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135 Cards in this Set

  • Front
  • Back
hereditary traits
a characteristic that results from gene action and is transmitted from one generation to another.
genotype
the complete genetic makeup (allelic composition) of an organism. the term is commonly used in reference to specific alleles present at just one or a limited number of genetic loci
phenotype
the observable characteristics of an organism that are produced by the genotype and its interaction with the environment.
self-fertilization
the union of male and female gametes from the same individual
cross-fertilization
the fusion of male gametes from one individual and female gametes from another
true-breeding/pure-breeding strains
a strain in which mating of individuals yields progeny with the same genotype as the parents
P generation
where the crossing begins
first filial generation F1
the offspring that result from the first experimental crossing of two parental strains of animals or plants
monohybrid cross
a cross between two individuals that are both heterozygous for the same pair of alleles by extension the tern also refers to crosses involving the purebreeding parents that differ with respect to the alleles of one locus
reciprocal crosses
a pair of crosses in which the genotypes of the male and female gametes for a particular trait is reversed. in the garden pea, for example, a reciprocal cross for smooth and wrinkle seeds is smooth female X wrinkled male and wrinkled female X smooth male
gene particulate factor
the term mendel used for the entities that carry hereditary information and are transmitted from parents to progeny through the gametes....they are now called genes
locus loci
the position of a gene on a genetic map. the specific place on a chromosome where the gene is located
allele allelomorphic
one of two or more alternate forms of a single gene that can exist in the same locus of the genome all the alleles of a gene determine the same hereditary trait but each has a unique nucleotide sequence
dominant
describing an allele or phenotype that is expressed in either the homozygous or the heterozygous state
recessive
describing an allele or phenotype that is expressed only in the homozygous state
heterozygous
describing a diploid organism having different alleles of one or more genes and therefore producing gametes of different phenotypes
homozygous
describing a diploid organism having the same allele at one or more genetic loci and therefore producing gametes of identical genotypes
dihybrid cross
a cross between two individuals of the same genotype that are heterozygous for two pairs of alleles at two different loci
gamete. zygote
mature reproductive cell that is specialized for sexual fusion. each gamete is haploid and fuses with a cell of similar origin but of opposite sex to produce a diploid zygote
test cross
a cross of an individual of unknown genotype usually expressing the dominant phenotype with a homozygous recessive individual to determine the unknown genotype
gene segregation/principle of segregation
mendel's first law stating that two members of a gene pair (alleles) segregate (separate) from eachother during the formation of gametes. as a result one-half the gametes carry one allele and the other half carry the other allele
principle of independent assortment
mendels' second law stating that the factors (genes) for different traits assort independently of one another. genes on different chromosomes behave independently of one another in the production of gametes
probability
the ratio of the number of times a particular event occurs to the number of trials during which the event could have happened
product rule
the rule that the probability of two different events occurring simultaneously is the product of each of their individual probabilities
sum rule
the rule that the probability of either of two mutually exclusive events occurring is the sum of their two probabilities
Punnett Square
a matrix that describes all the possible genotypes of progeny resulting from a genetic cross
chi-square test
a statistical test that determines what constitutes a significant different between observed resukts and results expected on the basis of a particular hypothesis, (a goodness of fit test)
null hypothesis
a hypothesis that states that there is no difference between the observed data and the predicted data
wild-type allele
term describing an allele or phenotype that is designated as the standard "normal" for an organism and is usually but not always the most prevalent in a "wild" population of the organism,
loss-of-function mutations
a mutation that leads to the absence or decreased biological activity of a particular protein
pedigree analysis
study of the inheritance of human traits by compilation of phenotypic records of a family over several generations
proband
a affected person with whom the study of a trait in a family begins
gain-of-function mutations
a mutation that confers a new property on a protein causing a new phenotype
homolog
each individual ,member of a pair of homologous chromosomes
sex chromosomes
a chromosome in eukaryotic organisms that differs morphologically or in number in the two sexes. in many organisms one sex possesses a pair of visibly different chromosomes
autosomes
a chromosome other than a sex chromosome
centromere
a specialized region of a chromosome seen as a constriction under the microscope that is important in the activities of chromosomes during cell division (kinetochore)
metacentric chromosome
a chromosome with the centromere near the center such that the chromosome arms are of about the same length
submetacentric chromosome
a chromosome with the centromere nearer to one end than the other such that one arm is longer than the other
acrocentric chromosome
a chromosome with the centromere near one end such that it has one long arm plus a stalk and a satellite
telocentric
a chromosome with the centromere more or less at one end so that only one arm is visible
karyotype
a complete set of all the metaphase chromatid pairs in a cell
mitosis
the process of nuclear division in haploid or diploid cells producing daughter nuclei containing identical chromosome complements and are genetically identical to one another and to the parent nucleus from which they arose
cytokinesis
division of the cytoplasm following mitosis or meiosis I/II during which the two new nuclei compartmentalize into separate daughter cells
cell cycle
the cyclical process of growth and cellular reproduction in unicellular and multicellular eukaryotes
sister chromatids
two identical copies of a chromosome derived from replication of the chromosome during interphase of the cell cycle. sister chromatids are held together by the replicated but unseparated centromeres
chromatid
one of two visibly distinct replicated copies of each chromosome that becomes visible between early prophase and metaphase of mitosis and is joined to its sister at their centromeres.
daughter chromosomes
detached sister chromatids after they separate at the beginning of mitotic anaphase or meiotic anaphase II
interphase
chromosomes are not extended and are not visible
E prophase
centrioles move apart chromosomes shorten and thicken and start to become visible Nucleolus begins to disappear
middle prophase (MITOSIS)
centrioles continue to move apart. mitotic spindles begins forming replicated chromosomes become visible
late prophase (MITOSIS)
centrioles reach opposite sides of nucleus. spindle begins to form nuclear envelope begins to disappear
metaphase (MITOSIS)
nuclear envelope has disappeared replicated chromosomes held together at centromere align on equator of spindle at the metaphase plate
anaphase (MITOSIS)
centromeres split and daughter chromosomes begin migration to opposite poles ...the two sets of daughter chromosomes approach the poles cytokinesis begins
telophase (MITOSIS
nuclear envelopes begin forming ..chromosomes begin to become extended and less visible nucleolus reform cytokinesis continues
metaphase plate
the plane in the cell where the chromosomes become aligned during metaphase
meiosis
two successive nuclear divisions of a diploid nucleus following one DNA replication that result in the formation of four haploid gametes or of spores having one-half the genetic material of the original cell
gametogenesis
the formation of male and female gametes
leptotene
1st stage of prophase I during which the chromosomes begin to coil and become visible
zygotene
2nd stage of prophase I during which homologous chromosomes begin to pair in a highly specific way along their lengths
synapsis
the intimate association of replicated homologous chromosomes brought about by the formation of a zipper like structure (the synaptonemal complex) between the homologues during prophase I of meiosis
synaptonemal complex
a complex structure that spans the region between meiotically paired (synapsed) chromosomes and facilitates crossing-over
e prophase 1 (leptotene)
chromosomes already replicated become visible
e prophase I (zygotene)
chromosomes already replicated become visible
m prophase I (pachytene)
homologous chromosomes shorten and thicken. the chromosomes synapse and crossing over occurs
l prophase I (diplotene)
results of crossover become visible as chiasmata. nuclear envelope disappears. spindle apparatus begins to form
l prophase I (diakinesis)
results of crossover become visible as chiasmata. nuclear envelope disappears. spindle apparatus begins to form
metaphase I
assembly of spindle is completed each chromosome pair (bivalent) aligns across the equatorial plane of the spindle
anaphase I
homologous chromosome pairs (dyads) separate and migrate toward opposite poles
telophase I
chromosomes (each with two sister chromatids) complete migration to the poles and new nuclear envelopes may form. (random sorting has occurred)
bivalent//tetrad
a pair of homologous, synapsed chromosomes, consisting of four chromatids during the first meiotic division
crossing-over
the process of reciprocal chromosomal interchange that occurs frequently during meiosis and gives rises to recombinant chromosomes
recombinant chromosome
a daughter chromosome that emerges from meiosis with an allelic composition that differs from that of either parental chromosome
genetic recombination
a process by which parents with alleles give rise to progeny with genotypes that differ from either parents. for example parents with AB and ab genotypes can produce recombinant progeny with Ab and Ba genotypes
chiasma
a crossshaped structure formed during cross-over and visible during diplotene stage of meiosis
sexual reproduction
mode of reproduction involving the fusion of haploid gametes produced directly or indirectly by meiosis
spermatogenesis
development of male gametes (sperm cells) in animals
oogenesis
development of female gametes (egg cells) in animals
sperm cells (spermatozoa)
a mature male gamete produced by the testes in male animals
primary oocytes
diploid cells that arise by mitoticdivision of primordial germ cells (oogonia) and undergo meiosis in the ovaries of female animals
secondary oocytes
the larger of the two daughter cells produced by unequal cytokinesis during meiosis I of a primary oocyte in the ovaries of female animals
ovum
a mature female gamete the larger of the two cells that arise from secondary oocyte by meiosis II in the ovary of female animals
gametophyte
the haploid sexual generation in the life cycle of plants that produces the gametes by mitotic division of spores
sporophyte
the haploid asexual generation in the life cycle of plants that produces haploid spores by meiosis
stamens
the male reproductive organ in flowering plants it usually consists of a stalklike filament bearing a pollen producing anther
pistils
the female reproductive organ in flowering plants usually consists of a pollen receiving stigma, stalklike style abd ovary
alternation of generations
type of life cycle characteristic of green plants in which haploid cells (gametophytes) alternate with diploid cells (sporophytes)
chromosome theory of inheritance
the theory that genes are located on chromosomes and that the transmission of chromosomes from one generation to the next accounts for the inheritance of hereditary traits
heterogametic sex
in a species the sex that has two types of sex chromosomes(XY)
and therefore produces two types of gametes
homogametic sex
in a species the sex that has only one type of sex chromosome (XX) and therefore produces only one kind of gamete
mutant alleles
any form of a gene that differs from the wildtype allele --can be dominant or recessive
hemizygous
possessing only one copy allele of a gene in a diploid cell. usually applied to genes on the X chromosome in males with the XY genotype
crisscross inheritance
transmission of a gene from a male parent to a female child and to a male grandchild
sex-linked (x-linked)
referring to genes located on the X chromosome
nondisjunction
a failure of homologous chromosomes or sister chromatids to separate at anaphase
primary nondisjunction
a rare event in cells with a normal chromosome complement in which sister chromatids (in mitosis or meiosis II) or homologous chromosomes (meiosis I) fail to separate and move to opposite poles
aneuploidy
any condition in which the number of chromosomes differs from an exact multiple of the normal haploid number in a cell or organism. it commonly results from the gain or loss of individual chromosomes but can also result from the duplication or deletion of parts of a chromosome or chromosomes
secondary nondisjunction
abnormal segregation of the X chromosomes during meiosis in the progeny of females with the XXY genotype produced by primary nondisjunction
genotypic sex determination
any system in which sex chromosomes play a decisive role in the inheritance and determination of sex
genic sex determination
system of sex determination found primarily in eukaryotic microorganisms in which sex determination is determined by different alleles at a small number of gene loci
testis-determining factor
gene product in placental mammals that causes embryonic gonadal tissue to develop into testes, in the absence of this factor the gonadal tissue develops into ovaries
Turner syndrome
a human clinical syndrome that results from monosomy for the x chromosome in the female, which gives a 45,x female affected females fails to develop secondary sexual characteristics tend to be short have weblike necks have poorly developed breasts are usually are infertile and have mental deficiencies
Klinefelter syndrome
a hman clinical syndrome that results from disomy for the x chromosome in a male, which results in a 47, xxy male many of the affected males are mentally deficient have underdeveloped testes and are taller than average
dosage compensation
any mechanism in organisms with genotypic sex determination for equalizing expression of genes on the sex chromosomes in makes and females
Barr body
a highly condensed and transcriptionally inactive x chromosome found in the nuclei of somatic cells of female mammals..occurs through lyonization
Lyon hypothesis
a mechanism of dosage compensation discovered by Mary Lyon in which one of the x chromosomes in the cells of female mammals becomes highly condensed and genetically inactive
epigenetic
referring to a heritable change in gene expression that does not result from a change in the nucleotide sequence of the genome
x chromosome-autosome balance system
a genotypic sex determination system in which the ratio between the numbers of x chromosomes and number of sets of autosomes is the primary determination of sex
hermaphroditic
referring to animal species in which each individual has both testes and ovaries and to plant species in which both stamen and pistil are on the same flower
dioecious
referring to plant species in which individual plants possess either male or female sex organs
monoecious
referring to plants species in which individual plants possess both male and female sex organs and thus produce male and female gametes ...can self fertilize
x linked recessive trait
a characteristic caused by a recessive mutant allele carried on the x chromosome
mating types
in lower eukaryotes two forms that are morphologically indistinguishable but carry different alleles and will mate equivalenet to the sexes in higher organisms
x linked dominant traits
a characteristic caused by a dominant mutant allele carried on the x chromosome
y linked or holandric
a characteristic controlled by a gene carried on the y chromosome for which there is no corresponding gene locus on the x chromosome
linkage /linked genes
the association of genes located on the same chromosome such that they tend to be inherited together
recombinants
a chromosome cell or individual that has nonparental combinations of genetics markers as a result of genetic recombination
genetic marker
any gene or DNA region whose sequence varies among individuals and is useful in genetic analysis for example in the detection of genetic recombination events
DNA marker
sequence variations among individuals in a specific region of DNA that are detected by molecular analysis of the DNA and can be used in genetic analysis
parental genotypes/classes
the genetic makeup (allelic composition) of individuals in the parental generation of genetic crosses. progeny in succeeding generations may have combinations of linked alleles like one or the other of the parental genotypes or new nonparental combination as the result of crossing-over
cytological markers
any cytological feature that distinguishes one pair of homologous chromosomes from other pairs
genetic map//linkage map
a representation of the relative distances separating genes on a chromosome based on the frequencies of recombinantion between nonallelic gene loci
coupling (cis)
in individuals heterozygous at two genetic loci the arrangement in which the wildtype alleles of both genes are on one homologous chromosome and the recessive mutant alleles are on the other.
repulsion (trans)
in individuals heterozygous for two gene loci the arrangement in which each homologous chromosome carries the wildtype allele of one gene and the mutant allele of the other gene
map units//centiMorgan
a unit of measurement for the distance between twp genes on a genetic map (a crossover frequency of 1 percent between two genes equals 1 map unit)
three-point testcross
a cross between an individual heterozygous at three loci with an individual homozygous for recessive alleles at the same three loci commonly used in mapping linked genes to determine their order in the chromosome and the distances between them
interference
phenomenon in which the presence of one crossover interferes with the formation of another crossover nearby
coefficient of coincidence
a measure of the extent of chiasma interference throughout a genetic map, ratio of the observed to the expected frequency of double crossovers
mapping functions
mathematical formula used to correct the observed recombination frequencies for the incidence of multiple crossovers
meiotic tetrad
the four haploid cells produced in a single meiosis in some lower eukaryotes there cells are contained within a common structure
ascospores
the name of the four haploid cells in lower eukaryotes produced after meiosis
ascus
the larger outer membrane that remains around the four haploid cells after meiosis in lower eukaryotes
parental ditype (PD)
one of three types of meiotic tetrads possible when two genes are segregating in a cross the PD tetrad contains four nuclei all of which are parental genotypes with two of one parent and two of the other parent
nonparental ditype (NPD)
one of three types of meiotic tetrads possible when twp genes are segregating in a cross. the NPD tetrad contains all four nuclei, all of which have recombinant genotypes (twp of each possible type)
Tetratype (T)
the T tetrad contains two parental and two recombinant nuclei, one of each parental genotype and one of each recombinant type