Test 2 Flashcards
(112 cards)
1
Q
T/F Most alleles act in a dominant recessive manner
A
F
2
Q
Mutation
A
the ultimate source of alleles
3
Q
how do new phenotypes arise
A
from changes in the functional activity of the gene product
4
Q
ways that functional activity of gene product is changed
A
eliminating enzyme function
changing relative enzyme efficiency
changing overall enzyme function
the enzyme could be more or less active
5
Q
what are the mutation types
A
loss of function mutations, gain-of-function muta tions, neutral mutations
6
Q
what is a loss of function mutation
A
"inactivating mutations" mutation causes loss of wild type function lose function of that allele gene is partially or fully inactive usually recessive
7
Q
what is a gain of function mutation
A
“activating mutation”
mutation enhances the function of wild type
quantity of gene product increases
enzyme or gene mutates so that it has extra activity than the original allele, need gene quantity to increase
causes enhanced activation of the gene or its products
dominant
8
Q
what is a neutral mutation
A
no change in phenotype
no change in evolutionary fitness of the organism
no selective benefit or negative selective effect
cant be seen
9
Q
what is the fitness of an organism
A
depends on how many offspring you have
10
Q
what is it called if the loss of a gene is complete
A
null allele
11
Q
dominant-negative mutation
A
called anti morphic mutations
mutant allele acts antagonistically to the wild type allele
overrides and actively shuts down activity of another allele
12
Q
example of a neutral mutation
A
silent mutation
13
Q
example of dominant-negative mutation
A
marphans
14
Q
incomplete or partial dominance
A
intermediate phenotype
neither allele is dominant
heterozygotes are an in between
15
Q
how to designate a gene without a dominant or recessive trait
A
Superscript
16
Q
Incomplete dominance
Cross true-breeding red flowers with true-breeding white flowers
A
get 100% heterozygote pink flowers
17
Q
Incomplete dominance
cross 2 heterozygotes
A
1:2:1 genotype and phenotypic ration
18
Q
example of incomplete dominance in humans
A
Tay-Sachs
19
Q
how does tay sachs work
A
heterozygotes will onyl have 1/2 the enzyme activty
homozygous dominant will have all enzyme activity
homozygous recessive will have no enzyme activity
20
Q
codominance
A
two alleles of a single gene produce 2 gene products
joint expression of both alleles in heterozygote
no dominance or recessiveness
see both alleles
Distinct expression of gene products of both alleles:
21
Q
example of codominance in humans
A
MN Blood Groups
22
Q
how is MN blood groups characterized
A
by antigen glycoprotein: found on surface of red blood cells
23
Q
what are the glycoproteins that exist on blood
A
M and N
24
Q
What glycoproteins can we exhibit on blood
A
either M or N or both
25
multiple alleles
3 or more alleles of the same gene
| resulting mode of inheritance is unique
26
human example of multiple alleles
ABO blood groups
27
what antigens are present on the surface of red blood cells
A and B
28
which antigens are dominant to eachother for blood
iA codominant to iB
| i recessesive to A and B
29
what are essential genes
absolutely required for survival
mutations can be tolerated if heterozygous
a gene is considered essential when loss of its function compromises the viability or fitness of the organism
30
what happens to homozygous recessive individuals of an essential gene
will not tolerate it, therefore will not survive
31
what are apart of essential genes
lethal alleles
32
recessive lethal allele
results in homozygous recessive individuals and do not survive
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dominant lethal allele
presence of one copy of the allele results in death
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example of a dominant lethal allele
Huntingtons
35
what is huntingtons
carry the allele, late-onset, characterized by progressive degeneration of nervous system, dementia, and early death
36
what is a homozygous lethal allele
must have 2 copies of the allele and could result in a mutant phenotype, 2 copies and the organism will die so you won't see a new phenotype, carrier of the allele may cause mutant phenotype
37
T/F phenotypes are influenced by only one gene
False
38
what can contribute to the development of common phenotypes
cellular functions
39
what is epistasis
the interaction of genes that are not alleles, in particular, the suppression of the effect of one such gene by another, an allele of one gene hides or masks the visible output, or phenotype of another gene,
40
what is the Bombay phenotype
incomplete formed H substance which is a rare recessive mutation at locus results in the inadequate substrate for the enzyme, rare mutation in gene FUT1
41
FUT1 gene
FUT1 gene encodes the enzyme fucosyltransferase
42
how does an AB and A blood parent get an O child?
the parents must be heterozygous for FUT1 at the fucosyltransferase locus which prevents the parent from producing H substance so she is behaving as a type O
43
dominant epistasis
the dominant allele at one loci masks an allele at second loci, phenotype happens regardless of the second loci allele
44
recessive epistasis
2 recessive alleles will be one color no matter the other alleles
45
complementation analyses
occurs when 2 strains of an organism with different homozygous recessive mutations that produce the same mutant offspring with the wild type phenotype when mated or crossed
46
what are the possibilities of complementation analyses
mutations occur in the same gene
one mutation affects the expression of another
one mutation may result in an inhibitory product
47
pleiotropy
expression of single gene has mutliple phenotypic events
48
example of pleiotropy
marfans
49
what is marfans syndrome
autosomal dominant mutation in gene encoding connective tissue protein fibrillin, results on multiple pleitropic events, affects eyes, aorta, bones and other tissues
50
what are pleiotropic expressions of a trait influenced by
environment and genotype
51
penetrance
Percentage of expression of mutant genotype in population
52
expressivity
Range of expression of mutant phenotype
| Result of genetic background differences and/or environmental effects.
53
eyeless mutation in drosophilia
Homozygous recessive mutant gene.
| Phenotype ranges from presence of normal eyes to absence of one or both eyes.
54
what can physical location on a gene do
influence gene expression
55
what events modify expression in terms of physical location
translocation and inversion
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conditional mutations
temperature effects phenotypes
| modifies exprected ratios
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examples of conditional mutations
siamese cats and himalayan rabbits
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what is special about siamese cats and himalayan rabbits
darker fur on extremities which are cooler because they are farther away from the core, enzymes responsible for functions loose catalytic function at different temperatures
59
extranuclear inheritance
inheritance patterns which vary from traditional biparental inheritance of nuclear genes, inherit things based on mitochondrial DNA, genes in mitochondrial are not inherited normally becuase they generally only come form mom
60
organelle heredity
organisms phenotype affected by genes in mitochondria and chloroplasts
61
maternal affect
Organism’s phenotype determined by genetic information expressed in maternal gamete.
Following fertilization, developing zygote’s phenotype is determined not by individual’s genotype but by gene products directed by mother’s genotype
62
heteroplasmy
Cell may or may not have mutant genes in organelles—phenotype may not be revealed.
More than one type of organellar genome
63
what are the identified mitochondrial gene products
13 proteins required or aerobic cellular respiration.
22 transfer RNA’s —required for translation.
2 ribosomal RNA’s —required for translation.
64
what does MERF stand for
Myoclonic epilepsy and ragged-red fiber disease
65
what is merf
Specifically the gene encoding tRNALys
Interferes with translation—leads to disorders.
Affected cells exhibit heteroplasmy.
Contain mixture of normal and abnormal mitochondria.
66
what are the types of chromosomal modifications
deletion, translocation, inversion, duplication,
67
what type of ploidy is a monosomy
aneuploidy
68
monosomy
loss of single chromosome from diploid genome
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what is a euploidy
complete haploid set of chromosomes are present
70
what is polyploidy
more than 2 sets of chromosomes are present
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what is an aneuploidy
where you are missing one or more chromosomes or you have an extra one
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autopolyploidy
Addition of one or more sets of chromosomes identical to the haploid complement of the same species, each identical set of chromosomes is identical to the parent species
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how does autoploidy occur
a diploid gamete is produced
| two sperm fertilize one ovum
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how to get a diploid gamete
failure of chromosomes to segregate during meiotic division
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allopolyploidy
results from hybridizing 2 closely related species, the hybrid plant may be sterile, chromosomes are not homologous, Combination of chromosome sets from different species as a consequence of hybridization
76
nondisjunction
chromosomes fail to separate in meiosis or mitosis
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disjunction
separation of homologous chromatids
78
what is occurring when nondisjunction happens in meiosis 1
tetrads fail to separate
79
what is occurring when nondisjunction happens in meiosis 2
sister chromatids fail to separate
80
what causes nondisjunction
mutations in the spindles if they aren't attached to all the centromeres
81
haploinsufficiency
a single copy of a gene is insufficient to provide life-sustaining function for organism
82
extra chromosome in a trisomy
produced more viable organism than loss of chromosome
83
deletion
remove part of chromosome
84
duplication
add genes we didn't see before
85
inversions
invert/flip the chromosomes
86
translocation
piece of a chromosome moves to another piece
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nonreciprocal translocation
genes are not swapped just taken from one, lost from another
88
reciprocal translocation
share, swap pieces on nonhomologous chromosomes, different pieces of genes
89
terminal deletion
the deletion that occurs near the end
90
intercalary deletion
deletion from the interior of the chromosome
91
can synapsis occur with intercalary deletions
yes
92
what is a chromosomal duplication?
a repeated segment of a chromosome that arises through replication error before meiosis, unequal crossing over between synapsed chromosomes
93
what does unequal crossing over cause
duplication in one and deletion in the other
94
what are the results of duplications
gene redundancy
phenotypic variation
source of genetic variability during evolution
95
when is gene redundancy seen
in ribosomal RNAs there are multiple copies of a genes that code of rRNA, need lots of this gene product in the cell to support protein synthesis
96
example of an organism that uses gene redundancy
frogs
97
where are the many copies of rDNA found in the chromosome
in the nucleolar organizer region
98
ways new genes arise
non functionalization
neo functionalization
sub functionalization
99
what is non-functionalization
the duplicated copy mutates on itself and is eroded away by the mutations
100
what is neo-functionalization
mutation takes up new sequence and forms a new function
101
what is sub-functionalization
both copies split up the chore of the original gene, split apart between copies
102
what is an inversion
rearrangment of linear gene sequences
no loss of genetic information
segment of a chromosome is turned 180 degrees
103
what must happen for an inversion to occur
there must be 2 breaks in the chromosome, chromosomal loop forms creating sticky ends that will join together
104
what are the types of inversion
pericentric and paracentric
105
what is paracentric
does not include the centromere
106
what is pericentric
includes the centromere
107
what are the consequences of inversion during gamete formation
linear synapse is not possible if only one member of the homologous pair has an inverted segment, inversion heterozygotes can form
108
what is an inversion heterozygote
an organism with one inverted chromosome and one noninverted homolog
109
how do inversion heterozygotes pair
requires an inversion loop
110
what happens with crossing over in paracentric inversion
can get dicentric and acentric recombinants
111
what is a dicentric chromatid
2 centromeres
112
what is a acentric chromatid
lacks a centromere
