a basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns
-- Mendelian genes have specific loci along chromosomes, and it is the chromosomes that undergo segregation and independent assortment
chromosome theory of inheritance
the two alleles for each gene separate during gamete formation
law of segregation
alleles of genes on nonhomologous chromosoems assort independently during gamete formation
law of independent assortment
traits that are alternatives to the wild type because they are due to alleles assumed to have originated as changes, or mutations in the wild-type allele
what is symbolized by a lowercase letter?
what is symbolized by a lowercase letter with a superscript +
wild type trait
an individual with the phenotype most commonly observed in natural populations; also refers to the phenotype itself
the chromosomal system located in humans?
ants and bees?
a gene located on the Y chromosome required for the development of testes; in its absence, gonads develop into ovaries
SRY (sex-determining region of Y)
a gene located on either sex chromosome (usually the X chromosome), resulting in a distinctive pattern of inheritance
For males, because they only have one locus, __ is used for describing the phenotype/ genotype
__ discovered the existence of sex-linked genes.
Thomas Hunt Morgan
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue; loss of coordination; affected individuals rarely live past their early 20s
Duchenne muscular dystrophy
sex-linked disorder characterized by hving blood with an inability to clot normally, caused by the absence of proteins required for blood clotting; human genetic disease caused by a sex-linked recessive allele resullting in the absence of one or more blood-clotting proteins; characterized by excessive bleeding following injury
__ regulates gene dosage in females. Although female mammals inherit two X chromosomes, one of the X chromosomes (randomly chosen) in each cell of the body becomes inactivated during embryonic development by methylation. As a result, males and females have the same effective dose of genes with loci on the X chromosome
a dense/ compact object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome
a condition in which an organism or part is composed of two or more genetically distinct tissues owing to experimental manipulation or to faulty distribution of genetic material during mitosis
Females consist of a __ of two types of cells: those with the active X derived from the mom and the active X derived from the father;
X chromosomes become inactive by addition of a __ added to a cysteine (cytosine) group that silences a gene
An X chromosome gene called __ that is active only on Barr body chromosomes
two or more genes located close enough together on a chromosome that they tend to be inherited together
a single gene on a sex chromosome
general term for the production of offspring with combinations of traits that differ from those found in either parent
an offspring with a phenotype that matches one of the parental phenotypes: also refers to the phenotype itself
an offspring whose phenotype differs from that of the parents; also refers to the phenotype itself
a genetic map based on the frequencies of recombinatio between markers during crossing over of homologous chromosomes
a chart of a chromosome that lcoates genes with respect to chromosomal features distinguishable with a microscope
the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis; accounts for the recombination of linked genes
a unit of measurement of the distance between gneses. ONe is equivalent to a 1% recombination frequency
map units (centrimorgans)
an ordered list of the genetic loci along a particular chromosome
Person who came up with the: the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency
an error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other (members of a pair ofhomologous chromosoems do not separate properly during meiosis I, or sister chromatids don't separate properly during meiosis II)
a chromosomal aberration in which one or more chromosoems are present in extra copies or are deificient in number; abnormal number of chromosomes
referring to a cell that has only one copy of a particular chromosome instead of the normal two (2n-1)
referring to a diploid cell that has three copies of a particular chromosome instead of the normal two (2n+1)
condition of having more than two complete sets of chromosoems, forming a 3n or 4n individual; a chromosomal alteration in which the organism possesses more than two complete chromosome sets; result of an accident in cell division
a deficiency in a chromosome resulting from the loss of a fragment through breakage
an aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated.
an aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated
an aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomolgous chromosomal fragment to a nonhomologous chromosome
removes a chromosomal segment; occurs when a chromosomal fragment is lost, resulting in a chromosome with missing genes
repeats a segment; when the chromosome fragment that broke off becomes attached to its sister chromatid; cause double does of genes located on that chromosome
reverses a segment within a chromosome;l chromosome fragment breaks off and reattaches to its orignial position, but backwards so that the part of the fragment that was originally at the attachment point is now at the end of teh chromosome
when hte deleted chromosome fragment joins a nonhomologous chromosome; moves a segment from one chromosome to a nonhomologous chromosome
nonhomologous chromosomes exchange frangments
a chromosome transfers a fragment without receiving a fragment in return
an aneuploid condition that is the result of having an extra chromosome 21 (trisomy 21); includes characteristic facial fetures, short stature, heart defects, and mental retardation
an aneuploid condition in which a male possesses the sex chromosomes XXY (an extra X); males have male sex organs but are sterile; moobs
males with this type of aneuploid are generally taller than average
Females with this aneuploidy are healthy and cannot be distinguished from XX females except by karyotype.
a monosomic condition in which the female has just one sex chromosome, an X; these females are sterile because the reproductive organs do not mature; only known viable monosomy in humans
Turner syndrome (X0)
when does nondisjunction occur?
anaphase I of meiosis or anaphase II
pairs of homologous chromosomes dont separate properly during meiosis
abnormal number of chromosomes
2n-1 (Turner Syndrome)
more than two complete sets of chromosoes
flipping around of chromosome segment
arm above centromere is known as? below?
many __ cause severe problems, such as __ resulting from a specific one in chromosome 5; child borm with this deletion is mentally retarded, has a small head with unusual facial features and has a cry that sounds like the mewing of a distressed cat
a phenomenon in which expression if an allele in offspring depends ib whether the allele is inherited from the male or female parent
__ may directly slience an allele.
genes located outside the nucleus in organelles in the cytoplasm
__ involves silencing of certain genes; phenotype affected by which parent passes the mutant allele;
different X's being activated
inactivated X chromosome
percentage of recombinant offspring; is related to the distance between linked genes
__ of chromosome structure is what results in deletion, duplication, inversion, translocation, aneuploidy, polyploidy, etc.
a set of traits
Describes an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two; refers in particular to X-linked genes in males who under usual circumstances have only one X chromosome
due to alleles assumed to have originated as changes, or mutations
a chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number