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Flashcards in Exam 1 Deck (109):

Define acrocentric

Chromosome with the centromere located very close to one end. (human chromosomes 13, 14, 15, 21, 22)


Define allele

One of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects


Define carrier

An individual heterozygous for a recessive trait


Define centromere

Specialized heterochromatic chromosomal region at which sister chromatids remain attached after replication, and the site to which spindle fibers attach to the chromosome during cell division. Location of the centromere determines the shape of the chromosome during the anaphase portion of cell division


Define chiasma

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


Define chi-square

Statistical test to determine whether or not an observed set of data is equivalent to a theoretical expectation.


Define chromosome

In prokaryotes, a DNA molecule containing an organism's genome; in eukaryotes, the DNA molecule complexed with proteins and RNA to form a threadlike structure containing genetic information that is visible during mitosis and meiosis


Define codominance

Condition in which the phentoypic effects of a gene's alleles are fully and simultaneously expressed in the heterozygote


Define epigenesis

Idea that an organism or organ arieses through the sequntial appearance and development of new structures


Define epistasis

Nonreciprocal interaction between nonallelic genes such that one gene influences or interferes with the expression of another gene (leads to a specific phenotype)


Define expressivity

The degree to which a phenotype for a given trait is expressed


Define consanguinity

Related by a common ancestor within the previous few generations


Explain crossing over/recombination

Exchange of chromosomal material (parts of chromosomal arms) between homologous chromosomes by breakage and reunion. The exchange of materila between nonsister chromatids during meiosis is the basis of genetic recombination


Define cytogenetics

Branch of biology in which the techniques of both cytology and genetics are used in genetic investigations


Explain a dihybrid cross

A genetic cross involving two characters in which the parents possess different forms of each character (yellow, round w/ green, wrinkled)


Define diploid

Condition in which each chromosome exists in pairs; having two of each chromosome


Define gamete

A specialized reproductive cell with a haploid number of crhomosomes


Define gene

A fundamental physical unit of heredity, whose existence can be confirmed by allelic variants and which occupies a specific chromosomal locus. A DNA sequence coding for a single polypeptide


Define genomic imprinting

Process by which the expression of an allele depends on whether it has been inherited from a male or a female parent (parental imprinting)


Define genotype

Allelic or genetic constitution of an organism; often, the allelic composition of one or a limited number of genes under investigation


Define haploid

Cell or an organism having one member of each pair of homologous chromosomes.


Define heterozygous

An individual with different alleles at one or more loci. Such individuals will produce unlike gametes and therefore will not breed true


Define homozygous

An individual with identical alleles for a gene or genes of interest. These individuals will produce identical gametes (with respect to the gene or genes in question) and will therefore breed true


Define homologous chromosomes

Chromosomes that synapse or pair during meiosis and that are identical with respect to their genetic loci and centromere placement


Define incomplete dominance

Expressing a heterozygous phenotype that is distint from the phenotype of either homozygous parent (partial dominance)


Explain G1 checkpoint

Point in G1 phase of the cell cycle when a cell either becomes commited to initiating DNA synthesis and continuing the cycle or withdraws into the G0 resting stage


Explain G0

A nondividing but metabolically active state that cells may enter from the G1 phase of the cell cycle


Define independent assortment

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


Define interphase

Interval between divisions, during the cell cycle


Define karyotype

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


Define lethal alleles

An allele whose expression results in premature death of the organism at some stage of its life cycle


Define locus (loci)

Site or place on a chromosome where a particular gene is located


Explain maternal effects

Phenotypic effecs in offspring attributable to genetic information transmitted through the oocyte derived from the maternal genome


Define maternal inheritance

Transmission of traits strictly through the maternal parent, usually due to DNA found in the cytoplasmic organeeles, the mitochondria, or chloroplasts


Explain meoisis

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


Explain mitosis

Form of cell division producing two progeny cells identical genetically to the parental cell- that is, the production of two cells from one, each having the same chromosome complement as the parent cell


Define metacentric

Chromosome that has a centrally located centromere and therefoe chromosome arms of equal lengths


Explain monohybrid cross

A genetic cross involving only one character


Define multiple alleles

Presence of three or more alleles of the same gene in a population of organisms


Define mutagen

Any agent that causes an increase in the spontaneous rate of mutation


Explain null hypothesis

Used in statistical tests, the hypothesis that there is no real difference between the observed and expected datasets. Statistical methods such as chi-squared analysis are used to test the probabiltiy associated with this hypothesis


Explain pedigree (kindred, family tree)

In human genetics, a diagram showing the ancestral relationships and transmission of genetic traits over several generations in a family


Define penetrance

The frequency, expressed as a percentage, with which individuals of a given genotype manifest at least some degree of a specific mutant phenotype associated with a trait


Define phenotype

Overt appearance of a genetically controlled trait


Define pleiotoropy

Condition in which a single mutation causes multiple phenotypic effects


Define population genetics

Branch of science that deals with the statistical anaylsis of the inheritance and prevalence of genes in populations and genetic divergence between populations.


Define preformation

Theory that the sperm or the fertilized egg contains a complete miniature adult


Define primary constriction

A cytologically defined chromosomal constriction associated with and determined by the centromeric region


Define probability

Study of the likelihood of the occurrence of a particular event or offspring


Define synapsis

The pairing of homologous chromosomes at meiosis


Define prokaryote

Microscopiic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles


Explain a Punnett square

Gid used to show the gamets of each parent and their possible offspring


Define quantatitive genetics

Branch of population genetics that deals with phenotypes that vary continuously, as opposed to discretely identifiable phenotypes and gene-products


Explain random chance

Genes are entirely based on chance


Define wild-type

The most commonly observed phenotype or genotype, designated as the norm or standard


Define reciprocal crosses

A pair of crosses between a male of one strain and a female of another, vice versa


Explain relative frequency

Value representing a proportion of the entire population under study


Explain Rh blood group system

System that classifies blood groups based on the presence or absence of the Rh antigen (Rh factor) on the cell membranes of the RBCs


Define RhoGAM

An injectable drug that is used to protect an Rh+ fetus from antibodies in an Rh- mother's blood and to prevent Rh allergy in the mother


Define antibody

A blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances that the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood


Define selfing

Union of male and female gamets from the same organism


Explain sickle cell anemia

Abnormal hemoglobin that can cause blockages that damage vital organs and tissues, recessive autosomal disorder, found on chromosome 11


Define sister chromatids

Two identical strands joined by a common centromere as a result of a chromosome that duplicated during the S phase of the cell cycle


Define spindle fibers

Protein structure that divides the genetic material in a cell, equally divides the chromosomes in a parental cell into two daughter cells during mitosis & meiosis


Define dihybrid cross

A cross between two parents that differ by two pairs of alleles (AABB x aabb)


Define daughter cells

Identical cells formed by mitosis


Explain cystic fibrosis

Buildup of mucus that damages the body's organs, autosomal recessive pattern


Define degrees of freedom

df=n-1, n is # of classes


Who is Darwin

Did not provide an adequat account of inheritance, so it was logically incomplete. He was not able to interpret his own data. Later, Mendel did


Define epigenesis

The idea that an organism or organ arises through the sequential appearance and development of new structures already present in the egg


Define true-breeding

When parents pass down a specific phenotypic trait to their offspring. Pure genotpe with only one phenotype


Define dominant

An allele or a gene that is expressed in an organism's phenotype, masking the effect of the recessive allele or gene when present.


Explain Ehlers-Danlos syndrome

Affects the connective tissues, usually autosomal recessive pattern


Explain ABO blood group system

Classification of human blood based on the inherited properties of RBCs as determined by the presence or absence of antigens A and B


Explain albinism

Congenital, autosomal redessive disorder characterized by the complete or partial absence of pigment in skin, hair, and eyes.


Define antibody

Immunoglobins, proteins that help stop intruders from harming the body


Define antigen

Substance that enters the body and starts a process that can start a disease


Define autosomal genetic disorder

Disorders caused by genes


Define Bombay phenotype

Rare condition first spotted in Bombay, India, where there is no expression of the A, B, or H antigens on the RBCs


Define chloroplast

Plastid containing chloropyll that has its own DNA


Define dihybrid cross

A cross showing two organisms with opposite phenotypes (yellow round vs green wrinkled)


Define daughter cells

Cells formed due to mitosis, genetically identical to the parent cell


Explain cystic fibrosis

Buildup of thick, sticky mucus that can damage the body's organs, autosomal recessive


Define degrees of freedom

(df)=n-1, where n is the number of classes


Who is Darwin

English naturalist whose scientific theory of evolution by natural selection


Define epigenesis

The idea that an organism or organ arises through the sequential appearance and development of new structures, in contrast to preformationism, which holds that development is the result of the assembly of structures already present in the egg


Define diplonema

The doubled form of chromosomes strand visible at the diplotene stage of meiosis


Define dominant

Effect on phenotype of one allele masks the contibution of a second allele at the same locus


Explain Ehlers-Danlos syndrome

Affect connective tissues, usually autosomal dominant pattern


Define epistasis

Nonreciprical interaction between nonallelic genes such that one gene influences or interferes with the expression of another gene, leading to a specific phenotype


Define eukaryote

Organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus


Define experimental error

Erros that may occur in the execution of a statistical experiment design (human, systematic, or random error)


Define expressivity

Degree to wich a phenotype for a given trait is expressed


Explain extranuclear inheritance

Transmission of traits by genetic information contained in cytoplasmic organelles such as mitochonria or chlorplasts


Explain a genetic disorder

Genetic problem caused by one or more abnormalities in the genome


Define heredity

Passing on of traits from parents to their offspring, through asexual or sexual reproduction


Define homunculus

A supposed microscopic but fully formed human being from which a fetus was formerly believed to develop


Explain Hutington disease

Degeneration of neurons in the brain, autosomal dominant,


Define H substance

Polysaccharide precursor molecule used to make the antigens on the surface of human RBCs that are classified in the ABO system


Explain identical twins

Develop from one zygote


Explain fraternal twins

Develop from two different eggs


Who is Mendel

Father of genetics, discovered the fundamental laws of inheritance


Explain independent events

Event whose occurence or non-occurence is not in any way influenced by the occurrence or non-occurence of another event. The probability that both events will occur is equal to the product of their separate probabilities


Explain mutually exclusive events

Two events that are disjoint, meaning that they both cannot occur


Define mitochondria

Organelle in the cytoplasm of cells that functions in energy production, it has its own DNA


Explain modifier genes

Gene that influences the expression of another gene


Define phenocopy

An individual showing features characteristic of a genotype other that its own, but produced environmentally rather than genetically


Explain non-sister chromatids

Either of the two chromatids of the paired homolgous chromosomes, form the chiasma to exchange genetic material during meiosis


Explain phenylkenoturia (PKU)

Causes an amino acid to buildup in the body, autosomal recessive