Genetics and Heredity in Agriculture Biology Agriculture Genetics in History Gregory Mendel – – – – Priest from a monastery in central Europe. High School teacher Became curious about traits.
Download ReportTranscript Genetics and Heredity in Agriculture Biology Agriculture Genetics in History Gregory Mendel – – – – Priest from a monastery in central Europe. High School teacher Became curious about traits.
Genetics and Heredity in Agriculture Biology Agriculture Genetics in History Gregory Mendel – – – – 1851 Priest from a monastery in central Europe. High School teacher Became curious about traits Genetics in History Traits: characteristics that are inherited. Heredity: the passing of traits from parent to offspring Mendel was first to succeed at predicting how traits are passed on Genetics in History Genetics – the study of heredity and traits Garden peas reproduce sexually – – Male sex cells – sperm cells Female sex cells – ovum cells Pollination: the transfer of pollen grains to the female reproductive organ. Genetics in History Garden peas can self-pollinate, this is why Mendel selected peas. – He could control traits Mendel was a good scientist – – He recorded accurate data He only tested on trait at a time Genetics and Heredity in Agriculture Biology Agriculture Genetics in History First trait tested was height. – – Crossed a short plant with a tall plant. Hybrid: offspring of the parents that have different forms of the trait. Genetics in History First Generation – He cross pollinated tall pea plants with short pea plants. – Mendel found that All the pea plants grew to be tall The short trait had disappeared Genetics in History Second Generation – – – He allowed the first generation to selfpollinate. Planted the seeds from the selfpollination. Grew 1000 plants Genetics in History Discovered that: – – – – ¾ were as tall as the parent plants ¼ were short like the parent generation. They occurred in a ratio of 3:1 The short trait reappeared out of no where. Genetics in History P1 Generation – F1 Generation – The original parent or the true breeding plant. The offspring of the parent (P1) F2 Generation – The offspring of the (F1) generation. Genetics in History Compare this to your family – – – P1 generation – Your parents F1 generation – You F2 generation – Your offspring Genetics in History Mendel ended up testing seven different traits. He had the same 3:1 ratio in all experiments. The Rule of Unit Factor Alleles – Alternate form of a gene Each peas had two alleles that determined it’s height, color, shape, etc… The Rule of Unit Factor Organism’s alleles are located on two different copies of a chromosome. – – One inherited from the male parent One inherited from the female parent The Rule of Dominance Dominant traits: – – – The trait that shows up ¾ of the time. Shown with uppercase letters. TT Recessive traits: – – – The trait that shows up ¼ of the time. Shown with lowercase letters tt The Law of Segregation The Law of Segregation: – – Every individual has two alleles of each gene. After meiosis, – Sperm cells have one allele for a trait Ovum cells have one allele for a trait. When combined at fertilization you have two alleles for each trait. Genetics Homozygous: – – Genes that possess two dominant alleles or two recessive. TT or tt Heterozygous: – – Genes that possess one dominant and one recessive trait. Tt Genetics Genotype: – Phenotype: – The genetic composition of an individual How the alleles express themselves. Ex. Two black calves might have the same phenotype, but different genotypes. – – One may be Heterozygous, (Bb) One may be Homozygous, (BB) Probability in Genetics Probability: the likelihood that a particular event is going to happen. Two Pennies – – – Heads = A - for attached earlobes Tails = a - for free hanging earlobes Flip them 20 times and record your genotype. The Punnet Square Mendel's pea plants Tall = TT P1 Generation T T t Tt Tt t Tt Tt Short = tt F1 Generation The Punnet Square Mendel's pea plants Tall = Tt F1 Generation T t T TT Tt t Tt tt Tall = Tt F2 Generation Gender The sex of an animal is determined by the sex chromosomes. – There are two types, X shaped chromosomes Y shaped chromosomes Vertebrate males have a XY Vertebrate females have a XX Sex-linked Genes Fruit Flies inherit sex chromosomes the same a humans. Traits located on the sex chromosomes are called sex-linked traits. All sex-linked traits are located on the X chromosomes. Sex-linked Genes Male Fruit Flies Phenotype = White Eyes Genotype = Xr Y Female Fruit Flies Phenotype = Red Eyes Genotype = XR XR Sex-linked Genes Xr Y XR XRXr XRY XR XRXr XRY Sex-linked Genes XR Y XR XRXR XRY Xr XRXr XrY Incomplete Dominance When traits are inherited incompletely, or they mix. Red Carnations Genotype (RR) White Carnations Genotype (R’R’) Incomplete Dominance When they reproduce the offspring are pink in color. New phenotype occurs because the trait that controls pigment is affected. Incomplete Dominance R’ R’ R R’R R’R R’R R’R R Incomplete Dominance R’ R R’ R’R’ R’R R’R RR R Codominance The expression of both alleles Neither one of the alleles are dominant or recessive, and is expressed in the offspring. Ex. - In some chickens, alleles for feather color are codominant. Codominance Alleles are written with superscripts. Genotype = FB FB Phenotype = Black Genotype = Fw Fw Phenotype = White Codominance FB FB Fw FBFW FBFW FBFW FBFW Fw Codominance Other example of Codominance. – Shorthorn Cattle Environmental Influences The genetic make-up of an organism only determines the potential of an organism. Environmental Influences External Influences – Temperature Light – Nutrition – Environmental Influences Internal Influences – Internal body functions Hormones Age DNA – Deoxyribonucleic Acid DNA ultimately determines an organisms traits. DNA achieves this by determining the structure of proteins. DNA – Deoxyribonucleic Acid DNA is capable of holding all its information because it is very long. DNA is coiled in a spiral called a helix DNA – Deoxyribonucleic Acid DNA is capable of holding all its information because it is very long. – When straitened out, it resembles a ladder. DNA – Deoxyribonucleic Acid At each point on the helix where the two points meet is a nitrogen containing base (A) Adenine (G) Guinine (C) Cytosine (T) Thymine DNA – Deoxyribonucleic Acid These attach to each other at the center of the helix They are shaped so that they will only pair with another specific base. – A=T – C=G DNA Sequence The order that the bases come in depends on what genes they are coded for. Ex. A-T-T-G-A-C carries different information then a sequence that reads T-C-C-A-A-A. Same six letters arranged differently. DNA – Deoxyribonucleic Acid Prior to cell division the DNA copies itself in a process called replication. – – – – The strands of DNA separate. The DNA begins to unwind. The two molecules of DNA are separated when the hydrogen bond is broken. The DNA begins to unzip. DNA – Deoxyribonucleic Acid Each strand builds its compliment base pair. – Forming new hydrogen bonds. – Coils back into a helix. – The DNA has been copied. Each half is reassembled into two forms, exactly alike. – DNA – Deoxyribonucleic Acid DNA is transferred to the rest of the cell by means of a messenger substance RNA. – RNA tells cells to differentiate into specific cells – – – – – hair muscle stems leaves roots Genetic Engineering The manipulation of genes within a cell or organism Gene Mapping – finding location of genes on the chromosomes. Gene Splicing Locate DNA Sequence Enzymes are used to separate the DNA of a particular location on the gene. New DNA can be spliced in or RECOMBINED with the remaining DNA. – This is known as Recombinant DNA Gene Splicing The new DNA will have new characteristics. First use of this new technology was to manufacture human insulin for diabetics. Gene Splicing One of the most interesting feats accomplished by genetic engineering is the splicing DNA from fire flies into a tobacco plant – The plant will glow in the dark.