This document discusses key concepts in genetics including loci, alleles, genotypes, phenotypes, Mendelian inheritance patterns, blood types, sex determination, and examples of inherited illnesses. It provides examples of monohybrid and dihybrid crosses in peas and explains the expected inheritance ratios. It also discusses karyotype, environmental and genetic factors that can determine sex.

1. •Locus: the location of a gene inside a chromosome
(plural loci )

2. •Allele:alternative forms of the same gene (i.e.: different eye
colours in humans; green and yellow bean seeds).

3. •A Homozygous indivudual:remembering that information is
duplicated with reference to the number of diploid
chromosomes, in a homozygous individual you can find identical
alleles in both homologous chromosomes.

4. •A heterozygotic individual: remembering that information is
duplicated with reference to the number of diploid chromosomes, in
a heterozygous individual has two different alleles of a gene.

5. •A dominant allele: the present allele in a heterozygous individual
In this example allele A is present, which represents the colour yellow.

6. •A recessive allele: in a heterozygous individual this allele remains
hidden
In this example the allele which represents the colour green is not present

7. •Genotype: a group of genes present in an individual
•Fenotype: An external manifestation of these genes
In the example the genotype is shown as aa and the fenotype is the green
colour of the seed.

8. •First experiment: he cross-pollinates two purebreeds
P Yelow seeds x Green seeds
F1 100% Yellow seeds

9. •First experiment analysis:The purebreed traits are repesented
by homozygotic individuals for a determined character. The cross
breeding produces heterozygous individuals where only the the
dominant allele is present (the yellow seed)
P Yellow seeds x Green seeds
AA aa
F1 100% Yellow seeds
Aa

10. •Second experiment: he crossbreeds the f1 hybrids
f1 Yellow seeds x Yellow seeds
F2 3:1 ratio of yellow to green seeds

11. •Interpreting the second experiment´s results: the f1 individuals
are heterozygous (Aa). We should remember that the new individuals are
formed through the union of halpoid gametes during fertilisation and that
the gametes come from chromosome separation during myosis. homólogos.
The two possible gametes for the two individuals are : A and a
A a
A AA Aa
a Aa aa
f1 Yellow seeds x Yellow seeds
Aa Aa
F2 3 yello seeds for every 1 green

12. •Third experiment. First part: He crossbreeds two purebreeds which
have two different characteristics
P Yellow and smooth x Green and wrinkly
F1 100% yellow and smooth seeds

13. •Third experiment. Second part: the breeds the f1 seeds with each
other
f1 yellow and smooth x yellow and smooth
F2 ratio9:3:3:1
• 9 yellow and smooth.
• 3 yellow and wrinkly.
• 3 green and smooth.
• 1 green and wrinkly.

14. •Interpreting the third experiment´s results. Part one: the
results for part one of the experiment indicate that the yellow alleles (A)
are dominant over the green ones (a) and that (L) are dominant over the
wrinkly ones (l). The gametes which form the parents (P) are explained by
the homólogos chromosome distribution during myosis. This distribution
happens randomly. If the seed´s colour and texture locus are in different
chromosome pairs, the distribution could happen in the following ways.
P Yellow and smooth x Green and wrinkly (pure parent breeds)
AALL aall
F1 100% yellow and smooth seeds
AaLl
AL
al AaLl

15. •Interpreting the third experiment´s results. Part two: The
gametes which form the f1 individuals are again explained by the homologo
chromosome distribution during myosis.This distribution happens at random.
If the seed´s colour and texture locus are in different chromosome pairs,
the distribution could happen in the following ways:
•The AaLl individual may form gametes: AL, Al, aL, al
AL Al aL al
AL AALL AALl AaLL AaLl
Al AALl AAll AaLl Aall
aL AaLL AaLl aaLL aaLl
al AaLl Aall aaLl aall
f1 Yellow and smooth x Yellow and smooth
AaLl AaLl
F2 ratio 9:3:3:1
• 9 yellow and smooth (AALL, AaLL, AaLl,
AALl).
• 3 yellow and wrinkly (AAll, Aall)
• 3 green and smooth (aaLL, aaLl)
• 1 green and wrinkly (aall)

16. Both alleles express the informaton.

17. Both alleles are visible in the phenotype.

18. • Genes relative to their blood type
contain information for the proteins in
red blood cell membranes.
•Our white blood cells recognise those
red blood cells with the same proteins as
their own.

19. A blood transfusion in a body with
differen proteins can provoke the
immune system to react badly and it
may even result in the death of the
patient.

20. Phenotype Genotype Can donate
blood to
A AA, A0 A, AB
B BB, BO B, AB
AB AB AB
O 00 A, AB, B, O

21. Genotypes Gametes
AO A y O
BO B y O
AB A y B
AA A
BB B
OO O

22. •Determined through chromosomes: the XY system (in humans) or
XO (in flies: the O represents an absence of chromosomes).
XX XY XO XX
male female

23. •Karyotype determination: haploid and diploid individuals will
develop different genders
•Diploid individual: feeds on honey
(it is born infertile).
•The diploid individual feeds on
royal gelatine.
•Haploid individual (male)

24. •Genetic determination: the sex depends on a combination of genes.
•The plantEcbalium elaterium or
exploding cucumber is one of the most
studied cases. The sex of this plant
depends on the genotype of the plant
with regards to a series of three
alleles.

25. •Environmental determination: the environmental conditions
determine the sex
• The temprature determines a
crocodile´s gender.
Temperatures of more than
27ºC will result in males.

26. The presence of an uncommon fragment between chromosomes X and Y
determines that those genes whose loci are situated in these
fragments will have different inheritance in males and females.
Healthy male Ill male
Healthy female Mujer portadora Ill female
An example of an inherited illness
related to gender (the allele which
causes the illness is recessive).