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A Level Biology > Patterns of Inheritance > Flashcards

Patterns of Inheritance Flashcards

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1
Q

For genetic diagrams?

A

pick a letter that looks diff as lowercase and uppercase and only put gametes in genetic diagram

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2
Q

pure bred?

A

homozygous

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3
Q

format of genetic diagram?

A
  • phenotype
  • genotype
  • gametes
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4
Q

a hetero cross produces?

A

9:3:3:1 ratio

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5
Q

CF?

A
  • gene that codes for a membrane carrier protein that allows Cl- into cells but not out
  • Cl- attracted to Na+, makes cell salty so dec WP
  • water moves in by osmosis
  • affects lungs - mucus becomes too thick, goes down through lungs, narrows airways
  • mucus takes bacteria into lungs
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6
Q

if someone is a carrier, their phenotype is?

A

normal

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7
Q

genetic diagrams generate?

A

theoretical data - just tell u the probability

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8
Q

F1 =

A

first generation

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9
Q

Co-dominance?

A

• not all genes are dominant and recessive
• both alleles have an effect
e.g. C^R C^W
must write gene and then allele in superscript

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10
Q

When there are more than 2 alleles for a gene?

A
  • pick a letter for the gene and show the alleles as superscripts
  • e.g. blood groups
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11
Q

blood groups?

A
  • A, B, AB, O
  • all determined by a single gene which has 3 alleles
  • I^A I^B I^O
  • A and B are codominant
  • O is recessive to A and B
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12
Q

O has?

A

no surface antigens

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13
Q

What happens if you receive the wrong type of blood?

A
  • most severe reactions: intraventricular haemolysis - the donor’s erythrocytes are destroyed by the recipients AB while they are in blood vessels
  • Hb leaked into plasma and excreted in urine turning urine dark brown
  • Bilirubin, a metabolite of hb usually secreted into bile by liver accumulates in blood causing jaundice
  • reaction is so severe that it can cause shock, kidney failure or death
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14
Q

Universal donor?

A

BG O, blood cells have no antigens on outside

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15
Q

Universal recipient ?

A

AB - can receive blood from O, B, A

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16
Q

Sex linkage denotion?

A

• have to use X and Y and have the alleles are superscript and include sex in phenotype

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17
Q

how many chromosomes are autosomes?

A

22 pairs

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18
Q

how many pairs of sex chromosomes?

A

1 pair - XY in boys, XX in girls

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19
Q

each gene has ? gene loci?

A

2 - one on each chromosome

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20
Q

homologous region of chromosome?

A

2 alleles per gene

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21
Q

non - homologous region?

A

•Y chromosome is short so genes found on the X only have one allele

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22
Q

E.g. of sex linked disorder?

A
  • red-green colour blindness
  • gene locus is found on the non-homologous region of the X chromosome
  • normal allele R = dominant
  • deficient allele r = recessive
  • so males only need 1 recessive allele, women need 2
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23
Q

when gene loci is on the non-hm bit of chromosome?

A

Y has no allele so no superscript

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24
Q

sex linked?

A

any genes only passed on through X chromosome

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25
Q

other example of sex linked inheritance?

A

haemophilia, normal is dominan, hameo = recessive

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26
Q

dihybrid inheritance?

A

• inheritance of 2 genes at once, on different chromosomes

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27
Q

parents are dipoloid so

A

have 2 alleles for each gene

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28
Q

DI: add up ratio to get

A

size of Punnett square

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29
Q

Chi squared?

A
  • compare observed data with expected data to see whether there’s a sig. difference
  • if there’s a big difference = big no.
  • small difference = small no.
  • always a bit of difference due to chance
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30
Q

Chi squared shows?

A

if the no.s are close enough or if something else is going on

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31
Q

if there is no sig diff between O and E value?

A

data proves DI inheritance

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32
Q

DF =

A

number of categories -1

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33
Q

if X2 is smaller than CV?

A

• no sig diff so cannot reject NH

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34
Q

Chi squared conclusion?

A
  • say whether test result was > or < than CV at p =0.05
  • is there a statistically significant difference
  • is the probability that the difference is due to chance less than 5%
  • reject/ accept null hypothesis
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35
Q

unlinked =

A

separate chromosomes

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36
Q

If X2 is Greater than CV

A
  • difference is significant

* so probability that the correlation is due to chance is less than 5%

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37
Q

if X2 is smaller than CV

A
  • not significant

* probability that diff due to chance is less than 5%

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38
Q

As X2 increases,

A

prob that diff due to chance dec

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39
Q

big probability that diff occurred by chance =

A

accept hypothesis

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40
Q

What is epistasis?

A

where more than 1 gene affects the same characteristic - 2 genes affect the same phenotype
e.g. petal colour

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41
Q

can use X2 on anything that has?

A

observed or expected

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42
Q

autosome =

A

chromsome other than sex chromosome

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43
Q

epistasis impacts?

A

the ratio

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44
Q

Autosomal linkage?

A
  • if a phenotypic ratio is not as expected, could be bc genes are linked - don’t et 9:3:3:1 ratio
  • not the same as epistasis
  • linkage = 2 genes are located on the same chromosome
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45
Q

why is there no independent assortment with autosomal linkage?

A
  • genes on the same chromosome
  • unless the genes are separated by chiasmata, both genes would be inherited together
  • if chiasma forms, there’s the possibility of other gametes forming
  • recombinant gametes are less likely to form than non-recombinant gametes
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46
Q

what are recombinant offspring?

A

different combinations of either of the 2 parents allele - chiasma formed between the genes

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47
Q

autosomal linkage: the closer the genes are

A
  • the less likely it is that recombinants will form bc the lower the chance of chiasma forming
  • the ratio depends on how close the 2 gene loci are - closer= fewer recombinant offspring
  • further apart = more recombinant offspring
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48
Q

recombinant frequency?

A

how much crossing over has occurred

= no. of recombinant offspring/ total no. of offspring

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49
Q

recomb freq values?

A
  • 50% = not linked
  • less than 50% = some gene linkage
  • very low = genes are very close together
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50
Q

recomb freq tells u

A

how far apart the 2 gene loci are

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51
Q

how is recom freq found out?

A

crossing hetero indiv for the 2 linked genes with a ‘double recessive’ - test cross

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52
Q

chromosome mapping?

A
  • finding the relative positions of linked gene loci on chromosome
  • can tell the order of genes of a chromosome
53
Q

max % of recombinants =?

A

49% - of 50 then not linked

54
Q

Hardy Weinburg principle?

A
  • if we know how many people in a population have a phenotype that is caused by a homo r genotype, when we can use it to estimate how many are hetero/ homo dom
  • to calc how many ppl have the allele
55
Q

what is assumed w the HWP?

A

• Allele and genotype freq in a pop remain constant from generation to generation

56
Q

5 conditions that need to be met in order for the HWP to be met?

A
  • no mutations so that new alleles don’t enter pop
  • no gene flow can occur (no immigration/ emigration from pop)
  • random mating must occur (individuals must pair by chance)
  • pop must be large so no genetic drift can cause allele freq to change
  • no selection so certain alleles are not selected for/ against
57
Q

in reality (HWP)

A
  • theoretical situation
  • always disturbing influences in nature
  • so these conditions are never met by a pop
58
Q

p =

A

freq of dominant allele

59
Q

q =

A

Freq of recessive allele

60
Q

continuous variation?

A

• a continuous range of values between extremes

61
Q

discontinuous variation?

A

a few clear cut categories e.g. blood group

62
Q

polygenic inheritance is?

A
  • characteristics that show continuous variation often have an environmental component but some show CV can be purely genetic
  • this is polygenic inheritance
63
Q

Polygenic inheritance bckgrnd?

A
  • many characteristics determined by combined effects of many genes, often w multiple alleles
  • shows continuous normal distribution
  • bell shaped curve is distinctive of a characteristic that exhibits cont. variation
64
Q

Factors affecting evolution of a species?

A

• factors that can change the freq of alleles in a gene pool and thfr cause evolution to happen

  1. selection
  2. genetic drift
  3. genetic bottleneck
  4. the founder effect
65
Q

gene pool?

A

All of the alleles of all of the genes present in a population of interbreeding organisms

66
Q

evolution =

A

a change in the characteristics of a population over successive generations

67
Q

3 types of selection?

A
  1. stabilising selection
  2. directional selection
  3. disruptive selection
68
Q

stabilising selection?

A
  • the forms at the 2 extremes of CV are at a selective disadvantage
  • selected against
  • flatter graphs
69
Q

directional selection?

A
  • one of the extreme forms is at a selective advantage - 1 allele is selected for
  • graphs shifts to the right
70
Q

disruptive selection?

A
  • extreme phenotypes selected for and intermediate phenotype is selected against
  • rare
71
Q

genetic drift?

A
  • changes in the allele freq of a population (the gene pool)
  • as a result of a chance
  • much more sig in small isolated population
  • smaller population = more chance of allele going extinct quicker
72
Q

What is speciation?

A
  • formation a new species

* can be allopatric or sympatric

73
Q

species =

A

a group of organisms that can breed to produce fertile offspring with similar morphology, physiology and biochemistry

74
Q

morphology =

A

form and structure

75
Q

physiology =

A

function and activity

76
Q

in order for a new species to form,

A
  • some of the individuals must become morphologically and/ or physiologically different
  • no longer be able to interbreed w members of the original species to produce fertile offspring -> reproductively incompatible
77
Q

how can speciation occur?

A
  • if a pop is split (isolated) for a long time, when they are reintroduced, they can no longer interbreed
  • so, are now 2 diff species
78
Q

allopatric speciation?

A
  • geographical
  • diff appear due to selection pressures/ genetic drift
  • population has become geographically sep, so gene flow between 2 groups stops so indiv are physically sep
  • bc the 2 groups have diff envir, diff selection pressures act on pop so diff physical adaptations - evolution
79
Q

what is sympatric speciation?

A

• Sympatric speciation is speciation that occurs when two groups of the same species live in the same geographic location, but they evolve differently until they can no longer interbreed and are considered different species

80
Q

sympatric speciation?

A
  • changes in some traits keeps species reproductively isolated, so gene flow between the 2 groups stops
  • e.g. colourful flap of skin under lizard’s thorats
  • colour changes bc of light
  • over many gens, lizards body changes to adapt to envir
81
Q

why does sympatric speciation occur?

A

bc of prezygotic and post zygotic isolating mechanisms

82
Q

prezygotic =

A

anything that prevents mating and fertilisation

83
Q

types of prezygotic isolation?

A
  • ecological
  • behavioural
  • temporal
  • mechanical
  • gametic
84
Q

Prezygotic: ecological?

A
  • groups may occur diff ecological niches - their role in a habitat may be different
  • e.g. 2 crickets - 1 prefers to live on sandy soil and the other on natural soil at the edge of rainforests - which contributes to reproductive isolation
85
Q

Prezygotic: behavioural?

A
  • during selection of a possible mate, indiv may reject each other bc they don’t have same courtship behaviour
  • e.g. diff in songs sung by males of 2 grass hopper species - females attached to song of own species
86
Q

Prezygotic: temporal?

A
  • indivs may be fertile at diff times of the year

* e.g. some frog species reproduce earlier in the year than others

87
Q

Prezygotic: mechanical?

A
  • diff species may have diff sex organs which aren’t compatible
  • e.g. male reprod organs of related species of damselfly have distinctive shapes
  • each enables male to mate only w own species
88
Q

Prezygotic: gametic?

A
  • sperm must reach ovum for fertilisation
  • chemicals that the sperm and ovum use to attract each other may vary from species to species
  • so gametes won’t recognise each other, no fertilisation
  • e.g. coral species release eggs and sperm into water
89
Q

if a hybrid has an odd number of chromosomes?

A

cannot produce gametes - chromosomes have diff pairing up

90
Q

post zygotic isolating mechanisms?

A
  • gamete incompatibility - digestive enzymes of sperm don’t work on egg
  • zygote inviability
  • hybrid sterility
91
Q

Post zygotic isolating mechanisms?

A
  • prevent a hybrid zygote from developing into a viable, fertile adult
  • hybrid inviability
  • hybrid infertility
92
Q

why do some plant species reproduce to produce plants that cannot interbreed with the parent species?

A

• diff chromosome number

93
Q

hybrid inviability?

A

sometimes hybrid dies prematurely :(

94
Q

hybrid infertility?

A

even if an offspring is produced from the mating of diff species, infertile as diff chromosome number - why mules are sterile

95
Q

Population bottleneck?

A
  • size of population decreases dramatically
  • OP has a large GD
  • bottneck event means only few remain
  • bc new pop is the offspring of the few remaining individuals, less GD
96
Q

Founder effect?

A
  • few ppl start their own colony
  • non-rep sample of alleles
  • dec GD in new population
97
Q

gene =

A

specific length of DNA coding for a protein

98
Q

allele =

A

one form of a particular gene

99
Q

locus =

A

position of gene on chromosome

100
Q

phenotype =

A

observable characteristic, caused by genotype

101
Q

genotype =

A

alleles of a gene/ genes possessed by an organism

102
Q

dominant =

A

causes phenotype if genotype is hetero or homozygous

103
Q

recessive=

A

causes phenotype only when homozygous

104
Q

heterozygous =

A

genotype has 2 diff alleles for a particular gene

105
Q

homozygous =

A

alleles for a particular gene are the same

106
Q

homozygous =

A

alleles for a particular gene are the same

107
Q

codominant =

A

both alleles contribute to the phenotype when genotype is heterozygous

108
Q

AS is the same as

A

SB, they both speed evolution up

109
Q

natural selection?

A
  • selection pressures cause survival of fittest & more likely to reproduce
  • variation within a population
  • selection pressures act on a population
110
Q

AS:

A
  • SP controlled by humans, not natural
  • ‘fitness’ determined by humans based on what are the desirable characteristics
  • parents selected for these characteristics
111
Q

cows?

A
  • Friesan - milk production
  • Highland - hardiness
  • Jersey - maturity speed and quality of milk
112
Q

General principles of SB?

A
  • select cow w desirable characteristic
  • select bulls that have produced high quality progeny - bc milk yield is sex limited
  • artificial insemination to cross
  • carefully monitor for desirable characteristics
113
Q

Modern AS techniques are?

A
  • automated milking &feeding
  • progeny testing
  • artificial insemination
  • sexed semen
  • genomics
  • IVF and embryo splitting
114
Q

Modern AS techniques: milking

A

automated milking and feeding machinery which tracks each cow’s yield precisely

115
Q

Modern AS techniques: progeny testing?

A

accurate and detailed

116
Q

Modern AS techniques: artifical

A

insemination and online semen purchase

117
Q

Modern AS techniques: sexed semen

A

sperm cells w only X chromosome

118
Q

Modern AS techniques: genomics?

A

selecting parents based on genetic markers rather than phenotype

119
Q

Modern AS techniques: IVF and

A

embryo splitting - cloning

120
Q

how to ensure pollen gets to right plants w no genetic contamination?

A
  • removing anthers b4 they mature, produce pollen and self pollinate
  • transfer pollen by hand
  • keeping plants isolated after pollination, by bagging flowers
121
Q

Problems associated w AS can be:

A

physical, due to linked genes or interbreeding

122
Q

physical problems associated w AS?

A
  • can cause sig. health problems
  • e.g. selecting high milk ield Holstein Freisans causes mastitis
  • flattened fce of bulldog causes issues w breathing
123
Q

linked genes?

A
  • if the gene locus of a DC is v close to gene locus of another characteristics, then these alleles will often be inherited together
  • e.g. in Dalmatians, gene for pots is close to gene for ear canal -> leads to deafness
124
Q

interbreeding?

A

• increases channce of rare homo recessive allele combinations which can cause problems like birth and development defects

125
Q

solutions to problems assoc w AS?

A
  • can be min. by:
  • maintaining resource of genetic material for in SB
  • to include ‘wild type’
  • avoid crossing closely related individuals
126
Q

this can be done thu?

A
  • conservation of wild type organisms in situ or ex situ- e.g. millennial seed bank, conservation parks
  • constant movement of male parents to prevent em breeding w daughters
  • genetic monitoring, progeny testing and record keeping to avoid inbreeding
127
Q

ethical considerations of AS? +

A

+ organisms selected based on DS, so offspring better suited to envir and more liekly to survive
+ same effect as NS but selection pressure caused by humans, =ethical bc would happen anyway

128
Q

ethical considerations of AS? -

A
  • harmful - can cause health problems
  • reduced GV -> pop less robust
  • genes may be linked so undesirable characteristics can be inherited too

A Level Biology (28 decks)

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