Flashcards in Exam 1-Chs 2-7 Deck (105)
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1
Homologous pair
-A pair of chromosomes that are alike in structure and size
-Carry genetic info for the same set of hereditary characteristics
-1 Chromosome of a homologous pair is inherited from male parent, 1 from female parent
2
Diploid
-Possessing 2 sets of chromosomes (2 genomes)
3
Haploid
-Possessing a single set of chromosomes (1 genome)
4
Polyploid
-Possession of more than 2 sets of chromosomes
5
Centromere
-Constricted region on a chromosome that stains less strongly than rest of chromosome
-Serves as attachment point for spindle microtubules
6
Telomeres
-Stable end of a euaryotic chromosome
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Sister Chromatids
-Two copies of a chromosome that are held together at the centromere
-Each chromatid consists of a single DNA molecule
8
Cell cycle
-Stages through which a cell passes through from one cell division to the next
9
Checkpoints
-A key transition point at which progression to the next stage in the cell cycle is regulated
10
Interphase
-Major phase of cell cycle btwn cell divisions
-Cell grows, develops, and prepares for cell division
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M (mitotic) phase
-Major phase of cell cycle that encompases active cell divisions
-Includes mitosis (nuclear division) and cytokinesis (cytoplasmic division)
12
Mitosis
-Process by which the nucleus of a eukaryotic cell divides
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Cytokinesis
-Process by which the cytoplasm of a cell divides
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Prophase
-Stage of mitosis in which:
1. Chromosomes contract and become visible
2. Cytoskeleton breaks down
3. Mitotic spindles begin to form
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Condensins
- A group of proteins that bind to chromosomes as a cell enters prophase, causing the chromosome to become more compact and visible under a light microscope
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Prometaphase
-Stage of mitosis
-Nuclear membrane breaks down
-Spindle mictrotubules attach to chromosomes
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Metaphase
-Stage of mitosis
-Chromosomes aligh in middle of cell (metaphase plate)
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Anaphase
-Stage of mitosis
-chromatids separate and move toward spindle poles
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Telophase
-Stage of mitosis
-chromosomes arrive at the spindle poles
-Nuclear membrane reforms
-Chromosomes relax and lengthen
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Meiosis
-Process by which the chromosomes of a eukaryotic cell divide to give rise to haploid reproductive cells
-Meiosis 1 and 2
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Fertilization
-Fusion of gametes (sex cells) to form zygote
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Prophase I
-Stage in meiosis 1
-Chromosomes condense and pair
-Crossing over takes place
-Nuclear membrane breaks down
-Mitotic spindles form
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Synapsis
-Close pairing of homologous chromosomes
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Crossing Over
-Exchange of genetic material btwn homologous chromosomes but nonsister chromatids
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Metaphase I
-Stage of meiosis I
-Homologous pairs of chromosomes align at metaphase plate (center of cell)
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Anaphase I
-Stage of meiosis I
-Homologous chromosomes separate and move towards spindle poles
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Telophase I
-Stage of meiosis I
-Chromosomes arrive at spindle poles
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Interkinesis
-Between meiosis I and II
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Prophase II
-Stage of meiosis after interkenesis
-Chromosomes condense
-Nuclear membrane breaks down
-Spindles form
**Some cells skip this stage
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Metaphase II
-Stage of meiosis II
-Individual chromosomes align in the center of the cell
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Anaphase II
-Stage of meiosis II
-Chromatids sepearate and move towards spindle poles
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Telophase II
-Stage of meiosis II
-Chromosomes arrive at spindle poles
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Recombination
-Process that produces new combinations of alleles of a chromatid
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Cohesin
-Molecule that holds the two sister chromatids of a chromosome together
-Breakdown at centromeres enables chromatids to separate in anaphase of mitosis and anaphase II
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Genotype
-Set of alleles possessed by an individual organism
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Homozygous
-Having two identical alleles at a locus
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Heterozygous
-Having 2 non-identical alleles at a locus
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Phenotype
-Appearance or manifestation of a characteristic
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Monohybrid crosses
-A cross btwn individuals that are homozygous for diff alleles at same locus
-Also refers to cross btwn two individuals that are heterozygous for 2 alleles at single locus
*Differ in one characteristic
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P (Parental) Generation
-1st set of parents in a genetic cross
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F1 (First filial) Generation
-Offspring of the initial parents (P) in a genetic cross
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Reciprocal crosses
-Pair of crosses in which the phenotype of the male and female parents are reversed
-Ex: cross w/ tall male and short female, another cross with short male and tall female
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F2 (2nd filial) generation
-Offspring of F1 gen. in a genetic cross
-3rd gen. of genetic cross
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Principle of segregation
-Principle of heredity discovered by Mendel
-Each diploid individual possesses 2 alleles at locus
-2 alleles separate when gametes are formed, one allele goes to each gamete
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Back cross
-Crosses btwn 1 F1 individual and 1 P individual
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Probability
-Liklihood of the occurence of a particular event
-# of times a particular event occurs/ # of possible outcomes
-Ranges 0-1
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Multiplication Rule
-Rule stating that the probability of 2 or more independent events occuring together is calculated by multiplying the probability of each of the individual events
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Addition rule
-Ruel stating the probability of any 2 or more mutually exclusive events occuring is calculated by adding probabilities of the individual events
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Conditional Probability
-Probability that is modified by additional info that another event has occured
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Testcross
-Cross btwn an individual w/ an unknown genotype and an individual w/ the homozygous recessive genotype
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Wild type
-The trait or allele that is most commonly found in natural populations
52
Dihybrid crosses
-Crosses btwn 2 individuals that differ in 2 characteristics
-Ex: cross btwn individuals that are homozygous for diff alleles at 2 loci OR cross btwn 2 individuals that are heterozygous at 2 loci
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Principles of Independent Assortment
-Principle of heredity discovered by Mendel
-Genes encoding diff characteristics (genes at diff loci) separate independently
-Applies only to genes located on diff chromosomes or genes far apart on same chromosome
54
Chi^2
x^2= sum [(observed-expected)^2/expected]
Independent assortment: DF= n-1
Crossover-
--Df= (# of rows-1)x (#of columns-1)
-Expected= (row totalx column total)/ grand total
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Hemizygous
-Possession of a single allele at a locus
-Males of X-X/X-Y determination are hemizygous for x-linked loci bcuz only have 1 X chromosome
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Nondisjunction
-Failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis
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Dosage Compensation
-Equalization in males and females of the amount of protein produced by X-linked genes
-In placental mammals, accomplished by random inactivation of one x-chromsome in cells of females
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Barr bodies
-Inactive X chromosome that appears as a condensed, darkly stained structure in most cells of female placental mammals
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Pedigree
-Pictorial representation of a family history outlining the inheritance of one or more traits or diseases
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Proband
-A person having a trait or disease who a pedigree is constructed
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Consanguinity
-Mating btwn relatives
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Genetic mosaics
-Condition in which regions of tissue w/in single individual have diff chromosome constitutions
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Complete Dominance
-Type of dominance
-Same phenotype is expressed in homozygous and heterozygotes
-Only dom allele is expressed
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Incomplete dominance
-Type of dom
-Phenotype of heterozygote is intermediate btwn phenotype of 2 homozygotes
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Codominance
-Type of allelic interaxction in which the heterozygote simultaneously expresses traits of both homozygotes
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Incomplete penetrance
-A case in which some individuals possess the genotype for a trait but do not express the expected phenotype
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Penetrance
-% of individuals w a particular genotype that express the phenotype expected of that genotype
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Lethal Allele
-Allele that causes death of an individual organism
-Early in development
-Organism does not appear in progeny of genetic cross
-Recessive lethal allele kills homozygous recessive, dom lethal allele kills heterozygotes and homozygotes
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Compound Heterozygote
-An individual w/ two diff recessive alleles at locus that result in a recessive phenotype
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Gene Interaction
-Interaction btwn genes at diff loci that affect the same characteristics
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Epistasis
-Type of gene in which gene at one locus masks or supresses the effects of a gene at a diff locus
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Epistatic gene
-Genes that mask or supress the effect of a gene at diff locus
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Hypostatic gene
-Gene that is masked by the action of a gene at a diff locus
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Complementation test
-Test designed to determine whether 2 diff mutations at the same locus (allelic) or a diff locus (nonallelic)
-Two individuals who are homozygous for 2 diff mutations are crossed, producing F1 progeny that are heterozygous for the mutation
-If mutation at same locus= f1 mutant phenotype
-If at same locus= wildtype
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Complementation
-Manifestation of 2 diff mutations in the heterozygous conditions as the wild-type phenotype; indicates that the mutations are at diff loci
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Sex-influenced characteristics
-Characteristics encoded by autosomal genes that are more radically expressed in one sex
-Ex: autosomal dom gene may have higher penetrance in males than females, or gene is dom in males and recessive in females
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Sex-limited characteristics
-Characteristics encoded by autosomal genes and expressed in only 1 sex
-Both males and females carry genes for sex-limited characteristics, but the characteristics appear in only one of the sexes
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Cytoplasmic inheritance
-Inheritance of characteristics encoded by genes located in cytoplasm
-Most cytoplasmically inherited characteristics are inherited from 1 parent bcuz usually contributed by 1 parent
-Usually inherited from mother
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Genetic maternal effect
-determination of the phenotype of an offspring not by its own genotype, but the nuclear genotype of its mother
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genomic imprinting
-Differential expression of a gene that depends on the sex of the parent that transmitted the gene
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Epigenetics
-Phenomena due to alterations in dna that do not include changes in the base sequence
-Often affect the way in which dna sequences are expressed
-Such alterations are often stable and heritable in the sense that they are passed to decendant cells or individuals
82
Temp-sensitive allele
-Allele that is expressed only at certain temps
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Phenocopy
-Phenotype produced by environmental effects that is the same as the phenotype produced by a genotype
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Discontinous characteristics
-Characteristics that exhibit only a few, easily distinguished phenotypes
-Ex: seeds being either round or wrinkled
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Continuous characteristics
-Characterisitics that display large # of possible phenoytypes that are not easily distinguished
-Ex: human height
*or is encoded 4 multiple genetic factors
*Quantitative characteristics
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Polygenetic characteristics
-Characteristics encoded by genes at many loci
-aka mutliple genes 4 one characteristic
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Pleiotropy
-Single gene influences multiple genes/phenotypes
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Multifactorial Characteristics
-Characteristic determined by multiple genes and environmental factors
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Recombination frequency
-Portion of recombinant progeny produced in a cross
= # of recombo progeny/total # of progeny
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Coupling
-Arrangement of linked genes
-wild type alleles of two or more genes are on one chromosome and their mutant alleles are on the homologous chromosome
-Also known as cis-configursation
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Repulsion/trans configuration
-Arrangenment of 2 linked genes
-each of a homologous pair of chromosomes contain one wild type (dominant) and one mutant (recessive) allele
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Genetic Map
-Map of relative distances btwn genetic loci, markers, or other chromosome regions
-Determined by rates of recombination
-Measured on recombination frequencies or map units
93
Physical maps
-Map of physical distances btwn loci, genetic markers, or other chromosome segments
-Measured in base pairs
94
Two-point testcross
-Cross btwn an individual heterozygous at 2 loci and an individual homozygous for recessive alleles at those loci
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Three-point testcross
-cross btwn an individual heterozygous at 3 loci and an individual homozygous for recessive alleles at 3 loci
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Interference
-Degree to which one crossover interferes w/ additional crossovers
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Coefficient of coincidence
# observed double crossovers/ # expected doubel crossovers
98
Haplotype
-A specific set of linked genetic variants or alleles on a single chromosome or on part of a chromosome
99
Kinetochore
-Multiprotein comlex that assembles the centromere b4 cell division
-Spindle microtubules attach to it
100
Xist
-Activity of gene leads to a barr body being created
101
Allelic Series
-Multiple alleles at single gene that show a rank in order in their dominance relationships
102
Gene's w/ recombination of 50% or greater
-Tends to underestimate the true physical distance btwn them
-Doesn't take into account double crossovers that might take place--> restores original parental combo of alleles
103
Pangenesis
-Genetic information travels from different parts of the body to reproductive organs
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Preformationism
-Minature organism resides in sex cell, all traits inherited from one parent
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