Biology midterm 2 key terms

cell division

the reproduction of a cell to produce two new cells

Asexual reproduction

the formation of new individuals without the union of genetic material from two different parents

clones

genetically identical cells or organisms produced from a common ancestor by asexual means

mutations

a change in the genetic material that is not caused by recombination

binary fission

reproduction of a prokaryote by division of a cell into two comparable progeny cells

mitosis

nuclear division in eukaryotes leading to the formation of two daughter nuclei, each with a chromosome complement identical to that of the original nucleus

sexual reproduction

reproduction in which the genes of two individuals are combined to produce offspring

gametes

the mature sexual reproductive cell

meiosis

division of a diploid nucleus to produce four haploid daughter cells

somatic cell

all the cells of the body other than the germ cells and gametes

diploid

having a chromosome complement consisting of two copies (homologs) of each chromosome

homologous pairs

a pair of matching chromosomes made up of a chromosome from each of the two sets of chromosomes in a diploid organism

homologs

one of a pair of chromosomes having the same overall genetic composition and sequence

haploid

having a chromosome complement consisting of just one copy of each chromosome

zygote

the fertilized egg

fertilization

the union of gametes

haplontic

life cycle in which the mature organism is haploid and the zygote is the one diploid stage

diplontic

life cycle in which the organism is diploid and the gametes are the only haploid stage

haplo-diplontic

life cycle in which the organism spends significant time in both the haploid and diploid stages

Cell division signals

the one or more signals required to initiate cell division

DNA replication

the creation of a new strand of DNA in which the DNA polymerase catalyzes the exact reproduction of an existing strand of DNA

DNA segregation

the separation of two DNAs formed by replication into two new cells during cell division

cytokinesis

the division of the cytoplasm of a dividing cell

Z-ring

protein fibers on the inside of a prokaryotic cell membrane in the middle of the cell that tightens, causing cytokinesis

cell cycle

the stages through which a cell passes between one division and the next

spindle

array of microtubules emanating from both poles of a dividing cell during mitosis and playing a role in the movement of chromosomes at nuclear division

G1 phase

the gap between the end of mitosis and the onset of S phase

G0

a resting phase in which a cell is not preparing for the cell cycle

S phase

the stage of interphase during which DNA is replicated

G2 phase

the gap between S phase and the onset of mitosis

M phase

the portion of the cell cycle in which mitosis takes place

interphase

the period between successive nuclear divisions during which the chromosomes are diffuse and the nuclear envelope is intact

chromatin

the nucleic acid-protein complex that makes up eukaryotic chromosomes

centromere

the region where sister chromatids join

chromosome arm

the part between a centromere and telomere

sister chromatids

each of a pair of newly replicated chromatids

karyotype

the number, forms, and types of chromosomes in a cell

prophase

the first stage of nuclear division, during which chromosomes condense from diffuse

kinetochores

a specialized structure on a centromere to which microtubules attach

centrosomes

the major microtubule organizing center of an animal cell

centrioles

a paired organelle that helps organize the microtubules in animal and protist cells during nuclear division

prometaphase

phase of nuclear division that begins with the disintegration of the nuclear envelope

metaphase

the stage in nuclear division at which the centromeres of a highly supercoiled chromosomes are all lying on a plane

anaphase

the stage in cell nuclear division at which the first separation of sister chromatids

telophase

the final phase of mitosis or meiosis during which chromosomes become diffuse

meiosis 1

division of a diploid nucleus to produce two haploid daughter cells

meiosis 2

division of a diploid nucleus to produce four haploid daughter cells

independent assortment

during meiosis, the random separation of genes carried on nonhomologous chromosomes into gametes so that inheritance of these genes is random

chiasmata

an x-shaped connection between paired homologous chromosomes in prophase 1 of meiosis

crossing over

the mechanism by which linked genes undergo recombination

recombinant chromatids

in meiosis, a chromatid after crossing over that contains part of a sister chromatid

nondisjunction

failure of sister chromatids to separate in meiosis 2 or mitosis, or failure of homologous chromosomes to separate in meiosis 1

aneuploidy

a condition in which the number of one or more chromosomes is either lacking or in excess

polyploidy

the possession of more than two entire sets of chromosomes

polyspermy

the fertilization of a single female gamete by more than one male gamete

growth factors

a chemical signal that stimulates cells to divide

restriction point

the specific time during G1 of the cell cycle at which the cell becomes committed to undergo the rest of the cell cycle

cyclin-dependent kinases

a protein kinase whose target proteins are involved in transitions in the cell cycle and which is active only when complexed with additional protein subunits

cyclin

a protein that activates a cyclin-dependent kinase, bringing bout transitions in the cell cycle

cell cycle checkpoints

points of transition between different phases of the cell cycle

necrosis

premature cell death caused by external agents such as toxins

apoptosis

programmed cell death

Hayflick limit

the maximum number of cell division for a normal cell before apoptosis occurs

cross-fertilization

the mating of one parent with another

self-fertilization

a cross in which the male and female parent are the same individual

character

an observable feature

trait

a specific form of a character

reciprocal cross

a cross in which the genotypes of the male and female parent are switched

parental generation

individuals that mate in a genetic cross

the first filial generation F1

the immediate progeny of a parental mating

monohybrid crosses

a mating in which the parents differ with respect to the alleles of only one locus/gene of interest

allele

a specific form of a gene at a given locus on a chromosome, among multiple possible forms

genotype

an exact description of the genetic constitution of an individual

phenotype

the observable properties of an individual resulting from both genetic and environmental factors

locus

a specific location on a chromosome

homozygous

having identical alleles of a given gene on both homologous chromosomes

heterozygous

having different alleles of a given gene on the pair of homologs carrying that gene

dominant

an allele that determines the phenotype in an individual who is heterozygous for it and a different allele

recessive

an allele that does not determine phenotype in an individual who is heterozygous for it and a different allele

Punnett square

a method of predicting the results of a genetic cross by arranging the gametes of each parent at the edges of a square

law of segregation

the separation of alleles, or of homologous chromosomes, from each other during meiosis so that each of the haploid daughter nuclei produced contains one or the other member of the pair found in the diploid parent cell

test crosses

mating of a dominant phenotype individual with a homozygous recessive individual

dihybrid cross

a mating in which the parents differ with respect to the alleles of two loci of interest

law of independent assortment

during meiosis, the random separation of genes carried on nonhomologous chromosomes into gametes so that inheritance of these genes is random

linkage

the observation that parental gametes/offspring are more frequent than recombinant gametes/offspring. indicating that genes are on the same chromosome

pedigrees

the pattern of transmission of a genetic trait within a family

mutations

a change in the genetic material that is not caused by recombination

wild type

the standard or reference type

polymorphic

referring to the coexistence in a population of two or more distinct traits

sex chromosomes

in organisms with a chromosomal mechanism of sex determination

autosomes

any chromosome other than a sex chromosome

hemizygous

in a diploid organism, having only one allele for a given trait

sex-linked inheritance

inheritance of a gene that is carried on a sex chromosome

recombinant

any genotype gametes produced by an individual that is different from the two gametes that fused to make the diploid cell undergoing meiosis

recombination frequency

the proportion of offspring of a genetic cross that received gametes that are different from the gametes that fused to make the diploid cell

genetic map distance

the distance between genes on a chromosome in terms of the sum of the frequencies of recombinant offspring produced in crosses between intervening genes

map units

measure of map distance that is equivalent to 1 percent recombination

incomplete dominance

a condition in which the heterozygous phenotype is intermediate between the two homozygous phenotypes

codominance

a condition in which two alleles at a locus produce different phenotypic effects and both effects appear in heterozygotes

pleiotropic

the influence of a single gene on more than one character