Genetics | Mediateca de EducaMadrid

In this unit, we are going to study genetics. 00:00:00

All of us, sometimes we have asked why we look the way we look. 00:00:03

Siblings have the exact same parents, and due to this, they will have similar physical characteristics 00:00:08

because of the sort of the DNA is exactly the same. 00:00:13

We are going to study three points, genes, early genetics studies, and location of genes. 00:00:19

In the first point, we are going through different important definitions. 00:00:26

Heredity. 00:00:32

It is basically just the passing on of genetic traits from parents to offspring. 00:00:33

Genetics is the study of heredity. 00:00:39

Heredity trait is a characteristic which can be passed on to the offspring. 00:00:42

A gene is a section of the DNA in a specific location on a chromosome that contains information that determines a trait. 00:00:47

The genotype is a set of genes that an individual has and a phenotype is a set of observable traits that an individual has. 00:00:53

Blue eyes, big nose, etc. 00:01:01

A gene can have different variants called alleles. 00:01:04

An individual has two alleles for each trait, one from the mother and other from the father. 00:01:07

If both alleles are the same for a trait, we will have a homozygous individual. 00:01:13

but if both alleles are different from this trait, we will have a terzaigos individual. 00:01:19

Here is an example for the trait hair color in guinea pigs. Two alleles are possible, 00:01:26

black and white. A big N for black which is dominant allele and little n which is a recessive 00:01:31

allele. If we cross two guinea pigs, we have different genotypes related with this phenotype 00:01:37

exposed in the table. If we have a big L we will have black guinea pigs and if we have a recessive 00:01:45

homozygous with double little n we will have white pigs. Another example for the trade flower color 00:01:53

in morning glory flowers. Two alleles are possible. Double big R red and double little R white. 00:02:00

These two alleles are equally strong, they are co-dominant alleles and cause intermediate 00:02:08

inheritance, which means the heterozygous individual will be pink. 00:02:15

If we talk about the earliest studies of genetic, we can mention Aristotle, but the father of 00:02:21

the genetic was George Mendel, an Austrian monk who discovered for the base of the modern 00:02:26

genetic. He worked with pea plants and seven traits which are on the table. He started working with 00:02:32

purebred individuals, homozygous. They reproduce sexually, they have male and female sex called 00:02:39

gametes and the traits are easy to isolate. Mender was a careful researcher due to he used carefully 00:02:47

controlled experiment, a study was trained at a time, keep detailed data. He wrote different 00:02:56

laws. The first one is the principle of uniformity. When two purebred individuals are crows or their 00:03:04

offspring, F1 will have identical phenotypes and these phenotypes are the same from one parental. 00:03:10

The principle of segregation is when two heterozygous individuals found F1 are crows, in the EF2 appear again the two phenotypes of the parental. 00:03:19

In this case, we will have red and white flowers. 00:03:29

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. 00:03:33

In this case, he crossed smooth yellow peas with wrinkled green peas. 00:03:45

In the F1, all of them were smooth and yellow. 00:03:51

But if we cross F1 individuals, we got all of these individuals in the F2 generation. 00:03:56

Round yellow, round green, wrinkled yellow, and wrinkled green. 00:04:03

Remember, the yellow is dominant over the green and the smooth is dominant over the wrinkled. 00:04:06

It's the same, the phenotype probabilities are 9, 3, 3, 1, and there are some special 00:04:11

cases with the width. 00:04:19

If we cross red and white, we have an intermediate color, and if we cross this F1 individual, 00:04:21

we have another proportion with intermediate colors between red and white. 00:04:27

Point number three, the location of genes. 00:04:34

Morgan developed the theory of heredity. 00:04:36

and he said that genes are located on chromosomes on a specific place called locus. 00:04:41

Each gene is made of a segment of DNA as we studied before. 00:04:47

Two alleles which determine a specific trait are located on two homologous chromosomes. 00:04:54

An example, and a good individual for studying this, is the Drosophila melanogaster. 00:04:59

Here you can see that genes are located in different areas, 00:05:06

color, hair color etc. Mender's work lead him to the understanding that traits such 00:05:10

as plant height are carried in plant or in person information, not by single set of information. 00:05:18

All got chromosomes which are the form that our DNA takes in order to get passed on from 00:05:26

parents to child. Human cells have 20 pairs of chromosomes which you can see in this picture. 00:05:32

Thank you very much. 00:05:39

Genetics - Contenido educativo

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