1. Najaf, Henry, Shugofa, Kelly
4.1
Chromosomes are bundles of long strands of DNA.
A human cell contain enough DNA to stretch for nearly two metres.
Chromosomes always come in pairs in eukaryotes.
Humans have 46 chromosomes in 23 pairs.
Prokaryotes have only one chromosome, and the DNA is not associated with proteins.
Genes
A gene is a heritable factor, meaning passing on from parent to offspring, that controls a specific
characteristic.
Variations of a gene are called alleles.
An allele is one specific form of a gene, differing from other alleles by one or a few bases.
Mutations
A mutation is a random, rare change in genetic material.
One type involves a change of a sequence of bases in DNA.
Base substitution mutation
In humans, a mutation is sometimes found in the gene which creates haemoglobin for red blood
cells. This mutation gives a different shape to the haemoglobin molecule.
The difference leads to red blood cells which look very different from the usual flattened disk
pinched in the middle. The condition which results from this mutation is therefore called sickle
cell anaemia.
The kind of mutation which causes sickle cell anaemia is called a case substitution mutation. One
base is substituted for another so the codon GAG becomes GTG.
Sickle cell anaemia
Symptoms are weakness, fatigue, and shortness of breath.
People affected by sickle cell anaemia have a risk of passing the mutated gene to their offspring.

2. Henry, Najaf, Kelly, Shugufa
4.2
Genotype-The combination of alleles of a gene carried by an organism
Phenotype-The expression of alleles of a gene carried by an organism
Centromeres join chromatids together
Alleles a are different versions of a gene, dominant and recessive
Humans have 46 chromosomes
Crossing over occurs in prophase 1
TT= Tall
Tt= Short
What percentage of the plants will be homozygous recessive short?
Pedigree charts can be used to trace family histories and deduce genotypes and risk in the
case of inherited gene-related disorders
Antibodies (immunoglobulins) are specific to antigens.
Sex genes are not homologous
eukaryotic chromosomes are made of DNA and proteins
meiosis is A reduction division of a diploid nucleus to form 4 haploid nuclei
homologous chromosomes are Chromosomes with the same gene loci in the same
sequence

3. Najaf, Henry, Kelly, Shogufa
4.3
Meiosis
Meiosis is a form of cell division which results in gametes (sex cells).
Cells which contain half the chromosome number are called haploid cells.
Cells with the full chromosome number are called diploid cells.
In a diploid human cell, the 46 chromosomes can be grouped into 23 pairs of chromosomes
called homologous chromosomes.
One of the characteristics which distinguishes meiosis from mitosis is that during the first
step, called prophase I, there is an exchange of genetic material between non-sister
chromatids in a process called crossing over.
Prophase I
1. Chromosomes become visible
2. Homologous chromosomes pair up
3. Crossing over occurs
4. Spindle fibers form
Metaphase I
1. Homologous chromosomes line up across equator
2. Nuclear membrane disintegrates
Anaphase I
1. Spindle fibers attach to chromosomes and pull them to opposite poles
Telophase I
1. Spindle fibers disintegrate
2. Chromosomes uncoil and new nuclear membranes form
- Cytokinesis happens: cell splits into two separate cells.
- Meiosis II takes place in order to separate the sister chromatids.
Prophase II
1. DNA condenses into visible chromosomes again
2. New spindle fibers form
Metaphase II

4. 1. Nuclear membranes disintegrates
2. The individual chromosomes line up along the equator
3. Spindle fibers from opposite poles attach to each of the sister chromatids at the centromeres
Anaphase II
1. Centromeres of each chromosome split, releasing each sister chromatid as an individual
chromosome
2. Spindle fibers pull individual chromatids to opposite ends of the cell
3. Because of random orientation, the chromatids could be pulled towards either of the newly
forming daughter cells
Telophase II
1. Chromosomes unwind their strands of DNA
2. Nuclear envelopes form around the four haploid cells
Down’s Syndrome
In case of Down’s Syndrome, non-disjunction happens in the 21st pair of chromosomes: the
child receives 3 instead of 2. Such an anomaly is called a trisomy and Down’s Syndrome is also
referred to as trisomy 21.
Karyotypes
1. The cells are stained and prepared ona glass slide to see their chromosomes under a light
microscope.
2. Photomicrograph images are obtained of the chromosomes during mitotic metaphase.
3. The images are cut out and separated, a process which can be done using scissors or using a
computer.
4. The images of each pair chromosomes are placed in order by size and the position of their
centromeres.

5. Henry, Najaf, Kelly, Shugufa
4.3
Genotype-The combination of alleles of a gene carried by an organism
Phenotype-The expression of alleles of a gene carried by an organism
Centromeres join chromatids together
Alleles a are different versions of a gene, dominant and recessive
Humans have 46 chromosomes
Crossing over occurs in prophase 1
TT= Tall
Tt= Short
What percentage of the plants will be homozygous recessive short?
Pedigree charts can be used to trace family histories and deduce genotypes and risk in the
case of inherited gene-related disorders
Antibodies (immunoglobulins) are specific to antigens.
Sex genes are not homologous
eukaryotic chromosomes are made of DNA and proteins
meiosis is A reduction division of a diploid nucleus to form 4 haploid nuclei
homologous chromosomes are Chromosomes with the same gene loci in the same
sequence

6. Najaf, Henry, Shugofa, Kelly
4.4 Genetic Engineering and Biotechnology
Polymerase Chain Reaction
1. Polmerser chain reaction- the polymerase chain reaction is a method for
making copies of a specific segment of DNA, starting with a very small amount
2. The technique is used to identify specific micrograms from a small amount of
DNA and to identify persons involved in crimes from DNA on cigarites or in single
hair follicles.
3. The DNA to be amplified is mixed with deoxyribonuclitides, a thermal stable
DNA polymerase called Taq polymerase and DNA primers
4. The mixture is heated to break the hydrogen bonds in the DNA, forming single
stranded molecules. The mixture is then cooled sufficiently to allow the DNA
primers to anneal to each end of the segment to be copied.
5. Taq polmerser then synthesis the complementary strand of DNA, using the
primer as the starting point.

7. 6. The temperature is raised again to separate then lowered sufficiently to allow
perimeters to attach
7. This processes is repeated until enough DNA has been produced to identified.
DNA Profiling- is the process of matching an unknown sample of DNA with a
known sample to see if they correspond.
Applications- DNA profiling can be used in paternity suits when the identity of
someone’s biological father must be known.
Human Genome Project- hoped to determine the order of all bases A, T, C, and G
in human DNA. In 2003, the project announced that it had succeeded in achieving
its goal. The Human Genome Project has pushed forwards medical and
pharmacological research.

8. Cutting, copying, and pasting genes
The ‘scissors used for cutting base ’Restriction enzymes called endonucleases find
and recognize a specific sequence of base pairs along the DNA molecule. The
endonucleases cut DNA at specified points. If both the beginning and the end of a
gene are cut, the gene is released and can be removed from the donor organism.
Copying DNA (DNA cloning)
Host cell is needed- Escherichia coli.
Some DNA can be found in plasmids (small circles of extra copies of DNA
floating in the cell’s cytoplasm.
To copy a gene it must be glued into a plasmid- plasmid must be removed
from the host cell and cut open using a restriction endonuclease (gene
splicing)
Vector is placed inside the host bacterium and the bacterium is giving its
ideal conditions to grow and proliferate. Done by placing a bacterium into a
bioreactor.