ANS 330 Exam 3

What is genetics?

The science of heredity

What are genes?

Units of heredity carried on chromosomes coposed of DNA

What is a genotype?

An organism’s genetic consititution

What is a phenotype?

The observable or measureable characteristics of an organismWhat

What is a locus?

The specific location of a gene on a chromosome

What are alleles?

Different forms of the same gene at a particular locus

What is a homozygote?

An individual with two identical alleles for a gene

What is a heterozygote?

An individual with two different alleles for a gene

What is a dominant allele?

An allele whose expression masks a recessive allele when both are present

When is a recessive allele expressed?

When two copies of the recessive allele are present

What is a carrier?

An inidvidual with one disease associated allele and one normal allele with normal phenotype

Can one gene affect mutiple traits?

Yes

Can multiple genes affect one trait?

Yes, phenotypes like coat color are controlled by multiple genes

What is a Punnett square used for?

To show possible allele combinations in offspring

What is a chromosome?

A structure containing DNA and genes

Diploid

two copies of each chromosome

Haploid

One copy of each chromosome

What is independent assortment?

The independent distribution of chromosome pairs into gametes during meiosis

What is segregation of alleles?

The separation of alleles during gamete formation

What is genetic linkage?

Genes located on the same chromosome tend to be inherited together

How can linked genes become separated?

Through crossing over or recombination during meiosis

What is crossing over?

Exchange of genetic material between homologous chromosomes during meiosis

How many possible chromosome combinations can humans theoretically produce via independent assortment?

2^ 23 = 8mil

What is inbreeding?

Breeding closely related individuals over multiple generations

What is an inbred strain?

A group of animals that are nearly genetically identical because of extensive inbreeding

How many generations of inbreeding are needed to create an inbred strain?

More than 20

Why are inbred animals useful in research?

Minimal genetic variation that helps reduce experimental variation

What is inbreeding depression?

Reduced biological fitness that results from inbreeding

Why can recessive genetic abnormalities become apparent in inbred animals?

Inbreeding increases homozygosity, allowing recessive alleles to be expressed

Why are genetically identical animals useful in organ-transplant research?

Genetic differences can cause tissue rejections, so similar animals reduce variation

Why are embryonically lethal genes important?

homozygous genes, analyzing the developmental stage allows insight into gene function and developmental processes disrupted by the particular allele

What is a congenic line?

An inbred line in which a specific locus has been replaced with an allele from another strain

How are congenic lines produced?

Through repeated backcrossing, selection and inbreeding for more than 20 generations

Why are congenic lines useful?

Help determine how a specific gene locus can influence a trait

How are recombinant inbred strains created?

Two different inbred strains are crossed, followed by brother-sister mating or selfing

When is a recombinant inbred line established?

After more than 20 generations

Why are recombinant inbred lines useful?

Help study inheritance, multiple genes affecting traits, and gene interactions/linkage

What happens to chromosomal segments during the creation of recombinant inbred lines?

Become fixed as homozygous segments from either parental strain.

What is a foundation colony?

The original animals used to establish a colony

What happens to offspring from the foundation colony?

Used to expand the colony and provide animals for research

What is outbreeding?

Mating unrelated individuals

Why is outbreeding used in colony management?

Introduce alleles not present to increase genetic diversity

What are typical effect of outbreeding?

More genetically different animals with greater vigor and larger litter

What is line breeding?

Breeding animals with common ancestor

What is cross breeding?

Mating animals of different breeds

What factors affect litter size?

Nutrition, inbred vs outbred strain and parental age

Dystocia

Difficult parturition

What is a breech birth?

Fetus positioned incorrectly, may cause dystocia

What are two ways infectious agents can spread through a colony?

vertical and horizontal

What is a teratogen?

An agent that causes developmental abnormalities

Scientific name of lab mice

Mus musculus

Why are mice commonly used in research?

Inexpensive, efficient breeders, produce many offspring quickly, useful models for genetics, cancer and infectious disease research

What is a hybrid mouse?

Offspring of two different inbred strains

What is an outbred stock?

Mice produced by mating unrelated animals within closed colony

What is a conventional mouse colony?

A colony housed without barriers

How are SPF colonies managed?

Barriers to prevent contamination with specific pathogens

How are adult mice commonly restrained for brief procedures?

Grasp loose skin at the back of the neck

How should pups under 10d old be handled?

Cup hands around the body, make sure hands smell like their environment or the pups

What is the basic technique for more extensive restraint?

Catch base of tail, grasp loose skin near head and secure tail between fourth and fifth fingers

Why should skin be grasped close to head?

Grasping too far back can allow the mouse to bite

What is normal mouse body temp?

35.8-37.4C

What is the normal mouse heart rate?

328-780 bpm

What is normal mouse respiratory rate?

90-220 bpm

What is the typical adult mouse weight? newborn weight?

25-40g, 1g

What is typical mouse lifespan?

1-3 years

How are male and female mice distinguished?

Males have longer anogenital distance

What are two common mouse mating systems?

Monogamous pairing and polyamorous/harem breeding

What does polyestrus mean?

Females can undergo multiple estrous cycles in a year

How often does the mouse estrous cycle occur?

Approximately every 4-5 days

What is postpartum estrus?

Estrus occuring after giving birth, in mice it is often successful pregnancy if mated

What age are mice generally sexually mature?

40-60 days

How long is mouse gestation?

19-21 days

What is a typical litter size?

2-12+ pups

What is average weaning age?

21 days

Why should newborn litters not be disturbed for several days?

Disturbance can increase the risk of cannibalism or destruction of the litter

How long are the individual stages of estrous in mice?

Proestrus= 13hr, estrus= 15hr, metestrus = 13hr, diestrus= 56hr

Lee-Boot effect

Group-housed females isolated from males tend to stop cycling and enter anestrus

Whitten effect: why is it used?

Phermones in male urine induce estrus in females within 3 days, used to synchronize estrus among females

Vandenbergh effect

Adult males accelerate puberty in prepubertal females

Bruce effect: how is it adaptive?

Exposing recently mated female or pregnant female to unfamiliar male can cause pregnancy failure

• delaying pregnancy can increase reproductive success when survival is threatened by infanticide

What is a copulatory plug? Explain purpose and duration

A plug formed from secretions of the male’s accessory sex glands after mating.

• prevents mating with another male

• does NOT guarantee pregnancy

• Lasts up to 24hr

Pseduopregnancy: what? how? duration?

Reproductive state induced by mating stimulation without a true pregnancy

• mating with vasectomized males

• lasts around 12 days

  • helpful in case another female cannot carry (surrogate)

What is vaginal cytology used for?

Identifiying estrous stage by examining cells

What is lordosis?

Sexual posturing

What makes an ideal foster mother?

A female that has successfully weaned a litter and has her own litter close in age to pups being fostered

What is a good sign that fostering is successful?

Pups are gathered together in mothers nest

What is barbering?

Fur chewing, done by dominant mouse on subordinate mouse

What is coprophagy?

Eating feces, normal rodent behavior

What are common mouse cage enrichment items?

Nesting materials, hiding structures, chewing materials

What is malocclusion?

Improper alignment of the incisors causing them to become excessively long

Why is a pelleted diet useful? How is it provided?

Keeps incisors worn down, provided above their heads in “basket” encourages enrichment since mice work for their food

What is a nude mouse?

An immunodeficient mouse with impaired thymus development and deficient T-cell function

Why are nude mice valuable to cancer research?

Immune deficiency allows them to accept tumors or tissue transplants that normal mice might reject

What is a humanized mice used to study?

Human diseases, cancer therapies, immune responses and human gene function

What is a gnotobiotic animal? germ free? How much do they cost typically?

An animal in which every microorganism is known or defined

• germ free = raised without microorganisms

  • $500/mouse

What did the obses vs lean microbiota mouse study demonstrate?

Germ-free mice receiving microbiota from obese or lean human donors developed differences associated with donor microbiota

• however, coprophagy introduced lean microbiota into obsese mice and caused microbiome shift