Science 8 Module 4-c3 3

SCIENCE 8 MODULE 3 – C3
CHAPTER 3: GENETICS
Objectives:
1. Identify the importance of genetics;
2. Demonstrate an understanding that cells divide to produce new
cells; and
3. Identify the organelles involved in cell division.
Genetics is the science that deals with the study of heredity and
variation. Heredity is the inheritance or transmission of traits from
generation to generation. Traits are the seen or unseen characteristics
of living things. Examples of traits are color, height, and texture. The traits
that are determined by the information that genes contain are called
genetic traits or genotypes. The visible traits manifested by each living
thing are called phenotypic traits or phenotypes. Genes are the units of
inheritance and the biological code that each living thing has. The
word gene comes from the Greek word genos, which means "race
"stock," or "offspring." Genes may be dominant or recessive. Dominant
genes are those that are always expressed. Recessive genes are those
that are unexpressed. Variation refers to the differences among living
things. These variations can be due to differences in the genetic
makeup or the result of environmental factors. Traits may be influenced
by the Surroundings, temperature, or nutrition. Variations in traits can be
explained by cellular division and sexual reproduction, which is the
union of sex cells from two living things.
Gregor Johann Mendel (1822-1884; fig. 11.1) is an Austrian
Augustinian fig. friar popularly known as the "Father of Genetics." He
formulated the basic principles of genetics and conducted experiments
to demonstrate trait inheritance and variation. He used pea plants as
the subject of his experiments because of their availability, fast growth
and s reproduction, and easy manifestation e of traits. He inspired many
scientists e to conduct studies on inheritance and h variation among
living things.
Page 1 | 6
Science 8 / Chapter 3
Fig. 11. 1 Gregor Johann Mendel is known as the “Father of Genetics”
Heredity-Associated Structure
A cell is the basic building block of all living things. Some living things
are made of a single cell (unicellular organisms), whereas others are
made of numerous cells (multicellular organisms). Typical animal and
plant cells are shown in figure 11.2.
Page 2 | 6
Fig. 11.2 (a) A typical animal cell and (b) a typical plant cell has many
cells organelle in common. Each organelle has a specific function in the
cell.
A cell has three main parts, namely, the cell wall (in plants) or cell
membrane (in animals), the cytoplasm, and the nucleus. The cell wall
and cell membrane control the entry and exit of substances in the cell.
They enclose the protoplasm, which is the living part of the cell. The
protoplasm is structurally differentiated into the cytoplasm and the
nucleus. The cytoplasm consists of a jelly-like material or substance
called the cytosol and organelles such as the mitochondria, centrioles,
Golgi apparatuses, lysosomes, peroxisomes, ribosomes, smooth and
rough endoplasmic reticula, vesicles, vacuoles, chloroplasts (in plants),
and cytoskeleton. Each of these organelles carries out specific
functions. All of the chemical reactions of the cell (metabolism) take
place in the cytoplasm. Meanwhile, the nucleus is the control center of
the cell. It is positioned at the center, on one side, or at the end of the
cell. Cells make up all living things. They absorb the nutrients from food,
which provide protection for and energy to the body.
Cells contain hereditary materials that are involved in the growth
and development of living organisms The nucleus, cytoskeleton, and
ribosomes are cell structures that are involved in the inheritance and
transmission of traits.
Nucleus
Living organisms are classified based on the presence or absence of
a nucleus in their cells. Living things that have a true nucleus (nucleus
Page 3 | 6
contained within a membrane) are called eukaryotes. Living things that

do not have a true nucleus are called prokaryotes.
The nucleus is the command center of eukaryotic cells. It is a
spherical organelle that is bigger than all the other organelles.
Surrounded by the cytoplasm, the nucleus consists of three main parts,
namely, the nuclear membrane, the nucleoplasm, and the nucleolus.
The nuclear membrane or nuclear envelope is a porous double
layer that separates the contents of the nucleus from the cytoplasm. It
also controls the entry and exit of substances in the nucleus. The
nucleoplasm or karyoplasm is the protoplasmic part of the nucleus. Its
fluid content is called the nuclear sap or karyolymph, within which the
nucleoli and chromatin are suspended.
The nucleolus (plural, nucleoli) is a large, spherical body in the
nucleus. Called the "nucleus of the nucleus," the nucleolus is responsible
for the production of ribosomal units, which make up the ribosomes.
Chromatins are dark, threadlike structures and granules in the
nucleoplasm of an undivided cell. During cell division, chromatins
condense into threadlike bodies called chromosomes. Chromosomes
are nucleoproteins that bear the genetic information in the form of
genes. Each chromosome consists of strands of DNA and associated
proteins. DNA or deoxyribonucleic acid is a nucleic acid that carries the
genetic code, which determines the traits of each living thing
A chromosome consists of coiled, threadlike, filamentous structures
called chromonemata. The fixed point that controls the movement of a
chromosome during cell division is called the centromere, whereas the
beadlike bodies along the length of the chromosome are called
chromomeres. One-half of the two identical copies of a replicated
chromosome is called a chromatid. The structure of a chromosome 15
shown in figure 11.3.
Page 4 | 6
Fig. 11.3 In a chromosome, a single DNA molecule is tightly coiled

several times around proteins called histones, which support its
structure. The resulting chromatin strand loops several times to form a
chromatid. Two identical sister chromatids comprise the chromosome.
Cytoskeleton
The cytoskeleton is a network of protein fibers in the cytoplasm. It
serves as the structural framework of the cell and determines the cell's
Page 5 | 6
shape. It includes structures that participate in cell division. Microtubules

are cytoskeleton components that rearrange themselves into spindle
fibers. Spindle fibers are structures that stretch between centrioles.
Chromosomes attach to these structures during cell division. Centrioles
are paired structures in the cytoplasm. They are engaged in the
organization and completion of cytokinesis, which is a process that
starts during the last stage of cell division. Each centriole is duplicated
during cell division. In addition, centrioles anchor the spindle fibers.
Centrosomes are structures from which microtubules arise. These
structures function as resisting girders of the cytoskeleton.
Ribosomes
Ribosomes are cellular organelles produced by nucleoli. These
structures are made up of ribonucleic acid (RNA) and proteins. RNA is a
kind of nucleic acid that functions in protein synthesis. Proteins are
biological molecules that take part in almost all biological processes in
the cell. They also determine the characteristics of an organism.
Page 6 | 6

Science 8 Module 4-c3 3

Uploaded by

Copyright:

Available Formats

Science 8 Module 4-c3 3

Uploaded by

Document Information

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Science 8 Module 4-c3 3

Uploaded by

Copyright:

Available Formats

SCIENCE 8 MODULE 3 – C3

Fig. 11. 1 Gregor Johann Mendel is known as the “Father of Genetics”

contained within a membrane) are called eukaryotes. Living things that

Fig. 11.3 In a chromosome, a single DNA molecule is tightly coiled

shape. It includes structures that participate in cell division. Microtubules

You might also like