ANSC 107 Exam 3

What is the “Animal’s Blueprint”?

Their Genotype

What is a chromosome?

A large molecule made of genes containing DNA

What is a Gene?

A segment of a chromosome made of DNA

What is DNA?

Two strands of sugar phosphate backbone with bridges of nitrogen bases.

What is a Nucleotide?

Sugar, phosphate, and one of the 4 nitrogen bases.

What are the 4 bases of a Nucleotide?

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G)

What is the order of building blocks from smallest to largest?

Chromosome —> Gene —> DNA —> Nucleotide

How is genetic selection and expression used in production?

• Genotypes can be expressed as economically important traits, making more money

• There is an emphasis on the transmission of traits from parents to offspring in breeding systems

What is Inheritance?

The passing of traits from parent to offspring

What are Alleles?

Alternate forms of a gene (A and a) that affect the same trait

• Homozygous (AA)(aa) or Heterozygous (Aa)

What are Gametes?

Reproductive cells (Sperm and Ova)

• Carry ½ the parent’s genetic code i.e. only a single allele for each gene from each parent

Homozygous Dominant

RR

Heterozygous Dominant

Rr

Homozygous Recessive

rr

Define Codominance

Both alleles are expressed

Define Incomplete Dominance

No dominant gene, to heterozygotes appear as an intermediate

Define Sex-Influenced Traits

Phenotypes expressed differently between sexes

—> Dominance differs between sexes

• Ex. In males, horns (H) is dominant, and polled (h) is recessive

• In females, polled (h) is dominant to horned (H)

• HH is always horned, hh is always polled, but Hh in females is polled and Hh in males is horned

Define Sex-Limited Traits

Traits unique to one sex

—> Both sexes carry the genes but only one capable of expressing them

• Ex. Milk production

Define Sex-Linked Traits

Genes found only in X or Y chromosmes

• Males = XY chromosomes

• Females - XX Chromosomes

  • Majority of sex-linked traits are X-linked

    • Can go to males or females

    • recessive X-linked conditions are more commonly expressed in males as they have only one X chromosome

  • Y-linked traits only occur in males

    • Fewer than X b/c Y chromosome is smaller

    • Difficult to determine

What are the majority of sex-linked traits?

X-Linked

Who are recessive X-linked traits more commonly shown in and why?

Males, because they only have one X chromosome

Why are there fewer Y-linked traits than X-linked traits?

Only males have the Y chromosome, and the Y chromosome is smaller.

What are the three rules of Y-linked traits?

• Must only occur in males

• Must occur in all sons of affected males

• Must not occur in daughters of affected males or their offspring

Define Selection in terms of species survival

Factors determining which individuals reproduce

What factors influence Natural Selection?

• Suitability (injured/weak animals less likely to reproduce)

• Opportunity (exposure to more potential mates (via geography/aggression) increases likelihood of reproduction)

What determines Artificial Selection?

• Management (via decisions to regulate opportunity)

  • —> Culling, castrating, specified mating, etc

Define Qualitative traits

• Traits classified into groups

• Clearly Visible

• Typically controlled by few genes (easy to control)

• Ex. Coat color, horns, amount of hair, etc

Define Quantitative traits

• Traits measured numerically (requires an instrument to measure)

• Typically controlled by many genes

• Frequently additive in nature

• Ex. Speed, muscularity, marbling, fiber, etc

Define Heritability

Variation (or lack-thereof) in phenotype from parent to offspring

—> Proportion of percentage from 0-1

T/F: In heritability, a greater number means the trait is more likely to be passed on.

True

What does heritability indicate in a breed/species?

Indicates potential genetic progress with each generation

What are the considered factors when calculating heritability?

• Selection Differential

• Heritability of trait (% expected to be inherited)

What is the “Selection Differential” in calculating heritability

The mean advantage (value) of the parents minus the mean value of the population

• Ex. A litter size of 11 when the mean is 7 = differential of 4

What are the values for determining the Heritability of a trait?

• 0.4 - 0.6 = Highly Heritable Trait

  • Ex. carcass merit traits

• 0.2 - 0.4 = Moderately Heritable Trait

  • Ex. growth traits

• 0.0 - 0.2 = Lowly Heritable Traits

  • Ex. reproductive traits

    • **Ex. Litter size is .1, there is a 4 pig selection differential, 10% of the 4 pig differential is inherited, so .4 pigs more = litter size increases from 7 pigs to 7.4 pigs per litter

Define Inbreeding

The mating of closely related individuals

What are some advantages and disadvantages to Inbreeding?

• Increases homozygous gene pairs for higher expression of desired traits

• Decreases vigor and production

• Increases expression of potentially detrimental recessive genes

Inbreeding Depression

The reduction in survival, fertility, and overall biological fitness that occurs when closely related individuals mate

T/F: The first thing that leaves when inbreeding in reproductive efficiency.

True

What are some common genetic disorders?

• Overo Lethal White Foal Syndrome

• Spider Lamb

• Curly Calf Syndrome

• Porcine Stress Syndrome

• Hyperkalemic Periodic Paralysis (HyPP)

Define Linebreeding

Form of inbreeding using repeated crossings to ancestors (ancestor typically shows up multiple times on both sides of pedigree)

• The risk of recessive genetic disorders is not as high

What is the goal of linebreeding?

To maintain the influence of outstanding ancestors

Define Outbreeding

Mating less closely related animals than the general population

• —> can include crossing within a breed or between breeds

What is the main advantage to outbreeding?

Increases hybrid vigor and performance

Define Crossbreeding

The mating of two individuals from different breeds for complementarity of traits

What is the goal of crossbreeding?

For offspring to outperform the average performance of the parents

What is the basis for change in mating and breeding decisions?

An animal/breed’s current performance

• Making choices on one trait is not advised

• Goals are complex and often in correlation with simpler traits

  • Ex: Feed efficiency (product made per product of gain) is complex

  • Ex: Rate of gain (lbs gained

Define the Breeding Value of an individual

Estimated value of an individual as a parent (based on the performance of the individual and its close relatives)

Define Expected Progeny Difference (EPDs)

Predicted difference in performance between a individual’s offpspring and the offspring’s contemporary group

• Important tool for comparison within breed or group (NOT POSSIBLE TO COMPARE ACROSS BREEDS)

What traits to EPDs include?

• Birth - weight, type, gestation length

• Growth - weight at/time to benchmarks, frame size

• Maternal - milk production

• Terminal - carcass merit

• Reproduction - scrotal circumference, litter size

• Behavior - maternal instinct, docility, speed, agility

T/F: Accuracy is a measure of reliability.

True

What is the accuracy value range for EPDs?

0-1

What are the high and low accuracy ranges for EPDs?

High accuracy (high confidence) = >0.7

Low accuracy (lower confidence/likely to change) = <0.4

T/F: Accuracy increases with increased information.

True

What factors influence accuracy?

Progeny numbers

• Males typically have a higher accuracy than females

• Older animals typically have a higher accuracy than younger animals

T/F: In EPDs, it is important to optimize genetics to fit the environment rather than maximize the genetics.

True

What is the function of the testes?

Produce sperm and testosterone

What is the function of the Epididymis?

Acts as the passageway from testes to vas deferens

How long does it take sperm to travel through the Epididymis?

~60 days

What is the purpose of the accessory sex glands?

Secrete components of seminal fluid

What are the overall functions of the male?

• Spermatogenesis

• Detect females in estrus

• Inseminate females and fertilize the female gamete

Define spermatogenesis.

To produce and maintain a supply of sperm

How do males detect females in estrus?

Through the detection of pheromones (estrogen) and visual cues

What three things are contained in the spermatic cord?

• Vas deferens

• Pampiniform plexus

• External cremator muscle nerves

What is the function of the vas deferens?

Transport sperm during ejaculation from testes to penis.

What are the seminiferous tubule?

Sperm-producing cells - the true germinal epithelium

What is the function of the Rete Testes?

They function in sperm transport from seminiferous tubules - 100 tubules

What are the three parts of the Epididymis and their functions?

• Caput Epididymis (head) - function in maturation of the sperm and fluid absorption; sperm are not capable of mobility or fertilization

• Corpus Epididymis (body) - maturation of sperm; sperm gain mobility

• Clauda Epididymis (tail) - final maturation and storage of sperm until ejaculation; only sperm capable of fertilization

What are the Efferent Ducts?

6-12 tubules that absorb fluid

Label the Diagram of the Structure of the Testis

What is the function of the Scrotum?

Protection and temperature regulation of the testes and sperm.

What is the Tunica Albuginea?

Connective tissue surrounding the testes (holds the testes together); found below the scrotum and associated fat tissue.

• **Acts as an insulator for temperature control

What are methods for temperature control in the scrotum?

• Sweat Glands

• Thermo-sensitive neurons

What are the Leydig Cells responsible for?

Act as a source of testosterone

What are the Seminiferous Tubules responsible for?

Act as a source of spermatozoa.

What are the Sertoli Cells?

Found inside the Seminiferous Tubules and support spermatogenesis.

What are the Basement Membrane responsible for?

Surrounds the Seminiferous Tubules, separating them from blood vessels containing warm blood.

What is the process of Sperm Maturation in the Seminiferous Tubules?

1. Mitosis (Proliferation)

2. Meiosis 1 & 2

3. Differentiation

What is Mitosis/Proliferation?

Spermatogonia undergo multiple mitotic divisions to generate a larger number of spermatocytes.

What is Meiosis 1 & 2?

Replication of DNA to produce haploid spermatids.

What is Differentiation?

There are no further cell divisions. Differentiation results in a fully differentiated immature sperm (spermatids) that is released into the lumen. *Spermatids have developed flagella (tails)*

Where is the Mediastinum and what is its function?

Located in the center of the testes, it transports spermatozoa from lobules within testes to epididymis.

What is the process of transport from Epididymis to Penis?

1. Exit Epididymis and enter Vas Deferens

2. Vas Deferens becomes Urethra (carries urine to bladder) once past bladder

3. Pass Accessory Sex Glands that secrete components of seminal fluid

What are the components of the Accessory Sex Glands?

1. Ampullae

2. Seminal Vesicles

3. Prostate

4. Cowper’s Gland

What is the Penile Configuration in the body?

1. Retained in body until excitation/ejaculation

2. Compressed into Sigmoid Flexure (S-Shaped curve) by the Retractor Penis Muscle **Horses do not have Sigmoid Flexure**

3. At Excitation, the Retractor Penis Muscle relaxes to extend penis for mating

Which animals have a Fibroelastic Penis?

Boar, bull ram

What are the defining qualities of a Fibroelastic Penis?

• Fibrous, hard sheath of connective tissue all the way through the penis

• Penis becomes rigid and extends during erection, rather than growing in diameter

What animals have a Vascular Penis?

Stallions and Humans

What are the defining qualities of a Vascular Penis?

• Penis increases in diameter and length when aroused

• “Bells out” to plug cervix of female during ejaculation

What are the two forms of stimulation in male animals?

• Flehmen Response (Scent)

• Visual/Audtitory/Tactical

What is the Flehmen Response?

A scent response that involves the exposure of the nasopalatine duct to absorb pheromones and stimulate an erection.

What is the process for Visual/Auditory/Tactile Stimulation in males?

• Trained to mount live animals (called stimulating animals (SA)) or dummies for stimulation for breeding and/or collection of semen

What is the relationship between Volume and Sperm Concentration?

Inversely related

What does the concentration of semen depend on?

• Whether the specie is a multiple ovulatory

• Complexity of the Cervix

What are Pendulous Testes?

Hanging away from main body in Bulls and Rams

• Purpose is thermoregulation because breeding season is fall after a hot summer

What are Horizontal Testes?

Testes within the body in Horses

• Purpose is to allow the horse to run faster without hindrance

What are the characteristics of Inverted Testes?

Testes are found at the back of Boars

• Purpose is protection because the males will fight and bite to cause infertilization

Define Cryptorchidism

Lack of testis descent into scrotum (balls didn’t drop) and thus thermoregulation is absent

• Bilateral —> infertile/sterile (no spermatogenesis); testosterone is produced

• Unilateral —> fertile, but reduced sperm producing capacity

*Common in boars and stallions

What temperature should the testis be at for spermatogenesis to occur?

4-6°C less than body temperature

What are the five factors that influence temperature regulation of the testis?

1. Location - testis are outside and away from body for air circulation

2. Insulation - thin scrotal skin with subcutaneous fat

3. Sweat Glands - for evaporative cooling

4. Tunica dartos muscle - smooth muscle under scrotum that can contract to move testis closer to or relax to help testis move away from the body

5. Blood Supply to Testis - warm arterial blood is cooled before entering the testis by crossing over cooler veins that are leaving the testis

Define Haploid

Half the normal number of chromosomes (found in sperm and ova)