1. Department of Natural Sciences Inheritance of Characteristics and Breeding in Animals NSCI3770 Introduction to Animal Husbandry. CAC.

2. Introduction, some videos, discussion Basics of cell division, growth and gamete production Genetics, basic ideas and a tutorial exercise Examples of inherited genetic disorders 2 In this session…

3. After viewing the first video discuss: –What was the video about? –Why do breeders do this? –What are the welfare implications of this practice? 3 Starter video and discussion:

4. GENETICS Section 1 4

5. Two types of cell division in cells –Mitosis growth and repair of tissues in all body cells involves replication and division from one cell to form two identical cells –Meiosis Prior to sexual reproduction – only in ovaries & testes. Produces male and female gametes (eggs & sperm) Chromosome numbers are halved Types of Cell Division

6. Made of DNA Carry genes which are information to build parts of the animal’s body 6 What do we know about chromosomes?

7. Diploid (2n) The normal state. –The full complement of chromosomes in body cells. –Two of each chromosome (one inherited from father & one from the mother) –Mitosis maintains the diploid state when cells divide for growth & repair of tissues. Haploid (n) Only in ‘gametes’ (egg & sperm) –Half the number of chromosomes. Only one of each chromosome –Produced ONLY in reproductive cells when Meiosis produces the haploid egg and sperm. Number of chromosomes

8. Mitosis Meiosis Videos

9.  Mitosis  Division of the nucleus  Results in the formation of two identical ‘daughter’ nuclei with diploid chromosomes (2n)  The way body cells divide for growth & repair Mitosis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. Stages of Mitosis Duplication Single chromatids  Interphase  No cell division occurs  The cell carries out normal metabolic activity and growth  Synthesis (S) phase, chromosomes duplicate  Prophase  First part of cell division  Centromeres migrate to the poles S (DNA synthesis) G1G1 G2G2 Cytokinesis Mitosis I NTERPHASE M ITOTIC PHASE (M)

11. Chromosome duplication 11 Centromere Chromosome duplication Sister chromatids Chromosome distribution to daughter cells

12. Stages of Mitosis Centrosomes (with centriole pairs) Kinetochore Early mitotic spindle Chromatin INTERPHASE PROMETAPHASEPROPHASE Centrosome Fragments of nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Nuclear envelope Spindle microtubules Nucleolus Centromere

13. Stages of Mitosis Metaphase plate Nucleolus forming METAPHASETELOPHASE AND CYTOKINESISANAPHASE Cleavage furrow Daughter chromosomes Nuclear envelope forming Spindle

14. Metaphase –Chromosomes line up‘in single file’on the spindle Stages of Mitosis Sister chromatids Centromere

15.  Anaphase  chromatids separate & are pulled toward the poles  Telophase  Daughter nuclei begin forming. Each new cell has a chromatid from each original chromosome. (These will make a new copy before the next cell division)  Cell begins to divide

16. Meiosis (halves the number of chromosomes) Only occurs in ovaries & testes to produce eggs & sperm (gametes) Chromosomes line up ‘in pairs’ on spindle (4 chromosomes) One chromosome from each pair moves to each end of the cell The 2 new cells have half the number of chromosomes (2) These new cells divide again by mitosis to separate the chromatids. (4 haploid gametes)

17. SELECTING ANIMALS FOR BREEDING 17

18. Genotype – Description of actual forms of a gene (alleles) present in the individual. (e.g. BB/Bb/bb in the rabbit example) Phenotype – the appearance of the animal as a result of genes inherited –physical characteristics e.g. coat colour –Metabolic characteristics e.g. blood clotting –behaviours can also be an expression of the inherited genes. Select breeding animals

19. Alleles - –the alternative forms of a gene at the same locus on paired chromosomes. –Homozygous - both alleles exactly alike –Heterozygous - both alleles different Dominant –some alleles are dominant over others and will ‘mask’ the recessive gene. E.g. brown eyes are dominant over blue eyes. Recessive –These characteristic only show up when both alleles inherited are recessive. E.g. blue eyes.

20. Humans select animals for and against some physical characteristics. –breed standards for the competition ring –‘good looks’ –inheritable diseases eg hip dysplasia –neotony (breeds that retain ‘infantile’ characteristics – e.g. big eyes, short, flat muzzle) think pugs, pekes and persians –ease of care short haired varieties people friendly characteristics –ragdolls

21. Humans select animals for and against some behaviours –For those that ensure survival and easy care easy birthing and good mothering animals with high libido –For those that increase suitability for intended use highly trainable for competition / work low aggression for family pets –Against those that are socially unacceptable breeding aggressive bitches and producing aggressive pups

22. Inbreeding –breeding together animals that are closely related eg brother- sister, father - daughter. –Usually done to produce animals that are homozygous for desirable characteristics Line breeding (is a form of inbreeding) –breeding related individuals, less closely related eg cousins, grandsire - grandchild –again to breed for desirable characteristics Outbreeding –breeding animals with no relationship. Hybrid vigour. Types of breeding

23. Can you guarantee homes? Do you have room for a litter? Can you afford to? –Stud fee –feeding mother –feeding young –preventative health care Do you have appropriate breeding animals? Are you experienced enough to choose good animals for mating? Breeding, should I or shouldn’t I?

25. Choosing an appropriate breeding animal Ethics Pedigree Physical assessments –general health and soundness –hip scores (dogs) –elbow scores (dogs) –eye tests (typically golden retrievers) –FIV (cats) –FeLV (cats) –other breed specific issues Behavioural assessments –temperament tests Breed society requirements Age Health

26. Predicting the likely Offspring Punnet Squares

27. Each gene may have 2 or more forms called alleles E.g. these may be black or white in a rabbit 27 Alleles

28. If coat colour in rabbits is If coat colour in rabbits is – dominant for black (B) – & recessive for white (b) – what are the phenotype (colour) of the following? Hint, we see the dominant allele Try This Bb bb BB

29. Monohybrid Cross Black hair is dominant, white is recessive Genotype & Phenotype? bb BB

30. Result Result Parents BB Xbb Gametes BB b b Offspring Bb BbBb Bb (F1) Result100% Bb, 100% Black Result100% Bb, 100% Black

31. b B b B Doe Buck Bb Parents Doe Buck Phenotype:All Black Genotype:100% Bb (heterozygous) bb BB

32. Phenotype:3 Black : 1 white Genotype:25% BB : 50% Bb : 25% bb Parents B B b b Doe Buck Doe Buck BB Bb bb Bb

33. Work in pairs Each person needs a coin Use heads for the dominant black allele (B) Use tails for the recessive white allele (b) Each pair should toss one coin each to represent the random selection of alleles from the heterozygous parents (Bb) to create a new ‘rabbit’ Do this 8 times, class results scored 33 Let’s try an experiment

34. Phenotype:50% Black, 50% White Genotype:50% Bb : 50% bb b B b b Doe Buck Bb bb Bb bb Parents Doe Buck

35. Female: a pair of large X chromosomes (XX) Male: one large X like female and one small Y chromosome (XY) Sex-linkage: Loci which are located on the sex chromosome => sex-linked. g. colour blindness in males Sex Chromosomes

36. Sex Determination Parents: Sire x Dam Chromosomes: XYXX segregation segregation segregation segregation Germ Cells: X Y X X (gametes) Offspring: XX XX XY XY (zygotes) Sexes: Females Males

38. Quiz - Definitions What do the following terms mean? Chromosome Gene Allele Dominant Recessive Homozygous Heterozygous Phenotype Genotype Gamete –What kind of cell division forms them? –Where does this occur? –What are the two kinds? Zygote –What kind of cell division will take place as this divides & grows into a foetus? Sex Linked characters

39. Inherited problems Cats –Manx – no tail –Folded ears –Polydactyl –xtra toes –Deafness- white, blue eyes. Dogs –Haemophilia –Collie eye –Progressive Retinal Atrophy –Hip/Elbow dysplasia

40. HIP DYSPLASIA Progressive deformity of hip joints First 12 motnhs Shallow ‘ball and socket’ joints Partially dislocate-instability Osteoarthritis PAIN

41. Hip Dysplasia Inherited condition Other factors can be involved –Nutrition imbalance/ overfeeding –Exercise, overexercise, jumping –trauma

42. Lameness under 1 year if severe Affected by weight and exercise Reluctant to jump/mount stairs Stiffness on rising Permanent hind leg lameness CLINICAL SIGNS

43. Scored on joint depth and osteoarthritic change –Total score = sum of 9 separate scores of various features on both hip joints Average hip score varies by breed The following are particularly susceptible: –German shepherd. Giant schnauzer gordon setter, rottweiller, samoyed tibetan terrier, newfoundland, blood hound, bullmastiff, St Bernard, welsh springer spaniel BREED SUSCEPTABILITY

44. Selectively breed only from dogs with good hip joints will decrease the disease incidience Alleviate pain and suffering AIM of SCORING

45. ELBOW DYSPLASIA A number of different conditions impairing the function of the elbow joint: –Labradors & Golden retrievers –German shepherds Strong hereditary base Masked in heterozygous animals

46. Forelimb lameness between 4-12months Older dogs become lame with x-rays showing Osteoarthritis Sound breeding dogs but produce pups with Elbow Dysplasia Phenotype not always = genotype CLINICAL SIGNS

47. Minimize pain and slow development Limit exercise, weight control, pentoson, nsaid, glucosamine chondroitin Surgery Still likely to lead to arthritis TREATMENT

48. A congenital fissure in the roof of the mouth forming a communication between the nasal passages and the oral cavity. Found in various breeds especially brachycephalics and Siamese cats. Inherited as a recessive trait in English Bulldogs. Can be caused by hypervitaminosis A, corticosteroids, griseofulvin Cleft Palate

49. Failure of clotting mechanism in blood At least 9 different types due to different abnormalities in the chain of events leading to clotting Most common forms sex linked. Von Willebrand’s Disease Most common inherited bleeding disorder in dogs Deficient in clotting Factor VIIIR Inherited esp Dobermans. Himalayan cats. Haemophilia A Deficient in clotting Factor VIII Inherited in a number of dog breeds BLEEDING DISORDERS

50. http://www.ufaw.org.uk/geneticwelfareproblems.php 50 Check your breed issues

52. This powerpoint used material from Diane Fraser (Unitec) who previously taught this section. Picture sources (most drawings are from this text or earlier versions): Campbell, N.A., Reece, J.B., and Simon, E.J. (2006) Biology: Concepts and Connections. San Francisco: Benjamin Cummings 52 References and acknowledgements