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50 Cards in this Set

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binary fission
bacterial reproduction into two daughter cells without the utilization of a mitotic spindle
gamete
haploid sex cell; the egg or a sperm that join during fertilization to form a zygote
sperm
male sex cell with three distinct parts at maturity: head, middle piece, and tail
zygote
diploid cell formed by the union of sperm and egg; the product of fertilization
follicle
structure in the ovary that produces the egg and, in particular, the female sex hormones, estrogen and progersterone
ovulation
release of a secondary oocyte from the ovary; if fertilization occurs, the secondary oocyte becomes an egg
ovary
in animals, the female gonad, the organ that produces eggs, estrogen, and progesterone; in flowering plants the base of the pistil that protects ovules and, along with associated tissues, becomes a fruit
testis
male gonad that produces sperm and the male sex hormones
seminiferous tubule
highly coiled duct within the male testes that produces and transports sperm
cytokenesis
division of the cytoplasm following mitosis and meiosis
oogenesis
production of an egg in females by the process of meiosis and maturation
acrosome
cap at the anterior end of a sperm that partially covers the nucleus and contains enzmes that help the sperm penetrate the egg
fertilization
union of a sperm nucleus and an egg nucleus, which creates the zygote with the diploid number of chromosomes
haploid number of chromosomes
half the diploid number; the number characteristic of gametes that contain only one set of chromosomes
diploid number of chromosomes
twice the number of chromosomes found in gametes
somatic cell
a body cell; excludes cells that undergo meiosis and become a sperm of egg
homologous chromosome
similarly constructed chromosomes with the same shape and that contain genes for the same traits; also called homologues
dominant allele
allele that exerts its phenotypic eggect in the herterozygote; it maskes the expression of the recessive allele
recessive allele
hereditary factor that expresses itself in the phenotype only when the genotype is homozygous
punnet square
gridlike device used to calculate the expected results of simple genetic crosses
monohybrid
individual that is herterozygous for one trait; shows the phenotype of the dominant allele but carries the recessive allele
neurotransmitter
chemical stored at the ends of axons that is responsible for transmission across a synapse
dendrite
part of a neuron that sends signals toward the cell body
cell body
portion of a neuron that contains a nucleus and from which dendrites and an axon extend
positive feedback
mechanism of homeostatic response in which the output intensifies and increases the likelihood of response, instead of counterin it and canceling it
budding
new viruses bud from the cell surface
hormone
chemical signal produced in one part of the body that controls the activity of other parts
sister chromatids
one of two genetically identical chromosomal units that are the result of DNA replication and are attached to each other at the centromere
centromere
constricted region of a chromosome where sister chromatids are attached to one another and where the chromosome attaches to a spindle fiber
interphase
stages of the cell cycle (G, S1, G2) durind which growth and DNA synthesis occur when the nucleus is not actively dividing
metaphase
mitotic phase during which chromosomes are aligned in the middle
prophase
mitotic phase durind which chromatin condenses so that chromosomes appear; chromosomes are scattered
anaphase
mitotic phase during which daughter chromosomes move toward the poles of the spindle
telophase
mitotic phase during which daughter cells are located at each pole
mitosis
type of cell division in which daughter cells receive the exact chromosome and genetic makeup of the parent cell; occurs during growth and repair
meiosis
type of nuclear division that occurs as part of sexual reproduction in which the daughter cells receive the haploid number of chromosomes in varied combinations
spermatogenesis
production of sperm in males by the process of meiosis and maturation
cleavage furrow
indentation that begins the process of cleavage, by which animal cells undergo cytokenesis
cell plate
structure that precedes the formation of the cell wall as a part of cytokinesis in plant cells
karyotype
chromosomes arranged by pairs according to their size, shape, and general appearance in mitotic metaphase
trisomy 21
one more 21st chromosome
homozygous
having identical alleles (AA or aa) for a given trait; pure breeding
heterozygous
having two different alleles (Aa) for a given trait
dihybrid cross
individual that is heretozygous for two traits; shows the phenotype governed by the dominant alleles but carries the recessive alleles
axon
fiber of a neuron that conducts nerve impulses away from the cell body
negative feedback
mechanism of homeostatic response by which the output of a system suppresses of inhibits activity of the system
asexual reproduction
reproduction that occurs without sex
sexual reproduction
reproduction that occurs with sex
benign tumor
a ball of cells that do not spread
malignant tumor
a ball of cells that do spread