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Prokaryote
lack nuclear membrane and possess no membrane-bound organelles
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Eukaryotes
Have a nuclear membrane and membrane-bound organeles
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What is the fundamental unit of heredity?
the gene
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Principle of segregation
Diploid's alleles separate in equal proportions
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What is a testcross?
Crossing an individual of unknown genotype with a homozygous recessive individual to reveal the unknown.
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When a het has a phenotype intermediate between the phenotypes of two homo, the trait is said to be _______
incomplete dominance
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When two alleles separate, their separation is independent of the separation of alleles at other loci. What principle is this?
Independent assortment
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What kind of crosses reveal the principle of independent assortment?
Dihybrid
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How do you determine the chi-square value for inheritance of crosses?
chi-square = sum((obs_i - exp_i)/exp_i), with degrees of freedom one less than the expected number of phenotypes
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What type of sex determination has males with only one X?
XX-XO sex determination
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What type of sex determination has males with two of the same chromosome?
ZZ-ZW sex determination
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What determines phenotype in Drosophila?
X:A ratio, A is number of autosomes
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In humans, what does the combination of XO chromosomes lead to?
Turner's syndrome
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In humans, what does the combination of XXY chromosomes lead to?
Klinefelter syndrome
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In humans, what does the combination of XXX chromosomes lead to?
Poly-X females
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What is a reciprocal cross?
It is a breeding experiment designed to test the role of parental sex on a given inheritance pattern. In one cross, a male expressing the trait of interest will be crossed with a female not expressing the trait. In the other, a female expressing the trait of interest will be crossed with a male not expressing the trait.
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If only one copy of a chromosomal region is present, such as X-linked genes in humans, this is called ______
Hemizygous
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__________ equalizes the amount of protein produced by X-linked genes in the two sexes.
Dosage compensation
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What is the Lyon hypothesis?
Darkly staining bodies in the nuclei of female cats (known as Barr bodies) were inactive X chromosomes
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_______ is when the phenotype of the het is intermediate between the two homozygotes
Incomplete dominance
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The MN blood group is an example of _________.
Codominance
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__________ is the percentage of individuals with a particular genotype that express the expected phenotype.
Penetrance
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_______ describes the degree to which a genotype is phenotypically expressed.
Expressivity
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A ____________ causes death at an early stage of development, often before birth
lethal allele. Note that this affects the phenotypic ratio outcome
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An allele is said to be ______ when it has more than one phenotype.
pleiotropic
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_______ occurs when genes at multiple loci affect a single phenotype.
Gene interaction
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The mallard example with duck feather pattern highlighted _________
multiple alleles at a single locus.
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______ is a phenomenon in which a one gene masks (hides) the effect of another gene at a different locus
Epistasis
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The gene that does the masking is called the _______
epistatic gene
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The gene that is masked is called the ______ gene.
hypostatic
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The presence of either of two recessive alleles at two different loci resulting in a recessive phenotype is called ______
duplicate recessive epistasis
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When a single copy of an allele is sufficient to mask the phenotype of alleles at a second locus, this is ______
dominant epistasis
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Interpreting dihybrid cross ratios is often easier if the amount is ...
multiplied by 16 and then divided by the total
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______ traits are present in males and females, but are inherited only from the mother and can result in phenotypic variation.
Cytoplasmically inherited
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__________ is a phenomenon in which the phenotype of the offspring is determined by the genotype of the mother.
Genetic maternal effect. Note that the offspring's phenotype is determined by mother's genotype, not her phenotype.
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_________ is the differential expression of genetic material depending on whether it is inherited from the male of female parent.
Genomic imprinting
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At the ______________, the mutant protein functions normally.
permissive temperature
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At the ____________, mutant protein is inactivated and endocytosis is halted, resulting in paralysis.
non-permissive temperature
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Characteristics that have a few easily distinguished characteristics, such as seed color or shape, are called _____.
discontinuous characteristics
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_________ are characteristics, such as height, for which a continuous distribution of phenotypes is observed. Also called _________.
Continuous characteristics, quantitative characteristics
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Continuous characteristics frequently arise because genes at many loci interact to produce the phenotype: ________.
polygenic characteristics
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What is the number of genotypes encoded by n loci with two alleles?
3^n
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Name useful characteristics of genetic model organisms.
- short generation time
- large number of progeny
- adaptable to lab environment
- housed and propagated relatively inexpensively
- genomes sequenced
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What model organism has a homolog whose mutant in a human eye disease?
Drosophila melanogaster
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What model organism taught us about differences in skin color?
Zebrafish (Danio rerio)
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What is the most widely studied prokaryote?
Escherichia coli, regulation of expression of genes
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What is the simplest eukaryotic genetic model organism?
Baker's yeast (Saccharomyces cerevisiae), DNA damage/repair
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What is the most basic multicellular animal that is a genetic model organism?
roundworm (Caenorhabditis elegans), neurotransmitters
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What is the mammalian genetic model organism?
House mouse (Mus musculus), white blood cells
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What is the primary plant model organism?
Thale cress plant (Arabidopsis thaliana); genome structure, plant evolution
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_______, the person from whom the pedigree is initiated.
Proband
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Characteristics of autosomal recessive traits in pedigrees
- Normal parents have affected children
- Equal number of males and females
- 1/4 of offspring of two carriers are affected
- Normal children with affected siblings have a 2/3 chance of being a carrier
- Consanguineous marriages are sometimes involved
- Example: tay-sachs
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Characteristics of autosomal dominant traits in pedigrees
- Does not skip generations (unless incompletely penetrant/express)
- Approx equal number males and females
- Most affected individuals are heterozygous
- 1/2 offspring of an affected individual are affected
- These alleles tend to be very rare, even more so for homozygous
- Example: elevated blood cholesterol
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Characteristics of X-linked recessive traits in pedigrees
- Males usually affected
- Usual transmission from carrier woman to son
- Daughters of carrier mothers have 1/2 chance of being carriers
- Not passed from father to son
- Affected woman must have an affected father and either an affected mother or carrier mother
- Example: Hemophilia A
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Characteristics of X-linked dominant traits in pedigrees
- Affected males only have affected daughters.
- Affected mothers have 1/2 affected kids, and 1/2 normal
- Trait does not skip generations
- Rare: assume heterozygous
- Example: Hypophosphatemia - vitamin D resistant rickets
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Characteristics of Y-linked traits in pedigrees
- Very rare
- Father to son transmissions
- All male offspring are affected
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______ genes do not assort indepently.
Linked
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______ is the soring of alleles into new combinations
Recombination
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Genes on the same chromosome belong to the same ________
linkage group
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If the genes of interest are linked, only _______ progeny are produced.
nonrecombinant
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Genes that exhibit crossing over are ________.
incompletely linked
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A single crossover produces what ratio of recombinant to nonrecombinant gametes?
half
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_____ is the percentage of progeny produced in a cross.
Recombination frequency
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Wild-type alleles in a _____ configuration are on the same chromosome.
coupling
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Wild-type alleles in a _____ configuration are on different chromosomes.
repulsion
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What are the two types of recombination?
Interchromosomal and intrachromosomal.
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Which type of recombination arises from independent assortment?
interchromosomal
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Who discovered that Intrachromosomal Recombination Results from Physical Exchange Between Chromosomes?
Harriet Creighton and Barbara McClintock
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______ are chromosome maps calculated by using the genetic phenomenon of recombination.
Genetic maps, 1 m.u. = 1% recombination
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______ are chromosome maps calculated by using physical distances along the chromosome.
Physical maps, distance in base pairs
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Why are genetic maps based on short distances more accurate than those based on long distances?
Double crossovers are not detected
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In a 3-point cross, classes with the fewest progeny are ____.
double-crossovers
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In a 3-point cross, classes with the most progeny are ____.
nonrecombinants
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In a 3-point cross, the recombination frequency is calculated by adding all the crossovers (single and double) between two genes and dividing by the total number of progeny.
See example Lecture 10, Slide 7
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The degree to which one crossover interferes with additional crossovers in the same region is termed ________.
interference
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The ratio of observed double crossovers to expected double crossovers is called the _______.
coefficient of coincidence
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The number of expected double crossovers can be calculated by multiplying the total number of progeny by _____.
the product of the probability of recombination for the single crossovers.
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Interference =
1- coefficient of coincidence
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Disease causing genes are mapped by _______ analysis which examines the probability of having linkage at a particular RF compared to the probability of independent assortment.
logarithm of odds
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A LOD score of 3 indicates linkage with the specified recombination is _____ times as likely to produce what was observed as independent assortment.
1000
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Variable genes with easily observable phenotypes are called ____.
genetic markers
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Variations in in DNA sequence detected by cutting the DNA with restriction enzymes are called _____.
Restriction Fragment Length Polymorphisms (RFLPs)
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Variable numbers of short DNA sequences repeated in tandem are called ____.
microsatellites
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Individual variations in the DNA nucleotides are called ____.
Single Nucleotide Polymorphisms (SNPs)
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Describe deletion mapping.
- Individual homozygous for a recessive mutation in the gene of interest is crossed with an individual heterozygous for a deletion.
- If the gene of interest is in the deletion region, half of the progeny will dislay the mutant phenotype.
- If it's not, all the progeny will be wild type.
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Describe somatic-cell hybridization
See first 3 slides of Lecture 11. It's used for gene mapping
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_____ is a method for determining the chromosomal location of a particular gene through molecular analysis.
in situ hybridization
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Wild-type bacteria are called ____.
prototrophic
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_____ contains all the nutrients required by prototrophic bacteria.
Minimal media
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Mutant strains called _____ lack enzymes necessary for metabolizing nutrients or synthesizing essential molecules.
auxotrophs
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_____ contains all substances required by bacteria for growth and reproduction.
Complete media
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Most bacteria have __#__ _____ (shape) chromosome(s) several million base pairs long.
1, circular
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Many bacteria also contain small (several thousand base pairs), circular DNA molecules called ____.
plasmids
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_____ are plasmids capable of freely replicating and able to integrate into the bacterial chromosome.
Episomes
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The ______ in E. coli controls mating and gene exchange between E. coli cells.
F (fertility) factor
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Plasmids Replicate _____ of the Bacterial Chromosome.
Independently
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What are three types of gene transfer in bacteria?
Conjugation, transformation, and transduction
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In ______, a cytoplasmic bridge forms allowing transfer of part of DNA from one bacteria to another.
conjugation
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In _____, naked DNA is tken up by the recipient cell/bacteria.
transformation
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In ______, a virus attaches to a bacteria cell to inject DNA.
transduction
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_____ is usually the only DNA transferred during conjugation.
F factor
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Conjugation between an F+ cell with an F- cell results in an ____ cell.
F+
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____ cells contain an F factor integrated into the bacterial genome.
Hfr (high frequency)
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Bacterial genes can be transferred from an ___ cell to an F- cell in conjugation.
Hfr
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An Hfr cell can be converted into an F' cell during ______.
sexduction
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Sexduction produces _______, cells with two copies of some genes.
merozygotes (partial diploids)
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The transfer times of genes between bacteria indicate the order and relative distances which can be used to construct a ______.
genetic map
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_______ are small circular plasmids that carry genes that encode antibiotic resistance and can be transferred by conjugation.
R plasmids
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