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cell cycle
series of events that cells go through as they grow and divide
G1 checkpoint
Checks the surroundings to make sure the conditions are favorable and the cell is healthy enough to enter the next stage
G2 checkpoint
The cell checks to make sure the DNA is copied correctly
M checkpoint
Spindle assembly checkpoint. Mitosis will not continue if chromosomes are not properly aligned.
benign tumor
A mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin.
malignant tumor
An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor.
metastasis
spread of cancer cells beyond their original site in the body
Proto-oncogenes
normal cellular genes that are important regulators of normal cellular processes, they promote growth.
Oncogenes
mutated forms of proto-oncogenes that cause normal cells to grow out of control and become cancer cells
tumor suppressor genes
A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.
Purine
a nitrogenous base that has a double-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either adenine or guanine
Pyrimidines
a nitrogenous base that only has a single ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either thymine, cytosine, or uracil
Polymer
A long molecule consisting of many similar or identical monomers linked together.
DNA backbone
5' to 3' phosphodiester bonds form phosphate backbone
phosphodiester bond
the type of bond that links the nucleotides in DNA or RNA. joins the phosphate group of one nucleotide to the hydroxyl group on the sugar of another nucleotide
semi-conservative replication
in each new DNA double helix, one strand is from the original molecule, and one strand is new
conservative replication
Conservative replication is a theoretical method of replication where the original strands of DNA are left intact and two new strands are formed bonded together.
dispersive replication
a disproved model of DNA synthesis suggesting more or less random interspersion of parental and new segments in daughter DNA molecules
Primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
single strand binding proteins
bind to the unpaired DNA strands, keeping them from re-pairing
Topoisomerase
Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
DNA polymerase III
synthesizes new DNA only in the 5' to 3' direction
DNA polymerase I
removes the RNA primer and replaces it with DNA
DNA ligase
an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments
Helicase
An enzyme that untwists the double helix of DNA at the replication forks.
Okazaki fragments
Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
nucleotide triphosphate
origin of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
Centromere
Area where the chromatids of a chromosome are attached
Euchromatin
The less condensed form of eukaryotic chromatin that is available for transcription.
Heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
Histones
protein molecules around which DNA is tightly coiled in chromatin
Gamates
reproductive cells
chromosome number
The total number of chromosomes in a cell of a given species.
Karyotype
A display of the homologous chromosome pairs of a cell arranged by size and shape.
somatic cells
body cells
Ploidy
number of sets of chromosomes in a cell
homologous chromosomes
Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.
Haploid
having a half set of chromosomes
Diploid
2 sets of chromosomes
asexual reproduction
A reproductive process that involves only one parent and produces offspring that are identical to the parent.
sexual reproduction
Process by which cells from two different parents unite to produce the first cell of a new organism.
Fertilization
Fusion of an egg and sperm cell
crossing over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis.
chiasmata
site of crossing over
synapsis
the fusion of chromosome pairs at the start of meiosis.
Recombination
the genetic process by which one chromosome breaks off and attaches to another chromosome during reproductive cell division
law of independent assortment
Each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random
recombinant chromosomes
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
Allele
An alternative form of a gene.
dihybrid cross
Cross or mating between organisms involving two pairs of contrasting traits
Law of Dominance
In many traits one allele is dominant over the other allele. The "weaker recessive" allele is only expressed when it is paired with another recessive allele
Genotype
genetic makeup of an organism
Phenotype
An organism's physical appearance, or visible traits.
Heterozygous
An organism that has two different alleles for a trait
Homozygous
An organism that has two identical alleles for a trait
Law of Segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete
locus
Location of a gene on a chromosome
monohybrid cross
A cross between individuals that involves one pair of contrasting traits
P generation
parent generation
F1 generation
the first generation of offspring obtained from an experimental cross of two organisms
F2 generation
the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation
progeny
offspring
testcross
cross between an organism with an unknown genotype and an organism with a recessive phenotype
true-breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate
Pedigree
A diagram that shows the occurrence of a genetic trait in several generations of a family.
product rule of probability
The chance of two or more independent events occurring together is the product of their chance of occurring separately
sum rule of probability
the chance of an event that can occur in more than one way is the sum of the individual chances
independent events
The outcome of one event does not affect the outcome of the second event
mutually exclusive events
events that cannot happen at the same time
Carrier
A person who has one recessive allele for a trait, but does not have the trait.
plieotropy
The ability of a single gene to have multiple phenotypic effects.
epistatis
gene at one locus on the chromosome alters the phenotypic expression of a gene at different locus
Co-dominance
A pattern of inheritance in which the phenotypic effect of two alleles in a heterozygous genotype express each phenotype of each allele fully and equally; a phenotype which would not be expressed in any other genotypic combination.
incomplete dominance
A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.
polygenic inheritance
occurs when multiple genes determine the phenotype of a trait
heterogametic
sex chromosomes are of different types
homogametic
sex chromosomes are of one type
sex linkage
the presence of a gene on a sex chromosome
Autosomes
Any chromosome that is not a sex chromosome
wildtype
the most common genotype/phenotype observed in a population
X-linked
referring to a gene located on the X chromosome
SRY gene
the sex determining region of the Y chromosome in males. Encodes the testis-determining factor, which turns the primordial gonads into the testes