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IB Bio > 3.4 + 10.2 inheritance > Flashcards

3.4 + 10.2 inheritance Flashcards

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1
Q

what are the mendelian laws?

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

how many alleles for a gene does one organism have?

A

2

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3
Q

gametes are [haploid/diploid]

A

haploid

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4
Q

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

A

1

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5
Q

what is the law of segregation?

A

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

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6
Q

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

A
  • non-disjunction
  • leads to gametes w abnormal no. of chromosomes –> abnormal no. of alleles
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7
Q

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

A

no

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8
Q

what is the law of independent assortment?

A

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

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9
Q

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

A
  • linked genes
  • sex linked genes
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10
Q

what is the law of dominance

A

recessive alleles will be masked by dominant alleles

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11
Q

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

A

1

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12
Q

homozygous D and heterozygous forms ____________ cannot be distinguished

A

phenotypically

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13
Q

why does co-dominance occur?

A

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

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14
Q

give an example where there are codominant alleles

A
  • ABO blood groups
  • where allele A and B are equally expressed –> co-dominant
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15
Q

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

A

ii

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16
Q

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

A

IA, IB, i

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17
Q

what happens when A blood is transfused to B blood?

A

agglutination and then haemolysis

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18
Q

who is the universal donor for blood?

A

O

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19
Q

who is the universal recipient for blood?

A

AB

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20
Q

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

A

autosomal

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21
Q

why are carriers usually heterozygous?

A
  • they have one copy of the faulty, usually recessive allele but do not develop disease symptoms
  • they may pass on this allele to offspring
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22
Q

cystic fibrosis is a _________ genetic disease

A

recessive

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23
Q

huntington’s disease is a __________ genetic disease

A

dominant

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24
Q

what systems does cystic fibrosis affect?

A

it affects respiratory, digestive and reproductive systems

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25
Q

how does cystic fibrosis arise?

A
  • arises from mutation to the gene coding for a chloride channel
  • results in production of abnormally thick and sticky mucus
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26
Q

what is the main symptom of cystic fibrosis

A

clogged airways and secretory ducts

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27
Q

what type of disease is huntington’s disease

A

autosomal

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28
Q

how does huntington’s disease arise?

A
  • it arises from a mutation of the gene coding for huntingtin protein
  • results in neurodegeneration
29
Q

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

A
  • in affected individuals, symptoms only show in adulthood
  • they might have already passed the faulty allele to their children
30
Q

why are genetic diseases rare?

A

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

31
Q

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

A

XX, XY

32
Q

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

A
  • 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
33
Q

do males have allele masking for alleles on sex chromosomes?

A

nope

34
Q

what are two sex-linked recessive conditions?

A
  1. red-green colour blindness
  2. haemophilia
35
Q

how does red-green colour blindness arise?

A
  • 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
36
Q

how does hemophilia arise?

A
  • arises from a mutation in any gene encoding for clotting factors
  • results in persistent bleeding
37
Q

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

A

X chromosome

38
Q

what factors increase the rate of mutations?

A

exposure to radiation and mutagenic chemicals

39
Q

what are two examples of the mutations caused by radiation?

A

bombing of Hiroshima and accident at Chernobyl

40
Q

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

A
  • increased incidence in thyroid cancer due to radioactive iodine
  • increase in birth defects
41
Q

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

A
  • increased incidence in cancer development
  • altered immune functions –> higher rates of infection
42
Q

how is genetic variation ensured?

A

through independent assortment and crossing over

43
Q

which mendelian law does linked genes defy?

A

the law of independent assortment

44
Q

what are linked genes?

A

genes on the same chromosome

45
Q

how are linked genes represented?

A

AB –> same chromosome

ab –> same chromosome

46
Q

what does the notation represent? (understanding)

A

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

47
Q

who discovered non-mendelian ratios

A

morgan

48
Q

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

A

drosophila

49
Q

what did morgan’s experiments show about inheritance?

A

it showed that linked genes were not independently assorted

50
Q

what did morgan discover

A
  1. sex linked genes
  2. and the fact that they were not independently assorted
  3. non-mendelian ratios
51
Q

how can recombinants be detected?

A
  • by observing the phenotypes
  • if the offspring has a new combination of traits it is recombinant
52
Q

what is the chi squared formula?

A

-

53
Q

how do you find degree of freedom

A

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

54
Q

what is the p value when are results statistically significant?

A

when p<0.05

55
Q

what are the two types of variation?

A

discontinuous, continuous

56
Q

what is polygenic traits

A

traits that are controlled by more than two genes

57
Q

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

A
  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
58
Q

is discontinuous variation mendelian inheritance?

A

yassss

59
Q

what is an example of polygenic traits

A

height, skin tone

60
Q

what are the characteristics of polygenic traits (3)

A
  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
61
Q

what are the mendelian ratios in monohybrid cross of homoD homoR

A

1

62
Q

what are the mendelian ratios in monohybrid cross of hetero hetero

A

3:1

63
Q

what are the mendelian ratios in monohybrid cross of hetero homoR

A

1:1

64
Q

what cross results in 1:1 mendelian ratio

A

monohybrid cross of hetero homoR

65
Q

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

A

dihybrid cross hetero hetero

66
Q

what are the mendelian ratios in dihybrid cross hetero hetero

A

9:3:3:1

67
Q

what genotype is used for test crosses?

A

homoR

68
Q

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

A

dihybrid cross hetero homoR

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