The Gene Lab Report

The Gene Lab

1. Introduction
The purpose of this report is to inform dog breeders of a very common genetic disease known as Progressive retinal atrophy (PRA). The report will also inform buyers of the disease so they are aware of the disorder and they can check to dog’s pedigree for the disease. PRA could affect any dog, as a result of this it is recommended that the offspring should be examined by a board-certified veterinary ophthalmologist and screened for the existence of the disorder.
2. Recessive and dominant genes
Genes are genetic instructions that define what we look like, a phenotype, and how our cells are made up, a genotype. “Genes are made up of DNA and are organized into larger structures called chromosomes, which are
located within the nucleus of the cell.” (Lofts, G. 2012)

(Image 1: The link between DNA, Genes, Chromosomes, Nucleus and Cells)
Genes play an extremely important part in how we look.
Genes carry information about our cells that create a persons characteristic. (eg. Eye Colour, Hair Colour, Skin colour etc.) Genes can also be described as instruction manuals. Genes are made up of DNA, which carries the instructions to make and operate parts of our bodies. (learn.genetics.utah.edu, 2004)
Genes are passed from parent to offspring through a type of cell division called meiosis. Meiosis is used in the production of sex cells. (Gametes) The Female gamete is the ova and the male gamete is the sperm. “This process results in the chromosome number being halved, so instead of pairs of chromosomes in each resulting cell, there is only one chromosome from each pair.” (Lofts, G. 2012) This genetic information was then put into 23 chromosomes from each your mother and your father. This results in 46 chromosomes, which makes up a zygote.
The difference between a dominant and a recessive gene is that a dominant gene is a gene overrides the recessive gene. It can suppress the recessive gene therefore it changes the allele even though a recessive allele existed.
3. Description of
PRA
PRA is a protein that affects the dog’s sight, in most cases it leads to complete blindness.
It is a recessive gene (pp) which means that if the dogs have correct breeding partners than the whole disease can be removed from their species. When PRA is attached it interrupts common and essential gene repair processes known as homologous recombination and it effects one of the pre stages of meiosis, it also attaches to single stranded DNA, found in eukaryotic cells, this causes the DNA to be unable to become a secondary structure and it doesn’t allow the DNA strand to wind back on itself. This disorder is known to be spread because of pure breeding, dogs such as Labradors are bred because they are smart and easy to train, however because many people want their dogs to have a pure blood line they force the trainers to breed their dogs with a carrier of PRA and as a result they risk the offspring of the dogs to be carriers of PRA. The disorder has no known cure; the only treatment available just postpones the effects of the
disease.

4. Analysis of Pedigrees
Pedigree: Sundae Crème
Sundae Crème’s parents have a particular combination of alleles in their genotype. To work out the possible genotype of Sundae Crème, the granparents genotypes must be first looked at. Chocolate Sundae has no PRA which means his genotype is (PP) or (Pp) therefore this dog has either Homozygous dominant genes or heterozygous genes. Midnight Run has PRA and therefore has homozygous recessive genes and a genotype (pp). Chocolate Fudge has PRA and therefore has homozygous recessive genes and a genotype (pp). Peanut butter has no PRA and therefore has Heterozougus because when mated with Chocoate Fudge they produced butter crème who had homozygous recessive genes and a genotype (pp) therefore Peanut could only have a genotype. (Pp) Sundae crème’s father was also heterozygous. He carried a dominant and recessive gene and his genotype was therefore a (Pp). Pedigree: Brown Charlie
Brown Charlie’s grandfather Clarion Call Diva has no PRA therefore his genotype is (PP) or (Pp) and has either Homozygous dominant genes or heterozygous genes. Lynx Obsidian Blue has PRA and therefore has homozygous recessive genes and a genotype (pp). Sunstorm Amber has PRA and therefore has homozygous recessive genes and a genotype (pp). Peanut butter has no PRA and therefore has Heterozougus because when mated with Sunstorm Amber they produced butter crème who had homozygous recessive genes and a genotype (pp) therefore Peanut could only have a genotype. (Pp) Brown Charlies father was also heterozygous. He carried a dominant and recessive gene and his genotype was therefore a (Pp).

Pedigree: Black Douglas
All of Black Douglas’ grandparents has PRA and have homozygous recessive genes. Therefore the offsprings of the grandparents all have the same homozygous recessive gene. Black Douglas’ parents and grandparents also all have (pp) alleles.

Pedigree: Diggety Dog
Diggety Dog’s grandfather, Dog Day Afternoon has PRA and therefore has a homozygous recessive gene and a (pp) alleles. This is the same for his grandmother on his mothers side who also has PRA. His grandmother on his fathers side has no PRA and it is likely that she has Homozygous dominant genes and a (PP) alleles. His Grandfather on his mothers side also has no PRA and is likely that she has Homozygous dominant genes and a (PP) alleles. Diggety Dog’s parents both do not have PRA and therefore are likely to have (Pp) or (PP) alleles.
5. Predicted Results of Breeding
Pedigree: Sundae Crème
The following punnat square is a prediction of outcome of the gentic crossbreeding of Sundae Crème’s parents. Possible Gamete | P | p | p | Pp | pp | p | Pp | pp |
Sundae crème has a 50% of having PRA and a 50% chance of not having PRA.

Pedigree: Brown Charlie
The following punnat square is a prediction of outcome of the gentic crossbreeding of Brown Charlie’s parents. Possible Gamete | P | p | p | Pp | pp | p | Pp | pp |
Brown Charlie has a 50% of having PRA and a 50% chance of not having PRA.

Pedigree: Black Douglas
The following punnat square is a prediction of outcome of the gentic crossbreeding of Sundae Crème’s parents. Possible Gamete | p | p | p | pp | pp | p | pp | pp |
Sundae crème has a 100% of having PRA and a 0% chance of not having PRA.

Pedigree: Diggety Dog
The following punnat square is a prediction of outcome of the gentic crossbreeding of Diggety Dogs’ parents. Possible Gamete | P | p | P | PP | Pp | p | Pp | pp |
Diggety Dog has a 25% of having PRA and a 75% chance of not having PRA.
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6. Discussion and Recommendation
The results depicted on the previous two pages states that the Sundae Crème and the Brown Charlie pedigrees both have a 50% chance of having PRA. The Black Douglas has a 100% chance of having PRA. The Diggety Dog has a 25% chance of getting PRA and therefore is the pedigree out of the four that is least likely to get PRA.
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7. Reference List
Health, K. (1995-2013). for kids. Retrieved 3 16, 2013, from Kids Health : http://kidshealth.org/kid/health_problems/birth_defect/what_is_gene.html
Jacplus. (n.d.). Retrieved 3 16, 2013, from Jacplus : http://content.jacplus.com.au/secure/ebooks/17424/1742461492/images/lightwindow/2_source-05.jpg
Wave, P. (n.d.). Progressive Retinal Atrophy in Dogs. Retrieved 3 16, 2013, from Pet Wave : http://www.petwave.com/Dogs/Dog-Health-Center/Ear-and-Eye-Disorders/Progressive-Retinal-Atrophy.aspx