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Genetics
The scientific study of heredity
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Trait
Any observable property of an organism
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Gene
- The fundamental unit of heredity and the basic structural and functional unit of genetics
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DNA
A helical molecule consisting of two strands of nucleotides that is the primary carrier of genetic informationDeoxyribose Nucleotide subunitsAdenine, thymine, guanine, or Cytosine
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Transmission genetics
the branch of genetics concerned with the mechanisms by which genes are transferred from parent to offspring
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Pedigree analysis
the construction of family trees and their use to follow the transmission of genetic traits in humans
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cytogenetics
the branch of genetics that studies the organization and arrangement of genes and chromosomes by using the techniques of microscopy
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Karyotype
a complete set of chromosomes from a cell that has been photographed during cell division and arranged in a standard sequence (chart arranged in order of size and centromere position)
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molecular genetics
the study of genetic events at the biochemical level-uses recombinant DNA technology to identify, isolate, clone, and analyze genes-tremendous impact in last 40 years-debate over social, legal, and ethical issues
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recombinant DNA technology
a series of techniques in which DNA fragments from an organism are linked to self-replicating vectors to create recombinant DNA molecules, which are replicated or cloned in a host cell
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Clones
genetically identical molecules, cells, or organisms, all derived from a single ancestor
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Genome
the set of DNA sequences carried my an individual (all the genes present in an organism plut other DNA sequences that do not encode genes)
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genomics
the study of the organization, function, and evolution of genomes
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Gene therapy
procedure in which normal genes are transplanted into humans carrying defective copies, as a means of treating genetic diseases
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population genetics
the branch of genetics that studies inherited variation in populations of individuals and the forces that alter gene frequency
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eugenics
the attempt to improve the human species by selective breeding
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hereditarianism
the mistaken idea that human traits are determined solely by genetic inheritance, ignoring the contribution of the environment
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Single nucleotide polymorphism (SNP)
single nucleotide differences between and among individuals in a population or species
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Haplotype
a set of genetic markers located close together on a single chromosome or chromosome region
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Genome-wide association study
Analysis of genetic variation across an entire genome searching for associations (linkages) between variations in DNA sequence and a genome region encoding a specific phenotype
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Biotechnology
The use of recombinant DNA technology to produce commercial goods and services
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macromolecules
large cellular polymers assembled by chemically linking monomers together
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Carbohydrates
macromolecules including sugars, glycogen, and starches composed of sugar monomers linked and cross-linked (energy)
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Lipids
A class of cellular macromolecules including fats and oils that are insoluble in water (membranes)
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Proteins
A class of cellular macromolecules composed of amino acid monomers linked together and folded into a three-dimensional shape (structures & enzymes)
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Nucleic Acids
A class of cellular macromolecules composed of nucleotide monomers linked together. there are two types- DNA and RNA, which differ in the structure of the monomers (genetic materials)
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molecules
structures composed of two or more atoms held together by chemical bonds
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organelles
cytoplasmic structures that have a specialized function
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Endoplasmic Reticulum
a system of cytoplasmic membranes arranged into sheets and channels whose function it is to synthesize and transport gene products
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ribosomes
Cytoplasmic particles that aid in the production of proteins
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golgi complex
Membranous organelles composed of a series of flattened sacs. They sort, modify, and package proteins synthesized in the ER-final protein folding; stores secreted material; forms sugars, glycoproteins and glycolipids; vesicles of material are released
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Lysosomes
Membrane-enclosed organelles in eukaryotic cells that contain digestive enzymes (Tay-sacs = lysosome disorder)
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Mitochondria
membrane-bound organelles, present in the cytoplasm of all eukaryotic cells, that are the sites of energy (ATP) production-has its own circular DNA, inherited from mother
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Nucleus
The (double-layered nuclear membrane) membrane-bound organelle in eukaryotic cells that contains the chromosomes
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nucleolus
a nuclear region that functions in the synthesis of ribosomes
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chromatin
The DNA and protein components of chromosomes, visible as clumps or threads in nuclei
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Chromosomes
the threadlike structures in the nucleus that carry genetic information
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sex chromosomes
in humans, the X and Y chromosomes that are involved in sex determination
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Autosomes
Chromosomes other than the sex chromosomes. In humans, chromosomes 1-22 are autosomes
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cell cycle
the sequence of events that takes place between successive mitotic divisions
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Interphase
the period of time in the cell cycle between mitotic divisions-prepare for cell division; replicates DNA; composed of G1, S, G2; Cells may progress to mitosis or enter G0; quiescent phase
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mitosis
form of cell division that produces two cells, each of which has the same complement of chromosomes as the parent cell
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cytokinesis
the process of cytoplasmic division that accompanies cell division
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Prophase
A stage in mitosis during which the chromosomes become visible and contain sister chromatids joined at the centromere
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Centromere
a region of a chromosome to which spindle fibers attach during cell division. the location of a centromere gives a chromosome its characteristic shape
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sister chromatids
Two chromatids joined by a common centromere. each chromatid carries identical genetic information
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Metaphase
a stage in mitosis during which the chromosomes become arrange near the middle of the cell
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anaphase
a stage in mitosis during which the centromeres split and the daughter chromosomes begin to seperate
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Telophase
The last stage of mitosis, during which the chromosomes of the daughter cells decondense and the nucleus re-forms, spindle disappears
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Meiosis
The process of cell division during which one cycle of chromosomal replication is followed by two successive cell divisions to produce four haploid cells
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diploid (2n)
The condition in which each chromosome is represented twice as a member of a homologous pair
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Haploid (n)
The condition in which each chromosome is represented once in an unpaired condition
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Homologous Chromosomes
Chromosomes that physically associate (pair) during meiosis. Homologous chromosomes have identical gene loci
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Assortment
the result of meiosis I that puts random combinations of maternal and paternal chromosomes into gametes
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Crossing over
A process in which chromosomes physically exchange parts
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allele
One of the possible alternative forms of a gene, usually distinguished from other alleles by its phenotypic effects-different alleles result from mutations
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spermatogonia
mitotically active cells in the gonads of males that give rise to primary spermatocytes
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spermatids
the four haploid cells produced by meiotic division of a primary spermatocyte
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oogonia
mitotically active cells that produce primary oocytes
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secondary oocyte
the large cell produced by the first meiotic division
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oocyte
a cell from which and ovum develops by meiosis
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ovum
haploid cell produced by meiosis that becomes the functional gamete
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polar bodies
Cells produced in the first and second meiotic division in female meiosis that contain little cytoplasm and will not function as gametes
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dominant trait
the trait expressed in the F1 (or heterozygous) condition
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recessive trait
the trait unexpressed in the F1 but re-expressed in some members of the F2 generation.
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Phenotype
the observable properties of an organism
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genotype
the specific genetic constitution of an organism
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segregation
the separation of members of a gene pair from each other during gamete formation
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homozygous
having identical alleles for one or more genes
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heterozygous
carrying two different alleles for one or more genes
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independent assortment
the random distribution of alleles into gametes during meiosis
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locus
the position occupied by a gene on a chromosome
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pedigree construction
use of family history to determine how a trait is inherited and to estimate risk factors for family members
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pedigree
a diagram listing the members and ancestral relationships in a family; used in the study of human heredity
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proband
first affected family member who seeks medical attention for a genetic disorder
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incomplete dominance
expression of a phenotype that is intermediate to those of the parents
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codominance
full phenotypic expression of both members of a gene pair in the heterozygous condition
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multiple alleles
genes that have more than two alleles
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Epistasis
the interaction of two or more non-allelic genes to control a single phenotype
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population
a group of interbreeding individuals who possess a particular collection of alleles or gene pool
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human genome
3 billion base pairs of DNA28,000 to 34,000 genesorganized as 23 pairs of chromosomes (22+ X&Y)
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mutations
changes on the DNA
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somatic cells
majority of an individual's body, make proteins using different subsets of genes
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Germline cells
within the testis or ovary produce gametes (sperm or ovum)
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prokaryotic cells
lack a nucleus
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eukaryotic cells
contain a nucleus and complex organelles
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Human cells
>260 cellsFour catergories:Epithelial, muscle, nerve, conncetive
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peroxisomes
contain several types of enzymes; break down lipids and rare biochemicals; synthesize bile acids; detoxify compounds from free radicals; abundunt in liver and kidney cells; Adrenoleukodystrophy (ALD)= inherited trait of a peroxisome enzyme transport protein
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plasma membrane
double layered, dynamic and active, selectively permeable, regulates exchange of materials, contains molecules important in identity
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G naught/ G0
cell stops dividing
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apoptosis
cell death that is part of normal development
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necrosis
cell death in response to injury
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telomeres
located at the end of chromosomes, contain 100s to 1000s of six nucleotide repeats, lose 50-200 repeats after each division, signal cell to stop dividing after about 50 divisions
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telomerase
produced by sperm, eggs, bone marrow, and cancer cells; prevents shortening of telomeres
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Autosomal dominant inheritance
-heterozygotes exhibit the affected phenotype; males and females are equally affected and may transmit the trait; affected phenotype does not skip generations
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autosomal recessive inheritance
heterozygotes carry the recessive allele but exhibit the wildtype phenotype; males and females are equally affected and may transmit the trait; may skip generations
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X- linked traits
males are hemizygous, have trait or do not because they only have one X chromosomeFemales can be heterozygotes and inherit x chromosomes from both parents
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X-linked recessive traits
always expressed in males, female homozygotes show the trait but heterozygotes do not
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cystic fibrosis
an often fatal recessive genetic disorder associated with abnormal secretions of the exocrine glands
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x-linked
the pattern of inheritance that results from genes located on the X-chromosome
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Y-linked
the pattern of inheritance that results from genes located on the Y-chromosomes
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Hemizygous
a gene present on the x chromosome that is expressed in males in both the recessive and the dominant conditions
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Color blindness
Defective color vision caused by reduction or absence of visual pigments. There are three forms: red, green, and blue blindness
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Muscular dystrophy
A group of genetic diseases associated with progressive degeneration of muscles. Two of these, Duchenne and Becker muscular dystrophy, are inherited as X-linked allelic recessive traits
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Huntington Disease
An autosomal dominant disorder associated with progressive neural degeneration and dementia. Adult onset is followed by death 10-15 years after symptoms appear
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Penetrance
The probability that a disease phenotype will appear when a disease-related genotype is present.
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Expressivity
the range of phenotypes resulting from a given genotype
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Campotdactyly
a dominant human genetic trait that is expressed as immobile, bent, little fingers
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Discontinuous variation
phenotypes that fall into two or more distinct nonoverlapping classes
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continuous variation
a distribution of phenotypic characters that is distributed from one extreme to another in an overlapping, or continuous, fashion
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Complex traits
traits controlled by multiple genes, the interaction of genes with each other, and with environmental factors where the contributions of genes and environment are undefined
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polygenic traits
traits controlled by two or more genes
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multifactorial traits
traits controlled by two or more genes
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genetic variance
the phenotypic variance of a trait in a population that is attributed to genotypic differences
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Heritability
An expression of how much the observed variation in a phenotype is due to differences in genotype
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correlation coefficients
An expression of how much the observed variation in a phenotype is due to differences in genotype
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correlation coefficients
Measures the degree of interdependene of two or more variables
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monozygotic
twins derived from a single fertilization involving one egg and one sperm, such twins are genetically identical
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Dizygotic
twins derived from two separate and nearly simultaneous fertilizations, each involving one egg and one sperm. Such twins share, on average, 50% of their genes
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concordance
agreement between traits exhibited by both twins
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leptin
a hormone produced by fat cells that signals the brain and ovary. As fat levels become depleted, secretion of leptin slows and eventually stops
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Intelligence quotient (IQ)
A score derived from standardized test that is calculated by dividing the individual's mental age (determined by the test) by his or her chronological age and multiplying the quotient by 100
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General cognitive ability
Characteristics that include verbal and spatial abilities, memory, speed of perception, and reasoning
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metacentric
describes a chromosome that has a centrally placed centromere
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submetacentric
describes a chromosome whose centromere is placed closer to one end than the other
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acrocentric
describes a chromosome whose centromere is placed very close to, but not at, one end
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amniocentesis
a method of sampling the fluid surrounding the developing fetus by inserting a hollow needle and withdrawing suspended fetal cells and fluid; used in diagnosing fetal genetic and developmental disorders; usually performed in the sixteenth week of pregnancy
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chronic villus sampling (CVS)
A method of sampling fetal chorionic cells by inserting a catheter through the vagina or abdominal wall into the uterus. Used in diagnosing biochemical and cytogenetic defects in the embryo. Usually performed in the eighth or ninth week of pregnancy
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polyploidy
a chromosomal number that is a multiple of the normal haploid chromosomal set
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Aneuploidy
a chromosomal number that is not an exact multiple of the haploid set
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monsomy
a condition in which one member of a chromosomal pair is missing; having one less than the diploid number
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trisomy
a condition in which one chromosome is present in three copies, whiereas all others are diploid; having one more than the diploid number
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triploidy
a chromosomal number that is three times the haploid number, having three copies of all autosomes and three sex chromosomes
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Tetraploidy
a chromosomal number that is four times the haploid number, having four copies of all autosomes and four sex chromosomes
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nondisjunction
The failure of homologous chromosomes to separate properly during meiosis or mitosis
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Trisomy 21
Aneuploidy involving the presence of an extra copy of chromosome 21, resulting in down syndrome
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Turner Syndrome
A Monosomy of the x chromosome (45,x) that results in female sterility
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Klinefelter syndrome
aneuploidy of the sex chromosomes involving an xxy chromosomal consitution
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XXY karyotype
Aneuploidy of the sex chromosomes involving an xxy chromosomal condition
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cri du chat syndrome
a deletion of the short arm of chromosome 5 associated with an array of congenital malformations, the most characteristic of which is an infant cry that resembles a meowing cat
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Uniparental disomy (UPD)
a condition in which both copies of a chromosome are inherited from one parent
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copy number variation
A dna segment at least 1000 base pairs long with a variable copy number in the genome
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Fragile X syndrome
An X chromosome that carries a gap, or break, at band q27; associated with mental retardation in males
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Zygote
the fertilized egg that develops into a new individual
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gametes
unfertilized germ cells
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gonads
organs where gametes are produced
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testes
male gonads that produce spermatozoa and sex hormones
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ovaries
female gonads that produce oocytes and female sex hormones
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scrotum
a pouch of skin outside the male body that contains the testes
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seminiferous tubules
small, tightly coiled tubes inside the testes where sperm are produced
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spermatogenesis
the process of sperm production
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epididymis
a part of the male reproductive system where sperm are stored
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vas deferens
a duct connected to the epididymis which sperm travels through
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ejaculatory duct
in males, a short connector from the vas deferens to the urethra
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urethra
a tube that passes from the bladder and opens to the outside. It functions in urine transport and, in males, also carries sperm
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seminal vesicles
Glands in males that secrete fructose and prostaglandins into the semen
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Prostaglandins
locally acting chemical messengers that stimulate contraction of the female reproductive system to assist in sperm movement
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prostate gland
a gland that secretes a milky, alkaline fluid that neutralizes acidic vaginal secretions and enhances sperm viability
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bulbourethral glands
glands in the male that secret a mucus-like substance that provides lubrication for intercourse
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semen
a mixture of sperm and various glandular secretions containing 5% spermatozoa
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Follicle
developing egg surrounded by an outer layer of follicle cells, contained in the ovary
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oviduct
a duct with fingerlike projections partially surrounding the ovary and connecting to the uterus. Also called the fallopian, or uterine, tube
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uterus
a hollow pear-shaped muscular organ where an early embryo will implant and develop throughout pregnancy
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endometrium
the inner lining of the uterus that is shed at menstruation if fertiliztion has not occured
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cervix
the lower neck of the uterus, opening into the vagina
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vagina
that opening that receives the penis during intercourse and also serves as the birth canal
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Oogenesis
the process of oocyte production
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oogonia
cells that produce primary oocytes by mitotic division
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chorion
a two layered structure formed during embryonic development from the trophoblast
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Teratogen
any physical or chemical agent that brigns about an increase in congenital malformations
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fetal alcohol syndrome
constellation of birth defects caused by maternal alcohol consumption during pregnancy
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sex ratio
the proportion of male to females, which changes throughout the life cycle. The ratio is close to 1:1 at fertilization, but the ratio of females to males increases as population ages
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SRY
A gene, called the sex-determining region of the Y, located near the short arm or the y chromosome that plays a major role in causing the undifferentiated gonad to develop into a testis
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testosterone
A steroid hormone produced by the testis; the male sex hormone
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Anti-mullerian hormone (AMH)
A hormone produced by the devloping testis that causes the breakdown of the mullerian ducts in the embryo
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complete androgen insensitivity
an x linked genetic trait that causes XY individuals to develop into phenotypic females
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pseudohermaphroditism
an autosomal genetic condition that causes xy individuals to develop the phenotypic sex of females
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Dosage compensation
a mechanism that regulates the expression of sex linked genes
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barr body
a densely staining mass in teh somatic nuclei of mammalian females; an inactivated x chromosome
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lyon hypothesis
the proposal that dosage compensation in mammalian females is accomplished by partially and randomly inactivating one of the two x chromosomes
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X inactivation center
a region on the x chromosome where inactivation begins
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sex-influenced traits
traits controlled by autosomal genes that are usually dominant in one sex but recessive in the other sex
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pattern baldness
a sex influenced trait that acts like an autosomal dominant trait in males and an autosomal recessive trait in females
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sex-limited genes
loci that produce a phenotype in only one sex
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imprinting
a phenomenon in which expression of a gene depends on whether it is inherited from the mother of the father
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