Download Genètica Mendeliana

Mendel’s laws
• Mendel is considered the father of genetics
• He was a monk, biologist and botanist, born in Austria in
1822 and who died in 1884
• His experiments consisted of crossing pea plants with
distinct characteristics (size, seed colour,…), cataloging
the results and interpreting them
•
The experiments led him to develop his laws
Mendel’s 1st law: law of segregation
•One of two principles of heredity first formulated by Mendel states that
during the production of gametes the two copies of each hereditary factor
[gene] segregate, so that offspring acquire one factor from each parent
•When a plant with two dominant alleles [genotype: DD, phenotype: pink
flowers] is crossed with a plant having two recessive alleles [genotype rr,
phenotype white flowers], the first generation of plants will have one
dominant and one recessive allele [genotype: Dr], and they will show de
characteristic of the dominant father [phenotype: pink flowers]
Mendel’s 2nd law: law of independent
assortment
•The second of Mendel’s principles states that each member of a pair of
chromosomes segregates during meiosis independently of the members of other
pairs, with the result that alleles carried on different chromosomes are distributed
randomly to the gametes
•In the second generation (bottom row) on average one of four plants will have two
recessive alleles (genotype: rr) and will have the characteristic of the recessive
parent [phenotype: white flowers]
•Three of four plants will have at least one dominant allel [genotypes: DD, Dr] and
will present the characteristic of the dominant father [phenotype: pink flowers]:
Glossary
English
Definition
Català
Gene
Segment of DNA that is the molecular unit of heredity. It
encodes the genetic information for one characteristic
Gen
Allele
One of the alternatives forms of the same gene (for
example: the gene that determines the colour of the flowers
has two alleles: red and white)
Al·lel
Genotype
An organism full hereditary information (all its genes, but we
can refer to the genotype concerning one unique trait)
Genotip
Phenotype
An organism actual observed properties. It depends on the
genotype, but also on environmental factors.
Fenotip
Dominant
It always shows, even if the individual has a single copy of
the allele
Dominant
Recessive
It only shows if the individual has two pies of the allele
Recessiu
Homozygous
Having identical alleles for a single trait
Homozigot
Heterozygous
Having different alleles for a single trait
Heterozigot
GEP 2015/16