Exam 1- Ch 1-5, 8,9 Flashcards
When a single phenotype is affected by more than one set of genes
Gene Interaction
Genes that are present on the X chromosome
X-linkage
An alternative form of a gene
Allele
A mutation that produces alleles encoding proteins with reduced or no function
Loss of function mutation
Mutations that enhance the function of the wild-type product
Usually, the quantity of the gene product increases
Gain of function mutations
A mutation that has no detectable change in function
No change to the phenotype
No change to the evolutionary fitness of the organism
Neutral Mutations
Expressing a heterozygous phenotype that is distinct from the phenotype of either homozygous parent
Incomplete/partial dominance
Where a normal phenotype expression occurs anytime a minimal level of gene product is attained
Threshold effect
Joint expression of both alleles in a heterozygote
No dominance or recessiveness; no incomplete or blending
Codominance
Three or more alleles of the same gene; resulting mode of inheritance
Can only be studied in populations
Multiple Alleles
Has potential to cause death of organism
Result of mutations in essential genes
Usually recessive
Lethal Allele
Presence of one copy of allele results in death
Dominant Lethal Allele
Expression of one gene masks/modifies effect of another gene pair
Gene masks phenotypic effects of another gene
Each step of development increases complexity of organ
Under control and influence of many genes
Epistasis
Screens number of individual mutations resulting in the same phenotype
Can predict total number of genes determining a trait
Complementation Analysis
All mutations present in any single gene
Complementation Group
Expression of single gene has multiple phenotypic effects
Pleiotropy
Expression of specific phenotype is absolutely limited to one sex
Sex-limited inheritance
Sex of individual influences expression of phenotype
Not limited to one sex or the other
Sex-influenced inheritance
Percentage of expression of the mutant genotype in a population
Penetrance
Range of expression of mutant phenotype
Result of genetic background differences and/or environmental effects
Expressivity
Physical location of gene influences expression
Position Effect
Genetic disease has earlier onset and increased severity with each succeeding generation
Genetic Anticipation
Individuals with heritable traits that allow them to adapt to the environment are better able to survive and reproduce
Long periods of time allow slightly advantageous variations to accumulate
Natural Selection
Descent with modification from ancient species
Evolution
All organisms are composed of structural units called cells, which are derived from pre-existing cells
Cell Theory
The study of the origin, transmission, and expression of genetic information
Genetics
? leads to production of sex cells: gametes/spores
Meiosis
Egg contains a homunculus (mini adult)
Theory of Preformation
Proteins associated with centromere
Spindle fibers bind to kinetochore, chromosomes migrate
Kinetochore
Site of oxidative phosphorylation
Contains its own set of DNA
Mitochondria
Find a mutation, determine what gene is affected
Forward Genetics
Plants, algae, protozoans
Site of photosynthesis
Contains its own set of DNA
Chloroplasts
Unit of inheritance that codes for a specific trait
Gene
The physical expression of a trait
Phenotype
A dominant-recessive relationship
Discontinuous Variation
Genetic material in living organisms contained in chromosomes
Separation of chromosomes during meiosis serves as a basis for Mendel’s principles of segregation and independent assortment
Chromosomal Theory of Inheritance
Family tree with respect to given trait; reveals patterns of inheritance of human traits
Pedigree
Parents are related
Consanguineous
S phase: DNA is synthesized
Two gap phases: G1 & G2
Interphase
Interphase and mitosis
Cell Cycle
How genes are transmitted from parents to offspring
Transmission Genetics
Point in G1 where cells are non-dividing, but at a metabolically active state
G0 Phase
Offspring were a blend of parental phenotypes
Continuous Variation
The individual whose phenotype first brought attention to the family
Proband
Genetic material partitioned to daughter cells during nuclear division
Karyokinesis
Exact copy attached by the centromere
Sister chromatids
Similar in size and shape but not identical
Carry genes for the same inherited characteristics at the same location
May carry different versions (alleles) of the same gene
Homologous Chromosomes
Between the middle and end
Submetacentric
Unit factors (traits) assort independently during gamete formation All possible gamete combinations form with equal frequency
Independent Assortment
Alleles are different
Heterozygous
Genetic makeup of an individual
Genotype
- Centrioles move to cell ends. Centrosomes organize microtubule spindle fibers.
- Nuclear envelope dissolves with nucleolus. Chromatin condenses -> visible chromosomes
Sister chromatids connected by cohesin
Prophase
Characterized by the absence of visible chromosomes
Interphase
Cells won’t divide, but are still metabolically active
Quiescent cells
Chromosomes and centromeres align on metaphase plate
Metaphase
Transferring genes between species to a model disease
Transgenic Species
DNA that encodes rRNA
Nucleolus Organizer Region (NOR)
The centromeres are positioned on the metaphase plate
Metaphase II
Everything in the cell membrane
Cytoplasm
Recognition sites that transfer specific chemical signals across the cell membrane
Receptor Molecules
Movement of chromosomes to metaphase plate (spindle fibers form)
Prometaphase
Where ribosomal RNA (rRNA) is synthesized
Nucleolus
Microtubules (tubulin) and microfilaments (actin)
Cytoskeleton
Synthesizes lipids, steroid hormones, detoxes and strokes and metabolizes calcium ions
Smooth ER
Found in centrosome of animal and plant cells
Organize spindle fibers for movement of chromosomes during mitosis and meiosis
Derived from the basal body
Centrioles
Offspring of F1 generation crossed; second filial generation
F2 generation
Produces cilia and flagella, made up of microtubules
Basal Body
Cytoplasmic division follows, two new cells produced
Cytokinesis
Constricted regions on chromosomes
Location of centromere establishes appearance of chromosome
Centromere
Genetic exchange between members of homologous pairs of chromosomes
Crossing Over
Results from symbiotic or parasitic association with a microorganism
Inherited phenotype affected by microbe in host’s cytoplasm
Infectious Heredity
Same as mitosis with a few additions: Synapsis- homologous chromosomes pair up Create bivalent Further condensation -> tetrad with sister chromatids Crossing over
Prophase I
Where nonsister chromatids join and swap genetic material during crossing over
Chiasmata
Sister chromatids are separated to opposite poles; each haploid daughter from meiosis II has one member of each pair of homologous chromosomes
Anaphase II
One member of each pair of homologous chromosomes present at each pole
Telophase II
Studies protein functions and interactions, identifies a set of proteins present in cells under a given set of conditions
Proteomics
Maternal and paternal chromosomes
Mosaic chromosomes
Equational division
Meiosis II
Chromsomes at maximum condensation
Terminal chiasmata holding nonsister chromatids together
Binding to spindle fibers moves chromatids to metaphase plate
Random orientation of tetrads
Metaphase I
Reduction division
Half of each tetrad or homologous pair are pulled to each pole
Nondisjunction- errors in separation
Anaphase I
Both alleles are the same
Homozygous
Alternative form of a single gene
Allele
Covers plasma membrane
Function: biochemical identity at cell surface
Cell coat
During non divisional phases, chromosomes uncoil into a diffuse network within the nucleus
Chromatin
Know the gene and use molecular techniques to induce a specific mutation of the gene to study the genotype
Reverse Genetics
Organisms develop from a fertilized egg by a series of developmental events in order to form an adult
Theory of epigenesis
Produces proteins
Rough ER
original parents/parental generation
P1 generation
Offspring, first filial generation
F1 generation
At end
Telocentric
Makes proteins
Ribosomes
Same as mitosis but,
2 haploid cells result
Sometimes a nuclear forms and enters interphase, sometimes it’s skipped
Telophase I
Reductional division
Meiosis I
Transmission of genetic information to offspring through the cytoplasm, not the nucleus, usually from one parent
Extranuclear inheritance
DNA contained in mitochondria or chloroplasts determines certain phenotypic characteristics of offspring
Organelle heredity
Nuclear gene products are stored in the egg, then transmitted through the ooplasm to offspring—influence phenotype
Maternal effect
Close to end
Acrocentric
Reduces amount of genetic material by half
Produces haploid gametes or spores with unique combination of maternal and paternal derived chromosomes
DNA synthesis
Meiosis
Partitions chromosomes into dividing cells
Produces daughter cells with a full diploid complement of chromosomes
Mitosis
A constriction of the cytoplasm in animal cells
Cell furrow
Uncoiling of the chromosomes
Reformation of the nuclear envelope
Spindle fibers disappear
Nuclear envelope forms
Telophase
Membrane bound
Houses genetic material, DNA
Nucleolus, NOR
Nucleus (eukaryotes)
? leads to the production of two cells
Mitosis
Each dyad is composed of one pair of sister chromatids attached by the common centromeric region
Prophase II
Sister chromatids separate
Disjunction
Centromeres split and daughter chromosomes migrate to opposite poles
Anaphase
Protein that protects cohesin from being degraded by separase
Shugoshin
Middle
Metacentric
Enzymes that degrades cohesin
Separase
Uses hardware and software for processing nucleotide and protein data
Bioninformatics
Any heritable change in the DNA sequence, source of all genetic variation
Mutation
Protein complex that holds sister chromatids together
Cohesin
Have one end near the centrosome region and the other end anchored to the kinetochore
Kinetochore Microtubules
Not membrane bound
Circular DNA
No coiling or condensing
No proteins incorporated
Nucleoid
Fluid inside the cell
Cystol
Studies the structure, function, and evolution of genes and genomes
Genomics
Loss of a single chromosome in a diploid genome, 2n-1
Monosomy
Double exchanges of genetic material
Used to determine distance between three linked genes
Genes must be heterozygous for two alleles
Double Crossover
More than 2 multiples of haploid chromosomes found
Polyploidy
Only consistently shared characteristic—males are over 6 ft tall
Subnormal intelligence
Personality disorders
47, XXY Condition
Inhibition of further crossover event nearby
Reduces expected number of multiple crossovers; complete when no double crossovers occur
Interference
Relies on probability calculations in linkages based on pedigrees
Assesses probability that pedigree with two traits reflects genetic linkage between them
Requires large extensive pedigrees
Lod score method
Proved to be helpful in assigning human genes to their respective chromosomes, involves fusing two cells into a single hybrid cell
Somatic cell hybridization
3n, 4n, 5n chromsomes
Tri, tetra, penta-ploid
A somatic cell containing nuclei from two different sources
Heterokaryon
Heterokaryons cultured in vivid—nuclei are fused together
Synkaryon
Presence or absence of each chromsome, with presence or absence of each gene product
Synteny testing
Short segments of DNA with known sequence and location
Use landmarks for mapping
DNA Markers
Movement of chromosomal segment to a new location in the genome
Translocation
Synapsis between chromosome with large intercalary deletion and normal complete homolog
Requires unpaired region of normal homolog to loop out linear structure
Compensation Loop
Repeated segment of chromosome
Single locus is present more than once in genome
Can produce compensation loop
Arise from unequal crossing over between synapses chromosomes during meiosis
Duplications
Synapsed chromosomes in meiosis wrap around each other
Chiasmata
No crossing over between two genes Produces parental (non-crossover) gametes
Complete Linkage
The presence of several genes in an organism’s genome that all have variations of the same function
Gene Redundancy
The process by which gene sequences are selected and differentially replicated either extrachromosomally or intrachromosomally
Gene Amplification
Rearrangement of linear gene sequence
No loss of genetic info
Segment of chromosome turned 180 degrees within chromosome
Requires 2 breaks in chromosomes and reinsertion inverted segment
May arise from chromosomal looping
Inversion
Two examples of mitochondria messing up, but phenotype is still normal?
Bread mold, yeast
Small percent of mutation are a result of nuclear mutations
Segregational petites
Demonstrate cytoplasmic transmission
Lack mtDNA or lack a portion of it
Mitochondria inherited by both parental cells (not for humans)
Neutral petites
Mutant and wild type cross gives diploid zygotes
Express petite phenotype
Suppressive mutation
Mitochondria and chloroplasts arose independently 2 billion years ago from free-living bacteria
Organelles possessed attributes of aerobic respiration and photosynthesis
Endosymbiotic Theory
Inverted and noninverted chromosomes in meiosis paired only if they form an inversion loop
Inversion loops
Organisms with one inverted chromosome and one non-inverted homolog
Inversion Heterozygotes
One recombinant chromatid is dicentric (2 centromeres) and one is acentric (lacking a centromere)
Paracentric inversion crossover
Crossover between pericentric inversion and noninverted homolog
Recombinant chromatids have duplications and deletions
Pericentric inversion crossover
Three sets of chromosomes are present
Triploid
Involves exchange of segments between two nonhomologous chromosomes
Genetic information is lost or gained
Has unusual synapsis configuration during meiosis
Reciprocal translocation
The gain of a single chromosome, 2n+1
Trisomy
The number of trinucleotide repeats increases with generations
Genetic Anticipation
Gives rise to chromosomal variation
Paired homologs fail to disjoin during segregation
During meiosis I or II
Nondisjunction
More than two sets of chromosomes are present
Polyploidy
Complete haploid sets of chromosomes are present
Euploidy
Variations in chromosome number
Organisms gain or lose one or more
Aneuploidy
Segregation pattern at first meiotic division
Has complete complement of genetic information
Alternate segregation
Leads to gametes containing duplications and deficiencies
If these participate in fertilization in animals the resultant offspring do not usually survive
Parent is said to have semisterility
Adjacent segregation
Sister chromatids involved in mitotic exchanges
Patch-like appearance when stained and viewed under a microscope
Harlequin chromsomes
Occur during mitosis but do not produce me alleic combinations
Sister chromatid exchanges
Short repetitive sequences found throughout the genome
Micro satellites
Polymorphic sites generated when specific DNA sequences are recognized and cut by restriction enzymes
Restriction fragment length polymorphisms: RFLP’s
Exists in eukaryotes as double-stranded circular DNA
Smaller than DNA in chloroplasts
Size varies based on species
mtDNA- mitochondrial DNA
Genes encode products involved in photosynthesis and translation
cpDNA- chloroplast DNA
Variations in the DNA within organelles such as mitochondria and chloroplasts within the same cell
Heteroplasmy
1% recombination between two genes on chromosomes
Relative distances, not exact
Map Units
3 X chromosomes
Normal set of autosomes
Results in female differentiation
Perfectly normal or underdeveloped secondary sex characteristics
47, XXX Syndrome
Missing regions of chromosomes
Chromosome breaks in one or more places
Portion is lost
Deletions
Does change lengths of two arms of a chromosome, centromere is part of inverted segment
Pericentric inversion
More susceptible to chromosome breakage when cultured in the absence of folic acid or other chemicals
Sites indicate regions of non tightly coiled chromatin
Fragile Sites
Involves breaks at extreme ends of short arms of two nonhomologous acrocentric chromosomes
Small segments are lost
Large submetacentric or metacentric chromosome produced
Robertson translocation (centric fusion)
Combination of chromosome sets from different species as a consequence of hybridization
Allopolyploidy
Occurs between two nonsister chromatids
Recombination is observed in 50% of gametes
In genes 50 mu apart, crossing over can be expected between 100% of tetrads
Single Crossover
Condition where only certain cells in a diploid organism are polyploid
Set of chromosomes replicates repeatedly without nuclear division
Can occur in cancer cells
Endopolyploidy
Addition of one or more sets of chromosomes identical to the haploid complement of the same species
Autopolyploidy
Doesn’t change lengths of two arms of a chromosome
Paracentric Division
