(2!26!2008)mouse reproduction and genetic crosses

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Mouse Reproduction,Genetic Crosses,Inbred and Congenic Strains

February 26, 2008


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The Life Cycle of the Mouse

~70


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Important inbred strains of Mus musculus

Mouse Genetics, Lee M. Silver, Oxford University Press, 1995.


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The Jackson Laboratory (JAX)

Charles River Laboratory (CR)

Taconic Farms (Taconic)

Laboratory Mouse Suppliersin the USA


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March 9, 2004


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Reproductive performance:

FecundityProductive mating frequency X (litter size) X (number of litters)

Fecundity:Female: reduced by the age of 8-10 monthsMale: remain fertile through their lives. However,

older male that have become obese and sedentaryare unlikely to breed.

Puberty:

Female: first ovulate naturally between 6-8 weeks3-6 weeks can be induced to ovulate

Male: onset of puberty occurs 34-38 days


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The Estrus Cycle of Female

1. Normal estrus cycle is 4-6 days in length.

2. Four phases of the estrus cycle:a. Proestrus: a new bath of eggs reach maturity

b. Estrus: ovulation of fully mature oocytes (beginafter midnight and last for 6-8 hours)

c. Metestrus: mature eggs move through theoviducts and into the uterus. (The act of

successful copulation induces hormonalchanges that prepare the uterus for pregnancy.)

d. Diestrus: unfertilized eggs are eliminated

Sterile copulation (no fertilization):Induce a state of pseudopregnancy.


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Plug:

1. After a successful copulation has been completed,particular components of the male ejaculate (fromthe vesicular and coagulating glands) will

coagulate to form a hard plug that occludes theentrance to the vagina.

2. Plugging should be performed as early aspossible in the morning after a potential mating.Usually persists for 16-24 hours after copulation.

Weaning:Mice can be weaned at 18-28 days old.


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Categories of Genetic Crosses


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Locus (gene): A, a

Male, A/A

Female, A/A

Male or female, A/ASex unknown

Male, a/a

Female, a/a

Male or female, a/aSex unknown

A/A A/A a/a a/a

Incross


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a/a A/A A/a A/a

a/a a/a A/a A/a A/A A/A A/a A/a

a/a A/a A/AA/a A/a A/a

A/A a/a

Backcross Backcross

Intercross

Outcross


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The Generation of Inbred Strains

A process leading to the production of inbred micethat are genetically homogeneous and homozygousat all loci.

Inbred Strain:

The International Committee on StandardizedNomenclature for Mice has ruled that a strain ofmice can be considered inbred at generation F20

of brother-sister matting.

Inbreeding:

F: filial generation

F1: first filial generation; F2: second filial generation


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Figure 3.1 Consequences of inbreeding at the F2 generation.Mouse Genetics, Lee M. Silver, Oxford University Press, 1995.

The Generation of Inbred Strains

1. There is a 12.5% chance that

both F2 progenitors (F3) areidentically homozygous at anyone locus.

2. All offspring in all subsequent

filial generations will also behomozygous for the samealleles at these particular loci.


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Homozygous status

F20: 98.7%

F30: 99.8%F40: 99.98%F60: 100%

Operational Definition of Inbred


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Coisogenic Strain

Effects of genetic background

Normal development and physiology can vary significantlyfrom one strain of mice to the next. It is often not possible todistinguish subtle effects due to the mutation itself from

genetic background.

The mutant animal differs at only a single locus from non-mutantanimals of the same strain. The new mutant strain is coisogenicbecause its genome is identical (isogenic) to that of its sisterstrain except at the mutant locus.

e.g. BALB/cJ-nu, mice with nude mutation of BALB/cJ strain


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Congenic Strain

Mice that have been bred to be essentially isogenic with an inbredstrain except for a selected differential chromosomal segment.

Consomic Strain

Mice that have been bred to be essentially isogenic with an inbredstrain except for a selected whole chromosome.


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Congenic Strain


N275%

N3

87.5%

N493.75%

F150%

FVB/N B6


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N2

75%

N3

87.5%

N4

93.75%

N5

96.875%

N6

98.4375%

N7

99.21875%

F1

50%

N9

99.8%

Backcross


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DonorStrain A

RecipientStrain B

F1

N2

N3

N4

100%100%


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Genesis 28: 164-166 (2000)

- ES cells are usually derived from 129Svstrains

- Knockout mice are usually mixed strains of

C57BL/6 and 129Sv

- Screening with simple sequence length

polymorphism (SSLP)

- MIT/Whitehead database

- The 56 primer pairs spread ~ 30cM apart

- Regular agarose electrophoresis


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Volume 14: 350-356 (2003)

Mouse Informative Markers Multiple Strains

http://www.well.ox.ac.uk/rat_mapping_resourses/

http://jaxmice.jax.org/services/speedcongenic.html

http://www.cidr.jhmi.edu/mouse/mult_inf.html


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Normal Karyote of Mus musculus

2N=40



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Normal Karyotype of Mus musculus

1. 20 pairs of chromosomes19 autosomal pairs, XY sex chromosomes

2. Telocentric chromosomes

A centromere at one end and a telomere at the other

3. Individual chromosome can be distinguished bybanding patterns.

G-bands: Giemsa-stained bands (DNA condenseearly, replicate late, relatively A:T rich)

R-bands: Reverse G-bands (DNA condense late,replicate early, relatively G:C rich)


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(2!26!2008)mouse reproduction and genetic crosses

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