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6.2 Patterns of Inheritance > 6.2 Patterns of Inheritance > Flashcards

6.2 Patterns of Inheritance Flashcards

1
Q

what is a Gene?

Genetic Variation

A

the basic unit of heredity

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2
Q

what is a Genotype?

Genetic Variation

A

the full set of genes in an organism

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3
Q

what is a Phenotype?

Genetic Variation

A

the observable characteristics of an organism

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4
Q

what is a Locus?

Genetic Variation

A

the position of a particular gene on a chromosome

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5
Q

what is an Allele?

Genetic Variation

A

alternative form of the same gene.

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6
Q

what are the genetic causes of variation?

Genetic Variation

A

A. gene mutations
B. chromosome mutations during meiosis
C. gamete formation during meiosis

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7
Q

what are the causes of phenotypic variation?

Genetic Variation

A

genetics and the environment

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8
Q

what are the environmental causes of variation?

Genetic Variation

A

D. the environment
E. the impact of environment on genes

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9
Q

A

What are the three types of mutagenic agents?

Genetic Variation

A
  1. physical
  2. chemical
  3. biological
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10
Q

what are examples of physical mutagenic agents?

Genetic Variation

A
  • UV
  • gamma
  • x rays
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11
Q

what are examples of chemical mutagenic agents?

Genetic Variation

A
  • free radicals
  • mustard gas
  • nitrous acid
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12
Q

what are the examples of biological mutagenic agents?

Genetic Variation

A
  • viruses
  • food contaminants e.g mycotoxins from fungi
  • transposons (jumping genes)
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13
Q

what effects can genetic mutations have?

Genetic Variation

A

harmful, advantageous or neutral. these are either persistant or random

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14
Q

B

when do chromosome mutations occur?

Genetic Variation

A

meiosis

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15
Q

what type of chromosome mutations can occur?

Genetic Variation

A
  • deletion
  • inversion
  • translocation
  • duplication
  • non disjunction
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16
Q

what is deletion?

Genetic Variation

A

when part of a chromosome containing genes and regulatory sequences is lost

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17
Q

what is inversion?

Genetic Variation

A

when part of a chromosome break off, turn 180° and reattach. some may not be fully expressed/

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18
Q

what is translocation?

Genetic Variation

A

when a piece of chromosome breaks off and becomes attached to another. the gened transferred aren’t transcribed

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19
Q

what is duplication?

Genetic Variation

A

when a piece of chromosome leads to too much expression of a protein, disrupting metabolism

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20
Q

what is non disjunction?

Genetic Variation

A

when a pair of chromatids fail to separate leaving one gamete with an extra chromosome.

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21
Q

what is aneuploidy?

Genetic Variation

A

when the chromosome number in kargotype is not an exact multiple of haploid number.

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22
Q

what is polyploidy?

Genetic Variation

A

when a diploid gamete is fertilised.

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23
Q

how is a triploid zygote made?

Genetic Variation

A

when a diploid gamete is fertilised by a haploid gamete

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24
Q

how is a tetraploid zygote made?

Genetic Variation

A

when two diploid gametes are fused.

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25
Q

C

how does sexual reproduction create variation?

Genetic Variation

A
  • random fertilisation
  • independent assortment
  • crossing over
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26
Q

D

what are examples of environmental factors that create variation?

Genetic Variation

A

accents, lanaguge, scars, losing a limb

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27
Q

E

what is an example of the environment acting on genes?

Genetic Variation

A

plants kept in dim light after germination or without sufficent magnesium.

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28
Q

how do these deficiencies act on genes?

Genetic Variation

A
  • plant has genotype to make chlorophyll
  • chlorophyll production limited
  • plant cannot photosynthesise due to environment
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29
Q

what is meant by monogenic cross inheritance?

Monohybrid Inheritance

A

inheritance of a characteristic that is controlled by a single gene but may have 2+ alleles.

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30
Q

who was Gregor Mendel?

Monohybrid Inheritance

A

an austrain monk who established the basics of inheritance, including dominant and recessive alleles via peas.

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31
Q

why did Mendel use pea plants?

Monohybrid Inheritance

A
  • easy to grow
  • natuarlly self fertilising
  • easy to cross fertilise artifically
  • have 7 distinct observable characteristsics e.g colour, stem length, wrinkles etc.
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32
Q

what are true breeding strains?

Monohybrid Inheritance

A

strains of plant (pea in this case) where traits were unchanged for generations.

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33
Q

why did Mendel use true breeding strains?

Monohybrid Inheritance

A

to avoid the appearance of unexpected traits in offspring.

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34
Q

what is a monohybrid cross?

Monohybrid Inheritance

A

mating individuals from contrasting true breeding parents strains to determine dominant and recessive alleles.

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35
Q

how did Mendel perfom a monohybrid cross?

Monohybrid Inheritance

PUNNETT SQUARES USED

A
  • mated individuals from contrasting true breeding parents -> P1
  • the offspring from this cross (F1) were phenotypically identical to parent with dominant allele (100% Tt)
  • F1 were allowed to self fertilsie to make F2
  • the F2 generation will give 25% chance of recesssive allele. (25% TT, 25% tt, 50% Tt)
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36
Q

what is test crossing used for?

Monohybrid Inheritance

A

to determine whether an organism showing the dominant characteristic is homozygous dominant or heterozygous

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37
Q

how does test crossing work?

Monohybrid Inheritance

PUNNETT SQUARES USED

A

crossing the organism with the dominant characteristic with another that is homozygous recessive

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38
Q

what does it mean if any offspring show the recessive trait in test crossing?

Monohybrid Inheritance

A

the parent (investigated organism) must have been heterozygous.

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39
Q

what is Dihybrid Inheritance?

Dihybrid Inheritance

A

the inheritance of 2 genes from 2 seperate loci on different chromosomes

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40
Q

what did Mendel deduce from his dihybrid crosses?

Dihybrid Inheritance

A
  • alleles of 2 genes are inherited independently.
  • each gamete will have one allele for each locus.
  • independent assortment means any one allele can combine with any other allele.
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41
Q

what is the ratio of dihybrid inheritance?

Dihybrid Inheritance

A

9:3:3:1

42
Q

is the chance of one trait being inherited influenced by the other?

Dihybrid Inheritance

A

no.

43
Q

what did Mendel study?

Dihybrid Inheritance

A

the inheritance of seed shape and seed colour in pea plants

44
Q

how did Mendel investigate this?

Dihybrid Inheritance

A

crossed true bred yellow and round pea plants (YYRR) with true bred green and wrinkled pea plants (yyrr)

45
Q

what traits did the F1 generation have?

Dihybrid Inheritance

A

yellow and round, so heterzygous.

46
Q

what equation is used to predict traits in dihybrid crosses?

Dihybrid Inheritance

A

product of individual probabilities = combined probability of occurence.

47
Q

how can we predict F2’s traits?

Dihybrid Inheritance

PUNNETT SQUARE USED!

A

consider the 2 crosses as two independent monohybrid crosses and then use equation

48
Q

EXAMPLE

what is the probability of F2 generation being yellow and round?

Dihybrid Inheritance

A
  • 3/4 will be yellow, 1/4 will be green
  • 3/4 will be round, 1/4 will be wrinkled
  • 3/4 x 3/4 = 9/16
49
Q

what is meant by multiple alleles?

Multiple Alleles

A

when a characteristic has 3 or more alleles in the population’s gene pool

50
Q

what is codominance?

Multiple Alleles

A

when both alleles present in the genotype of a heterozygous individual contribute to the phenotype.

51
Q

what are human blood groups an example of?

Multiple Alleles

A

multiple alleles and codominance

52
Q

what is blood group determine by?

Multiple Alleles

A

3 alleles of a single gene on chromosome 9

53
Q

what does the human blood group gene code for?

Multiple Alleles

A

isoagglutinogen on surface of erythrocytes.

54
Q

**

what are the genotypes and phenotypes of human blood groups?

Multiple Alleles

A

IAIA or IAIO = A
IBIB or IBIO = B
IAIB = AB
IOIO = O

55
Q

which blood group alleles are dominant?

Multiple Alleles

A

IA and IB

56
Q

how many alleles will an individual have for blood group?

Multiple Alleles

A

only 2 out of the 3 available

57
Q

what are the 4 coat colours of rabbits?

Multiple Alleles

A
  1. Agouti (Wild)
  2. Albino
  3. Chinchilla
  4. Himalayan
58
Q

what is an agouti coat?

Multiple Alleles

A
  • grey base, yellow band and a black tip
  • dominant over all alleles (C)
59
Q

what is an albino coat?

Multiple Alleles

A
  • no pigment at all
  • recessive to all alleles (c)
60
Q

what is a chincillia coat?

Multiple Alleles

A
  • a silvery grey, missing a yellow band
  • dominant (Cch) over himalayan
61
Q

what is a himalayan coat?

Multiple Alleles

A
  • white with black feet.
  • recessive to only chinchilla (Ch)
62
Q

what is an example of codominance in animals

Codominance

A
  • coat colour in short horn cattle has 2 alleles CW for White and CR for Red
  • cattle that are homozygous have their respective colours
  • cattle that are heterozygous have a roan coat.
63
Q

what is the inheritance in short horn cattle?

Codominance

A
  • if red and white cattle are bred, all offspring will have ROAN COATS
  • if roan cattle are bred, all offspring will have all 3 phenotypes (50% roan, 25% white, 25% red)
64
Q

what are examples of codominance in humans?

Codominance

A
  • MN blood groups
  • ABO blood groups
  • sickle cell anaemia
65
Q

why are MN blood groups an example of codominance?

Codominance

A
  • controlled by a gene with 2 alleles
  • gene codes for protein of erythrocyte surface
  • children of a heterozygous couple will have GROUP MN
66
Q

why are ABO blood groups an example of codominance?

Codominance

A

someone with IAIB genotype will express both and have both type of isoagglutinogen.

67
Q

why is sickle cell anaemia an example of codominance?

Codominance

A

in heterozgous people, half haemoglobin is normal (HBn) and half is abnormal (HBs)

68
Q

what is an example of codominance in plants?

Codominance

A

some types of camellia flower have red petals, some have white.
if these are crossed, the offspring will have both red and white petals as both alleles expressed.

69
Q

what is sex linkage?

Sex Linkage

A

when a particular gene is located on a sex chromosome

70
Q

what is a homogametic sex chromosome?

Sex Linkage

A

the XX chromsome in females

71
Q

what is a heterogametic sex chromosome?

Sex Linkage

A

the XY chromosome in males.

72
Q

how is sex in mammals determined?

Sex Linkage

A

two chromosomes/heterosomes: X and Y

73
Q

which is larger, X or Y?

Sex Linkage

A

X - contains over 2000 genes whilst Y contains less than 100

74
Q

why is X linkage more common?

A
  • x chromosome is larger
  • part of the X chromosome doesn’t have an homologous region on the Y so only one allele present and is therefore always expressed.
75
Q

what does it mean if the female has a faulty allele on one X?

Sex Linkage

A

she will have a functioning copy on the other X

76
Q

what happens if a male inherits the faulty allele on the X?

Sex Linkage

A

it will result in a genetic disease

77
Q

how are male chromosomes described for X linked genes?

Sex Linkage

A

as functionally haploid or hemizygous; they cannot be hetero or homozygous

78
Q

what are examples of X linked diseases?

Sex Linkage

A
  • haemophillia
  • duchenne muscular dystrophy
  • colour blindness
79
Q

why are Y linked diseases rare?

Sex Linkage

A

as there is little room on the Y chromosome for anything other than genes controlling testes formation and function

80
Q

what is Haemophillia A?

Sex Linkage

A

blood being unable to clot fast enough, leading to bleeding and internal haemorrhage

81
Q

what causes Haemophillia A?

Sex Linkage

A

lack of the coagulation factor 8 which is coded for on a mutated allele on the non homologous region in females.

82
Q

what are the alleles for haemophillia?

Sex Linkage

PUNNETT SQUARE USED!

A

XHXh - female carrier
XhY - male sufferer

83
Q

what causes sons to inherit haemophillia?

Sex Linkage

A

if Xh is passed down.

84
Q

what is X-Inactiviation?

Sex Linkage

A

when one X chromosome is inactivated at random (either male or female) to ensure the effective dosage of X-linked genes is equalized between men and women.

85
Q

what is an example of sex linkage in cats?

Sex Linkage

A

the allele CO produces ginger fur whilst CB produces black.
cats with XCO and XCB have patches of both colours in their fur.

86
Q

what happens during X-Inactivation in cats?

Sex Linkage

A

the orange allele (CO) is only expressed in cells where black allele is inactivated and vice versa.

87
Q

what is an autosome?

Autosomal Linkage

A

a chromosome that doesn’t determine sex

88
Q

what is an autosomal linkage?

Autosomal Linkage

A

when gene loci present on the same autosome are quite likely to be inherited together

89
Q

hwo many autosomal linkage groups are there in humans?

Autosomal Linkage

A

22 as 22 autosome pairs.

90
Q

what genes are inehrited together in autosomal linkage?

Autosomal Linkage

A

ones that are closely located on the same chromosome

91
Q

why does autosomal linkage reduce variation?

Autosomal Linkage

A

as there are fewer gene combinations of alleles

92
Q

what causes offspring to be of parental type?

Autosomal Linkage

A

crossings where linkage is a contributing factor.

93
Q

what causes more genetic variation?

Autosomal Linkage

A

genes on seperate chromosomes

94
Q

what happens if linked genes aren’t affected by crossing over?

Autosomal Linkage

DIAGRAMS IN NOTES!

A

they are inheirted as one unit.

95
Q

is there variation when no crossing over occurs?

Autosomal Linkage

A

no.

96
Q

what is recombination?

Autosomal Linkage

A

the reassortment of genes or traits into different combinations from those of their parents

97
Q

what is a recombinant?

Autosomal Linkage

A

offspring with a genotype unlike either parent.

98
Q

what happens if linked alleles are affected by crossing over?

Autosomal Linkage

DIAGRAMS IN NOTES!

A

they are not inherited as one unit.

99
Q

what is the ratio of inheritance when linked alleles are crossed over?

Autosomal Linkage

A

12:1:1:2

100
Q

what does this ratio depend on?

Autosomal Linkage

A

length as the further apart 2 gene loci, the more likely recombinant genes are to form.

6.2 Patterns of Inheritance (1 decks)

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