3. A gene is the molecular unit of heredity of a living organism
The word gene is derived from the Greek word genesis meaning "birth", or genos meaning "origin"
5. Deoxyribonucleic acid (DNA) is a molecule that encodes the
genetic instructions used in the development and functioning of all
known living organisms and many viruses
6. DNA is a nucleic
acid; alongside
proteins and
carbohydrates,
nucleic acids
compose the three
major
macromolecules
essential for all
known forms of life.
8. Ribonucleic acid (RNA) is a polymeric
molecule. It is implicated in a varied sort
of biological roles in coding, decoding,
regulation, and expression of genes
9. Living beings depend on genes, as they specify
all proteins and functional RNA chains.
10. Genes hold the
information to
build and
maintain an
organism's cells
and pass
genetic traits to
offspring
What do the genes do?
11. All organisms have genes corresponding to various biological traits, some of which are instantly
visible, such as eye color or number of limbs, and some of which are not, such as blood type,
increased risk for specific diseases, or the thousands of basic biochemical processes that
comprise life.
12. The existence of genes was first implied from the work of Gregor Mendel (1822–1884), who,
between the years of 1857 to 1864 planted 8000 common edible pea plants and studied and
tabulated the inheritance patterns in pea plants (Pisum) tracking inheritance of traits from
parent to offspring and describing these mathematically as 2n combinations where n is the
number of differing characteristics in the original peas.
16. Reproduction (or procreation) is the biological process by which new individual organisms –
"offspring" – are produced from their "parents". Reproduction is a fundamental feature of all
known life; each individual organism exists as the result of reproduction.
20. Asexual reproduction is a mode of reproduction by which offspring arise from a single organism,
and inherit the genes of that parent only; it is reproduction which almost never involves ploidy
or reduction.
22. Sexual reproduction is a biological process that creates a new organism by combining the
genetic material of two organisms in a process that starts with meiosis, a specialized type
of cell division. Sexual reproduction is the primary method of reproduction for the vast
majority of macroscopic organisms, including almost all animals and plants
23. Explain heredity?
Heredity is the passing of phenotypic traits from parents to their
offspring, either through asexual reproduction or sexual
reproduction.
24. This is the process by which an offspring cell or organism acquires or
becomes predisposed to the characteristics of its parent cell or
organism.
25. In humans, eye color is an example of an inherited characteristic: an individual might inherit the
"brown-eye trait" from one of the parents.
26. The complete set of observable traits of the structure and
behavior of an organism is called its phenotype.
What is phenotype?
27. These traits arise from the interaction of its genotype with
the environment.
28.
29. As a result, many
aspects of an
organism's
phenotype are not
inherited. For
example, suntanned
skin comes from the
interaction between
a person's
phenotype and
sunlight; thus,
suntans are not
passed on to
people's children
30. Albinism in humans is a congenital disorder characterized by the complete or partial absence of
pigment in the skin, hair and eyes due to absence or defect of tyrosinase, a copper-containing
enzyme involved in the production of melanin.
31. Heritable traits are known to be passed from one generation to the next via DNA, a molecule
that encodes genetic information.
32. DNA is a long polymer
that incorporates four
types of bases, which
are interchangeable.
The sequence of bases
along a particular DNA
molecule specifies the
genetic information:
this is comparable to a
sequence of letters
spelling out a passage
of text. Before a cell
divides through
mitosis, the DNA is
copied, so that each of
the resulting two cells
will inherit the DNA
sequence.
33. A portion of a DNA molecule that specifies a single functional unit is called a gene; different genes have
different sequences of bases. Within cells, the long strands of DNA form condensed structures called
chromosomes
34. Organisms inherit genetic material from their parents in the form of
homologous chromosomes, containing a unique combination of DNA
sequences that code for genes
