Genetics ANIMSCI 2200.01 - 0010
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Date Created: 10/10/15
Genetics Organismal structure The cell is the most basic unit of life A cell has all the things it needs to live in an environment with appropriate nutrition A cell is made up of molecules and organelles Molecules are fatty acids polysaccharides and proteins Organelles help the cell maintain life A single cell organism undergoes replication determination differentiation and death 10 trillion cells are estimated in the living body One cell gives rise to 10 trillion cells and that one cell also gives rise to different features of the cell then overtime has to become over 200 different cells Cells give rise to tissues organs organ systems Modern Cell Theory In 1655 Robert Hook discovered actual cells Using a compound microscope to look at plants he noticed that when you magnify the plants that there are the appearance of little chambers occurring throughout the plant structure The Cell theory states 0 All living things are composed of cells 0 The cell is the fundamental unit of structure and function in all living things 0 All cells come from preexisting cells Animal Cell The nucleus holds the DNA Nuclear DNA is found in every cell type in the body Every cell has the same DNA Plasamembrane 50 phosolipids gives cell shape also known as the cell membrane Endoplasma reticulum smooth and rough 0 Smooth synthesis fatty acid 0 Rough nd protein synthesis they are rough because ribosomes o Ribosomes are components of RNA and protein 0 Ribosome necessary to produce protein Lysosome help break down proteins Mitochondria is the powerhouse because it produces ATP Red blood cell loses mitochondria as it ages to focus on oxygen Red blood cell then relies on glucose because glucose can rely on ATP outside of the mitochondria Glucose can partially be broken down to ATP with absence of mitochondria Peroxisome detoxifies breaks down big fatty acids produces a lot of heat known as brown fat Cell fate The animal body is made of over 200 different cell types Overtime the cells become determinate ln Determination the cell acquires its fate that it39s going to become a skeletal cell a liver cell or a heart cell A cell is determined based on its environment Determination is similar to its preexisting cell In Differentiation the cell acquires the structure and function of its determined fate There are different appearances in cells because they have different functions within the body Proliferation is the ability for a cell to replicate itself Though not all cells are able to proliferate When a cell replicates or proliferates it does this through mitosis Apoptosis receives a signal to carry out a cellular process of death Skin cells and blood cells have a short life span Red blood cells live for about 100120 days Red blood cells have a stem cell population Stem cells will either reside in a cell that went under determination but not differentiation With the skin cells the differentiation cell goes through the replication process to replace it Cardiac cells heart cells have a long life span and do not replicate themselves A Totipotent cell can do anything The Totipotent cell can become the organism and the immediate environment of the organism Overtime Totipotent cells become pluripotent Pluripotent are the cells of the embryo It39s not just the embryo that has to form but its external environment After being pluripotent some cells become multipotent cells Multipotent cells start to identify a limited number of fates You nd these cells in tissues Mitosis A cell giving rise to two identical daughter cells is through mitosis The cell cycle has two phases 0 Mitosis o lnterphase Mitosis is only a small part of what a cell does Interphase consists of a theory of processes 0 Gap 1 Growth 0 Synthesis DNA synthesis 0 Gap 2 Growth Most of the cells life happens during Interphase It is known as the cells resting place Mitosis is divided as o Prophase o Metaphase o Anaphase o Telophase During Prophase you see the condensing of the actual DNA During Metaphase you see sister chromatids line along the equator of the cell In Anaphase the chromatids pull apart During Telophase two cells begin to form as cytoplasm increases and begins to separate Deoxyribonucleic Acid Deoxyribonucleic acid have 3 generalized features 0 Ribose backbone Ribose is a 5 carbon sugar 0 Deoxy hydroxyl group is an OH group Hydroxyl group is lost at the second carbon 0 Phosphate group associated with the 5th carbon It39s important because it39s how the different nucleotides come together and interact to give rise to a single strand of DNA The nucleotides in DNA are Adenine Thymine Guanine and Cytosine These act to form a single strand of DNA The second strand forms and acts with the rst strand through complementary base pairing Adenine pairs with Thymine Guanine pairs with Cytosine Genes We have about 3 billion base pairs of DNA About 10 will function to give rise to protein DNA will give rise and tell the cell what proteins to make DNA is the blueprint of life A gene is an organization of nucleotides that will give rise to protein within the cell The junks turns genes on and off Flow of genetic information RNA is required in the ow on information from DNA to protein DNA is found in the nucleus and mitochondria R Proteins are produced associated with ribosomes Ribosomes are outside the nucleus bonucleic acid RNA is single stranded There is no Thymine in RNA Thymine in RNA is replaced with Uracil RNA comes in because of complementary base pairing rules If DNA says Adenine you have Uracil Cytosine you have Guanine Thymine you have Adenine Guanine you have Cytosine Adenine you have Uracil RNA read from a DNA is transcription RNA taken into a protein is translation Forms of RNA There are 3 different forms of RNA Messenger RNA mRNA has the code for what protein is going to be produced rRNA carriers out the process and makes sure the protein is produced mRNA is 3 if the total RNA tRNA transfer RNA is how the amino acids get there tRNA associates with mRNA and forms a series of 3 nucleotides The 3 nucleotides that are exposed are called codons tRNA also relies on complementary base pairing to recognize the mRNA Predicting nucleotide sequences If you know the mRNA you can determine the DNA template and the tRNA They interact and respond based on complementary base pairing rules Codon in reference to the 3 nucleotides of mRNA Each codon corresponds to an amino acid The cell knows to stop and a protein is complete through the stop signals Summary DNA is double stranded DNA has to unwind one of those strands serves as the template The strand that serves as the template is dependent on the extra DNA AS mRNA is synthesized it can leave the nucleus and can associate with ribosomes Ribosomes may be associated with endoplasmic reticulum or may exist free mRNA is recognized by the ribosomes will then be decoded so then you ll have the process of translation Methionine is the start codon Inheritance Transfer of genetic material 0 Life begins with a single cell c To help the wellbeing of a cell you need to look inside the cell Inheritance is the transfer of the genetic material Early Studies in Inheritance In the 184039s Mendel began owering fruit trees and noticed they were slow to reproduce then adapted his studies for Pea Plants then Snap Dragons Prior to Mendel it was believed that inheritance was the result of mixing blood or some other substance contributed by each parent Mendel realized 20 years later that this was not the mode of inheritance but instead he found that for each characteristic and individual carried two particles he referred to these as factors 0 He found that one factor is inherited by the male parent and the other by the female parent 0 These factors would be transferred to the offspring Since only one of the factors from the parent is going to end up in the offspring that sometimes traits skip a generation Mendel s observations 0 Many inherited characteristics traits are under the control of two distinct factors genes one coming from the male parent and the other from the female parent Genes are carried in chromosomes 3 E 3 in EE 4 39539 E E i E I H 5 EH a a a 7 It HHPll id I39ll Hi all 35 gLl run an a an T Gaining r They take a picture of what occurs within a cell after chromosomes have condensed DNA associates with histones proteins and these allow the DNA to condense Using a computer they pair up chromosomes similar to size 0 These represent one chromosome coming from the female parent and one from the male parent Autosomes are chromosomes that are not sex chromosomes Sex chromosomes are the X and Y In males X and Y are referred to as heterogenic different In females they are homogenic same The X and Y5 are copies of one another even though they are not the same In Abvians the sex chromosomes are 22 or ZW Female is heterogenic in Abvians In birds the W is what determines the gender Diploid 2n is how the chromosomes exists within the cells of the body Haploid n is the actual gamete Sex chromosomes are haploid Number of chromosomes differs by species SHE n Elfi hrcflr l m ri i HLEIIIIIII 39 ii I ruinI fail till 1 remissJ lli 39m lid i1 WHITE5i EVAN 35quot I IH pair quotirilyrgn E39il IT pilier Lilithxv T5 I3 sniffJ huh Jfill L1 shirtJ LieInn TL I 13917 ltli ai my fix i m riggier Aria if 39Il39a39 l39iIIE IJ HJitilll 39FII I39 mmI We have 46 chromosomes or 23 pairs the haploid number is 23 and the diploid number is 46 The number of chromosomes differs from species Chromosomes can differ in length Chickens have more chromosomes but that doesn39t mean that they have more DNA They have micro chromosomes short chromosomes What is one long chromosome may be two chromosomes in another species Organization of genes Homologous chromosomes are coded with matching information from male and female So if a gene responsible for hair color is on chromosome 1 of the female the homologous chromosome of the male will also contain the gene for hair color so they will have matching information Locus is the location of the gene Alleles is the given copy of the gene Homozygous the gene copies are the same AA Heterozygous the gene copies are different Aa Mendel s observations Two A trait may not show up in an individual but be passed to the next generation Laws of Inheritance Meiosis gives rise to cells that are not identical daughter cells because in the end of meiosis we start out with a diploid cell but it is the reproductive process that gives rise to the haploid cell Meiosis is divided into two stages Meiosis 1 and Meiosis 2 ln Meiosis 1 the DNA replicates then that cell divides and one cell gives rise to two cells following the end of the rst phase The DNA found in each of the cells represent duplicate DNA In the second stage when the cell divide that duplicated DNA will separate so now you have a haploid cell You can have 4 potential haploid cells In females Meiosis 1 happens before birth Meiosis is for making haploid cells Meiosis is the underline biological mechanisms by which the laws of inheritance are based The laws of inheritance are Principles of Segregation and Independent Assortment Principles of Segregation only one randomly chosen allele is found within each gamete Independent Assortment is the process that makes you look like you siblings or not like them The process is very random Down Syndrome is a common example of trisomy Absurd to real Mule horse and donkey Horse has 64 chromosomes and the donkey has 62 The haploid number of a horse is 32 and the donkey39s is 31 The diploid is 53 which is an odd number so with that we nd that these don39t form homologous pairs They can reproduce but the offspring will be sterol because of an extra chromosome Expression of traits Dominant Allele gene quotoverpowersquot and prevents expression of the gene at the corresponding loci on the homologous chromosome Recessive Allele corresponding gene that is quotmaskedquot by the dominant allele at the corresponding loci l 39 r Fr A 51 33911 F 392 a e l a lFlEJ a l i feathers both of the inherited alleles mus Iln order for lire d spring to have blank be recessive hernia our A punnet square is a way in which we can draw out and make predictions of what we are going to see in the actual offspring Complete dominance Predicting the likelihood of inheritance of a dominant trait depends on the alleles of the parents When it is a dominant trait you have two possibilities for those parents Homozygous the prediction is increased Heterozygous the prediction is decreased Dominance is associated with a trait that confers an advantage The actual corresponding recessive gene is usually associated with a trait that can be detrimental to the organism Recessive trait can commonly be associated with the loss of an enzyme function As little as one enzyme being altered and losing function of that enzyme can have very drastic consequences for that animal Dominance has evolved to offer advantage for that animal Red coat color in cattle is recessive Horns in cattle is also recessive Spider lamb is when the legs are out It is associated with chondrodysplasia Different forms of chondrodysplasia include absence of tail in a Manx cats and dwar sm Chondrodysplasia can be either dominant or recessive The short tail of a Manx cat is associated with a dominant trait If you breed two Manx cats together you will have reduced litter size because many will not survive Syndactyly is when the webs in between your ngers don39t go away this can be surgically removed Nonclassical dominance Incomplete or Partial dominance an allele is expressed in a dose dependent manner 0 Instead of both colors being observed in the offspring with two different colored parents what we nd is that the colors blend Sex related inheritance Sex linked expression of a gene that is located on the X chromosome 0 The calico cat is an example of sex linked Sex limited Traits are limited to gender 0 Cryptorchidism absence of one or both testes 0 Milk production 0 Sex in uenced Trait is in uenced by gender an allele that is dominant in one sex is recessive in the other sex Some variation can not be predicted Crossing over Occurs during initial meiosis Mutation DNA can be misread when replicated o Insertion deletion or substitution of nucleotide 0 AS this happens you can change a codon if a codon changes a protein can change 0 New Protein better performanceworse performance Collapse double muscling Collapse is the consequences of alteration of a gene known as myostatin Myostatin is a muscle stopping gene Myostatin is important for the growth and development of an animal When the Myostatin gene is mutated muscles grow unchecked Commonly known as double muscling syndrome does not mean twice the amount of muscle This mutation can be a consequence of hypertrophy or hyperplasia ln sheep it is a consequence of hypertrophy ln Cattle it is a consequence of hyperplasia Animal breedingApplied genetics 0 Objective produce animals that excel for desired traits while eliminatingminimizing occurrence of undesirable traits lnvolves culling of less desirable animals and selection of superior replacements Cull to eliminate an animal that has undesirable features or traits that we don39t want passed on to offspring When we select animals ultimately for breeding we select them based on their genetics and also based on their genotype and their phenotype Phenotype observable measures of traits Moved away from fat to leanness because that is what the population needed Qualitative traits Subjective measure descriptive or categorical and classi ed into groups Qualitative traits include 0 Red or black angus o Horned or polled sheep Controlled by a few genes progress of selection not dif cult Quantitative traits Objectiver numerically measured milk production loin eye area weight and speed Polygenic Controlled by many genes often on different chromosomes each contributing a small effect More dif cult to achieve desirable traits Tools for genetic change Selection obtaining a desirable phenotype through choosing animals for mating Phenotypic Selection Selection is based on phenotype This can change in the future Quantitative traits greater environmental in uence variable heritability Heritability shows the relationship between phenotype and genotype Qualitative less envriomental in uence greater heritability o Coat color Heritability Greater heritability greater improvement Carcass merit traits are highly heritable Growth traits are immediately heritable Reproductive traits are lowly heritable If we select for litter size we will make progress but it will take longer to progress because it is a lowly heritable trait Predicting genetic progress Heritability is bearable it is not a xed unit because it is ultimately determined through mathematics What they do is look at a trait in a parent population and look at a trait as it is passed on to the offspring and look at the relationship of those traits If you have a litter size and average the litter size of your pigs and nd your average litter of those born alive is 10 per litter you want to increase litter size so you select males and females that are associated with that you notice will give you increased litter size So you look at your selected animals and those have 12 per litter The difference between your animals selected and your herd average is known as the selection differential Which is 2 1210 If your heritability of litter size is 10 2 x 1 You can predict you will increase litter size by 2 pigs So it will take you 10 generations to increase your entire herd average to 12 per litter 22 Generation interval is 2 years 0 Selection Differential Phenotypic advantage of chosen parents Superiority of selected animals compared to the herd average for a particular trait Heritability of the trait Proportion of phenotypic variation that can be passed from parent to offspring Generation interval Average time required to replace one generation with the next The shorter the generation interval the greater rate of change Pigs 2 years Horses 58 years Dairy Cattle 34 years Chickens 812 months Beef Cattle 56 years Sheep 3 years Genomic based selection 0 Traditional animal breeding requires assigning a breeding value based on desired production traits with expectation the traits are inherited within offspring MAS Marker assisted selection allows identi cation of regions of DNA associated with a trait SNPS single nucleotide polymorphisms can be identi ed in animals that are identi ed by key selection traits The presence of SNPs allows prediction of breeding value Unlike MAS SNPs scan the entire genome not just predetermined regions Tools for genetic change Mating pairing of males and females 0 Can be random or nonrandom Mating depends on desired results 0 Increased homozygosity Increase predictability of progeny as future breeding animals by decreasing variation of contrasting alleles Aa 0 We can predict the offspring because we have more alleles that are matching 0 Increased heterozygosity Increase performance of progeny for production by increasing variation of contrasting alleles Aa Can result in hybrid vigor heterosis 0 An advantage is that the offspring in situations can outperform the parents 0 What will increase homozygosity o Inbreeding Mating system strategies Inbreeding intensive breeding of close relatives practiced to maintain breed standards and achieve predictability of offspring Decreases variation increases homozygosity of desired and recessive genes Outbreeding Mating of unrelated animals within lines amp breeds or between breeds Increases variation increases heterozygosity increases productivity through hybrid vigor Greatest effects in lowly heritable traits and within the rst generation of crossbreeding Outcrossing Same bred but of two different populations of animals When you cross breed animals your rst generation is the generation that will show greatest hybrid vigor Second generation hybrid vigor will decrease and most likely not be seen Selection is a tool which permits change in genetic frequency and phenotypes
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