Animal Science: Genetics, Breeding, and Reproduction Review

Comprehensive practice flashcards covering key concepts from Animal Science lecture notes on genetics, cellular division, quantitative traits, breeding evaluations (EPDs, DHI, NSIP), and reproductive anatomy, endocrinology, and biotechnologies.

What is the difference between genotype and phenotype?

Genotype refers to the genetic makeup of an animal, whereas phenotype is the observable expression or physical manifestation of those traits.

What three molecular components make up a single DNA nucleotide?

A deoxyribose sugar molecule, a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine).

What is the process of synthesizing complementary mRNA from a DNA sequence called?

Transcription.

How do somatic cells and germ cells differ in their chromosome content?

Somatic cells contain a diploid ($2n$) number of paired chromosomes, while germ cells (sperm and egg) contain a haploid ($n$) number of single chromosomes.

What are the haploid ($n$) and diploid ($2n$) chromosome numbers for cattle and goats?

The haploid number ($n$) is $30$ and the diploid number ($2n$) is $60$.

What are the haploid ($n$) and diploid ($2n$) chromosome numbers for swine?

The haploid number ($n$) is $19$ and the diploid number ($2n$) is $38$.

How many total diploid ($2n$) chromosomes do horses and donkeys possess?

Horses possess $64$ diploid chromosomes, whereas donkeys possess $62$ diploid chromosomes.

How do mitosis and meiosis differ in terms of cell types produced and genetic output?

Mitosis is somatic cell division that produces two identical diploid ($2n$) daughter cells from one diploid cell. Meiosis is gametogenesis division that produces four haploid ($n$) cells containing half the genetic information.

How many functional haploid gametes are generated from a single precursor diploid cell in spermatogenesis compared to oogenesis?

Spermatogenesis produces $4$ functional haploid sperm cells, whereas oogenesis produces only $1$ functional haploid ovum (egg) cell.

What is epistasis in animal genetics?

An interaction where one gene pair influences or masks the expression of another separate gene pair.

How do qualitative traits differ from quantitative traits?

Qualitative traits are categorical, typically controlled by one gene pair (e.g., coat color or presence of horns). Quantitative traits are continuously measurable, controlled by many gene pairs, and influenced by environmental factors.

What is the definition and typical numerical range of heritability?

Heritability is a measure ranging from $0$ to $1$ that indicates the proportion of total phenotypic variation in a population attributable to genetic factors passed from parent to offspring.

What is heterosis (hybrid vigor), and how is it related to heritability?

Heterosis is the phenomenon in which crossbred offspring outperform the average performance of their parents; it is inversely related to heritability.

How are inbreeding, outbreeding, and crossbreeding distinguished?

Inbreeding is the mating of closely related individuals; outbreeding is the mating of individuals less closely related than the population average; crossbreeding is the mating of individuals from different breeds.

What is a contemporary group in livestock genetic evaluations?

A group of animals of the same sex and age raised under similar management conditions, giving them an equal opportunity to perform.

What does EPD stand for, and how are EPDs utilized in beef cattle selection?

EPD stands for Expected Progeny Difference. EPDs estimate genetic merit and allow direct performance comparison among breeding stock within the same breed across different herds.

How are heritability values categorized for reproductive, growth, and carcass traits in beef cattle?

Reproductive traits have low heritability ($< 0.20$), growth traits have moderate heritability ($0.20\text{--}0.40$), and carcass traits have high heritability ($> 0.40$).

What system and genetic evaluation model are used to assess dairy cattle performance in the United States?

The Dairy Herd Improvement (DHI) system and the USDA-DHI Animal Model, which calculate Predicted Transmitting Ability (PTA) and Reliability (REL / $\%R$).

Which biological factors allow for rapid genetic progress in swine production?

A high reproductive rate and a short generation interval.

What is NSIP in sheep breeding?

The National Sheep Improvement Program, which calculates EPDs for genetic evaluation of sheep.

What defines puberty in animal reproduction?

The transition from a non-functional reproductive state to a reproductively competent state capable of gamete and hormone production, influenced by age and body weight.

What role does Gonadotropin-Releasing Hormone (GnRH) play in the Hypothalamus-Pituitary-Gonad axis?

GnRH is secreted by the hypothalamus and stimulates the anterior pituitary gland to release Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).

What are the primary functions of FSH and LH in female ovarian activity?

FSH stimulates ovarian follicle growth and estrogen secretion. LH triggers follicle rupture (ovulation) and the subsequent formation of the progesterone-secreting corpus luteum.

What are the main functions of progesterone produced by the corpus luteum?

Progesterone inhibits FSH and LH release (preventing new follicle development) and maintains pregnancy.

What are the anatomical classifications of uterine structures in mammals as shown in the diagram?

Duplex (two cervices; found in marsupials and rabbits), Bicornuate (poorly to moderately developed horns in mares and cows; highly developed horns in bitches, queens, and sows), and Simplex (no uterine horns; found in primates).

What anatomical structures in the scrotum regulate testicular temperature for spermatogenesis?

Thermosensors in scrotal skin, the external cremaster muscle, the tunica dartos muscle, and the pampiniform plexus (which provides countercurrent heat exchange).

How do vascular and fibroelastic penis structures differ across livestock species as illustrated?

Vascular penises (stallions) enlarge significantly via erectile tissue engorgement. Fibroelastic penises (bulls, boars, rams) maintain a firm structure and extend outward by straightening an S-shaped curve called the sigmoid flexure.

What is a freemartin in cattle?

A sterile female calf born twin to a bull calf, occurring in $10$ out of $11$ male-female twin sets due to placental blood supply fusion during embryonic development.

Which hormone released from the posterior pituitary induces uterine contractions during parturition?

Oxytocin.

What is colostrum, and why must newborn livestock ingest it rapidly?

Colostrum is the first milk secretion following birth; it is exceptionally high in immunoglobulins and provides essential passive immunity before the gut loses the ability to absorb intact proteins.

What is the definition of the postpartum interval?

The length of time from parturition (birth) until the female exhibits her first subsequent estrus.

What are the stages, functions, and durations of egg formation within the hen's reproductive tract?

1. Infundibulum ($0.5\,\text{hrs}$): captures ovum and site of fertilization. 2. Magnum ($2\text{--}3\,\text{hrs}$): adds thick albumen. 3. Isthmus ($1.5\,\text{hrs}$): forms shell membranes. 4. Uterus/Shell Gland ($18\text{--}20\,\text{hrs}$): completes albumen, uptake of water ('plumping'), and calcifies shell. 5. Vagina: adds cuticle prior to oviposition via the cloaca.

What three chemical/hormonal strategies are used for estrous synchronization in farm animals?

Prostaglandin ($\text{PGF}_{2\alpha}$) injections to cause regression of the corpus luteum; exogenous Progesterone (oral feed or vaginal inserts) to suppress estrus; and GnRH to time both estrus and ovulation.

What hormone is administered to donor females during an embryo transfer (ET) procedure, and what is its purpose?

Follicle-Stimulating Hormone (FSH) is administered to superovulate the donor female, causing her ovaries to produce and release multiple ova.