Exam Prep 1 Flashcards
(140 cards)
1
Q
DNA
A
The hereditary material in almost all living organisms
2
Q
Larger molecules of DNA
A
Guanine and adenine
3
Q
Smaller molecules of DNA
A
Cytosine and thymine
4
Q
Gene
A
Unit of hereditary information
5
Q
Telomere
A
Stable ends of linear chromosome
6
Q
Centromere
A
Constricted region of the chromosome where the kinetochore form and spindle micortubules attach
7
Q
Locus
A
The position of a gene on a chromosome or particular location
8
Q
Chromosome structures
A
Meta centric
Sub meta centric
Acrocentric
Telocentric
9
Q
Autosomes
A
All chromosomes other than sex chromosomes
10
Q
Sex chromosomes
A
A pair of chromosomes that differ between males and females
11
Q
Prokaryotes and eukaryotes do this
A
Copy each chromosomes and separate DNA into each daughter cell
12
Q
Eukaryotes do this only
A
Accommodate nuclear envelope, ensure one copy of each linear DNA strand in a daughter cell
13
Q
The cell cycle
A
G1
G0
S
G2
14
Q
Kinetochore
A
A complex of proteins that assembles at the centromere and serves as a site of micro tubule attachment during cell division
15
Q
Spindle microtubule
A
Filaments responsible for moving chromosomes during cell division
16
Q
Sister chromatids
A
2 linear chromatids that are connected by a centrimere, chromatids are genetically identical
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Q
Phases of mitosis
A
Interphase Prophase Prometaphase Metaphase Anaphase Telophase
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Q
Meiosis
A
The production of haploid gametes
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Fertilization
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The restoration of diploid state in the next generation
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Crossing over
A
Physical exchange of genetic material amount non-sister chromatids
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Independent assortment
A
Of chromosomes into gametes, yields different haploid sets
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Q
Formula for possible combinations of haploid sets
A
2^n
23
Q
Types of genes
A
- Protein coding genes
- RNA encoding genes
- Regulatory signal genes
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Q
Genotype
A
The complete genetic makeup of an individual organism
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Phenotype
A measurable trait of an organism that is controlled by one or more genes but can be influenced by environmental factors
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Dominant allele
Trait is expressed in heterozygous
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Recessive allele
Trait is not expressed in hererozygotes
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Key points of Mendelian a d modern transition genetics
1. Genotype does not equal phenotype and visa Versa
2. A gene is a heritable factor that determines a phenotype
3. Genes are located on chromosomes
4. Individuals are diploid
5. Principal of segregation
6. Independent assortment
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Principal of segregation quick def
Allele variation at a locus
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Independent assortment quick def
Allelic variation across loci
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The principal of segregation full definition
An individual organism possesses two alleles for any particular trait and these two alleles segregate such that each is transferred to its own gamete with equal probability
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The principal of independent assortment long def
Alleles at the different loci on different chromosomes segregate independently of one another
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Mono hybrid cross
A cross between two parents that differ by a single trait
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Reciprocal cross
Test both pollen of ovum of each plant, cross happens both ways with genotype switching for male and female
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Doubley heterozygous
Two traits that are heterozygous
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Dihybrid cross
Cross between two parents that differ by 2 traits
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Probability
The number of times an event is expected to occur out of total outcomes
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Wild type
The allele most often found in the natural population
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Allelic series
A set of greater then 2 alleles that occur within a given natural population
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Biochemical basis of dominance
Typically, in a biochemical pathway, half the amount of “normal” protein is produced by the heterozygote compared to the dominant homozygote. When half the amount of “normal” protein is sufficient to obtain a given phenotype the heterozygote is haplosufficient
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Incomplete dominance
The phenotype of the heterozygote is intermediate between phenotypes of the 2 homozygotes. The heterozygote phenotype may fall at any point within the range of homozygotes. (Haploinsufficient)
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Codominance
The phenotype of the heterozygote simultaneously expresses the phenotype of both homozygotes. The phenotype of the heterozygote does not fall within the range of homozygote phenotype
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Cyclic fibrosis
Recessive, a non function protein in cell wall results and cannot pop out chloride ions
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Test cross
Unknown vs known homozygous
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Epistasis
One allele mask another allele on a different locus
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Independent gene action ratio
9:3:3:1
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Recessive epistatic allele ratio
9:4:3
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Dominant epistatic allele ratio
12:3:1
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Duplicate dominance epistatic ratio
15:1
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What is dominant epistatic pathway
Dominant 1 overpower dominant 2
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What is duplicate dominant epistasis
Dominant 1 and dominant 2 inhibit recessive product
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What is duplicate recessive epistasis
Must have dominant one and dominant 2 to have pigment, will not show if there is only one dominant
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Duplicate rescues such epistasis ratio
9:7
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Complementation of mutants
Two mutants cancel each other out and produce a non mutant but only when on different loci, when they’re mutants on the same loci they will still produce mutants
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Complementation
The expression of a wild type phenotype in an individual carrying two mutant alleles. This is an indication that the alleles are on different loci.
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Combination of events
How many ways can each event happen; Pascal’s triangle
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Formula for number of combinations
N factorial/ x factorial times y factorial
N= group size
X = way 1 (girls)
Y= way 2 (boys)
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Probability formula
P=n!/x!y! (p)^x (q)^y
```
N=total number of events
X=number of event 1
Y= number of event 2
P= probability of event 1
Q= probability of event 2
```
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Sexual reproduction
Alternation between haploid and diploid cell types; process of organism reproduction that creates genetically unique offspring
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Meiocyte
Sperm or egg (haploid)
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Sex
Phenotype of sex; a classification system based on biological differences between males and females roots in anatomy and physiology
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Monoecious
The condition of having both male and female reproductive structures in the same organism
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Dioecious
Species of organisms that have either male or female reproductive structures
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Points on dioecious organisms
1. Chromosomal sex determination
2. Genetic sex determination
3. Environmental sex determination
4. Haplodiploidy (3&4 can be combined)
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Gender
A classification system based on the social construction or cultural distinctions between males and females
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Genetic sex determination
Sexual phenotype is determined by genes at one or more loci carried on autosomes. There are no sex chromosomes in this system
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Environmental sex determination
Sexual phenotype is determined in part of in full by environmental factors (turtles)
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Chromosomal send determination
Includes specific sex chromosomes
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Heterogametic sex
Different set of chromosomes in males
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How heterogametic sex determination evolved
1. Started with ancestral autosomes
2. Gain sex determining genetic systems
3. Crossing over gets suppressed
4. Chromosomes diverge between males and females
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4 systems of chromosomal sex determination
1. XX XY - some insects, all mammals
2. XX X0 - insects
3. ZZ ZW - male is ZZ - birds, moths
4. Haploidy - female is diploid
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Primary sex characteristics
Type of gamete that is made
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Secondary sex characteristics
Traits that tend to differ between sexes but are not directly part of reproductive system - often on autosomes
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SRY and DAS genes
Sex related genes can use to change sex in mice, found in all mammals
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Nondsyjunction
Improper separation of chromosomes - meiosis 1 or 2
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dosage compensation
Mechanism that equalizes the amount of protein produced by x-linked genes between heterogametic and homogeneity sexes
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Mechanisms of dosage compensation
1. Double activity if x-linked genes in males
2. Half the activity of x-linked genes in females
3. One x-chromosomes is absent
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Bar body
A mostly inactivated X chromosome in females
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Lyonization
- occurs 16 days after fertilization
- activation is random
- females transcriptional equal to single male X
- X inactivation due to x-ist gene
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Colour in cats
Sex linked on X chromosome
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Anhydrotic ectodermal dysplasia
Human x-linked trait characterized by several conditions including skin having no hair, etc.
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Haploid set
Random combination of 23 chromosomes
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What happens with two genes of different chromosomes
All possible combinations of alleles are produced with equal frequencies
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What happens with 2 genes on the same chromosome
50:50 of parental types : new combination of alleles were not produced
Here we assumed no crossing over occurred
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Linkage group
A collection of genes that do not assort independently into gametes because they are located on the same chromosome
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Types of linkage groups
- strongly linked genes
- weakly linked genes
- genes very far apart sort independently
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Meiocyte
Diploid cell in which meiosis can take place
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Recombination
Assortment of alleles into novel (non-parental) combination
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Inter-chromosomal recombination
Assortment of alleles for genes on different chromosomes into novel combinations
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Inter chromosomal recombination mechanism
Random alignment of chromosome pairs at metaphase 1 and segregation at anaphase 1 in meiosis
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Intra-chromosomal recombination
Assortment of alleles for genes located on the same chromosome into novel combinations
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Infra-chromosomal recombination mechanism
Exchange of DNA by crossing over in propose 1 in meiosis
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When are genes unlinked
Is they are located very far apart on the same chromosome or if they are on different chromosomes
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Population of meiocytes
The observed population of the different gamete types for two genes on a chromosomes; depends on the distance between them
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Complete linkage
Only parental gamete types are produced
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Independence
Parental and recombinant genes are produced with equal frequencies
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Incomplete linkage
Parental gametes and recombinant gametes are produced by parent gametes and parental type is more frequent
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Cross location for where on chromosome they are
AB/ab
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NR type
Non recombinant type
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R type
Recombinant type
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Independence
Equal number of NR and R types
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Complete linkage
No R types will be observed among progeny
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Incomplete linkage
The NR progeny will be more frequent than R type progeny
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Recombination frequency def
The percentage of recombinant progeny produced in a test Ross maximum value is 50%
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Recombination frequency formula
Number of recombinant progeny/ total number of progeny x 100%
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Genetic map
Map of gene locations on chromosomes obtained by using genetic recombination data
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1 map unit =
1% recombination = 1 centimorgan
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Test cross can…
Reveal affects of linkage
| Cannot distinguish between inter chromosomal recombination among genes far apart on chromosome
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Coupling
Also called cis,
| Recessive are on one chromosome dominant on the other
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Repulsion
One dominant one recessive on each chromosome
| Also called trans
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Frequency of NR and R types depends on….
Physical distance
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In coupling…
Most frequent offspring match the parents
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In repulsion…
Most frequent offspring do not match the parental types
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Discontinuous (or qualitative) trait
A trait having only a few distinct phenotypes often with a simple relationship to genotype
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Polygenic trait
A trait determined by the affects of alleles at many different loci
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Types of polygenic traits
1. Quantitative traits (continuous)
2. Threshold traits (present or absent)
3. Meristic traits (countable)
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Continuous factors are…
Genetic factors plus environmental factors
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Environmental effects
One genotype will have a range of phenotypes
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Threshold trait
Phenotype is binary, but susceptibility varies continuously
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Meristic trait
Countable phenotype, varies continuously (can be very different between individuals when counted)
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Continuous trait
Have the potential to assume any value within a given range
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Binomial expansions formula
(p+q)^n
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Binomial expansion assumptions
1. Only 2 types of alleles (contributing or non-contributing)
2. Incomplete dominance
3. Additive affects of alleles
4. Each gene has small effect
5. No environmental factors
6. No linkage
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Base measurement
What to expect if there are no contributing alleles
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Definition of quantitative genetics
The branch of genetics that uses statistical and analytic procedures to understand how genes and environment influence continuous traits in a group of individuals and study the inheritance of those traits
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Quantitative traits
Arise from many genes with small effects to relative to segregation at other loci and non-genetic variation
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Quasi-quantitative trait
No really continuous trait
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Properties of a population
Mean
Variance
Covariance
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Heritability focuses on
Variance in the population
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Vp =
= Va+ Vd+Vl+Ve+Vgxe
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Statistical model
No genotype phenotype relation
Only variance components of phenotype
Protein useful to describe and understand phenotypic variation
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Broad sense heritability
H2= Vg/Vp
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Narrow heritability
H2= Va/Vp
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How to estimate heritability
1. Eliminating some of the variance components
2. Twin studies
3. Parent offspring regression
4. Resemblance among full and half siblings
5. Election experimentation
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When H2= 0,
Slope= 0, no effect on F1
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H2=0.5,
Some additive effects of genes on F2
| Slope = 0.5
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H2=1,
100% additive effects on F2, slope:1
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Quantitative trait loci
A chromosome segment containing genes that control a polygenic trait
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QTL mapping
Detect association between the inheritance of a trait and there in her of genetic markers
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Heritability is…
Statistical analysis
