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IB Biology > UNIT 3 - D 3.2 - Inheritance > Flashcards

UNIT 3 - D 3.2 - Inheritance Flashcards

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1
Q

What is the term diploid used to describe?

A

a nucleus that has chromosomes organized into pairs of homologous chromosomes

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2
Q

What are examples of exceptions to the adult form of an animal having almost all diploid cells?

A

male bee, wasp and ant cells are haploid

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3
Q

What does the variable n represent and what does it refer to?

A

it represents the haploid number and it refers to the number of sets of chromosomes that a nucleus can have

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4
Q

What did Mendel use artificial pollination to do during his famous experiments?

A

to get the sperm cells in the pollen of pea plants into the ovum cells inside the ovaries of other pea plants

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5
Q

When Mendel crossbred tall plants and short plants, which was the dominant allele?

A

the tall allele

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6
Q

What is a heterozygote?

A

an organism that has one dominant allele and one recessive allele for a particular trait

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7
Q

What can be used to show the dominant and recessive alleles for different traits?

A

a punnett grid

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8
Q

What is a punnett grid used to show?

A

how the alleles of parents are split between their gametes and how new combinations of alleles can show up in their offspring

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9
Q

What is the purpose of a punnett grid?

A

to show all the possible combinations of genetic information for a particular trait in a monohybrid cross

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10
Q

What is a monohybrid cross?

A

the parents have different alleles and it shows the results for only one trait

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11
Q

What are the steps in creating a punnett grid?

A
  1. choose a letter to represent the alleles - capital=dominant, lowercase=recessive
  2. Determine the parents’ genotypes - either TT, Tt, or tt
  3. determine the gametes that the parents could produce - TT can only make gametes with T…
  4. Draw a punnett grid - parents’ gametes are at the top and side of the grid
  5. Work out the chances of each genotype and phenotype occurring
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12
Q

What does TT mean for an individual’s genotype?

A

the genotype is homozygous dominant

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13
Q

What does Tt mean for an individual’s genotype?

A

The genotype is heterozygous

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14
Q

What does tt mean for an individual’s genotype?

A

the genotype is homozygous recessive

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15
Q

What is the first generation called?

A

`the first filial generation or F1 generation

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16
Q

What is the generation produced by crossing two members of the F1 generation called?

A

the second filial generation or the F2 generation

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17
Q

How many dominant alleles does a genotype need to have to produce the dominant trait?

A

only one dominant allele, to produce the recessive allele, there can be no dominant alleles

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18
Q

Why is it possible for some plants (such as peas) to self-pollinate?

A

they have flowers that can produce both male pollen and female ova so this is possible when they prepare gametes at the same time

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19
Q

What is self-pollination?

A

when a plant’s pllen lands on flower it has produced itself

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20
Q

What is possible as a result of self-pollination?

A

self-fertilization

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21
Q

What does self-fertilization result in?

A

less genetic diversity than cross-pollination

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22
Q

What can farmers use when they want plants with the same characteristics as previous generations?

A

self-pollination techniques

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23
Q

What can farmers use when they want to create new varieties of plants with combinations not seen before

A

cross-pollination techniques

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24
Q

What is an example of a common plant that has been cross bred over many years to acheive the desired combination of traits?

A

modern wheat

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25
Q

What is an allele?

A

one specific form of a gene

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26
Q

What do different alleles differ by?

A

one or a few bases

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27
Q

What is the genotype the symbolic representation of?

A

the pair of alleles possessed by an organism, typically represented by two letters

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28
Q

How will all eukaryotes that produce sexually inherit alleles?

A

one from the father and one from the mother

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29
Q

What does homozygous refer to?

A

having two identical alleles of a gene

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30
Q

What does heterozygous refer to?

A

having two different alleles of a gene

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31
Q

What is being heterozygous a result of?

A

when the paternal and maternal alleles are different

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32
Q

What is a carrier?

A

an individual who has a recessive allele of a gene that does not have an effect on the phenotype

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33
Q

What are examples of traits produced by genetics only?

A

ABO blood type, genetic conditions

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34
Q

What are examples of traits produced by the environment only?

A

learned behavior, acquired physical traits

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35
Q

What are examples of traits produced by both genetics and the environment combined?

A

Human height (max height is genetic, but poor nourishment may lead to shorter height), cancer (may have genetic component, could be triggered by mutagens)

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36
Q

What is a dominant allele?

A

an allele that has the same effect on the phenotype whether it is paired with the same allele or a different one

37
Q

How often are dominant alleles expressed in the phenotype?

A

always

38
Q

Why would the a in the genotype Aa not be expressed in the phenotype?

A

the a allele is masked, not transcribed or translated during protein synthesis

39
Q

What is a recessive allele?

A

an allele that has an effect on the phenotype only when no dominant allele is present to mask it

40
Q

What are codominant alleles?

A

pairs of alleles that affect the phenotype when present in a heterozygote

41
Q

What is phenotype plasticity?

A

an organism’s ability to express its phenotype differently depending on the environment

42
Q

What is an effective way of adapting?

A

phenotypic plasticity

43
Q

What are cyclical event such as seasonal food availiblity described as?

A

phenological

44
Q

Where does phenotypic plasticity generate changes?

A

physiology, morphology, behavior, phenology

45
Q

How does the freshwater snail Physa virgita stay safe from its predator, the bluegill fish, Lepomis macrochirus)?

A

It expresses its genes slightly differently in order to grow a more rounded, shorter shell which is more difficult for the predator to crush

46
Q

What is necessary for two healthy parents to have a child who is affected by a genetic condition?

A

both parents must be carriers of the version of the gene that causes the disease

47
Q

What is phenylketonuria/PKU?

A

a genetic disease that is caused by mutations in the autosomal PAH gene resulting in low levels of the enzyme phenylalanine hydroxylase

48
Q

What is a child at risk of if they have PKU?

A

if there is a large quantity of protein in their diet, the phenylalanine levels can become toxic and impair brain development

49
Q

What are autosomal recessive diseases caused by?

A

recessive alleles

50
Q

Where are the locus of autosomal recessive diseases’ gene found?

A

on one of the first 22 pairs of chromosomes but not on the sex chromosomes X or Y

51
Q

When do SNPs occur?

A

when a nucleotide of the genetic code is not found where it is expected and another is found at that position instead

52
Q

What may SNPs lead to?

A

another amino acid to be coded for which could modify the structure and properties of the protein that is translated

53
Q

Why can some people taste the bitterness of PTC but others can’t?

A

if a person has one version of a certain gene, they can taste PTC while people with a different version cannot taste it

54
Q

What are the possible blood types in humans?

A

A, B, AB, O

55
Q

How many alleles of a gene are there to produce the four possible blood types?

A

3

56
Q

How many genotypes can the three alleles for determining blood types produce?

A

6

57
Q

What does I^A represent?

A

the alleles for producing type A antigens, resulting in type A blood

58
Q

What does I^B represent?

A

the allele for producing type B antigens, resulting in type B blood

59
Q

What does i represent?

A

the recessive allele that produces neither A nor B antigens, resulting type O blood

60
Q

What is an example of codominance with alleles?

A

I^A with I^B giving type AB blood

61
Q

What does incomplete dominance result in?

A

neither phenotype, rather something in between

62
Q

For the four o’clock flower, how would its colour end up pink?

A

If the genotype was C^R C^W (both red and white)

63
Q

Why is incomplete dominance called what it is?

A

because the two parent alleles are mixed and each one contributes to the phenotype but neither is masked

64
Q

How does the X chromosome compare to the Y chromosome in the 23rd pair of chromosomes?

A

The X chromosome is longer and contains more genes

65
Q

What do the genetics of being male or female depend on?

A

whether you inherit an X or a Y chromosome from your father

66
Q

How is higher oestradiol and progesterone prodcution allowed?

A

by alleles that interact on both of the X chromosomes of female embryos

67
Q

What are genes on the Y chromosome responsible for?

A

early testes development and relatively high testosterone production, resulting in male reproductive structures

68
Q

Why does the Y chromosome have fewer loci and therefore carries fewer genes?

A

because it is significantly smaller than the X chromosome

69
Q

Why do most of the alleles in the X chromosme have nothing to pair up with?

A

because it has so many more genes, so a gene whose locus is at an extremity of the X chromosome wouldn’t have a partner from the Y because the Y chromosme doesn’t extend that far from its centromere

70
Q

What are sex-linked traits?

A

Any genetic trait that has a gene locus on the X or Y chromosome

71
Q

What is an example of a sex-linked trait?

A

haemophilia

72
Q

What problem does haemophilia cause?

A

blood not being able to clot properly

73
Q

What are the alleles for haemophilia always found?

A

on the X chromosome

74
Q

What are the possible genotypes for haemophilia?

A

X^H X^H = non-affected female
X^H X^h = non-affected female who is a carrier
X^h X^h = affected female
X^H Y = non-affected male
X^h Y = affected male

75
Q

Why is it unlikely for an offspring to inherit any X^h alleles?

A

because they are rare in most populations of humans worldwide

76
Q

Why can only females be carriers of haemophilia?

A

because only females can be heterozygous

77
Q

What can males not be carriers for?

A

X-linked alleles

78
Q

What are pedigree charts used to show in genetics?

A

How a trait can pass from one generation to the next

79
Q

What does polygenic inheritance involve?

A

2 or more genes influencing the expression of one trait

80
Q

What is continuous for variation?

A

When an array of possible phenotypes can be produced

81
Q

What is an example of continuous variation?

A

Human skin color.

82
Q

What is the intensity of pigment in our skin the result of?

A

The interaction of multiple genes

83
Q

What is discrete variation?

A

When variation is not continuous

84
Q

How would an outlier be determined with a box and whisker plot?

A

Multiply the IQR ( difference between 75th and 25th percentiles) by one point five and add this value to quartile three or subtracted from quartile one

85
Q

What is part of the law of segregation?

A

Each gamete will receive only one of the 2 copies that the parent can give

86
Q

What is the distribution ratio?

A

9:3:3:1

87
Q

Why is the distribution ratio what it is?

A

Because of the movement of chromosomes during meiosis

88
Q

What is Mendel’s law of independent assortment?

A

The alleles of two or more different genes get sorted into gametes independently of another

89
Q
A

IB Biology (13 decks)

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