SBI3U
Label the following diagrams:
Animal
Cell:
Plant
Cell:
Name:_________
Date:__________
PARTS OF THE CELL
Name:______________
Date:__________
Read pp. 10-20 Nelson Biology 11 and discuss with your partner to help you complete
the following chart.
Cell Part
Function
1
Barrier between the cell and it’s
environment; controls what enters
and leaves the cell
2
Jelly-like contents of the cell
3
Co-ordinates, controls and
manages all of the cell’s functions
4
Encloses the genetic material of
the cell
5
Small, spherical structure in
nucleus that manufactures
ribosomal RNA
6
Long strands of DNA (genetic
material)
7
Extracts food energy and makes it
available for the cell
8
Produces protein; may float freely
or be attached to the endoplasmic
reticulum
9
Storage place for water, food,
wastes and other materials; larger
in plants
10
Contains enzymes that break down
food, wastes and old cells
11
Transports materials throughout
the cell; site of some chemical
reactions
12
Modifies and packages proteins
for secretion outside of the cell
13
Small sacs or packets that are
released by the Golgi apparatus
14
Cylindrical organelle in animal cells
that is involved in cell division;
form spindle fibres
15
Containing chlorophyll, they are
the site of photosynthesis; found
only in plant cells
16
Provides structure and support for
plant or bacterial cells
Introduction to Genetics
Genetics is the study of heredity (how characteristics are inherited from generation to
generation) and of variation (why individuals of a species are different from each other).
Genetics allow us to understand normal events such as development, growth, and ageing in
terms of the underlying molecular machinery that direct these processes, and provides an
understanding of why these processes go wrong in disease. Genetics also provides us with tools to
produce improved crops and livestock (we’ve been doing this for thousands of years).
We share about:
98% of our genes with an ape
80% of our genes with a mouse
50% of our genes with a fruitfly
20% of our genes with a tiny worm
The main ideas explored in the field of genetics are the genetic code (DNA, genes), how the
genetic code is passed on (probability), and how the genetic code is expressed (gene expression). A
genome is an entire system of genes that makes up a species. Genomics is the study of how genes
interact and influence the biology and physical characteristics of living things.
Levels of genetic information:
Inherited Characteristics and Genetic Material
In sexually reproducing species, offspring obtain a unique combination of genetic
information from their parents, resulting in a unique combination of characteristics. The
resemblances found among family members are due to shared characteristics from their
biological parents.
A trait is a characteristic of an organism, such as hair colour or the sound of a person’s
voice. Some traits, such as sun-bleached hair, we acquire as we live. Other traits, such as
naturally curly hair, we inherit. Before anyone understood how traits could be inherited,
people thought there must be a material that controlled these biological characteristics and
was passed down from one generation to the next.
Until the mid 1900s, the chemical nature of the genetic material remained unknown.
Scientists hypothesized that the genetic material consisted of proteins. Proteins could have
great variation in their chemical makeup and physical properties, features that the genetic
material would also have. However, after a series of experiments with the bacteria and
viruses, scientists had an incredible breakthrough. They demonstrated that the genetic
material was composed of a molecule called deoxyribonucleic acid (DNA). DNA was
transferred between generations of organisms and had the ability to transform the properties
of a cell.
Every Cell’s DNA is organized into genes. Genes are units of inherited information that
carry a code for specific traits or functions. Many genes code for proteins. The information
contained in genes is responsible for inheritance – the passing down of traits from parent
organisms to their offspring.
This image is an example of DNA
extraction and purification in a test tube.
Kate Hudson and Goldie Hawn.
Like mother like daughter: family
resemblance is obvious between
Packaging of DNA
Plants, fungi and animals belong t a group of organisms called the eukaryotes. A
eukaryotic cell has a nucleus and other internal organelles enclosed by membranes. The
nucleus contains the cell’s DNA. For much of a cell’s life, its DNA exists as a mass of very long
fibres called chromatin, a combination of DNA and protein. Chromatin is very thin and not
usually visible with a light microscope.
As a cell is preparing to divide, its chromatin fibres condense, becoming visible
compact structures called chromosomes. A chromosome consists of one long, condensed DNA
molecule containing hundreds or thousands of genes. A human body cell contains enough
DNA to stretch about two metres in length! In the stained animal cell shown below, each
dark-orange bar is an individual chromosome in the nucleus. The number of chromosome
varies among different species. Human body cells generally have 46 chromosomes, while the
body cells of dogs generally have 78 chromosomes.
The DNA in chromatin is tightly coiled around proteins called histones. The DNA and
histone packages form structures resembling beads, called nucleosomes. The organization of
the DNA prevents it from tangling and being damaged, much as winding thread around a
spool keeps the thread in good shape.
DNA Structure and Sequences
In the early 1950s, scientist Rosalind Franklin began to study the structure of DNA.
Using a method called X-ray crystallography, a technique that uses X-rays to determine the
geometry or arrangement of atoms in a molecule, Franklin determined that DNA had the form
of a spiral, or helix. Using Franklin’s findings and other research, James Watson and Francis
Crick modelled DNA’s structure as a twisting shape called a double helix. Their model placed
sugar-phosphate backbones on the outside of the double helix and subunits called
nitrogenous bases on the inside. This model successfully represented DNA’s structure.
We use the 26 letters of the alphabet to spell an almost countless number of words.
Like letters of the alphabet, nucleotides can combine in various sequences. For example, the
single DNA strand shown below has nine nucleotides arranged in the order CTGCTATCG. This
arrangement is only one of many possible. Since nucleotide chains also vary in length, from
only a few hundred nucleotides to millions of nucleotides, the number of possible nucleotide
sequences is essentially unlimited.
Like the arrangement of letters and words in an instruction booklet, the arrangement
of nucleotides in DNA stores information. The genes included in this information code for
specific cell proteins and functions.
Watson and Crick, DNA Model
DNA Structure
Components of DNA
DNA consists of a long chain of subunits called nucleotides. A nucleotide has three parts:
1. A ring shaped sugar called deoxyribose
2. A phosphate group
3. A nitrogenous base: a single or double ring of carbon and nitrogen atoms
There are four types of nucleotides in DNA, which differ only in their nitrogenous bases. The
bases thymine (T) and cytosine (C) are single-ring structures called pyrimidines. Adenine (A) and
guanine (G) are larger, double-ring structures called purines. Nucleotides are joined to one another by
covalent bonds that connect the sugar of one nucleotide to the phosphate group of the next. This
repeating pattern of sugar-phosphate is called the sugar-phosphate backbone.
Scientists noticed very specific pairings between the nucleotides of the two strands of the
double helix. They discovered that there are bonds between specific base pairs that provide enough
force to hold the two strands in the helix together. It is the placement of these bonds that twists DNA
into a spiral shape. The purine adenine pairs with the pyrimadine thymine, and the purine guanine
pairs with the pyrimidine cytosine. The bases are called complementary bases. A is complementary to
T, and G is complementary to C.
Along the strands of the double helix, each base is paired up with its complementary base.
Therefore, if the sequence of one strand is known, the sequence of the other strand can be determined.
These base pairing rules set the stage for understanding how the information in DNA is replicated and
passed through generations.
Genetics Introductory Activity Questions
SBI3U
Name:__________________
Date:__________________
Introduction to Genetics
1. Genetics is the study of (define each term):
a)
b)
2. What does genetics allow us to understand?
3. Looking at the percentages of genes we share with other species, what can you infer?
4. What are the main ideas explored in the field of genetics?
5. What is a genome? What is genomics?
Inherited Characteristics and Genetic Material
6. Why do family members tend to look alike?
7. What is a trait?
8. What is inheritance?
9. What do we know ‘genetic material’ as?
10. What are genes and what do they do?
Packaging of DNA
11. What is a eukaryote?
12. Explain what chromatin is.
13. What are chromosomes?
14. What are histones?
15. What are nucleosomes?
DNA Structure and Sequences
16. Who is Rosalind Franklin and what does she mean to the field of genetics?
17. What is X-ray crystallography?
18. Explain Watson and Crick’s model of DNA and how it differs from Franklin’s model.
19. How long is a nucleotide chain?
20. Refer to question 14. What does this mean for the possibilities of sequence combinations?
Components of DNA
21. What are the three parts of a nucleotide? Draw an example.
22. What is a pyrimidine? Give two examples.
23. What is a purine? Give two examples.
24. Illustrate and label how the nucleotides pair up.
25. If the bases are complementary, what would the complementary strand look for the following
sequence of nucleotides:
GATTACA
ANIMAL CELL