William Harvey (1578-1657)
theory of epigenesis
theory of epigenesis
structures are not initially present and develop over time
Schleiden and Schwann
cell theory, all living things are composed of cells
Charles Darwin
natural selection and descent with modification
Mendel
quantitative data to support his findings published in 1866
Mitosis stages
prophase, metaphase, anaphase, telophase
Meiosis differs from mitosis in that:
4 gametes that are haploid, not diploid
Diploid number
cell condition when two of each type of chromosome are present (2 "sets" of chromosomes)
alleles
Different forms of a gene
Avery, MacLeod, McCarty
found DNA is the carrier of genetic information
DNA structure
antiparallel, double helix, phosphate - sugar - base
Pyrimidines
thymine and cytosine
purines
Adenine and Guanine
Transcription
DNA to RNA
translation
The process by which mRNA is decoded and a protein is produced
Recombinant DNA
DNA produced by combining DNA from different sources
Reverse Genetics
discovering gene function from a genetic sequence
Gene knockout
made by disrupting the function of a gene
Chromatin
long strands of DNA found in the eukaryotic cell nucleus; condense to form chromosomes
Peptidoglycan
makes up bacterial cell walls; sugars cross-linked by short polypeptides
Glycocalyx
The external surface of a plasma membrane that is important for cell-to-cell communication
Nucleoid
A dense region of DNA in a prokaryotic cell.
Centrioles
Cell organelle that aids in cell division in animal cells only, organizes spindle fibers
Homologous pairs
Chromosomes that each have a corresponding chromosome from the opposite-sex parent
Centromere
Area where the chromatids of a chromosome are attached
somatic cells
Any cells in the body other than reproductive cells
Karyokinesis
division of a cell nucleus during mitosis.
Cytokinesis
Division of the cytoplasm during cell division
cell cycle checkpoints
control mechanisms which ensure proper division of the cell
cell cycle checkpoints
G1 G2 M
Separase
enzyme that degrades cohesin
shugoshin
Maintains centromere cohesion until meiosis II
Kinetochore
protein structure where microtubules attach during mitosis
Disjunction
the separation of homologous chromosome pairs
Meiosis I
Homologous chromosomes separate
Meiosis II
sister chromatids separate
crossing over
the exchange of genetic material between homologous chromosomes during meiosis
Mendel model organism
peas
monohybrid cross
A cross between individuals that involves one pair of contrasting traits
F1 generation
the first generation of offspring obtained from an experimental cross of two organisms
F2 generation
Offspring resulting from the interbreeding of the hybrid F1 generation.
reciprocal cross
reverse the phenotypes of each parent relative to the initial cross
segregation
separation of alleles during gamete formation
Punnett square
diagram showing the gene combinations that might result from a genetic cross
test cross
Used to figure out if the genotype is heterozygous or homozygous dominant - cross between dominant phenotype and homozygous recessive
dihybrid cross
A cross between two individuals, concentrating on two definable traits
Independent Assortment
genes assort independently during gametes formation
trihybrid cross
three pairs of contrasting traits crossed
Discontinuous variation
The pattern of variation for a trait whose phenotypes fall into two or more distinct classes
Continuous variation
A characteristic that changes gradually after a range of values ex. Height
chromosomal theory of inheritance
The idea that the genetic material in living organisms is contained in chromosomes.
Chi-squared test
a test of association that is used with nominal data in the form of frequencies - to see if the outlying numbers are due to random chance
null hypothesis
2 sets of data are not statistically different from each other
degrees of freedom
n-1
pedigree
A diagram that shows the occurrence of a genetic trait in several generations of a family.
pedigree conventions
circle - female square - male diamond - unknown sex
gene interaction
the idea that several genes influence a particular characteristic
Mutation
a random error in gene replication that leads to a change
Wild type allele
Traits prevailing in nature (the more common traits) - Not necessarily the dominant trait
loss of function mutation
Mutation that results in a gene product or protein having less or no function
gain of function mutation
Mutation that results in the gene product or protein having a new and abnormal function
dominant allele
An allele whose trait shows up in the organism when the allele is present
recessive allele
An allele that is masked when a dominant allele is present
Incomplete dominance
situation in which one allele is not completely dominant over another, pink
Tay-Sachs disease
neuron membranes do not develop properly, therefore cannot conduct impulses properly
threshold effect
normal phenotypic expression results if 50% or less of a gene is expressed
Codominance
A condition in which neither of two alleles of a gene is dominant or recessive - joint expression
multiple alleles
three or more forms of a gene that code for a single trait
Bombay phenotype
Homozygous recessive for a mutation which masks the genotype for blood groups
lethal alleles
Mutated genes that are capable of causing death
Dominant lethal allele
presence of one or more copy of the allele means death
Huntington's disease
caused by a dominant allele for a protein found in brain cells, heterozygous delayed until adulthood, progressive degeneration of nervous system dominant autosomal allele
Mutant Allele
The less-occurring trait, not necessarily recessive.
Recessive Lethal Allele
sufficient for survival
gene interaction
the idea that several genes influence a particular characteristic
Epistasis
interaction between alleles in which one allele hides the effects of another allele
hereditary deafness
the mutation that interrupts many of the steps of ear development
Dominant Epistasis
- when dominance at one allele can overshadow other genes
Complementation Analysis
screens the number of individual mutations resulting in the same phenotype, and can predict the total number of genes determining a trait
Complementation Group
all mutations present in a single gene
Pleiotropy
The ability of a single gene to have multiple effects.
Marfan syndrome
autosomal dominant; pleiotropic; tall, weak heart
porphyria Variegata
autosomal disorder of toxic buildup of porphyrins in the body
X linked genes
Genes found on the X chromosome.
color blindness
a variety of disorders marked by the inability to distinguish some or all colors, X chromosome-linked
Duchenne Muscular Dystrophy
a form of muscular dystrophy that weakens and progressively destroys muscle tissue, lethal x linked recessive disorder
sex-limited inheritance
expression of the specific phenotype is absolutely limited to one sex
sex influenced trait
an autosomal trait that is influenced by the presence of male or female sex hormones
Phenotypic expression
influenced by the environment and by genes
Penetrance
percentage of expression of the mutant genotype in a population
Expressivity
the degree to which a particular genotype is expressed in the phenotype
position effect
Dependence of the expression of a gene on the gene's location in the genome
temperature-sensitive mutations
Phenotypic expression is partially determined by the surrounding temperature
nutritional mutation
phenotype expressed or not based on nutrition
Phenylketonuria
A birth defect that causes an amino acid called phenylalanine to build up in the body.
Galactosemia
absence of a necessary enzyme that breaks down fatty galactose
Lesch-Nyhan Syndrome
x linked recessive, purine salvage enzyme defect, normal for about 6 months and then dies
genetic anticipation
symptoms appear at an earlier age and with more severity across generations
genomic imprinting
One parent imprints (inactivates) the gene during transmission to offspring
Prader-Willi Syndrome
the paternal segment is deleted
Angelman Syndrome
Clinical features with molecular genetic testing and/or cytogenetic analysis, the maternal segment is deleted
DNA methylation
chemical modification of parts of the genome may prevent gene expression
complete linkage
linkage without crossing over
linkage
the tendency of genes on a chromosome to be inherited together
crossing over
non-sister chromatids exchanging DNA segment
Linkage ratio
the complete linkage between 2 genes due to close proximity
linkage group
Genes located together on the same chromosome
chiasmata
X-shaped regions where crossing-over occurred.
Sturtevant
realized that genes could be linked and came up with the first genetic map of chromosomes
map units
unit of distance between genes. 1 = 1% recombination frequency.
single crossover
Leads to half recombinant, half non-recombinant
Double crossover
double exchanges of genetic material, used to determine the distance between three linked genes and genes must be heterozygous for 2 alleles
three-point mapping
the parent must be heterozygous for all 3 genes phenotype class must reflect the genotype of gametes parents sufficient number of offspring must be produced for a represented sample
Interference
inhibition of further crossing over events, inhibited by another crossing over event nearby and reduces the expected number of multiple crossovers
coefficient of coincidence
the ratio of observed double crossovers to expected double crossovers
Complete interference
no double crossovers
Positive interference
fewer double crossovers than expected
negative interference
more double crossovers than expected
somatic cell hybridization
assigning human genes to their respective chromosomes
heterokaryon
a cell composed of different nuclear types (i.e. multiple nuclei) in a common cytoplasm
synkaryon
heterokaryon where nuclei are fused
synteny testing
presence or absence of each chromosome with the presence or absence of each gene product
DNA marker
a unique DNA sequence linked to a trait or disease
Restriction Fragment Length Polymorphisms (RFLPs)
polymorphic sites generated when specific DNA sequences are recognized and cut by restrictive enzymes
Microsatellites
Non-coding stretches of DNA that are highly repetitive and have a high mutation rate
single nucleotide polymorphism
variation in a DNA sequence occurring when a single nucleotide in a genome is altered.
Cystic fibrosis
A disease that affects the mucous glands throughout the body
