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100 Cards in this Set
- Front
- Back
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First Law of Segregation
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Each trait is controlled by particulate factors that occur in pairs. Split -> Gamete -> Fertilization -> Restored double number
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Test cross
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Cross with a homozygous recessive
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Gene
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A Mendelian Factor - Physical character that determines inheritance of trait
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Allele
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alternate form of a gene
ex: Y, y |
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gamete
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sex cell
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Animal gametes:
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Sperm and Egg
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Plant gametes
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Pollen or Ovum
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homozygote/heterozygote
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zygote where 2 alleles of gene are identical/different
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Dihybrid Cross ratio
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9:3:3:1
Adds to 16 |
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Standard monohybrid cross ratio
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3:1
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Mendel's Second Law
Law of Independent assortment |
Segregation of each gene pair is independent of all other pairs during gamete formation. (MANY exceptions)
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Exceptions to second law:
4 o'clock flowers |
red x white
.25 red, .5 pink, .25 white pink is combination of AB |
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Exceptions to second law
Multiple alleles |
C=black fully activated enzyme
cc=albino inactive enzyme c^hc=himalayan partial enzyme |
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exceptions to second law
More than 1 gene for a single character |
CCoo=ooCC=white
CcOo=colored colorless 1->colorless 2-> colored |
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Meaning of distorted mendelian ratio (e.g.) 12-3-1
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Suspect 2 or more genes at work
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epistasis
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epistasis= ,masking of effect of 1 gene by allele of another.
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recessive epistasis
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C_ allows for pigment
B gene is for color c allele is epistatic to B gene |
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dominant epistasis
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if A_, B gene has no effect
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exceptions to 2nd law
1 gene can effect more than 1 character |
Siamese cats
-cross eyed, coat color =same gene Warterberg syndrome -white forelock, often deaf, different eye colors |
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Pleiotropy
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production of superficially unrelated effects by a single allele
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exceptions to 2nd law
Some alleles when homozygous are lethal |
yellow rat x yellow rat
Aa Aa 2 yellow:1 gray modified 1:2:1 ratio |
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Essential (allele)
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Dominant deactivates recessive to prevent death. Yy =live
yy=dead Y is essential because it decativates y |
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exceptions to second law
Alleles don't have constant effects |
Polydactyly - extra digits
split hand deformity - two wide digits |
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penetrance
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percent of carriers that are affected
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expressivity
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degree to which phenotype is altered in those affected
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explanation for penetrance/expressivity?
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environmental and genetic factors
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Addition rule
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A+B if the two events are mutually exclusive
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multiplication rule
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A x B if the two are independant events
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Binomial formula
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p=n!(p^s)(q^t)/(s!t!)
n= # of trials p/q= probability of event 1/2 s/t=times event 1/2 has to occur |
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Chi squared test
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x^2=sum(observed-expected)^2/expected
degrees of freedom=# of classes-1 gives you the probability of obtaining data that fits our expectation as badly or worse than what we got. |
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Meiosis
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2 specialized divisions that germ cells undergo
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Diploid
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2 copies of each chromosome in nuclei e.g. 2N
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haploid
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1 of each chromosome in nuclei
e.g. 1N |
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zygote
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fusion of 2 haploid gametes
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homolog
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member of a pair of identical chromosomes
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autosome
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non-sex chromosome
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Prophase
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-chromatin condenses and becomes visible
-nuclear envelop breaks down -spindle produced |
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Centromere
Names based on location of centromere |
-primary constriction on given chromosome
-metacentric= middle -submetacentric=near middle -acrocentric=near end -telocentric = on end |
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sister chromatids
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different strands attached to same centromere
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karyotype
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appearance of chromosome sets at end of prophase
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Metaphase
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-chromosomes attach to spindles by centromeres
-migrate to equatore = metaphase plate formed |
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Anaphase
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-centromeres divide
-daughter chromosomes move to opposite poles |
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Telophase
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-spindle breaks down
-nuclear envelop reforms |
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harlequin chromosomes
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5 bromouracil is base analog. Through chromosomal replication and the semi-conservative model, when the daughter chromosome stained, half is dark, half is light.
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Meiosis I
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turns a diploid cell into 2 haploid cells
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Chiasma
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chromatids interchange when they condense in prophase I.
=point of intersection/interchange |
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Prophase I
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chromosomes condense and interchange
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bivalent
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physical association of 2 homologs
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Metaphase I
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bivalents attach to spindle by centromeres and migrate to equator
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anaphase I
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homologs split and move to opposite poles
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Telophase I
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chromosomes recondense
-nuclear envelop reformed |
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Meiosis II
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2 haploid cells split into 4 haploid cells. (1 strand of a haploid each)
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Acessory chromosome
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unpaired chromosome
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Grasshopper Female/Male genetic composition
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Female - 24 chromosomes
-2 accessories (Called XX) -11 pairs of homologs Male - (XO O=nothing) - 23 chromosomes -11 pairs -1 accessory |
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Criss Cross Inheritance
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Daughters =fathers
sons= mothers |
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Drosophila sex symbols
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Xy=male
XX = female |
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Standard notation for alleles
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wild type=superscript+
gene symbol lower case if first variant found is recessive to +. Upper case if first variant found to be dominant. / seperates alleles |
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Matroclinous females in drosophila
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-extraordinary (1/2000)
-daughters that look like mothers -All X chromosomes of mother and father taken to one pole in meiosis I |
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Patriclinous males in drosophila
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-sons look like fathers
-just receive the X of the father. |
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Non disjunction
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Both chromosomes are taken to one side in meiosis
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Determiner of Sex in Drosophila
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Number of X. Y has no effect.
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Moths, butterflies, and bird sex symbols
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ZZ=male
Zw=female |
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XO in Humans
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Turner's syndrome - Female
1/5000 -Underdeveloped sexual characters, sterile |
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XXY
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Klinefelter's syndrome- male
-1/1000 -FEMALE |
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Determiner of Sex in Humans
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Y chromosome determines male character, the X feminizes.
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Primary Sex determination
Secondary Sex Determination Tertiary Sex Determination |
1 - Sex of gonad - Y determines gonad to be testis which secretes androgens to cause maleness
2 - sex of genetalia 3 - events at puberty |
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Testicular Feminization
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Mutation on Sry causes absence of androgen internal testis remain. You get normal female with XY
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Testis determining factor
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Single gene on Y that contains sex determining region
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Sry
If XY female If XX Male |
encodes regulatory protein.
Sry mutated piece containing Sry is in X or autosome |
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PEDIGREES
Female= Male= Possibilities |
F=Circle
M=square X linked dom/recess y linked autosome dom/recess |
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Pedigree assumptions
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If rare recessive disease, assume those marry in in homozygous dom
Assume complete penetrance |
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Cis alleles/in coupling alleles
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alleles together on same homolog
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trans/in repulsion alleles
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on different chromosomes
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Recombination frequency
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nonparental gametes/total gametes x 100
=map unit= relative distance apart on chromosome |
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Recombination frequency range
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constant and reproducible value between 0 and 50 percent
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Linkage
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Association of 2 different genes on the same chromosome. In cis, usually inherited together.
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PROPHASE I
Leptotene |
Chromosomes appear as thin threads
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Prophase I
Zygotene Chromomeres |
"paired thread"
-bead-like regions of localized condensation along chromosomes=chromomeres -chromologs become associated at synapsis |
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Synapsis
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chromomere-chromomere pairing of homologs along length
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pachytene
synaptineal complex |
"thick thread"
-homologs are completely synapsed/condensation continues to form a synapineal complex. -Composed of central +lateral elements. homolog-glue-homolog |
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Diplotene
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-"two thread"
-can now see two homologs on each chromatid -homologs seem to repel )( but held together by chiasmata and glue |
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Anaphase I - fancy
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-Loss of sister chromatid adhesion allows for seperation to oppossite poles
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Crossover
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Interchange of chromatids
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interference
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after a crossover, there is interference within 10 map units=no double crossovers within that range.
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Coefficient of coincidence
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observed number of doubles/expected number of doubled
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translocation
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extra piece on end of chromosome
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Baker's yeast response to starvation
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undergoes meiosis, 4 products each covered by ascospore and all covered by ascus.
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Yeast under pressure!!!!!!!!!
Alleviation |
Undergoes meiosis, 2 are alpha, 2 are a alleles
When conditions better the 4 recombine to make a/a, alpha/alpha, and a/alpha diploids. |
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Drosophila egg production
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2n 1o oocyte
n n 2o oocyte very unsymmetrical n n n n 3o oocyte The 3 small polar bodies degenrate=can't study. |
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Adenine biosynthesis
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requires adenine-2 allele (ade-2)
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ade-2 stain
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red
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Different tetrad types
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Parental ditype PD
tetratype TT nonparental ditype NPD |
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Parental ditype
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2 types, both parental. No crossovers,
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Tetratype
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4 different types, 1 crossover
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Non parental ditype
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2 different nonparental types, 2 crossovers involving two different pairs.
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Analyzation given the tetrad types.
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Compare PD and NPD. If PD>>NPD, the genes in question are linked.
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Recomb frequencies with tetrad types
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NP types/total x 100
2(T)+4(NPD)/4(T+PD+NPD) |
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Why does recombination never exceed 50 percent
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All numbers of crossovers occur at once. If no crossovers, 0/4 recomb. If 1, 2/4, 2, 4/4.
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1st division segregation
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No crossovers between centromere and a
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2nd division segregation
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1 crossover between centromere and A=4 nonparental, 4 parental
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