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

Question 1

inheritance

Answer 1

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

Question 2

expression

Answer 2

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

Question 3

complete dominance

Answer 3

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

Question 4

dominance charactistics

Answer 4

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

Question 5

mendel based his principles on complete dominance

Answer 5

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

Question 6

incomplete dominance

Answer 6

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

Question 7

penetrance

Answer 7

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

Question 8

expressivity

Answer 8

degree to which a characteristic is expressed

Question 9

incomplete penetrance

Answer 9

the genotype does not produce expected phenotype

Question 10

codominant traits

Answer 10

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

Question 11

lethal allele

Answer 11

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

Question 12

multiple alleles

Answer 12

“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)

Question 13

gene pool

Answer 13

all genes carried by members of a population

Question 14

gene interaction

Answer 14

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

Question 15

epistasis

Answer 15

one gene masks the expression of a gene at another locus

Question 16

epistatic gene

Answer 16

the gene that does the masking

Question 17

hypostatic gene

Answer 17

the gene whose effect is masked

Question 18

recessive epistasis

Answer 18

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

Question 19

sex influenced traits

Answer 19

determined by autosomal genes, expressed differently in males and females

Question 20

sex limited characteristics

Answer 20

determined by autosomal genes, expressed in only one sex

Question 21

dominant epistasis

Answer 21

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

Question 22

negative epistasis

Answer 22

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

Question 23

qualitative traits

Answer 23

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

Question 24

quantitative traits

Answer 24

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

Question 25

polygenic traits

Answer 25

traits that are influenced by many genes

Question 26

multifactorial traits

Answer 26

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

Question 27

additive equal gene action

Answer 27

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

Question 28

continuous characteristic

Answer 28

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

Question 29

genomic imprinting

Answer 29

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

Question 30

epigenetics

Answer 30

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

Question 31

complementation

Answer 31

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

Question 32

modified dihybrid ratio

Answer 32

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

Question 33

general dihybrid genotypes

Answer 33

A_B_ ; A_bb; aaB_; aabb

Question 34

(expression pattern - monohybrid crosses) complete dominance

Answer 34

3:1

Question 35

(expression pattern - monohybrid crosses) incomplete dominance

Answer 35

1:2:1

Question 36

(expression pattern - monohybrid crosses) lethal alleles

Answer 36

2:1

Question 37

(expression pattern - monohybrid crosses) sex-linked

Answer 37

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

Question 38

(expression pattern - dihybrid crosses) complete dominance

Answer 38

9:3:3:1

Question 39

standard Mendelian cross - monohybrid

Answer 39

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

Question 40

standard Mendelian cross - dihybrid

Answer 40

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

Question 41

monohybrid cross (non-standard Mendelian cross)

Answer 41

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

Question 42

reciprocal mendelian cross - monohybrid

Answer 42

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

Question 43

anticipation

Answer 43

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

Question 44

genetic maternal effect

Answer 44

phenotype of offspring is determined by genotype of mother

Question 45

affected person on pedigree

Answer 45

shape is filled in

Question 46

unaffected person on pedigree

Answer 46

shape is not filled in

Question 47

deceased person on pedigree

Answer 47

slash through shape

Question 48

proband

Answer 48

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

Question 49

fraternal twins on pedigree

Answer 49

shapes are connected by a triangle

Question 50

identical twins on pedigree

Answer 50

shapes are connected by complete triangle

Question 51

pedigree

Answer 51

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

Question 52

autosomal recessive trait

Answer 52

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)

Question 53

autosomal dominant trait

Answer 53

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

Question 54

X-linked recessive trait

Answer 54

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

Question 55

X-linked dominant trait

Answer 55

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

Question 56

Y-linked trait (holandric trait)

Answer 56

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

Question 57

cytoplasmic inheritance

Answer 57

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)

Question 58

penetrance

Answer 58

proportion of individuals with a genotype who express expected phenotypes

Question 59

completely penetrant

Answer 59

individuals with genotype express expected phenotype 100% of the time

Question 60

incompletely penetrant

Answer 60

individuals with genotype do not always express expected phenotype

Question 61

expressivity

Answer 61

degree of expression of phenotype

Question 62

types of chromosomal mutations

Answer 62

chromosome rearrangement, aneuploidy, polyploidy

Question 63

chromosomal mutation

Answer 63

variations in number/structure of chromosomes

Question 64

euploid

Answer 64

normal/diploid state of chromosomes with correct structure

Question 65

chromosome rearrangement

Answer 65

altered structure of chromosome

Question 66

types of chromosomal rearrangements

Answer 66

duplication, deletion, inversion, translocation

Question 67

duplication

Answer 67

segment of chromosome is duplicated

Question 68

tandem duplication

Answer 68

duplicated region is immediately adjacent to original segment

Question 69

displaced duplication

Answer 69

duplicated region is located a distance away from original segment

Question 70

reverse duplication

Answer 70

duplicated region order is backwards from original order

Question 71

segmental duplication

Answer 71

duplications greater than 1000 bp in length

Question 72

deletion

Answer 72

segment of chromosome is deleted

Question 73

pseudodominance

Answer 73

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

Question 74

haploinsufficient gene

Answer 74

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

Question 75

duplication and deletion occur due to

Answer 75

unequal crossing over, where chromosomes "slip"

Question 76

inversion

Answer 76

segment of chromosome is turned 180 degrees

Question 77

paracentric inversion

Answer 77

does not include centromere

Question 78

pericentric inversion

Answer 78

includes centromere

Question 79

position effect

Answer 79

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

Question 80

translocation

Answer 80

segment of chromosome moves from one chromosome to a nonhomologous chromosome

Question 81

nonreciprocal translocation

Answer 81

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

Question 82

reciprocal translocation

Answer 82

two way exchange of segments between chromosomes

Question 83

aneuploidy

Answer 83

an increase or decrease in number of chromosomes

Question 84

aneuploidy types ("-omy")

Answer 84

nullisomy, monosomy, trisomy, tetrasomy

Question 85

nullisomy

Answer 85

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

Question 86

monosomy

Answer 86

loss of a single chromosome; 2n - 1

Question 87

trisomy

Answer 87

gain of a single chromosome; 2n + 1

Question 88

tetrasomy

Answer 88

gain of two homologous chromosomes; 2n + 2

Question 89

aneuploidy and polyploidy often caused by

Answer 89

nondisjunction (incorrect segregation of chromosomes)

Question 90

polyploidy

Answer 90

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

Question 91

polyploidy types

Answer 91

autopolyploidy, allopolyploidy

Question 92

autopolyploidy

Answer 92

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)

Question 93

allopolyploidy

Answer 93

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

Question 94

unbalanced gametes

Answer 94

gametes with varying number of chromosomes

Question 95

amphidiploid

Answer 95

allopolyploid consisting of two combined diploid genomes

Question 96

recombination

Answer 96

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

Question 97

linked

Answer 97

genes located closely together on same chromosome

Question 98

linkage group

Answer 98

linked genes belonging in the same group on same chromosome

Question 99

linkage groups are broken by

Answer 99

crossing over and recombination

Question 100

genes are unlinked

Answer 100

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

Question 101

genes are completely linked

Answer 101

only nonrecombinant progeny are produced

Question 102

genes are incompletely linked

Answer 102

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

Question 103

0% recombinant offspring

Answer 103

completely linked genes

Question 104

0.1-49.9% recombinant offspring

Answer 104

incompletely linked genes

Question 105

50% recombinant offspring

Answer 105

unlinked genes

Question 106

recombinant

Answer 106

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

Question 107

recombination frequency

Answer 107

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

Question 108

frequency of recombination between two loci is related to

Answer 108

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

Question 109

if recombination frequency is 50%

Answer 109

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

Question 110

interchromosomal recombination

Answer 110

between genes located on different chromosomes

Question 111

intrachromosomal recombination

Answer 111

between genes located on same chromosome

Question 112

linkage maps

Answer 112

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)

Question 113

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

Answer 113

located on different chromosomes or very far apart on same chromosome

Question 114

the further genes are apart on a chromosome

Answer 114

the greater the underestimation of genetic differences