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Flashcards in Exam 2 Deck (97):
1

3 point cross

Used to determine the loci of three genes in an organism's genome. An heterozygous individual is crossed with a homozygous recessive individual. Results in 8 different phenotypic classes

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Allopolyploid

Polyploid condition formed by the union of two or more distinct chromosome sets with a subsequent doubling of chromosome number

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Allosomes

Sex chromosome that differs from an ordinary autosome in form, size, or behavior

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Allotetraploid

An allopolyploid containing two genomes derived from different species

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Amphidiploid

A plant originating from hibridization between two species in which the chromosome number is the sum of the chromsosme numbers of both parental species

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Aneuploidy

A condition in which the chromosome number is not an exact multiple of the haploid set

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Autopolyploid

Polyploid condition resulting from the duplication of one diploid set of chromosomes

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Autosomes

Chromosomes other than the sex chromosomes

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Autotetraploid

An autopolyploid condition composed of four copies of the same genome

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Bar eye (Drosophila)

Eye of the fly is thinner than normal, due to a duplicated region in 16A of the chromosome

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Barr body

Densely staining DNA-positive mass seen in the somatic nuclei of mammalian females. Represents an inactivated X chromosome

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CentiMorgans/ map units

Unit of distance between genes on chromosomes representing 1 percent crossing over between two genes

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Chiasma (chiasmata)

Crossed strands of nonsister chromatids seen in diplotene of the first meiotic division. Regarded as the cytological evidence for exchange of chromosomal material (crossing over)

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Chromosome doubling

Brought about by chemical or physical agents that block the function of the spindle fibers. Used to induce polyploidy in species hybrids to restore the fertility of the hybrids

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Colchicine

An alkaloid compound that inhibits spindle formation during cell division used during the preparation of karyotypes

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Coupling phase

Dominant alleles on the same homolgue chromsome and both recessive alleles are on the other homologue chromosome. Parental gametes are AB and ab

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Cri du chat syndrome

5p- is a genetic condition caused by the deletion of genetic materila on the p arm of chromosome 5. Infants with this condituion usually have a high pitched cry that sounds like a cat. Intellectual disability and delayed development result

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Crossing over

Exchange of chromosomal material between homolgoous chromosomes by breakage and reunion

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Crossover gamete

Gamete that results which does not resemble either parent

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Deletion (deficiency)

A chromosomal mutation involving the loss of chromosomal material

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Diploid

Condirion in which each chromosome exists in pairs

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Disjunction

The separation of chromosomes during the anaphase stage of cell division

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Dosage compensation

A genetic mechanism that equalizes the levels of expression of genes at loci on the X chromosome

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Double cross-over

Two separate events of chromosome breakage and exchange occuring within the same tetrad during meiois

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Double fertilization in plants

Joining of a gemale gametophyte (embryo sac) with two male gametes (pollen grains)

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Down syndrome

Trisomy 21. Intellectual disability, characteristic facial appearance, and weak muscle tone in infancy

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Drosophila

Various, small fruit flies with the genus Drosophila, used in genetic research to study patterns of inheritance and the functions of genes

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Duplication

A chromosomal aberration in which a segment of the chromosome is repeated

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Euploidy

Polyploid with a chromosome number that is an exact multiple of a basic chromosome set

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Fragile X-Chromosome

Genetic condition leading to developalmental problems including learning disabilities and cognitive impairment. Males affected more than femals. Caused by mutations in the FMR1 gene

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Gametogenesis

The process by which gametes, or germ cells, are produced in an organism

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G-banding pattern

Giemsa banding, technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. Useful for identifying genetic diseases

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Gene dosage

Number of copies of a given gene present in the cell or an orgainsm

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Genetic anticipation

The phenomenom in which the severity of symptoms in genetic disorders increases from generation to generate and the age of onset decreases from generation to generation. It is caused by the expansion of trinucleotide repeats within or near a gene

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Genetic map

A graphic representation of the arrangement of a gene or a DNA sequence on a chromosome. Used to locate and identify the gene or group of genes that determines a particular inherited trait

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Haploid

Cell or organism having one member of each pair of homolgous chromsomes

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Hemizygous

Having a gene present in a single dose in an otherwise diploid cell. Usually applied to genes on the X chromosome in heterogametic males

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Heterogametic

Sex that produces gamates containing unlike sex chromosomes. In mammals, this is the male

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Homogametic

Sex that produces gametes containing like sex chromosome. In mammals, this is the female

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Homologous

Existence of shared ancenstre between a pair of structures or genes in different taxa

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Homologous chromosomes

Chromosome pairs that are similar in length, gene position, and centromere location

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Independent assortment

The independent behavior of each pair of homologous chromosomes during their segregation in meiosis I. The random distribution of maternal & paternal homologs into gametes

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Intercalary deletion

Also known as interstitial deletions, they occur on the interior of the chromosome

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Inversion

A chromosomal aberration in which a chromosomal segment has been reversed

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Karyotype

Chromosome complement of a cell or individual. Often used to refer to the arrangement of metaphase chromosomes in a seqence according to length and centromere position

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Klinefelter syndrome

Condition that occurs in men due to an extra X chromosome. Affects physical and cognitive development. Shortage of testosterone. Tall stature

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Linkage

Tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction

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Linkage map

Map of the genes on a chromosome based on linkage analysis. Does not show the physical distances between that genes but rather their relative positions, as determined by how often two gene loci are inherited together

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Lyon hypothesis

Proposal describing the random inactivation of the maternal or paternal X chromosome in somatic cells of mammalian females in early development

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Maternal age effect

Trisomies are more likely to occur as women get older; especially trisomy 21 (Down Syndrome)

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Meiosis

Process of cell division in gametogenesis or sporogenesis during which the diploid number of chromsomes is reduced to the haploid number

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Missegregation

Faulty segregation of chromosomes resulting in the gain or loss of chromosomes (monosomy/trisomy)

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Monosomy

An aneuploid condition in which one member of a chromsome pair is missing; having a chromosome number of 2n-1

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Male-specific region on Y chromosome (MSY)

Roughly 95% of the chromosomes length, with all the genes only being located on the Y chromosome

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Non-crossover gamate

A gamete whose chromosomes have undergone no genetic recombination

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Nondisjunction

A cell division error in which homologous chromosomes or the sister chromatids fail to separate and migrate ot opposite poles; responsible for defects such as monosomy & trisomy

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Nullisomy

A type of aneuploidy characterized by the loss of a pair of homologous chromosomes

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p arm/ q arm

p arm= short arm, q arm= long arm, separated by the centromere

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Pseudoautosomal region (PAR)

Homologous sequences of nucleotides on the X and Y chromosome so that they are able to pair and recombine during meiosis

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Paracentric inversion

A chromosomal inversion that does not include the region containing the centromere

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Pericentric inversion

A chromosmal inversion that involved both arms of the chromosome and thus the centromere

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Sex-influenced traits

Phenotypic expression conditioned by the sex of the individual. A heterozygote may express one phenotype in one sex and an alternate phenotype in the other

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Sex-limited traits

A trait that is expressed in only one sex even though the trait may not be X-linked

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Single crossing-over

Homologous chromsomes align and chromatids from two different chromsomes exchange segments, they are in contact in only one place

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Sister/non-sister chromatids

Crossing over occurs between non sister chromatids

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Sex- determining region of Y (SRY)

The sex determining region of the Y chromosome, found near the chromsomes pseudoautosomal boundary

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Testis determining factor (TDF)

DNA-binding protein that is responsible for the initiation of male sex determination in humans

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Terminal deletion

Removal of nucleotides from either the 5' or 3' end of the DNA strand

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Tetraploid

Four homologous sets of chromosomes

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Thomas Hunt Morgan

Discovered sex linked traits by studying fruit flies

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Translocation

A chromosomal mutation associated with the reciprocal or nonreciprocal transfer of a chromosomal segment from one chromosome to another.

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Triploid

Condition in which a cell or an organism has three haploid sets of chromsomes

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Trisomy

Condition in which a cell or an organism possesses two copies of each chromosome except for one, which is present in 3 copies

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Turner syndrome

Affects female development, cuases short stature and loss of ovarian function. Results when one X chromosome is missing or structurally altered

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Unbalanced gametes

Exchange of chromsome material is unequal, resulting in extra or missing genes (partial trisomy or monosomy). Caused by chromosome translocation.

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Unequal crossing over XX/XY mode of sex determination

Crossover between two improperly aligned homologs, producing one homolog with three copies of a region and the other with one copy of that region

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Bacterial genetics

Study of the mechanisms of heritable information in bacteria, their chromosoes, plasmids, transposons, and phages

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Prokaryote vs eukaryote

Organelles are membrane bound in eukaryotes. Eukaryotes have a nucleus, mitochondria, chloroplasts, etc, while prokaryotes are much simpler

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Conjugation

Temporary usion of two single-celled organisms for the sexual transfer of genetic material

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Transduction

Virally mediated bacterial recombination

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Tranformation

Heritable change in a cell or an organism brought about by exogenous DNA. Known to occur naturally & used in recombinant strands

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Plasmid

Small, circular, double-stranded DNA molecule that is distinct from the cell's chromosomal DNA. Can provide bacteria with genetic advantages, like antiobiotic resistance

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Parental type

Progeny of a cross that possess the phenotype of at least one of the individuals involved in the mating

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Polar body

Produced in femals at either the first or second meiotic division of gametogenesis, a discared cell that contains one of the nuclei of the divion process, but almost no cytoplasm as a result of an equal cytokinesis

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Polyploidy

A cell or individual having more than two haploid sets of chromosomes

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Recombinant type

A cell or an individual with a new combination of genes not found together in either parent

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Recombination frequency (RF)

Measures genetic linkage, the frequency with which a single chromsomal crossover wil take place between two genes during meiosis

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Repulsion phase

Each homologous chromosome has one dominant and one recessive allele from the two genes. Parental gametes are Ab and aB

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Coefficient of coincidence (C.O.C)

A ratio of the observed number of double crossovers divided by the expected number of such crossovers

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Hfr

Strains of bacteria exhibiting a high frequency of recombination. These strains have a chromosomally integrated F factor that is able to mobilize and transfer part of the chromosome to a recipient F- cell

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F factor

An episomal plasmid in bacterial cells that confers the ability to act as a donor in conjugation

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F pilus

On bacterial cells possessing an F factor, a filament-like projection that plays a role in conjugation

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Interference

A measure of the degree to which one crossover affects the incidence of another crossover in an adjacent region on the same chromatid. Negative interference increases the chance of another crossover; positive interference reduces the probability of a second crossover event

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Merozygote

Partially diploid bacterial cell containing, in additon to its own chromsome, a chromosomal fragment introduced into the cell by transformation, transduction, or conjugation

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Microsatellite

Short, highly polymorphic DNA sequence of 1-4 base pairs, widely distributed in the genome, that is used as a molecular marker in a variety of methods

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Sex pilus

Conjugative pili allowing for the transfer of DNA between bacteria

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Reciprocal translocation

A chromosomal aberration in which nonhomolgous chromosomes exchange parts