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100 Cards in this Set

  • Front
  • Back
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
A Mendelian Factor - Physical character that determines inheritance of trait
alternate form of a gene

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

Adds to 16
Standard monohybrid cross ratio
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

colorless 1->colorless 2-> colored
Meaning of distorted mendelian ratio (e.g.) 12-3-1
Suspect 2 or more genes at work
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
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
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
percent of carriers that are affected
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

n= # of trials
p/q= probability of event 1/2
s/t=times event 1/2 has to occur
Chi squared test

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.
2 specialized divisions that germ cells undergo
2 copies of each chromosome in nuclei e.g. 2N
1 of each chromosome in nuclei
e.g. 1N
fusion of 2 haploid gametes
member of a pair of identical chromosomes
non-sex chromosome
-chromatin condenses and becomes visible
-nuclear envelop breaks down
-spindle produced

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
appearance of chromosome sets at end of prophase
-chromosomes attach to spindles by centromeres
-migrate to equatore = metaphase plate formed
-centromeres divide
-daughter chromosomes move to opposite poles
-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
chromatids interchange when they condense in prophase I.

=point of intersection/interchange
Prophase I
chromosomes condense and interchange
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
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
XO in Humans
Turner's syndrome - Female
-Underdeveloped sexual characters, sterile
Klinefelter's syndrome- male
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

If XY female

If XX Male
encodes regulatory protein.

Sry mutated

piece containing Sry is in X or autosome

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
Association of 2 different genes on the same chromosome. In cis, usually inherited together.

Chromosomes appear as thin threads
Prophase I


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

synaptineal complex
"thick thread"
-homologs are completely synapsed/condensation continues to form a synapineal complex.
-Composed of central +lateral elements. homolog-glue-homolog
-"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
Interchange of chromatids
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
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!!!!!!!!!

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
Different tetrad types
Parental ditype PD
tetratype TT
nonparental ditype NPD
Parental ditype
2 types, both parental. No crossovers,
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
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