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BIO 375 - Genetics > Exam 2: Extension and Modifications of Mendelian Principles; Analyzing Pedigrees; Linkage and Eukaryotic Gene Mapping; Chromosome Variation (Bio 375 - Genetics) > Flashcards

Exam 2: Extension and Modifications of Mendelian Principles; Analyzing Pedigrees; Linkage and Eukaryotic Gene Mapping; Chromosome Variation (Bio 375 - Genetics) Flashcards

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1
Q

inheritance

A

principles of segregation and independent assortment; always the same (no matter expression of alleles); determined by movement of chromosomes during mitosis/meiosis

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2
Q

expression

A

how alleles at a single locus (or different loci) interact with each other during gene expression

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3
Q

complete dominance

A

interaction between alleles at same locus; heterozygote expresses dominant allele; phenotype of heterozygote is same as phenotype of one of homozygotes; GENOTYPIC RATIO DOES NOT EQUAL PHENOTYPIC RATIO; need a test cross to determine what is heterozygous as there is only two expressed phenotypes

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4
Q

dominance charactistics

A

interaction between alleles at same locus (allelic interaction); does not involve way genes are inherited only the way they are expressed

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5
Q

mendel based his principles on complete dominance

A

observed 3:1 or 9:3:3:1 phenotypic ratios in F2 offspring of a hybrid cross

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6
Q

incomplete dominance

A

when a heterozygote has an intermediate phenotype to those of homozygotes (based often on visual examination); depends on level of examination; 1:2:1 phenotypic ratio F2 progeny (3 expressed phenotypes); GENOTYPIC RATIO EQUALS PHENOTYPIC RATIO; no needed test cross because expressed phenotypes correlate with genotypic ratios

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7
Q

penetrance

A

percentage of individual organisms having a particular genotype that express the expected phenotype

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8
Q

expressivity

A

degree to which a characteristic is expressed

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9
Q

incomplete penetrance

A

the genotype does not produce expected phenotype

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10
Q

codominant traits

A

each allele is fully expressed; the heterozygote simultaneously expresses phenotype of both homozygotes (the “molecular level” of incomplete dominance)

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11
Q

lethal allele

A

cause death at early stage of development (so some genotypes may never appear among progeny); observed 2:1 phenotypic ratio; the allele that is present in heterozygous and surviving offspring is the survival allele while the other allele only present in heterozygote results in death

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12
Q

multiple alleles

A

“allelic series”; more than two alleles are present at a locus; leads to a greater number of possible phenotypes and genotypes: [n*(n+1)]/2 = number of genotypes possible (where n equals number of different alleles at a locus)

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13
Q

gene pool

A

all genes carried by members of a population

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14
Q

gene interaction

A

interactions between alleles at different loci; the products of alleles at different loci combine to produce phenotypes not predictable from single locus effects

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15
Q

epistasis

A

one gene masks the expression of a gene at another locus

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16
Q

epistatic gene

A

the gene that does the masking

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17
Q

hypostatic gene

A

the gene whose effect is masked

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18
Q

recessive epistasis

A

presence of two recessive alleles (homozygous genotype) inhibits expression of allele at a different locus

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19
Q

sex influenced traits

A

determined by autosomal genes, expressed differently in males and females

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20
Q

sex limited characteristics

A

determined by autosomal genes, expressed in only one sex

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21
Q

dominant epistasis

A

only a single copy of an allele is required to inhibit expression of allele at different locus

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22
Q

negative epistasis

A

negative effect on functional enzyme by inactivation (inactivates the functional enzyme)

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23
Q

qualitative traits

A

only a few distinct phenotypes; influenced by only one or a few genes

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24
Q

quantitative traits

A

many possible phenotypes; influenced by many genes and most are strongly influenced by environment; display wide variations in expression; determined by contributing alleles from multiple genes (additive equal gene action)… as the number of loci influencing a trait increases, the number of phenotypic classes increases

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25
Q

polygenic traits

A

traits that are influenced by many genes

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26
Q

multifactorial traits

A

traits that result from the interaction of one or more environmental factors and two or more genes

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27
Q

additive equal gene action

A

determined by “contributing” alleles from multiple genes, where each contributing allele contributes equally to the phenotype (while some alleles contribute nothing)

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28
Q

continuous characteristic

A

as number of loci influencing a trait increases, the number of phenotypic classes increases

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29
Q

genomic imprinting

A

non-mendelian inheritance where there is differential expression of genetic material depending on parental origin (from mother or father); selective inactivation of certain genes during spermatogenesis or oogenesis which is thus passed down

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30
Q

epigenetics

A

study of heritable changes not caused by a change in DNA sequence; changes are heritable and reversible; changes may due chromatin conformation (Barr body or genomic imprinting) or environmental controls

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31
Q

complementation

A

individual organism possessing two recessive mutations has a wild-type phenotype, indicating that mutation are nonallelic genes

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32
Q

modified dihybrid ratio

A

X/16 = # progeny with phenotype/total # progeny …. X = (16*[# progeny with phenotype]) / total # progeny

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33
Q

general dihybrid genotypes

A

A_B_ ; A_bb; aaB_; aabb

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34
Q

(expression pattern - monohybrid crosses) complete dominance

A

3:1

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35
Q

(expression pattern - monohybrid crosses) incomplete dominance

A

1:2:1

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36
Q

(expression pattern - monohybrid crosses) lethal alleles

A

2:1

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37
Q

(expression pattern - monohybrid crosses) sex-linked

A

2:1:1 and 1:1:1:1

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38
Q

(expression pattern - dihybrid crosses) complete dominance

A

9:3:3:1

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39
Q

standard Mendelian cross - monohybrid

A

can have F2 phenotypic ratios of complete dominance (3:1) or incomplete dominance (1:2:1)

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40
Q

standard Mendelian cross - dihybrid

A

can have F2 phenotypic ratios of complete dominance (9:3:3:1)

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41
Q

monohybrid cross (non-standard Mendelian cross)

A

can have F2 phenotypic ratio of lethal alleles (2:1)

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42
Q

reciprocal mendelian cross - monohybrid

A

can have F2 phenotypic ratio of sex-linked (2:1:1 or 1:1:1:1)

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43
Q

anticipation

A

genetic trait becomes more strongly expressed / is expressed at an earlier age as it is passed from generation to generation

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44
Q

genetic maternal effect

A

phenotype of offspring is determined by genotype of mother

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45
Q

affected person on pedigree

A

shape is filled in

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46
Q

unaffected person on pedigree

A

shape is not filled in

47
Q

deceased person on pedigree

A

slash through shape

48
Q

proband

A

p with an arrow pointing to the shape of the individual who was the first family member coming to the attention of geneticists

49
Q

fraternal twins on pedigree

A

shapes are connected by a triangle

50
Q

identical twins on pedigree

A

shapes are connected by complete triangle

51
Q

pedigree

A

pictorial representation of a family’s history; a family tree that outlines the inheritance of one or more characteristics

52
Q

autosomal recessive trait

A

usually appears equally in males/females (unless sex-limited/sex-influenced)… usually skips generations… offspring of two affected parents must be affected… are more likely to appear among progeny of related parents… more likely to appear among progeny of related parents (consanguineous mating - inbreeding)

53
Q

autosomal dominant trait

A

usually appear in males and females… there are no carriers of autosomal dominant allele (it is always expressed)… unaffected individuals do not transmit trait… most affected individuals are heterozygotes

54
Q

X-linked recessive trait

A

appears more frequently in males (because they are hemizygotes)… affected males are usually born to unaffected carrier females… usually skips generations… not passed from father to son

55
Q

X-linked dominant trait

A

appear similarly in males and females… affected have at least one affected parent (no skipping generations)… affected males must have affected mothers and pass trait to all daughters but not sons… affected females pass to half of sons and daughters

56
Q

Y-linked trait (holandric trait)

A

expressed only in males… passed from father to son (so all sons of affected father are affected)

57
Q

cytoplasmic inheritance

A

non-mendelian inheritance involving the characteristics encoded by genes in cytoplasm… involves extranuclear DNA from the mitochondria… usually inherited only from mothers (so if mother has a gene, it is passed to all offspring)… mitochondria segregate randomly during cell division and could thus lead to heteroplasmy (mix of mtDNA in one cell)

58
Q

penetrance

A

proportion of individuals with a genotype who express expected phenotypes

59
Q

completely penetrant

A

individuals with genotype express expected phenotype 100% of the time

60
Q

incompletely penetrant

A

individuals with genotype do not always express expected phenotype

61
Q

expressivity

A

degree of expression of phenotype

62
Q

types of chromosomal mutations

A

chromosome rearrangement, aneuploidy, polyploidy

63
Q

chromosomal mutation

A

variations in number/structure of chromosomes

64
Q

euploid

A

normal/diploid state of chromosomes with correct structure

65
Q

chromosome rearrangement

A

altered structure of chromosome

66
Q

types of chromosomal rearrangements

A

duplication, deletion, inversion, translocation

67
Q

duplication

A

segment of chromosome is duplicated

68
Q

tandem duplication

A

duplicated region is immediately adjacent to original segment

69
Q

displaced duplication

A

duplicated region is located a distance away from original segment

70
Q

reverse duplication

A

duplicated region order is backwards from original order

71
Q

segmental duplication

A

duplications greater than 1000 bp in length

72
Q

deletion

A

segment of chromosome is deleted

73
Q

pseudodominance

A

expression of a normally recessive condition upon lost wild-type allele no longer masking the recessive allele’s expression

74
Q

haploinsufficient gene

A

when single copy of gene is not enough to produce wild-type phenotype

75
Q

duplication and deletion occur due to

A

unequal crossing over, where chromosomes “slip”

76
Q

inversion

A

segment of chromosome is turned 180 degrees

77
Q

paracentric inversion

A

does not include centromere

78
Q

pericentric inversion

A

includes centromere

79
Q

position effect

A

if gene position is altered by an inversion, they may be expressed at inappropriate times or places

80
Q

translocation

A

segment of chromosome moves from one chromosome to a nonhomologous chromosome

81
Q

nonreciprocal translocation

A

genetic material is moved from one chromosome to another without any reciprocal exchange

82
Q

reciprocal translocation

A

two way exchange of segments between chromosomes

83
Q

aneuploidy

A

an increase or decrease in number of chromosomes

84
Q

aneuploidy types (“-omy”)

A

nullisomy, monosomy, trisomy, tetrasomy

85
Q

nullisomy

A

loss of both members of a homologous pair of chromosomes; 2n - 2

86
Q

monosomy

A

loss of a single chromosome; 2n - 1

87
Q

trisomy

A

gain of a single chromosome; 2n + 1

88
Q

tetrasomy

A

gain of two homologous chromosomes; 2n + 2

89
Q

aneuploidy and polyploidy often caused by

A

nondisjunction (incorrect segregation of chromosomes)

90
Q

polyploidy

A

extra sets of chromosomes due to nondisjunction of all chromosomes; “-oid”: triploid (3n) or tetraploid (4n)…

91
Q

polyploidy types

A

autopolyploidy, allopolyploidy

92
Q

autopolyploidy

A

when chromosome sets are from same species; caused by errors in mitosis during embryonic development (no cell division at end of mitosis) or errors in meiosis during gamete development (no cell division at end of meiosis I)

93
Q

allopolyploidy

A

when chromosomes sets are from different species; uses often in plants agronomically (more chromosomes, larger cells/plants)

94
Q

unbalanced gametes

A

gametes with varying number of chromosomes

95
Q

amphidiploid

A

allopolyploid consisting of two combined diploid genomes

96
Q

recombination

A

sorting of alleles into new combinations via crossing over between linked loci and independent assortment of unlinked genes

97
Q

linked

A

genes located closely together on same chromosome

98
Q

linkage group

A

linked genes belonging in the same group on same chromosome

99
Q

linkage groups are broken by

A

crossing over and recombination

100
Q

genes are unlinked

A

half of progeny are recombinant and half of progeny are nonrecombinant; 50 recombinant :: 50 nonrecombinant

101
Q

genes are completely linked

A

only nonrecombinant progeny are produced

102
Q

genes are incompletely linked

A

recombinant and nonrecombinant progeny are produced, but a higher percentage of nonrecombinant progeny predominates

103
Q

0% recombinant offspring

A

completely linked genes

104
Q

0.1-49.9% recombinant offspring

A

incompletely linked genes

105
Q

50% recombinant offspring

A

unlinked genes

106
Q

recombinant

A

offspring do not look like parents (having different phenotypes and thus different genotypes)

107
Q

recombination frequency

A

(# of recombinant progeny / # of total progeny) x 100%

108
Q

frequency of recombination between two loci is related to

A

distance between the two loci on a chromosome – the larger the distance, then the more likely crossing over will occur

109
Q

if recombination frequency is 50%

A

the two-point test cross is uninformative – can only determine that the loci are unlinked, but not whether or not they are on the same chromosome or on separate chromosomes

110
Q

interchromosomal recombination

A

between genes located on different chromosomes

111
Q

intrachromosomal recombination

A

between genes located on same chromosome

112
Q

linkage maps

A

use recombination frequencies to order and space genes on chromosomes, with distances being measured in centiMorgans (cM)…. 1% recombination frequency equals approximately 1 cM (but most be modified using Haldare function for accurate conversion)… map distances greater than 50 cM cannot be mapped in a single two-point cross (because 0.50 is maximum recombination frequency)

113
Q

when a two-point cross results in a recombination frequency of 0.50, then loci are in different linkage groups

A

located on different chromosomes or very far apart on same chromosome

114
Q

the further genes are apart on a chromosome

A

the greater the underestimation of genetic differences

BIO 375 - Genetics (8 decks)

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