genetic control of growth & maturation. gregor mendel (1822-1884) mendel studied the inherited...
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Genetic Control of Growth & Maturation
Gregor Mendel (1822-1884)Mendel studied the inherited traits of pea plants.
Gregor Mendel (1822-1884)From his observations Mendel deduced that:Each characteristic must be determined by a hereditary factorThere is a pair of hereditary factors; one from each parent
The law of uniformity: When two homozygotes with different alleles are crossed, all the offspring are identical and heterozygous. The law of segregation: Each individual possesses two genes for a particular characteristic, only one of which can be transmitted. The law of independent assortment: Members of different gene pairs segregate to offspring independently of one another.
Gregor Mendel (1822-1884)
Mendels ObservationsGeneration 1:Yellow Round x Green WrinkledAll Yellow Round offspringGeneration 2: Yellow Round x Yellow RoundGeneration 3:Yellow Round, Yellow Wrinkled, Green Round. Green Wrinkled
Explanation of Mendels ObservationsGeneration 1:Yellow Round (YYRR) x (Green Wrinkled (yyrr)Generation 2:Yellow Round (YyRr) x Yellow Round (YyRr)Generation 3: 9 Yellow Round (YYRR or YyRr)3 Yellow wrinkled (Yyrr or Yyrr)3 Green Round (yyRR or yyRr)1 Green Wrinkled (yyrr)
Pea ExperimentClick on the link below when you are connected to the internetPea Soup Website
AllelesThe two copies of each gene are called alleles, which may be identical (AA and aa) or different (Aa).
Refers to the state of carrying identical alleles at one or more gene loci (e.g. AABB or aabb).
HeterozygousRefers to the state of carrying different alleles at one or more gene loci (e.g. AaBb).
Law of segregation is that alleles segregate, or separate, when the F1 generation produces gametes. Alleles reside at specific loci, or sites, on the chromosomes within the DNA molecule. Segregation of AllelesA pair of homologous chromosomes contains two alleles at each locus and during gamete formation of meiosis, each gamete receives only one member of each homologous pair of chromosomes. Therefore, each gamete also receives only one allele of a particular locus.
CytogeneticsThe study of Chromosomes1903 Sutton and Boveri independently proposed that the vehicle of hereditary factors or genes were the thread-like structures seen by light microscopy in the nucleus of each cell. Chromosomes because of their affinity to take up certain stains (Greek: chroma, colour; soma, body). Chromosomes are only being seen during the metaphase stage of cell division when they are maximally contracted. Plant Chromosomes: von Ngeli in 1842. Animal Chromosomes: Flemming (mitosis) 1882.
KaryotypeChromosome Complement of the Cell (1956)Karyotyping is the process of imaging the chromosomes of the cell23 pairs of chromosomes44 autosomes + 2 sex chromosomes46, XX = Normal female46, XY = Normal male
GenotypeThe genetic make up of the individual.Typically, one refers to an individual's genotype with regard to a particular gene of interestIt refers to what combination of alleles the individual carries (either homozygous or heterozygous).
PhenotypeAny feature or characteristic of an organism or any group of characteristics (e.g. metabolism, physiology, or morphology). The phenotype is the result of the interaction of the gene and environmental components.
Human Genome ProjectThe Human Genome Project (HGP) aimed to map and understand of all the genes of human beings. In 1911, Alfred Sturtevant, then an undergraduate researcher in the laboratory of Thomas Hunt Morgan, realized that he could - and had to, in order to manage his data - map the locations of the fruit fly (Drosophila melanogaster) genes whose mutations the Morgan laboratory was tracking over generations. Sturtevant produced the very first gene map.
Human Genome ProjectThe hereditary material of all multi-cellular organisms is the famous double helix of deoxyribonucleic acid (DNA), which contains all of our genes. DNA, in turn, is made up of four chemical bases, pairs of which form the "rungs" of the twisted, ladder-shaped DNA molecules. All genes are made up of stretches of these four bases, arranged in different ways and in different lengths.
Human Genome ProjectBy February 2003 HGP researchers fully mapped the the human genome.determining the order, or "sequence," of all the bases in our genome's DNA; making maps that show the locations of genes for major sections of all our chromosomes; and producing what are called linkage maps, through which inherited traits (such as those for genetic disease) can be tracked over generations.The HGP has revealed that there are probably somewhere between 30,000 and 40,000 human genes 50,000 genes to as many as 140,000). National Human Genome Research Institute
Genetic Variation ProgramMost of any one person's DNA, about 99.5 percent, is exactly the same as any unrelated person's DNA. Differences in the sequence of DNA among individuals are called genetic variation.Genetic variation explains some of the differences among people, such as eye color and blood group. Genetic variation also plays a role in whether a person has a higher or lower risk for getting particular diseases. Single gene differences in individuals account for some traits and diseases, such as the ABO blood group, cystic fibrosis and sickle cell disease.
Genetic Variation ProgramMore complex interrelationships among multiple genes and the environment are responsible for many common diseases, such as diabetes, cancer, stroke, Alzheimer's disease, Parkinson's disease, depression, alcoholism, heart disease, arthritis and asthma. The Genetic Variation program supports research on genetic variation and how it relates to diseases, responses to drugs and environmental factors.
Genetic ExpressionIf all cells come from the one original zygote, how can the cells in the body vary so muchSome genes are permanently switched on enzymes required for respiration etc Some genes become switched off because they are no longer required to be functional in that particular cell or tissue.Insulin is produced in pancreas cells, which must have the gene that codes for insulin switched on, and genes that are un-related to the role of the pancreas can be switched off.Some other genes that will be functional during specialisation determine the physical characteristics of the cell, i.e. long and smooth for a muscle cell or indented like a goblet cell
Parental SizeAverage height of siblings approximates average height of parentsParental stature adjusted growth curvesBirth size poorly correlated with adult sizeBirth size correlated to mothers size
Walton and Hammond (1938) Crossed large Shire horses with small Shetland ponies.
Walton and Hammond (1938) Offspring of the crosses delivered to Shire dams were heavier than that of pure Shetland ponies, but below that of pure Shire offspring. In contrast, the reciprocal cross-delivered to the Shetland dam was of the same weight at birth as the Shetland purebred foal. The Shetland mother was able to down regulate the in utero growth of her foal sired by the much larger Shire horse, while the in utero environment provided by the larger Shire mother facilitated enhanced growth.
Allen et al. 2004Allen et al. (2004)Confirmed the original observations of Walton & Hammond (1938) that a genetically large foal cannot reach its normal birthweight when gestated in a uterus that is smaller than normal, and the runting effect persists throughout life. Furthermore, that genetically small foals will be born heavier than usual if gestated in the uteri of larger than normal mares and, similarly, this increased size persists to adulthood
14 months of ageTb-in-P vs Tb-in-Tb3 years of ageP-in-Tb vs P-in-PP-in-P vs P-in-TbTb-in-P vs Tb-in-Tb
Allen et al. 2004Clear maternal size influence at birthLasting effect in postnatal developmentLarger mother providedLarger placental areaGreater microcotyledon density
Skin ColourSkin colour depends on the degree of melanin found in skin cells. There are two genes that control the production of melanin, each of which has a dominant and recessive expression. 16 combinations of genotype when coding for skin colour, as seen below.
Skin ColourA person is born with one of five colours. External factors such as the UltraViolet light from the sun modify the genetic expression of colour.
# Genotype 1 M1M1M2M2 2 M1M1M2m2 3 M1M1m2m2 4 M1m1m2m2 5 m1m1m2m2 Phenotype Black Skin Dark Brown Skin Brown Skin Light Brown Skin White Skin
Sex Linked InheritanceA recessive trait on the X chromosome can find expression in a male
Sex Linked InheritanceFathers contribution determines the sex of the child.
Hemophilia AMainly exhibited in males, due to recessive gene on X chromosome.Only exhibited in double recessive females.Sons of hemophiliac males will not have the geneAll daughters of male hemophiliacs will be carriers
Genetic DisordersChromosomal DisordersNumerical (Aneuploidy) due to nondisjunction.
Structural chromosomal due to a break in chromosome(s).
Genetic DisordersChromosomal DisordersNumerical (Aneuploidy) due to nondisjunction1st or 2nd division of meiosis. An extra copy of a chromosome (trisomy) or a missing copy of a chromosome (monosomy). Aneuploidy can also occur at mitosis after conception and leads to chromosomal mosaicism, a mixture of two or more cell lines each having a different number of chromosomes.
Genetic DisordersMendelian Disorders Caused by