1 00:00:00,110 --> 00:00:02,589 In this unit, we are going to study genetics. 2 00:00:03,129 --> 00:00:07,830 All of us, sometimes we have asked why we look the way we look. 3 00:00:08,410 --> 00:00:13,689 Siblings have the exact same parents, and due to this, they will have similar physical characteristics 4 00:00:13,689 --> 00:00:19,089 because of the sort of the DNA is exactly the same. 5 00:00:19,510 --> 00:00:25,789 We are going to study three points, genes, early genetics studies, and location of genes. 6 00:00:26,750 --> 00:00:31,170 In the first point, we are going through different important definitions. 7 00:00:32,130 --> 00:00:32,689 Heredity. 8 00:00:33,549 --> 00:00:38,909 It is basically just the passing on of genetic traits from parents to offspring. 9 00:00:39,329 --> 00:00:41,270 Genetics is the study of heredity. 10 00:00:42,070 --> 00:00:46,409 Heredity trait is a characteristic which can be passed on to the offspring. 11 00:00:47,070 --> 00:00:53,929 A gene is a section of the DNA in a specific location on a chromosome that contains information that determines a trait. 12 00:00:53,929 --> 00:01:01,929 The genotype is a set of genes that an individual has and a phenotype is a set of observable traits that an individual has. 13 00:01:01,929 --> 00:01:04,930 Blue eyes, big nose, etc. 14 00:01:04,930 --> 00:01:07,930 A gene can have different variants called alleles. 15 00:01:07,930 --> 00:01:13,930 An individual has two alleles for each trait, one from the mother and other from the father. 16 00:01:13,930 --> 00:01:19,930 If both alleles are the same for a trait, we will have a homozygous individual. 17 00:01:19,930 --> 00:01:25,370 but if both alleles are different from this trait, we will have a terzaigos individual. 18 00:01:26,409 --> 00:01:31,530 Here is an example for the trait hair color in guinea pigs. Two alleles are possible, 19 00:01:31,530 --> 00:01:37,930 black and white. A big N for black which is dominant allele and little n which is a recessive 20 00:01:37,930 --> 00:01:45,530 allele. If we cross two guinea pigs, we have different genotypes related with this phenotype 21 00:01:45,530 --> 00:01:53,609 exposed in the table. If we have a big L we will have black guinea pigs and if we have a recessive 22 00:01:53,609 --> 00:02:00,969 homozygous with double little n we will have white pigs. Another example for the trade flower color 23 00:02:00,969 --> 00:02:08,569 in morning glory flowers. Two alleles are possible. Double big R red and double little R white. 24 00:02:08,569 --> 00:02:15,969 These two alleles are equally strong, they are co-dominant alleles and cause intermediate 25 00:02:15,969 --> 00:02:21,449 inheritance, which means the heterozygous individual will be pink. 26 00:02:21,449 --> 00:02:26,129 If we talk about the earliest studies of genetic, we can mention Aristotle, but the father of 27 00:02:26,129 --> 00:02:32,810 the genetic was George Mendel, an Austrian monk who discovered for the base of the modern 28 00:02:32,810 --> 00:02:39,689 genetic. He worked with pea plants and seven traits which are on the table. He started working with 29 00:02:39,689 --> 00:02:47,370 purebred individuals, homozygous. They reproduce sexually, they have male and female sex called 30 00:02:47,370 --> 00:02:56,169 gametes and the traits are easy to isolate. Mender was a careful researcher due to he used carefully 31 00:02:56,169 --> 00:03:04,250 controlled experiment, a study was trained at a time, keep detailed data. He wrote different 32 00:03:04,250 --> 00:03:10,250 laws. The first one is the principle of uniformity. When two purebred individuals are crows or their 33 00:03:10,250 --> 00:03:19,530 offspring, F1 will have identical phenotypes and these phenotypes are the same from one parental. 34 00:03:19,530 --> 00:03:29,430 The principle of segregation is when two heterozygous individuals found F1 are crows, in the EF2 appear again the two phenotypes of the parental. 35 00:03:29,689 --> 00:03:32,849 In this case, we will have red and white flowers. 36 00:03:33,729 --> 00:03:45,490 The second Mendel's law is the principle of independent assortment, when two individuals that have two or more different traits have crows, the transmission of each trait is dependent from other traits. 37 00:03:45,490 --> 00:03:50,930 In this case, he crossed smooth yellow peas with wrinkled green peas. 38 00:03:51,449 --> 00:03:55,629 In the F1, all of them were smooth and yellow. 39 00:03:56,150 --> 00:04:02,870 But if we cross F1 individuals, we got all of these individuals in the F2 generation. 40 00:04:03,270 --> 00:04:06,469 Round yellow, round green, wrinkled yellow, and wrinkled green. 41 00:04:06,729 --> 00:04:11,729 Remember, the yellow is dominant over the green and the smooth is dominant over the wrinkled. 42 00:04:11,729 --> 00:04:19,790 It's the same, the phenotype probabilities are 9, 3, 3, 1, and there are some special 43 00:04:19,790 --> 00:04:21,649 cases with the width. 44 00:04:21,649 --> 00:04:27,810 If we cross red and white, we have an intermediate color, and if we cross this F1 individual, 45 00:04:27,810 --> 00:04:34,350 we have another proportion with intermediate colors between red and white. 46 00:04:34,350 --> 00:04:36,329 Point number three, the location of genes. 47 00:04:36,329 --> 00:04:41,490 Morgan developed the theory of heredity. 48 00:04:41,490 --> 00:04:47,709 and he said that genes are located on chromosomes on a specific place called locus. 49 00:04:47,709 --> 00:04:54,050 Each gene is made of a segment of DNA as we studied before. 50 00:04:54,430 --> 00:04:59,009 Two alleles which determine a specific trait are located on two homologous chromosomes. 51 00:04:59,610 --> 00:05:05,850 An example, and a good individual for studying this, is the Drosophila melanogaster. 52 00:05:06,649 --> 00:05:10,089 Here you can see that genes are located in different areas, 53 00:05:10,089 --> 00:05:18,230 color, hair color etc. Mender's work lead him to the understanding that traits such 54 00:05:18,230 --> 00:05:26,470 as plant height are carried in plant or in person information, not by single set of information. 55 00:05:26,470 --> 00:05:32,209 All got chromosomes which are the form that our DNA takes in order to get passed on from 56 00:05:32,209 --> 00:05:39,689 parents to child. Human cells have 20 pairs of chromosomes which you can see in this picture. 57 00:05:39,689 --> 00:05:40,689 Thank you very much.