Studied by 17 people
heredity
transmission of traits from one generation to the next
genes
hereditary units containing coded information that account for resemblances
gametes
reproductive cells, have only half the number of chromosomes as body cells
somatic cells
body cells with 46 chromosomes
locus
a gene's specific location along the length of a chromosome
asexual reproduction
a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes
sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
homologous chromosomes
chromosomes with the same length, centromere position and staining position
autosomes
Chromosomes that do not determine the sex of an individual
diploid cell
cell with two sets of chromosomes (2n)
haploid cell
single set of chromosomes (n)
zygote
a fertilized egg, diploid cell
meiosis
a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.
crossing over
genetic rearrangement between non-sister chromatids involving the exchange of corresponding segments of DNA molecules
chiasmata
point where a crossover has occurred, and appears as a cross because the original sister chromatids are still held together
metaphase I
chromosomes line up by homologous pairs
anaphase I
each pair of homologous chromosomes separates but the sister chromatids are still attached
telophase I and cytokinesis
two haploid cells form; each chromosome consists of two sister chromatids
prophase II
spindle apparatus forms, chromosomes move to metaphase II plate
metaphase II
kinetochores of sister chromatids separate and move toward opposite poles as individual chromosomes
telophase II and cytokinesis
four genetically distant haploid cells form
trait
each variant for a characteristic (ex: purple/white)
true-breeding
produce only the same variety as the parent plant
hybridization
mating of two true-breeding varieties
alleles
alternative versions of genes that account for variations in inherited characters (DNA sequence variations)
law of segregation
two alleles for a heritable character segregate during gamete formation and end up in different gametes (the egg/sperm only gets one of two alleles)
punnett square
A chart that shows all the possible combinations of alleles that can result from a genetic cross
homozygous
having a pair of identical alleles for a gene
heterozygous
having two different alleles for a gene
phenotype
appearance/observable traits
genotype
genetic makeup
testcross
breeding an organism of unknown genotype with a recessive homozygote to reveal genotype
monohybrid cross
cross between two heterozygotes for one trait
dihybrid cross
heterozygous for two traits being followed in a cross
law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
multiplication rule
to determine probability, multiply the probabilities of two events
addition rule
the probability that any one of two mutually exclusive events will occur is calculated by adding their individual probabilities
complete dominance
phenotypes of the heterozygote and the dominant homozygote are indistinguishable
incomplete dominance
neither allele is completely dominant and the phenotype is somewhere between those of the two parental varieties
codominance
two alleles affect a phenotype in separate, distinguishable ways
pleiotropy
genes have multiple phenotypic effects
epistasis
phenotypic expression of a gene at one locus alters that of a gene at a second locus
ex: one gene in labs dictates brown/black color, another gene designates pigment deposition
polygenic inheritance
additive effect of two or more genes on a single phenotypic character
pedigree
family tree describing the traits of parents and children across generations
cystic fibrosis
-recessive
-caused by defective or absent chloride transport channels in the membrane and leads to a buildup of mucus in organs
sickle-cell disease
-recessive
-caused by a substitution of amino acid in a hemoglobin protein of red blood cells so the cells become sickle-shaped and can block blood vessels
-heterozygotes may show some symptoms (organismal), at the molecular level, the alleles are codominant
-evolutionarily advantageous to be heterozygous bc it prevents malaria
Thomas Hunt Morgan
showed that a specific gene is carried on a specific chromosome and that genes located on a sex chromosome exhibit unique inheritance patterns through his experiments with fruit flies
sex-linked gene
A gene located on either sex chromosome. Most sex-linked genes are on the X chromosome and show distinctive patterns of inheritance; there are very few genes on the Y chromosome.
X-linked genes
fathers pass x-linked genes only to daughters, and females will express a recessive allele only if she is homozygous recessive
ex: Duchenne Muscular Dystrophy, hemophilia
hemizygous
any male receiving a recessive allele from his mother will display the recessive phenotype
Barr body
inactive X in each female cell condenses and is reactivated in cells that give rise to eggs
-if a female is heterozygous for a sex-linked trait, half her cells will express one allele while the others will express the alternate allele because the selection of the inactive chromosome is random
linked genes
genes located near each other on the same chromosome tend to inherited together in genetic crosses
genetic recombination
production of offspring with combinations of traits that differ from those found in the parents
recombinant chromosomes
A chromosome created when crossing over combines the DNA from two parents into a single chromosome.
apoptosis
process of programmed cell death
aneuploidy
having an abnormal number of a particular chromosome
monosomic
2n-1 chromosomes
trisomic
2n+1 chromosomes
polyploidy
more than two complete chromosomes in all somatic cells
sex chromosomes
X and Y chromosomes.
wild-type allele
most common allele in a population
Anaphase II
The centromere divides. The chromatids seperate and move to opposite ends of the cell. Each chromatid is now an individual chromosome.
