Genetic Background and Phenotypic Variation

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Questions and Answers

Which background is associated with obesity and overt diabetes in mice?

129/SvEv background

C57BLKS/J background (correct)

B6 background

FVB/N background

What is the outcome of introducing the Alzheimer's amyloid precursor protein transgene in inbred FVB/N and B6 mice?

Increased IBD susceptibility

Transitional obesity

Lethality (correct)

Formation of amyloid plaques

How does the B6 background affect susceptibility to inflammatory bowel disease (IBD) compared to other strains?

Severely increases susceptibility

Not affected

Completely resists IBD

Slightly increases susceptibility (correct)

Which term describes animals that are genetically identical but may exhibit phenotypical differences?

Monozygotic Signup and view all the answers

What is the purpose of using monozygotic individuals in research?

To ensure genetic uniformity Signup and view all the answers

What is a characteristic feature of F1 hybrids compared to their parental strains?

Greater resistance to stress Signup and view all the answers

Which gene is represented by the notation ApcMin?

A dominant mouse allele Signup and view all the answers

What is one potential benefit of using F1 hybrids as hosts for tissue transplants?

Better viability than parental strains Signup and view all the answers

What is the term used to describe the increased survival and reproductive success observed in F1 hybrids?

Hybrid vigor Signup and view all the answers

In which scenario might F1 hybrids show more variability compared to their parental strains?

In behavioral characteristics Signup and view all the answers

How do F1 hybrids generally react to pentobarbital compared to their parent strains?

More uniformly Signup and view all the answers

Which statement about the fasting blood sugar levels of NZB/NZW F1 hybrids is true?

They exhibit higher fasting blood sugar levels than either parent strain Signup and view all the answers

Which factor may influence the behavioral characteristics of F1 hybrids?

The genetic contribution from the mother Signup and view all the answers

What is the primary goal when using the speed congenic method?

To minimize the number of back-crossings required Signup and view all the answers

What characterizes a chromosome-substitution strain?

The entire chromosome is replaced by a homologous chromosome Signup and view all the answers

How is the nomenclature for consomic strains structured?

It follows the format HOST STRAIN-Chr #DONOR STRAIN Signup and view all the answers

What is a key feature of double congenic lines?

They allow for the study of interactions between multiple genes Signup and view all the answers

What is necessary to achieve a chromosome-substitution strain?

A minimum of 10 generations of back-crossing Signup and view all the answers

What is the primary value of recombinant inbred strains in genetic research?

They are useful for identifying and analyzing complex genetic traits. Signup and view all the answers

After how many generations of inbreeding will the genome of a recombinant congenic strain primarily contain material from the background strain?

20 generations Signup and view all the answers

Which prefix is used in the nomenclature of recombinant congenic strains?

RCS Signup and view all the answers

In recombinant congenic strains, what percentage of the donor genome is typically found after two backcrosses?

12.5% Signup and view all the answers

Which type of strain is specifically derived from the second or third backcross generation of unrelated progenitor strains?

Recombinant congenic strain Signup and view all the answers

What distinguishes reciprocal F1 hybrids?

Their designations are different. Signup and view all the answers

Which method is most commonly used to introduce recessive characteristics into an inbred strain?

Intercross-backcross method Signup and view all the answers

What purpose does the Cg symbol serve in nomenclature?

It denotes a congenic strain with unknown mutation origins. Signup and view all the answers

What is a key outcome of repeated backcrossing in congenic strains?

Introduction of the selected gene into the recipient strain's genome. Signup and view all the answers

In the nomenclature of a congenic strain, what does the period signify?

Separates the recipient strain from the donor strain. Signup and view all the answers

Which statement is true regarding a congenic strain like B6.AKR-H2kA?

It differs from its background strain only by the differential allele introduced. Signup and view all the answers

What is the full designation of the D2B6F1 mouse strain?

(DBA/2N x C57BL/6J)F1 Signup and view all the answers

In the creation of congenic strains, which of the following is NOT required?

Initial cross with a genetically identical strain Signup and view all the answers

Study Notes

Effect of Background

The genetic background of a strain can significantly affect the outcome of experiments.
Diabetes and Obesity:
- The B6 background leads to obesity and transient diabetes.
- The BKS background results in obesity and overt diabetes.
Alzheimer's Amyloid Precursor Protein Transgene:
- Outbred mice show amyloid plaque formation in the brain.
- Inbred FVB/N and B6 mice experience lethality.
IL10 Deficiency:
- B6 background shows a slight increase in IBD susceptibility.
- 129/SvEv, BALB/c, and C3H/HeJBir backgrounds demonstrate a significant increase in IBD susceptibility.

Genetical Uniformity

Monozygotic animals are genetically identical.
The nine-banded armadillo is an example of a species that produces monozygotic pups.
Despite genetic identity, monozygotic animals may not always display identical phenotypes.
Subtle differences during intrauterine development can lead to variations in phenotype.
Monozygotic individuals are ideal when a high level of genetic uniformity is needed.
The C57BL/6J-Aqp2cph/J strain is an example of a monozygotic strain used for studying congenital progressive hydronephrosis.

Inbred Strains & Co-isogenic Strains

Inbred strains contain minimal genetic variability due to repeated brother-sister mating.
Co-isogenic strains are similar to inbred strains but differ in a specific gene.
Inbred strains are often used as a control for research.
F1 hybrids are the first generation offspring of two inbred strains.
F1 hybrids display features from the parental strains, with characteristics like:
- High levels of genetic and phenotypic uniformity.
- Hybrid vigor, also known as heterosis, which is a greater resistance to disease, an increased ability to survive under stress, greater longevity, and larger litters compared to either parental strain.
F1 hybrids are useful as hosts for tissue transplantation.
F1 hybrids often respond uniformly to treatments, but there can be variability in behavioral traits.
The choice of the mother or father strain in F1 hybrids can affect the outcomes of certain studies.
Inbred strains are frequently used for controlled genetic research, such as studying disease models.

Congenic Strains

A congenic strain is derived from an inbred strain by introducing a specific genetic quality from a donor strain.
The cross-intercross-backcross method is commonly used to introduce a recessive trait into an inbred strain.
Backcrossing involves repeatedly mating the offspring of the first cross to the recipient strain while selecting for the recessive gene.
DNA markers can expedite the congenic process.
Double congenic lines are created to investigate the interactions between genes.

Chromosome-Substitution Strains (Consomic Strains)

A consomic strain is an inbred strain where a single chromosome is substituted with the homologous chromosome from another inbred strain.
A consomic strain typically arises from repeated backcrossing for at least 10 generations.
A complete set of consomic strains, each with a different chromosome replaced, can be created for comprehensive studies.
The nomenclature for consomic strains uses the host and donor strain names, followed by the chromosome number.

Recombinant Inbred Strains (RIS)

Recombinant inbred strains are produced by repeatedly interbreeding F2 generation hybrids.
They are a valuable resource for genetic research, particularly linkage analysis and studying complex genetic traits.

Recombinant Congenic Strains (RCS)

Recombinant congenic strains are derived from a series of inbred strains.
These strains are important for studying background-specific traits and disease susceptibility.
These strains can be used to identify genes responsible for complex traits.

Random-Bred Populations

These populations are not genetically uniform, and are used in studies where genetic variability is expected and studied, such as in human populations.

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Description

This quiz explores the impact of genetic backgrounds on experimental outcomes, specifically regarding diabetes, obesity, and Alzheimer's research. It also examines the concept of genetic uniformity in monozygotic animals and the factors that can lead to phenotypic differences despite genetic identity.