Bio Final Review

anaphase

The fourth stage of mitosis, beginning when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell.

asexual reproduction

The creation of genetically identical offspring by a single parent, without the participation of sperm and egg.

autosome

A chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X or Y.

benign tumor

An abnormal mass of cells that remains at its original site in the body.

binary fission

A means of asexual reproduction in which a parent organism, often a single cell, divides into two genetically identical individuals of about equal size.

cancer

A disease characterized by the presence of malignant tumors (rapidly growing and spreading masses of abnormal body cells) in the body.

cell division

The reproduction of a cell through duplication of the genome and division of the cytoplasm.

cell plate

A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.

centromere

The region of a duplicated chromosome where two sister chromatids are joined (often appearing as a narrow "waist") and where spindle microtubules attach during mitosis and meiosis. The centromere divides at the onset of anaphase during mitosis and anaphase II during meiosis.

centrosome

A structure found in animal cells from which microtubules originate and that is important during cell division. A centrosome has two centrioles.

chiasma (plural, chiasmata)

The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis.

chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.

chromosome

A gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell.

cleavage furrow

The first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphase plate.

cytokinesis

The division of the cytoplasm to form two separate daughter cells.

crossing over

The exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis.

deletion

The loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome.

diploid

Containing two complete sets of chromosomes, one from each parent.

duplication

Repetition of part of a chromosome resulting from fusion with a fragment from a homologous chromosome; can result from an error in meiosis or from mutagenesis.

gamete

A sex cell; a haploid egg or sperm.

haploid

A cell containing a single set of chromosomes.

homologous chromosomes

The two chromosomes that make up a matched pair in a diploid cell.

interphase

The period in the eukaryotic cell cycle when the cell is not actually dividing.

inversion

A change in a chromosome resulting from reattachment of a chromosome fragment to the original chromosome, but in the reverse direction.

karyotype

A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position.

malignant tumor

An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body.

meiosis

In a sexually reproducing organism, the division of a single diploid nucleus into four haploid daughter nuclei.

metaphase

The third stage of mitosis, during which all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle.

metastasis

The spread of cancer cells beyond their original site.

mitosis

The division of a single nucleus into two genetically identical nuclei.

mitotic spindle

A football-shaped structure formed of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis and meiosis.

nondisjunction

An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase.

prometaphase

The second stage of mitosis, during which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids.

prophase

The first stage of mitosis, during which the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still intact.

sex chromosome

A chromosome that determines whether an individual is male or female.

sexual reproduction

The creation of genetically unique offspring by the fusion of two haploid sex cells (gametes), forming a diploid zygote.

sister chromatid

One of the two identical parts of a duplicated chromosome in a eukaryotic cell.

somatic cell

Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg.

telophase

The fifth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell.

translocation

A change in a chromosome resulting from a chromosomal fragment attaching to a nonhomologous chromosome.

tumor

An abnormal mass of rapidly growing cells that forms within otherwise normal tissue.

zygote

The diploid fertilized egg, which results from the union of a sperm cell nucleus and an egg cell nucleus.

allele

An alternative version of a gene.

carrier

An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder but who may pass on the recessive allele to offspring.

codominant

Inheritance pattern in which a heterozygote expresses the distinct trait of both alleles.

complete dominance

A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.

cross

A mating of two sexually reproducing individuals.

dihybrid cross

An experimental mating of individuals that are each heterozygous for both of two characters (or the self-pollination of a plant that is heterozygous for both characters).

dominant allele

The allele that determines the phenotype of a gene when the individual is heterozygous for that gene.

F1 generation

The offspring of two parental (P generation) individuals.

F2 generation

The offspring of the F1 generation.

genotype

The genetic makeup of an organism.

heredity

The transmission of traits (inherited features) from one generation to the next.

heterozygous

Having two different alleles for a given gene.

homozygous

Having two identical alleles for a given gene.

hybrid

Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species.

incomplete dominance

A type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygotes (AA and aa).

law of independent assortment

A general rule of inheritance (originally formulated by Gregor Mendel) that when gametes form during meiosis, each pair of alleles for a particular character segregates independently of other pairs.

law of segregation

A general rule in inheritance (originally formulated by Gregor Mendel) that individuals have two alleles for each gene and that when gametes form by meiosis, the two alleles separate, each resulting gamete ending up with only one allele of each gene.

monohybrid cross

An experimental mating of individuals that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant).

pedigree

A family genetic tree representing the occurrence of heritable traits in parents and offspring across a number of generations.

P generation

The parent individuals from which offspring are derived in studies of inheritance.

phenotype

The expressed traits of an organism.

recessive allele

An allele that has no noticeable effect on the phenotype of a gene when the individual is heterozygous for that gene.

rule of addition

A rule stating that the probability that an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways.

rule of multiplication

A rule stating that the probability of a compound event is the product of the separate probabilities of the independent events.

sex-linked gene

A gene located on a sex chromosome. In humans, the vast majority of sex-linked genes are located on the X chromosome.

testcross

The mating between an individual of unknown genotype for a particular character and an individual that is homozygous recessive for that same character.

trait

A variant of a character found within a population, such as purple or white flowers in pea plants.

true-breeding

The organisms are homozygous for the characters under consideration.

wild-type

The version of a character that most commonly occurs in nature.

X-linked gene

A gene located on the X chromosome.

anticodon

On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA.

codon

A three-nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination signal.

deoxyribonucleic acid (DNA)

A double-stranded helical nucleic acid molecule consisting of nucleotide monomers with deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T).

DNA ligase

An enzyme, essential for DNA replication, that catalyzes the covalent bonding of adjacent DNA polynucleotide strands.

DNA polymerase

A large molecular complex that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.

exon

The part of a gene that becomes part of the final messenger RNA and is therefore expressed.

frameshift mutation

A change in the genetic material that involves the insertion or deletion of one or more nucleotides in a gene, resulting in a change in the triplet grouping of nucleotides.

genetic code

The set of rules that dictates the amino acid translations of each mRNA nucleotide triplet.

intron

An internal, noncoding region of a gene that does not become part of the final messenger RNA molecule and is therefore not expressed.

messenger RNA (mRNA)

The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences.

missense mutation

A change in the nucleotide sequence of a gene that alters the amino acid sequence of the resulting polypeptide.

mutation

A change in the genetic information of a cell.

nonsense mutation

A change in the nucleotide sequence of a gene that converts an amino-acid-encoding codon to a stop codon.

plasmid

A small ring of independently replicating DNA separate from the main chromosome(s).

polynucleotide

A polymer made up of many nucleotide monomers covalently bonded together.

promotor

A specific nucleotide sequence in DNA located near the start of a gene that is the binding site for RNA polymerase and the place where transcription begins.

ribosomal RNA (rRNA)

The type of ribonucleic acid that, together with proteins, makes up ribosomes.

ribosome

A cell structure consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm.

RNA polymerase

A large molecular complex that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

RNA splicing

The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence.

semiconservative model

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.

silent mutation

A mutation in a gene that changes a codon to one that codes for the same amino acid as the original codon.

start codon

On mRNA, the specific three-nucleotide sequence (AUG) to which an initiator tRNA molecule binds, starting translation of genetic information.

stop codon

In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.

transcription

The synthesis of RNA on a DNA template.

transfer RNA (tRNA)

A type of ribonucleic acid that functions as an interpreter in translation.

translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule.

biotechnology

The manipulation of living organisms or their components to make useful products.