:1:1 mendelian ratio

Answer 68

dihybrid cross hetero homoR