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100 Cards in this Set

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First Law of Segregation
Each trait is controlled by particulate factors that occur in pairs. Split -> Gamete -> Fertilization -> Restored double number
Test cross
Cross with a homozygous recessive
Gene
A Mendelian Factor - Physical character that determines inheritance of trait
Allele
alternate form of a gene

ex: Y, y
gamete
sex cell
Animal gametes:
Sperm and Egg
Plant gametes
Pollen or Ovum
homozygote/heterozygote
zygote where 2 alleles of gene are identical/different
Dihybrid Cross ratio
9:3:3:1

Adds to 16
Standard monohybrid cross ratio
3:1
Mendel's Second Law

Law of Independent assortment
Segregation of each gene pair is independent of all other pairs during gamete formation. (MANY exceptions)
Exceptions to second law:

4 o'clock flowers
red x white

.25 red, .5 pink, .25 white

pink is combination of AB
Exceptions to second law

Multiple alleles
C=black fully activated enzyme
cc=albino inactive enzyme
c^hc=himalayan partial enzyme
exceptions to second law

More than 1 gene for a single character
CCoo=ooCC=white
CcOo=colored

colorless 1->colorless 2-> colored
Meaning of distorted mendelian ratio (e.g.) 12-3-1
Suspect 2 or more genes at work
epistasis
epistasis= ,masking of effect of 1 gene by allele of another.
recessive epistasis
C_ allows for pigment
B gene is for color

c allele is epistatic to B gene
dominant epistasis
if A_, B gene has no effect
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
Pleiotropy
production of superficially unrelated effects by a single allele
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
Essential (allele)
Dominant deactivates recessive to prevent death. Yy =live
yy=dead
Y is essential because it decativates y
exceptions to second law

Alleles don't have constant effects
Polydactyly - extra digits

split hand deformity - two wide digits
penetrance
percent of carriers that are affected
expressivity
degree to which phenotype is altered in those affected
explanation for penetrance/expressivity?
environmental and genetic factors
Addition rule
A+B if the two events are mutually exclusive
multiplication rule
A x B if the two are independant events
Binomial formula
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
Chi squared test
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.
Meiosis
2 specialized divisions that germ cells undergo
Diploid
2 copies of each chromosome in nuclei e.g. 2N
haploid
1 of each chromosome in nuclei
e.g. 1N
zygote
fusion of 2 haploid gametes
homolog
member of a pair of identical chromosomes
autosome
non-sex chromosome
Prophase
-chromatin condenses and becomes visible
-nuclear envelop breaks down
-spindle produced
Centromere

Names based on location of centromere
-primary constriction on given chromosome

-metacentric= middle
-submetacentric=near middle
-acrocentric=near end
-telocentric = on end
sister chromatids
different strands attached to same centromere
karyotype
appearance of chromosome sets at end of prophase
Metaphase
-chromosomes attach to spindles by centromeres
-migrate to equatore = metaphase plate formed
Anaphase
-centromeres divide
-daughter chromosomes move to opposite poles
Telophase
-spindle breaks down
-nuclear envelop reforms
harlequin chromosomes
5 bromouracil is base analog. Through chromosomal replication and the semi-conservative model, when the daughter chromosome stained, half is dark, half is light.
Meiosis I
turns a diploid cell into 2 haploid cells
Chiasma
chromatids interchange when they condense in prophase I.

=point of intersection/interchange
Prophase I
chromosomes condense and interchange
bivalent
physical association of 2 homologs
Metaphase I
bivalents attach to spindle by centromeres and migrate to equator
anaphase I
homologs split and move to opposite poles
Telophase I
chromosomes recondense
-nuclear envelop reformed
Meiosis II
2 haploid cells split into 4 haploid cells. (1 strand of a haploid each)
Acessory chromosome
unpaired chromosome
Grasshopper Female/Male genetic composition
Female - 24 chromosomes
-2 accessories (Called XX)
-11 pairs of homologs
Male - (XO O=nothing)
- 23 chromosomes
-11 pairs
-1 accessory
Criss Cross Inheritance
Daughters =fathers

sons= mothers
Drosophila sex symbols
Xy=male
XX = female
Standard notation for alleles
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
Matroclinous females in drosophila
-extraordinary (1/2000)
-daughters that look like mothers
-All X chromosomes of mother and father taken to one pole in meiosis I
Patriclinous males in drosophila
-sons look like fathers
-just receive the X of the father.
Non disjunction
Both chromosomes are taken to one side in meiosis
Determiner of Sex in Drosophila
Number of X. Y has no effect.
Moths, butterflies, and bird sex symbols
ZZ=male
Zw=female
XO in Humans
Turner's syndrome - Female
1/5000
-Underdeveloped sexual characters, sterile
XXY
Klinefelter's syndrome- male
-1/1000
-FEMALE
Determiner of Sex in Humans
Y chromosome determines male character, the X feminizes.
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
Testicular Feminization
Mutation on Sry causes absence of androgen internal testis remain. You get normal female with XY
Testis determining factor
Single gene on Y that contains sex determining region
Sry

If XY female

If XX Male
encodes regulatory protein.

Sry mutated

piece containing Sry is in X or autosome
PEDIGREES
Female=
Male=
Possibilities
F=Circle
M=square

X linked dom/recess
y linked
autosome dom/recess
Pedigree assumptions
If rare recessive disease, assume those marry in in homozygous dom

Assume complete penetrance
Cis alleles/in coupling alleles
alleles together on same homolog
trans/in repulsion alleles
on different chromosomes
Recombination frequency
nonparental gametes/total gametes x 100

=map unit= relative distance apart on chromosome
Recombination frequency range
constant and reproducible value between 0 and 50 percent
Linkage
Association of 2 different genes on the same chromosome. In cis, usually inherited together.
PROPHASE I

Leptotene
Chromosomes appear as thin threads
Prophase I

Zygotene

Chromomeres
"paired thread"
-bead-like regions of localized condensation along chromosomes=chromomeres
-chromologs become associated at synapsis
Synapsis
chromomere-chromomere pairing of homologs along length
pachytene

synaptineal complex
"thick thread"
-homologs are completely synapsed/condensation continues to form a synapineal complex.
-Composed of central +lateral elements. homolog-glue-homolog
Diplotene
-"two thread"
-can now see two homologs on each chromatid
-homologs seem to repel )( but held together by chiasmata and glue
Anaphase I - fancy
-Loss of sister chromatid adhesion allows for seperation to oppossite poles
Crossover
Interchange of chromatids
interference
after a crossover, there is interference within 10 map units=no double crossovers within that range.
Coefficient of coincidence
observed number of doubles/expected number of doubled
translocation
extra piece on end of chromosome
Baker's yeast response to starvation
undergoes meiosis, 4 products each covered by ascospore and all covered by ascus.
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.
Drosophila egg production
2n 1o oocyte
n n 2o oocyte very unsymmetrical
n n n n 3o oocyte
The 3 small polar bodies degenrate=can't study.
Adenine biosynthesis
requires adenine-2 allele (ade-2)
ade-2 stain
red
Different tetrad types
Parental ditype PD
tetratype TT
nonparental ditype NPD
Parental ditype
2 types, both parental. No crossovers,
Tetratype
4 different types, 1 crossover
Non parental ditype
2 different nonparental types, 2 crossovers involving two different pairs.
Analyzation given the tetrad types.
Compare PD and NPD. If PD>>NPD, the genes in question are linked.
Recomb frequencies with tetrad types
NP types/total x 100
2(T)+4(NPD)/4(T+PD+NPD)
Why does recombination never exceed 50 percent
All numbers of crossovers occur at once. If no crossovers, 0/4 recomb. If 1, 2/4, 2, 4/4.
1st division segregation
No crossovers between centromere and a
2nd division segregation
1 crossover between centromere and A=4 nonparental, 4 parental