LIFE SCIENCES

1. LIFE SCIENCES GRADE 12
UNIT 5
GENETICS AND INHERITANCE
By Vilakazi N.S
216010009

2. THE PROCESS OF HYBRIDIZATION
 Genetics: the study of heredity
 Heredity: relations between successive generations. Gregory Mendel was the father of
genetics.
 Mendel discovered the basic principles of heredity by breeding garden peas in
carefully planned experiments.
 Advantages of pea plants for genetic study: Cross-pollination (fertilization
between different plants) can be achieved by dusting one plant with pollen from
another.
 True breeding : breeding varieties of organisms with only one variety of type.

3. LAW OF SEGREGATION
 P-generation – true breeding parents
 F1-generation- hybrid offspring of the P-generation
 F2-generation- hybrid offspring of the F1 generation
 Alleles-alternative versions of a gene
 Locus- position of a gene in a chromosome
 Homozygous- identical alleles e.g(BB)
 Heterozygous- different alleles e.g(Bb)

4. LAW OF INDEPENDENT ASSORTMENT
 Two alleles for a heritable character separate during gamete formation
and end up in different gametes.

5. GENETIC CROSSES
 Each pair of alleles segregate independently of each other pair of alleles
during gamete formation. (applies to different non-homologous
chromosomes)
 Genotype-genetic composition of a gene
 Phenotype- physical appearance of a gene

6. DEGREES OF DOMINANCE
 1. MONOHYBRID CROSS-cross between 2 organisms where we look at
one pair of contrasting traits.(determine outcome of F1 generation)
 2. DIHYBRID CROSS- cross between 2 organisms where we look at
two pairs of contrasting traits at the same time.

7. SUMMARY OF GENETICS
 Complete dominance One allele suppresses the expression of the other allele.
 Incomplete dominance: phenotype of F1 hybrids is somewhere between the
phenotypes of the 2 parental varieties – neither allele completely dominant (White x
Red = Pink)
 Codominance, 2 dominant alleles affect the phenotype in separate, distinguishable
ways. (Red and white flowers = White and red visible.)

8. REFERENCES
 Chromosomes carry hereditary info (genes)
 Chromosomes (and genes) occur in pairs
 New combinations of genes occur in sexual reproduction
 Monohybrid vs. Dihybrid crosses
 Mendel’s Principles:
 Dominance: one allele masks another
 Segregation: genes become separated in gamete formation
 Independent Assortment: Members of one gene pair segregate independently
from other gene pairs during gamete formation
 ADDITIONAL RESOURCES
 https://www.youtube.com/watch?v=ya7h-Y-9l8c
 https://www.youtube.com/watch?v=bVk0twJYL6Y

9.  Hartwell, L. (2010). Genetics: From Genes to Genomes 4th Edition.
McGraw Hill. London.
 Available from slide share:
https://www.slideshare.net/rspawar007/genetics-70106620
Assessed: 13 December 2016