This document summarizes basic concepts of genetic inheritance and Mendel's laws of heredity. It defines key terms like gene, allele, genotype and phenotype. It describes Mendel's experiments with pea plants and his discovery of the principles of uniformity, segregation and independent assortment. The document also discusses Mendel's test crosses and how they proved alleles separate during gamete formation. Finally, it briefly outlines several special inheritance cases as well as the determination of sex and sex-linked inheritance.

1. UNIT 5
BIOLOGICAL INHERITANCE

2. GENETIC INHERITANCE
Mendel (XIX century) demonstrated
that hereditary characteristics are
determined by independent factors
which are transmitted from
generation to generation.
Chromosomes are the carriers of genetic
information. Mendel independent factors are
fragments of DNA that determine the
characteristic of a specific trait.

3. BASIC CONCEPTS
GENE: Unit of DNA that transmit genetic
information
ALLELE: Each variant of a gene
GENOTYPE: Set of genes that an individual has
FENOTYPE: Observable traits that an individual has

4. HOMOZIGOUS: both alleles are
the same
HETEROZIGOUS: both alleles are
different
Dominant allele prevent the alternative gene (recessive allele) from appearing

5. When both alleles are equally strong are called co-dominant and
cause intermediate inheritance

6. MENDEL’S LAWS
Mendel discovered the basic principles of
heredity by breeding garden peas in
carefully planned experiments
Mendel chose a plant whose varieties
displayed “pure” traits, which had been
selected long before and which remained
constant from generation to generation,
making them easy to identify.
He used a self-pollinating plant. The petals
enclose the stamens and the pistil
completely, which means that the plant
crosses with itself, so accidental crossing
with different plants is avoided, and pure
strains can be obtained.

7. Traits studied by Mendel

8. Principle of uniformity (1st law)

9. Principle of segregation (2nd law)

10. Principle of independent assortment (3rd law)

11. Test cross
The additional experiment which Mendel
carried out, to prove that alleles come in
pairs and separate at the moment when
gametes form, consisted of crossing F1
(yellow seeds) with the pure paternal line
of green seeds (recessive homozygote).
Let’s take the yellow seed to be Aa.
Green seed
Semilla verde
Yellow amarilla
Semilla seed F1 F1
Aa
x
a
aa
a
A
In this case, 50% green seeds and 50%
yellow seeds are obtained.
If the yellow seed had been AA, all of the
seeds would have been yellow (Aa).
Aa
Aa
aa
aa
a

12. Watch the video

13. SPECIAL CASES
Multiple alleles

14. SPECIAL CASES
Gene interaction

15. SPECIAL CASES
Lethal genes

16. SPECIAL CASES
Quantitative inheritance

17. LOCATION OF GENES

18. INDEPENDENT GENES

19. LINKED GENES

20. TYPES OF CHROMOSOMES

21. CHROMOSOMES MAPPING

22. EXERCISE

23. DETERMINING SEX

24. A single gene determines sex

25. ZZ/ZW

29. SEX LINKED INHERITANCE

30. GENE MUTATIONS

31. CHROMOSOMES MUTATIONS

32. NUMERICAL MUTATIONS