SCIM1040 Lecture Notes - Lecture 5: X-Ray, Y Chromosome, Zygosity
5 Jun 2018
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SCIM1040- Lecture 5
Cells and Genetics
(Living World)
Cell Theory
• A cell is the smallest unit that is capable of performing life functions.
• All cells come from preexisting cells through cell division.
• There are two types of cells:
➢ Prokaryotic – means Pro = efore, karyon = nuleus
➢ Eukaryotic – means Eu = true, karyon = nuleus
Prokaryotic cell
• Very simple cells, like bacteria
• Evolutionary ancient because they were the first living organisms to evolve
• Are primarily distinguished by the fact that they lack a membrane-bound nucleus.
Eukaryotic cell
• More complex cells than prokaryotes,
• Have a membrane bound nucleus separating the genetic material, DNA (deoxyribonucleic
acid), from the rest of the cell.
• Most of living things are composed of eukaryotic cells: animals, plants, fungi.
• Eukaryotic organisms can also be single-celled such as the microscopic amoeba and yeast
cell below.
Parts of the Cell
A cell basically consists of a:
1. Nucleus – is the control centre of the cell ad otais the ells DNA, the geeti ode in
coiled-up structures called chromosomes.
• Humans have 46 chromosomes in the nucleus of body cells.
• The DNA contains genes, small portions of the
DNA molecule which are instructions for traits
(characteristics).
• There are about 20000 genes arranged in
chromosomes in the human body cell.
find more resources at oneclass.com
find more resources at oneclass.com
2. Cytoplasm surrounding the nucleus – a jelly-like mixture that contains organelles, small
structures that carry out important life processes. In the cytoplasm are:
• Mitochondria are important for respiration and
therefore energy production in the cell. They
also contain some DNA passed down from the
mother only.
• Vacuoles: small in animal but very large in plant cells and play several roles such as storing
nutrients and waste products.
3. Cell membrane called a plasma membrane. It is a layer that surrounds the cytoplasm and
separates the cell from the external environment. This membrane is semi-permeable – it allows
only some substances in and out of the cell like water molecules, but not all substances. i.e., it
regulates the transport of materials in and out of the cell such as eliminating wastes and absorbing
nutrients and oxygen.
4. Cell wall (plant cells only): Plant cells have a rigid, protective cell wall made up of cellulose that
provides and maintains the shape of these cells and serves as a protective barrier.
Importance of DNA and genes
• DNA proides the reipe for akig proteis. These proteis give rise to the inherited
traits that we see everyday in many different organisms. Every activity in the body is
carried out by a protein.
• DNA molecule is made from two strands, twisted together in a double helix.
• At each level of the spiral or rungs of the ladder
are chemical pairs called bases. The arrangement
of these pairs along the DNA molecule determines
which kind of proteins will be formed in the cell.
• 99.9% of your DNA is identical to everyone else's
and the remaining 0.1% provides the differences
between us such as height, hair colour, eye colour.
Chromosomes in the Human
• Are rod-shaped structures found in the centre of the nucleus of every cell in the body.
• The chromosomes contain DNA
and carry the genes.
• Each sperm and each ovum contains
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Cell theory: a cell is the smallest unit that is capable of performing life functions, all cells come from preexisting cells through cell division. Prokaryotic means pro = (cid:862)(cid:271)efore(cid:863), karyon = (cid:862)nu(cid:272)leus(cid:863) Eukaryotic means eu = (cid:862)true(cid:863), karyon = (cid:862)nu(cid:272)leus(cid:863) Prokaryotic cell: very simple cells, like bacteria, are primarily distinguished by the fact that they lack a membrane-bound nucleus. Evolutionary ancient because they were the first living organisms to evolve. Eukaryotic cell: more complex cells than prokaryotes, have a membrane bound nucleus separating the genetic material, dna (deoxyribonucleic acid), from the rest of the cell, most of living things are composed of eukaryotic cells: animals, plants, fungi. Eukaryotic organisms can also be single-celled such as the microscopic amoeba and yeast cell below. A cell basically consists of a: nucleus is the control centre of the cell a(cid:374)d (cid:272)o(cid:374)tai(cid:374)s the (cid:272)ell(cid:859)s dna, the ge(cid:374)eti(cid:272) (cid:272)ode in coiled-up structures called chromosomes, humans have 46 chromosomes in the nucleus of body cells.
