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106 Cards in this Set

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Mendel's First Law
Each trait is controlled by particular factors that occur in pairs. These pairs separate during gamete formation so that each gamete receives one pair of diploid chromosomes. The double number is restored upon fertilization.
Test Cross
Crossing to a pure breeding recessive organism
Gene
One of Mendel's "factors" that controlled the traits that he observed.
Allele
An alternate form of a gene (ie yellow and red)
Gamete
Sex cell, sperm and egg, or ovum and pollen.

Gametes carry only 1/2 the regular number of chromosomes. This number is restored upon fertilization.
Zygote
Formed by the fusion of two gametes.
Homozygote
A cell that carries identical alleles of a gene (ie AA)
Heterzygote
A cell that does not carry identical alleles of a gene.
Mendel's Second Law
Law of independent assortment:

Genes for different traits assort independently of one another. In other words, genes on different chromosomes behave independently in the production of gametes.
How can you tell if two alleles are alleles of the same gene?
They separate during gamete formation.
When you see distorted Mendelian ratios, what should you expect?
two or more genes are involved in determining the phenotype.
Epistasis
Masking the effect of one gene by the allele of another gene.
Pleiotrophy

what is the disease associated with this word?
pleiotrophy is the production of superficially (phenotypically) unreleated effects by a single allele.

Waardenburg's Syndrome: white furlock, deafness and different colored eyes.
What did cuenot discover?
It was impossible to get a pure breeding line of yellow rats because the YY genotype was lethal and the rats died in utero. This means that y is an essential gene, without this allele the rat dies.
Penetrance
The percentage of carriers that are affected in the same way.
expressivity
The degree to which phenotype is altered in those that are affected.
probability
Proportion of time an even is expected to occur in repeated trials.
binomial formula
P= n!/((s!)(t!)) (p)to the s times (q) to the t
What is the cut off for the P value which says that our data does not fit the model well enough to keep it?
5%
what is chi squared?
(observed - expected )squared all over expected.
August Weismann
he did experiments to see if physical changes were incorporated into our genetic material and passed on to the next generations. He cut off the tails of 22 generations of mice to see if the trait would become heritable. It did not.
Interphase
-phase between cell divisions
- chromosomes are elongated and difficult to see under light microscope
-stain cell --> see chromatin
Prophase-
condensation occurs until separate bodies called chromosomes are distinguishable.
-centrioles slowly move to opposite poles.
-spindle proteins slowly form
-nuclear envelope completely breaks down by the end of prophase
Metaphase
Spindle fibers line the chromosomes up on the metaphase plate .

-microtubules attach at the kinetochore, or region near the centromere of the homolog
Anaphase
Movement of chromosomes to opposite ends of the cell.
what is a daughter chromosome?
the name for each of the sister chromatids once they have separated and begun to migrate towards opposite poles.
Telophase
-daughter chromosomes assemble at the opposite end and elongate.
-nuclear envelope reforms and the spindle breaks down.
-nucleolus reforms.
by looking at chromosomes we discovered?
1. chromosomes occur in morphologically identical pairs

2. chromosome types are constant within a species and form a karyotype
Describe prophase I of Meiosis I
the cell forms a temporary 2n stage, when the homologs double and there are 2 centromeres. the sister homologs associate and a bivalent is formed. This is where crossing over occurs.
chiasm
the place where crossing over takes place.
How are the products of meiosis II different from the products of mitosis
- Mitosis produces a cell that has the same number of chromosomes as it started out with.

-There is not crossing over in mitosis

-meiosis creates 4 haploid gametes which are NOT identical to the original diploid cell because crossing over has allowed the genetic material to recombine and enhance gametic diversity.
What did elanor carothers do?
observed that a mutant strain of grasshoppers had a short variation of one chromosome

-she observed and accessory chromosome that assorted independently of the short variant of chromosome.

-
Mclung
-the accessory chromosome determines sex: grasshoppers have XX if female and X0 if male.
Thomas Hunt Morgan
He proposed that the gene for eye color of flies is located on the x chromosome.

also showed criss cross inheritance, sons look pheontypically like the mothers and daughters look phenotypically like their fathers.
what is the condition of x linked genes in males called?
Hemizygous
What did Sutton propose?
chromosome theory of inheritance: genes are on chromosomes.
Calvin Bridges
discovered that in about 1/2000 cases of drosophila, there was not a criss cross inheritance pattern.

The exceptional white eyed daughters were called matroclineous acceptions.

acceptional sons were patroclineous acceptions.

these rare mistakes were caused by non disjunction.
define the wild type allele
designated with a superscript plus.

it is the allele that is considered "normal"
What is the difference between

w(plus)/w
and
W(plus)/W
If the first letter of the gene symbol is lowercase, that means that the first variant found is recessive to the wild type(wplus is dominant)

If the gene symbol uppercase, then the first variant found is dominant to the wild type (W is dominant
what determines sex in drosophila?
number of x's. one x is a male, and xx is a female
what sex is xxy in drosphila?

xo?
xxy is female

xo is male.
sex-linked
located on a sex chromosome
hemizygous
x linked gene in a male. There is only one copy of the gene (one x) in a male genotype
What did the moth study show?
some species, like birds, butterflies and moths have females that are heterogametic (ZW) and males that are homogametic (ZZ
what is XO in humans called?
What are the characteristics?
Turner's syndrome

-underdeveloped sex characteristics

-webbed skin on neck
xxy in humans
kleinfelters

males, feminized, with mild breast development, sparse body hair, almost always sterile, mentally subnormal.
XXX
female
relatively normal
sometimes tall, with subnormal intelligence.
What is the path the y gene takes to determine the sex?
Y causes the gonads to become testis.

testis secrete androgens and testosterone that stimulate the rest of the embryo to become a male.
what is the primary sex determination?

secondary?

tertiary?
primary: sex of gonads

secondary: sex of genetalia (controlled by hormones)

tertiary: events at puberty.
Describe the mutation that can occur with the Testicular Feminization Gene
Tfm encodes androgen receptors that detect when the testis secrete androgens.

if there is a mutation in this gene, the androgen receptors don't function and the secondary and tertiary sex characteristics develop as female.
How does Y determine gonad sex?
the testis determining function TDF contains a gene called Sry which encodes a transcription factor of 204 amino acids. If sry region is inherited into XX, then they can be phenotypically female.
consanguineous mating
mating between related individuals
What can you assume about pedigrees?
assume allele has complete penetrance.

assume that if the trait is rare, individuals who marry into the family carry only normal alleles.
How can a gene violate Mendel's second law?
If they are close together on the same chromosome.
cis
alleles on the same homolog
trans
alleles on different homologs
linkage
association together of genes on the same chromosome
recomgination
process of generating new gametic types (non parental gametes)
recombination frequency
(nonparental gametes)/ total gametes
why do different genes have different recombination frequencies?
morgan said that it had to do with the distance appart of the genes.
recombination frequency between any two genes is.........
a constant and reproductable value that is always less than 50%
What are the 4 stages of prophase I in Meiosis I
Leptotene
Zygotene
Pachytene
Diplotene
Leptotene
first stage of prophase I

"thin thread stage", chromosome condensation is just beginning and appear as thin threads.
zygotene
second stage of Prophase I

condensation continues and you can see beadlike regions of localized condensation along the chromosome.

homologs become physically associated in this stage! (synapses form)
chromomere
bead like regions along the chromosomes that appear during zygotene. The chromomeres on sister homologs line up to form synapses.
synapses
intimate chromosome by chromosome pairing along their length. produces bivalence.
Pachytene
thick thread stage;

homologs are completely synapsed
what is the synaptic complex made of?
central element and lateral elements
Diplotene
fourth stage of prophase

two thread stage

you can see that each chromosome has two chromatids

homologs seem to try to repell on another
What holds the homologs together in diplotene?
a. chiasma

b. sister chromatids adhere
what causes the sister homologs to separate in diplotene
sister chromatid adhesion vanishes
what is interference?
interference is the inhibition of one cross over by others nearby
what is the coefficient of coincidence?
(observed number of doubles)/(expected number of doubles)
How do you solve for interference?
1-(coefficent of coincidence)
When is interference complete?
Within 10 map units
crossing over takes place when how many cromatids are present?
4 (after replication)
what is

a. the name of baker's yeast
b. what is special about baker's yeast?
a. saccharomyces cervisial

b. they grow and divide by mitosis in either the diploid or haploid phase.
ascus
The meiotic products of sarchomyces cervisiae incorporated in a common cell wall.
ascospore
a highly resistant thick cell wall that envelopes each individual of the 4 meiotic products of sarchomyces cervisiae.
how can you stimulate sarchomyces cervisea to undero meiosis
starve them
what are the two mating types of yeast
a and alpha
a and alpha are what kinds of cells?
haploid
What are groups of 4 spores in an ascus called?
tetrad
polar bodies
nuclear material that is discarded during oogenesis, leaving only one haploid product and three polar bodies that degenerate.
If all spore types are parental, how many cross overs where there to produce that tetrad?
none
If two spore types are parental and two are non parental, how many cross overs where there to produce that tetrad?
1
If all 4 spores in a tetrad are non parental, how many cross over's where there?
2
what does the adenine 2 gene do?
colors the yeast red to show that it carries the mutant gene.
How should parental and non parental genes be related if they are not linked?
they should equal
how do you calculate recombination frequency?
non parental/ parental (100)
what is the maximum recombination frequency?
why is this so?
50%, because all 4 double cross over types are equally frequent
orange bread mold, ascomieces (incorporates miotic product into cell wall)
neurospora crassa
what is special about neurospora crassa?
the products of meiosis undergo mitosis
what is the shape of the ascus produced by neurospora crassa
tubular
1st degree segregation
where there has been no crossover in the 4 strand stage of neurospora crassa. aaaa++++
2nd degree segregation
one cross over in the 4 strand stage of nerospora crassa. aa++aa++
what is a polymorphism?
the fact that about 1/1000 base pairs differ between homologs
what are the two kinds of polymorphisms in gene mapping
1. single nucleotide basepairs
2. insertion/deletion polymorphisms (Indels)
How do you detect RFLP's
southern blotting
founder effect
change in allele frequency due to founding of a population by a small number of people.
what is glutamine encoded by?
CAG
anticipation
Huntington's disease get's worse with every generation
What is the relation between the number of glutamines and the severity of huntington's disease
the more glutamines, the more severe the disease (earlier age of onset, etc).
why do extra glutamines cause HD?
polyglutamines are resistant to proteolysis and accumulate in the neurons, specifically the nucleus.
Why do CAG repeats tend to grow over time?
-displacement of 5' end of okasawki fragment during the CAG run.

-normally a flap endonuclease could remove it.

-except the flap can bend back on itself and form a hair pin, with the C's and g's bonding togeher.

-the hairpiin and the normal run of CAG's is replicated and grow with each replication.
what did Holliday propose was a precise mechanism for crossing over?
a. pairing molecules
b. single strand's are nicked
c. exchange of 3' ends
d. ligase

creates a holliday structure in which the point of exhange can move back and forth.