Single Genes In Animal Breeding

Front 1

Coat colour inheritance

Back 1

Front 2

Melanocytes

Back 2

Dermal melanin is produced by melanocytes, specialized skin cells located in the basal layer of the epidermis.

Melanocytes insert granules of melanin into specialized cellular vesicles, or organelles, called melanosomes.

Front 3

Dominant white spotting

Back 3

2 characteristic features

White fur - usually on the belly or ventral surfaces rather than on the back or dorsal surfaces
The larger total white area – the larger individual patches of orange and non-orange colour

Front 4

White spotting allele Explanation

Back 4

During embryonic development – melanocyte precursor cells migrate from neural crest down either side of the body – eventually meeting at the center of the belly.
- proliferate sideways until they meet neighbouring cells
- fill up all available areas, resulting in a solid mass of melonocytes over the entire body – the areas become coloured by melanocytes
White areas – never reached by the melanocyte precursor cells

Front 5

White-spotting gene and cancer

Back 5

Front 6

Graying gene in horse

Back 6

Normal pigmentation at birth (Black or gray)
Gradual loss of pigmentation as the animal ages.
The colour becomes white, while retaining the dark pigmentation.
Disadvantage of this gene
– high incidence of dermal melanoma
– decrease life expectancy

Gene responsible: syntaxin-17 (STX17)

Front 7

Carpet wool gene

Back 7

solid unpigmneted wool fibers having a hollow core (medulla) running down the center of the fiber.
Autosomal, incomplete dominant allele – Nd

Medullated fibers are fibers with a central core, which may be continuous, interrupted, or fragmented

Front 8

Use of Carpet wool gene

Back 8

Fleece from (Nd Nd) sheep
- contain 65% medullated fiber by weight
- Ideal for carpet manufacture
Nd n : has a level of intermediate between the two homozygotes
- Free from pigmentation,
- good spinning quality,

Therefore, the number of (Nd Nd) and (Nd n) sheep increased

Front 9

Other carpet wool sheep

Back 9

Romaney Sheep

Drysdale
Tukidale
Elliottdale

All breeds are the result based on Romney breed

Front 10

Polledness

Back 10

Two alleles – autosomal, polled (P) dominant to horned (p)

Horns difficult to handle and cause injury, farmers prefer polled (horneless) livestock

Front 11

Muscular hypertrophy

Back 11

Also called double muscling

Advantages of:
- higher percentages of muscle
- lower fat percentage and
- increased food conversion efficiency
Associated with increased dystocia (difficulty during labour)
Caused by mutation in the gene encoding myostatin, another transforming growth factor

Front 12

Genes for sexing day old chickens

Back 12

genetically determined sex differences
based on Z-linked gene which effect on slow/fast feathering
Slow feathering allele (KS ) dominant over rapid feathering (K+)

Front 13

Methods of Pedigree checking

Back 13

Conventional (based on Mendelian inheritance - not powerful)

- coat color patterns of the breed
Molecular techniques ( powerful)
DNA finger-printing (DNA profiling - also called DNA testing, DNA typing, or genetic fingerprinting)