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Flashcards in Castle Williamson Deck (167):
1

genetics

study of genes, heredity and genetic variation in living organisms. it is generally considered a field of biology but overlaps many life sciences and is strongly linked with the study of informations systems

2

molecular genetics

studies structure and function of genes at a molecular level. study of chromosomes and gene expression of an organism can give insight into hereditary, genetic variation, epigenetics and mutation

3

luxturna

genetically modified virus that ferries a healthy gene into the eyes of patients with retinal dystrophy-- first gene therapy for inherited diseases

4

Genome

a complete set of genetic instructions for any organism

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transmission genetics

classical genetics, how traits are passed from one generation to the next

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molecular genetics

gene structure, function, and regulation

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population genetics

the study of genetic composition of groups (populations) and how gene frequency changes geographically or with time-- essentially the study of evolution. also the analysis of patterns, causes and effects of health and disease conditions in defined populations

8

model genetic organsims

organisms with charcteristics that make them useful for genetic analysis
- fruit fly, E. coli, C. elegans, yeast, zebrafish

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characteristics of model organisms

-short generation time
production of numerous progeny
-ability to carry out controlled genetics crosses
-ability to be reared in lab environment
-availability of numerous genetic variants
-accumulated body of knowledge about their genetics systems

*animal models are only valuable because of the basic similarity among all living things

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C. elegans

first multicellular organism to have its whole genome sequenced

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What are some of the implications of all organisms having similar genetic systems?

-that all life forms are genetically related
-research findings on one organisms gene function can often be applied to other organisms
-genes from one organism can often exist and thrive in another organsims

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Lamarckianism

if an adult organism changes during life in order to adapt to its environment, those changes are passed on to its offspring

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pangenesis

that that information needed to specify body parts traveled to the reproductive organs in packets (gemmules) which were packaged into sperm or eggs. the packets were then distributed as needed in the resulting embryo

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Theory of germ plasm

multicellular organisms organisms produce germ cells that contain and transmit heritable info, and somatic cells which carry out ordinary bodily functions and do not provide hereditary info

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gene

a distinct sequence of nucleotides forming part of a chromosome, a unit of hereditary that is transferred from parent to offspring

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allele

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

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chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carry genetic info in the form of genes

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Prokaryotic cells

nucleus- Absent
cell diameter- small 1-10 micrometer
genome-once circular DNA molecule
amount of DNA- relatively small
membrane-cound organelles- absent

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eukaryotic cells

nucleus- present
cell diameter- relatively large 10-100 micrometers
genome- multiple linear DNA molecules
DNA- complexed with histones
Amount of DNA- relatively large
membrane-bound organelles- present

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viruses

neither prokaryotic nor eukaryotic
outer protein coat surrounding nucleic acid

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homologous chromosomes

similar but not identical. each homolog carries the same genes in the same order, but the alleles for each trait may not be the same

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diploid cells

carry two sets of genetic information

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haploid cells

carry one set of genetic info-- gametes

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centromere

attachment point for spindle microtubules

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telomeres

tips of linear chromosomes-- gradually shorten over lifetime

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origin of replication

where the DNA synthesis starts

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submetacentric

centromere situated so that one chromosome arm is somewhat shorter than the other

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metacentric

centromere in the middle

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telocentric

centromere at the end with no short arm visible in a light microscope

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acrocentric

centromere near the end producing a short arm

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interphase

an extended period between divisions, DNA synthesis, and chromosome replication phase

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M phase

mitotic phase

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Check points

key transition points
G1/s- check point - regulated decision point
G2/M- check point- only passed if DNA completely replicated and undamaged

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mitosis

separation of sister chromatids

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cytokinesis

separation of cytoplasm

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prophase

chromosomes condense and mitotic spindle forms

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prometaphase

nuclear envelope disintegrates and spindle microtubules anchor to kinetochores

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metaphase

chromosomes align on the metaphase plate, spindle assembly check point

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anaphase

sister chromatids separate becoming indivual chromosomes that migrate toward spindle poles

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Telophase

chromosomes arrive at spindle poles, the nuclear envelope re-forms and the condensed chromosomes relax

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What is the correct order of stages in the cell cycle

G1, S, prophase, metaphase, anaphase

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meiosis

production of haploid gametes

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fertilization

the fusion of haploid gametes

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genetic variation

consequence of meiosis

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meiosis 1

separation of homologous chromosome pairs and reduction of the chromosome number by half

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meiosis 2

separation of sister chromatids also known as equational divison

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meiosis 1 -- prophase 1

synapsis- close pairing of homologous chromosomes
tetrad- closely associated 4-sister chromatids of 2 homologous chromosomes
crossing over

48

crossing over

crossing over of chromosome segments from the sister chromatid of one one chromosome to the sister chromatid of the other synapsed chromosomes- exchange of genetic info the first mechanism that generates genetic variation in newly formed gametes
-can result in unequal exchange of genetic material producing chromosomes with deleted or duplicated regions

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meiosis 1 -- metaphase 1

random alignment of homologous pairs of chromosomes along the metaphase plate

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meiosis 1-- anaphase 1

separation of homologous chromosome pairs and the random distribution of chromosomes into 2 newly divided cells- second mechanism of generating genetic variation in formed gametes

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which of the following events take place in meiosis 2 but not meiosis 1

separation of chromatids

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cohesin

is a protein complex that holds the chromatids together and is key to the behavior of chromosomes in mitosis and meiosis

53

spermatogenesis

male gamete production

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oogenesis

female gamete production

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Klinefelter sydrome

XXY male y overrides x always

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heredity

passing on of physical or mental characteristics genetically from one generation to another

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heritability

the proportion of total variation between individuals in a given population that is due to genetic variation

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pheomelanin

predominant pigment that results in red hair

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monohybrid cross

cross between two parents that differ in a single characteristic
-3:1

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homozygous

true breeding the alleles are identical

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principle of segregation (Mendel's First Law)

ech individual diploid organism possesses two alleles for any particular characteristic and only one is passed to offspring

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independent assortment

alleles segregate independently when gametes are formed

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Concept of dominance

when 2 different alleles are present in a genotype only the trait encoded by one of them - the dominant allele- is observed in the phenotype. the other is recessive

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multiplication rule

multiply the probability of independent events happening simultaneously

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addition rule

when two events are mutually exclusive the probability that either A or B will occur is the sum of the probability of each event

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conditional probability

the probability of an event A given that another B has already occurred

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dihybrid cross

involves 2 traits with differing alleles
-easiest if they are dominant and recessive
-relate the principle of independent assortment to meiosis
-genes located on different chromosomes will sort independently
- 9:3:3:1

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chi-square goodness of fit

a statistical test that indicates the probability that the difference between the observed and expected values is due to chance
assumptions:
- random sample- sample data is a random sample of a large population
-sample size- is sufficiently large to prevent small sample error
-independence- observations are independent of each other

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degrees of freedom

number of values that are free to vary minus 1

70

how are the principles of segregation and independent assortment related and how are they different

- genes encoding different characteristics separate and assort independently of one another when they are not located close together on the same chromosome
- during this process two alleles of the same gene encoding one characteristic still have to be segregated from each other during the formation of gametes

71

multiple testing correction

refers to recalculating probabilities obtained from a statistical test which was repeated multiple times
- threshold to achieve significance is more difficult to achieve

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heterogametic

produces 2 different gamete types - 2 different sex chromosomes

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hermaphroditism

both sexes in the same organism mostly invertebrates

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monoecious

both male and female reproductive structures in the same organism, plants

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dioecious

either male or female reproductive structures but not both

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how does the heterogametic sex differ from homogametic sex

gametes of heterogametic sex have different sex chromosomes, gametes of homogametic sex have the same sex chromosome

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haplodiploidy system

haploid set- male
diploid set- female
bees

78

turner syndrome

XO female

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dosage compensation

inactivation of 1 X chromosome to compensate for different X dosage between the sexes

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Lyon hypothesis

named after Mary Lyon suggested that dosage compensation in mammals by inactivation of all but 1 X chromosome in cells with more than one X chromosome. theBarr body visible in some female mammalian cells is an inactivated X chromosome

81

Mosaicism

a condition in which cells with in the same person have different genetic makeup
when different X chromosomes are inactivated in neighboring cells

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genetic linkage

the tendency of alleles that are located close together on a chromosome to be inherited together during meiosis. linked genes will segregate together and not obey mendels second law

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linkage disequilibrium

the non-random association of alleles at different loci. Loci are said to be in linkage disequilibrium when the frequency of association of their different allele is higher or lower that what would be expected if the loci were segregating independently

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non-mendelian inheritance

refers to any patter of inheritancein which traits do not segregate in accordance with Mendel's laws

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complete dominance

phenotype of the heterozygote is the same as the phenotype of one of the homozygotes

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incomplete dominance

phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes

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codominance

phenotype of the heterozygote includes the phenotypes of both homozygotes

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penetrance

the percentage of individuals having a particular genotype that express the expected phenotype

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expressivity

the degree to which a character is expressed

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complete penetrance

everyone who inherits the disease causing alleles has some symptoms

91

incomplete penetrance

some individuals do not express the phenotype even though they inherit the alleles ex: polydactyly

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variable expression

symptoms vary in intensity in different people
ex: two extra digits vs three

93

lethal allele

causes death at an early stage of development and so some genotypes may not appear among progeny

94

gene interaction

effects of genes at one locus depend on the presence of genes at other loci
-gene interaction can produce novel phenotype
-gene interaction with epistasis: one gene masks the effect of another

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epistasis

one gene masks or influences the effect of another gene
ex: coat color in dogs

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recessive epistasis

recessive alleles at one locus mask the mask the phenotypic locus of other gene locus

ex: bombay blood type-- no H antigen made

97

dominant epistasis

when the dominant allele masks the expression of all alleles of another gene

ex: summer squash need two enzymes to get yellow color if you only have one you get green but if you have a dominant W allele it blocks the whole cascade and you get a white squash

98

duplicate recessive epistasis

9:7 ratio when recessive alleles at either two loci can mask the expression of dominant alleles at the two loci
A.K.A complementary epistasis

ex: snails - to get a brown snail you have to have 2 enzymes so at least one dominant allele is needed at each locus to get brown snails. if either locus is homozygous recessive you get white snail

99

pleiotropy

one gene is able to affect multiple phenotypic characters

100

complementation

occurs when two strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype produce offspring with the wild type phenotype when mated or crossed
ex: change in wing structure in flies

101

sex- influenced traits

are controlled by genes present on autosomes hence such genes are present in both sexes but their expression is different in males vs. females usually because the expression responds differently to androgens and estrogens
Ex: soft vs coarse facial hair, male pattern baldness

phenotype determined by: autosomal genes that are more readily expressed in one sex

102

sex-limited characteristics

characteristics are inherited according to mendel's principles
-precocious puberty

phenotype determined by: autosomal genes whose expression is limited to one sex

103

genomic imprinting

differential expression of genetic material depending on whether it is inherited from the male or female parent

104

epigenetics

phenomena due to alterations to DNA that do not include changes in the base sequence often affect the way in which the DNA sequences are expressed

105

IGF2

protein hormone involved in the regulation of cell proliferation, growth, migration, differentiation, and survival. preferentially expressed in early embryonic and fetal development and in a wide variety of somatic tissues. exclusively from paternal allele

106

anticipation

a genetic trait becomes more strongly expressed or is expressed at an earlier state as it is passed from generation to generation
-occurs due to expansion of an unstable region of DNA from generation to generation
Ex- fragile X, Huntingtons, friedreich ataxia, myotonic dystrophy

107

Fragile X

genetic disorder which occurs as a result of a mutation of the fragile X mental retardation 1 (FMR1) gene on the X chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5" untranslated region of FMR1. most common cause of inherited learning difficulties

108

temperature dependent sex determination

changes in temperature during embryogenesis change gene expression resulting resulting in a significant change in phenotype

109

temperature sensitive allele

an allele whose product is functional only above or below a threshold temperature
Ex: simese cats and himalayan rabbits

110

discontinuous characteristics

relatively few phenotypes

111

continuous characteristics

continuous distribution of phenotypes; occurs when genes at many loci interact

112

polygenic characteristics

characteristics encoded by genes at many loci

113

heterosis

A.K.A- hybrid vigor
is the improved or increased function of any biological quality in a hybrid offspring of pure bred strains
-opposite of inbreeding
-increase of heterozygosity improves such characteristics as size, growth rate, or yield of a hybrid organism over either of its parents
-ex: mule

114

adermatoglyphia

the absence of ridges on the skin on the pads of the fingers and toes

gene: SMARCAD1

115

pedigree chart

a document used by genealogist in study family history

116

pedigree

pictorial representations of a family hx, a family tree that outlines inheritance of one or more characteristics

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proband

the person from whom the pedigree is initiated

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common rule

requirements for assuring compliance by research institutions, requirements for researchers obtaining and documenting informed consent, requirements for IRB membership, function, operations, review of research, and record keeping, additional protection for certain vulnerable subjects- pregnant women, prisoners, and children

119

autosomal recessive traits

normally appear with equal frequency in both sexes and seem to skip generations

120

autosomal dominant traits

normally appear with equal frequency in both sexes and don't skip generations
Ex: familial hypercholesterolemia: very high levels of LDL

121

X-linked recessive traits

appear more often in males than in females and are not passed from father to son
Ex: Duschenne's MD, hemophilia

122

X-linked hypophosphatemia

ex: of X-linked dominant disorder
form of rickets that differs bc ingestion of vitamin D doesn't really help

123

Y-linked traits

appear only in males and are passed from father to all of his sons

124

dizygotic twins

not identical

125

monozygotic twins

identical

126

concordant trait

a trait shared by both members of a twin pair

127

concordance

the percentage of twin pairs that are the same for a trait

128

chorionic villus sampling

-CVS can be performed early in pregnancy
-under US guidance a catheter is inserted through the vagina and cervix into the uterus
-placed into contact with the chorion, the outer layer of the placenta
-suction removes a small piece of chorion
-cells of chorion are used directly for many genetic tests and culturing is not required

129

Amniocentesis

-under US guidance a sterile needle is inserted through the abd wall into the amniotic sac
-a small amount of fluid is withdrawn through the needle
-the amniotic fluid contains fetal cells which are separated from the amniotic fluid
-cultured cells
-tests are performed on cultured cells

130

Recombination

alleles sort into new combinations

131

complete linkage

leads to nonrecombinant gametes and nonrecombinant progeny

132

crossing over

disrupts linked and leads to recombinant gametes and recombinant progeny

133

single crossover

half nonrecombinant gametes and half recombinant gametes

134

calculating recombination frequency

recombination= (No. recombinant progeny/total no. of progeny) x 100%

135

coupling (cis configuration)

one chromosome contains both wild type alleles, one chomosome contains both mutant alleles

136

repulsion (trans configuration)

wild-type allele and mutant allele are found on the same chromosome

137

genetic maps

are determined by recombinant frequency
map unit or centimorgan= crossover frequency of .01 in a single generation

138

physical maps

are determined by nucleotide position

139

coefficient of coincidence

number of observed double crossovers/number of expected double crossovers

140

interference

1- coefficient of coincidence

141

two-stand double cross over

0% detectable recombinants

142

three-strand double cross over

50% detectable recombinants

143

four-strand double cross over

100% detectable recombinants
50% average detectable recombinants

144

nail-patella syndrome

autosomal dominant- poorly developed nails and patellas, linkage between ABO blood types

145

haplotype

a set of DNA variations or polymorphisms that tend to be inherited together

146

genomic wide association studies (GWAS)

examine genetic sequence variants across the entire genome to find those that are associated with a trait or disease

147

karyotyping

chromosomes prepared form actively dividing cells, halted in metaphase with colchicine, chromosomes arranged according to size

148

Banding

G bands: giemsa stain, heterochromatin stains dark euchromatin stains light
Q bands: quinacrine stain, AT rich regions
C bands: reveals centromeric heterochromatin
R bands: regions rich in C-G base pairs
T bands: telomeric banding after heat denaturation

149

aneuploidy

loss or gain of chromosomes
causes: deletion of centromere during mitosis, robertsonian translocation, nondisjunction during meiosis and mitosis

150

polyploidy

those containing more than two complete paired homologous sets of chromosomes

151

deletion

loss of chromosomal segments
effects: imbalances in gene products, expression of normally recessive gene (pseudodominance), haplosufficiency

152

paracentric inversion

an inversion in which the breakpoints are confined to one arm of a chromosome, the inverted segment does not span the centromere

153

pericentric inversion

an inversion in which the breakpoints occur on both arms of a chromosome, the inverted segment spans the centromere

154

robertsonian translocation

rare chromosomal rearrangements that in humans generally occur in the five acrocentric chromosomes 13, 14, 15, 21, 22

155

reciprocal translocation

an exchange of material between two nonhomologous chromosomes

156

nonreciprocal translocation

transfer of genes from one chromosome to another nonhomologous chromosome

157

Dicentric

a fragment results without a centromere and the other had 2 centromeres
results in nonfxn'l gametes

158

nullisomy

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

159

monosomy

loss of a single chromosome
2n-1

160

trisomy

gain of a single chromosome
2n+1

161

tetrasomy

gain of two homologous chromosomes
2n+2

162

autopolyploidy

from a single species

163

allopolyploidy

from 2 or more species

164

medical cytogenetics

part of clinical medicine that studies a relationship between chromosomal alterations and genetic diseases in humans

165

fluorescence in situ hybridization (FISH)

technique in which DNA probe containing 1 or more genes is labeled with fluorescent dye and then hybridized to interphase or metaphase cells, used to detect small regions of deletions or duplications, used to examine specific regions of the genome in non-dividing tissues, used to map genes

166

constitutional cytogenetic abnormality

homogenous abnormality- anomaly in oocyte formation
mosaic abnormality- anomaly in zygote formation

167

acquired chromosomal

anomaly in somatic cells