Task 1

Task 1 (P1)
Which part of a cell controls all the activities that happen in the cell? What does it contain that enables it to carry out its function?
The nucleus is the control centre of the cell. A cell’s nucleus is able to control the other activities in a cell by expressing certain segments of its DNA, which creates proteins that perform specific activities. Proteins can vary from enzymes to structural components, but they are needed for almost all processes in a cell and the human body.

The nucleus directs all cellular activities by controlling the synthesis of proteins. The nucleus contains encoded instructions for the synthesis of proteins in a helical molecule called deoxyribonucleic acid (DNA). The cell’s DNA is packaged within the nucleus in a structural form called chromatin. Chromatin consists of DNA wound tightly around spherical proteins called histones. When the cell prepares to divide, the DNA unwinds from the histones and assumes the shape of chromosomes, the X-shaped structures visible within the nucleus prior to cell division. Chromatin packaging of DNA allows all of the cell’s DNA to fit into the combined space of the nucleus. If DNA was not packaged into chromatin, it would spill out over a space about 100 times as large as the cell itself.

The first step in protein synthesis begins in the nucleus. Within the nucleus, DNA is translated into a molecule called messenger ribonucleic acid (mRNA). mRNA then leaves the nucleus through the nuclear pores. Once in the cytoplasm, mRNA attaches to ribosomes (either bound to endoplasmic reticulum or free in the cytoplasm) and initiates protein synthesis. Proteins made for export from the cell function as enzymes that participate in all the body’s chemical reactions. Because enzymes are essential for all the body’s chemical processes-from cellular respiration to digestion-direction of the synthesis of these enzymes in essence controls all the activities of the body. Therefore, the nucleus, which contains the instructions for the synthesis of these proteins, directs all cellular activities and thus all body processes.

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Draw a flow diagram below that shows the relationship between a cell, the nucleus, chromosomes, genes and DNA.

(a) Write a description of what you understand by the term “gene”.
Include any appropriate diagrammatic illustration to support your text
(maximum 100 words).

Genes
A gene is a length of DNA that codes for a specific protein. So, for example, one gene will code for the protein insulin, which is important role in helping your body to control the amount of sugar in your blood.Genes are the basic unit of genetics. Human beings have 20,000 to 25,000 genes. These genes account for only about 3 per cent of our DNA. The function of the remaining 97 per cent is still not clear, although scientists think it may have something to do with controlling the genes.

(b) Research how wheat has changed since the 1950s.
What was the name of the man who enabled today’s wheat to be grown successfully?
What did he do to enable wheat to be grown around the
world and save 100 million people from starvation?
Dr. Norman Borlaug Studies :- Borlaug studied plant biology and forestry at the University of Minnesota and earned a Ph.D. in plant pathology there in 1941. From 1944 to 1960 he served as a research scientist at the Rockefeller Foundation’s Cooperative Mexican Agricultural Program in Mexico. Borlaug’s work was founded on earlier discoveries of ways to induce genetic mutations in plants. These methods led to modern plant breeding, with momentous results that included the tailoring of crop varieties for regions of climatic extremes. At a research station at Campo Atizapan he developed strains of grain that dramatically increased crop yields. Borlaug ultimately developed short-stemmed (“dwarf”) wheat, a key element in the Green Revolution in developing countries.

How is this connected to genes?
University of Minnesota alumnus Norman Borlaug left an indelible mark on the world. The late agronomist’s work in developing new varieties of wheat starting in the 1940s spawned the “Green Revolution,” and is credited with saving at least a billion lives.

For his unparalleled contributions in using science to feed the world, Borlaug was awarded the Nobel Peace Prize in 1970, the Presidential Medal of Freedom (1977), the Public Welfare Medal (2002) by the National Academy of Sciences, the National Medal of Science (2005), and the Congressional Gold Medal (2007). In 2014 a statue of him was placed in the National Statuary Hall of the United States Congress; he is the sole scientist represented there.

Borlaug also received more than 50 honorary degrees, was inducted into the collegiate National Wrestling Hall of Fame, and helped introduce Little League baseball in Mexico. And just last month, at the “9 Billion and Counting” conference on campus, he was lauded as being “the single greatest graduate of a land-grant institution.”
Beyond all the accolades, Borlaug was a plant pathologist/breeder, a teacher of scientists, a scientific collaborator, and a team builder. His unique teaching and training methods for young scientists became part
If you complete the above correctly then you will achieve AC. P1
Task 2 (M1)
An example of Natural Selection – The case of the English peppered Moth
The English peppered moth rests on tree trunks during the day. Its speckled grey colouring provides a good camouflage on the lichen-covered trunks of the trees. In about 1850, a black English peppered moth was discovered in Manchester.
It was not an advantage for these moths to be black as they stood out against the white lichen and were therefore easily seen by predators.

With the spread of the Industrial Revolution and the expanding use of steam power, pollution became a problem in large cities. The trees once covered in lichen turned black. The number of black moths increased dramatically and by 1895 they made up about 98% of the population of English peppered moths. How did the moths get to be black?
Natural selection!
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Two different varieties of the peppered moth. The distribution of peppered moths in
They are on a tree that is covered in lichen. the 1950s. The black variety is in
Industrial areas and the light variety is
in rural farm areas
Using the information given above, and some of your own research, answer the following questions:
What changes occurred in the genes of the peppered moth, and how did the changes occur, that led to the creation of the black moth? (Max 100 words).

The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism.

Explain why the population of black moths was so low in the 1850s. (Max 100 words).

Industrialisation and domestic coal fires had caused sooty air pollution which had killed off lichens and blackened urban tree trunks and walls. So now it was the pale form of the moth that was more obvious to predators, while the melanic form was better camouflaged and more likely to survive and produce offspring.

Explain why the population of black moths increased to 98% of the whole population by 1895. (Max 100 words).
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during theIndustrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism.

What happened to the numbers of light moths between 1850 and 1895? Look at the map that shows the distribution of moths between 1895 and 1950? Explain the pattern shown. (Max 150 words).

The melanic phenotype is due to underlying homozygous (BB) and heterozygous (Bb) dominant genotypesIn the mid 1950’s, air pollution controls were introduced in BritainWhen smoke pollution decreased in Britain, natural selection acted very quickly to favor survival of the wild type peppered morphs as bird predation eliminated melanic forms in progressively less polluted forestsThe frequency of the melanic form has declined ever since
If you complete the above correctly then you will achieve AC. M1
Task 3 (D1)
Explain how a genetic code leads to the formation (synthesis) of a protein.

You need to explain in detail the sequence of events involved in protein synthesis. Draw a diagram to represent this.

Transcription • Information transcribed from DNA into RNA – mRNA carries information for protein structure, but other RNA molecules formed in same way • RNA polymerase binds to promoter nucleotide sequence at point near gene to be expressed • DNA helix unwinds • RNA nucleotides assemble along one DNA strand (sense strand) in complementary sequence to order of bases on DNA beginning at start codon (AUG – methionine) • Transcription of DNA sense strand ends at terminator nucleotide sequence • mRNA moves to ribosome • DNA helix rewinds From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and Physiology (9th Ed). New York: John Wiley & Sons. P88.

11. Transcriptional control • Each cell nucleus contains all genes for that organism but genes only expressed as needed • Transcription regulated by transcription factors – Proteins produced by their own genes • If transcription factors promote transcription – activators • If transcription factors inhibit transcription – repressors • General transcription factors interact with RNA polymerase to activate transcription of mRNA – Numerous transcription factors required to initiate transcription – General transcription factors set base rate of transcription – Specific transcription factors interact with general transcription factors to modulate rate of transcription • Some hormones also cause effects by modulating rate of gene transcription
12. Protein synthesis occurs in ribosomes
13. Protein synthesis occurs in ribosomes

Explain why proteins are important in the functioning of organisms? Give examples of at least three specific proteins and their functions.
Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs. … Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.

Collagen
Strengthens bones, ligaments, and tendons (a fibrous protein)
Elastin
Provides stretch in skin, blood vessels, and lung tissue (a fibrous protein)
Keratin
Forms structure of hair and nails and water proofs the skin (a fibrous protein)
DystrophinReinforces parts of muscle cells (a fibrous protein)
Fibrin
Forms blood clots (a fibrous protein)
Actin and Myosin
Are involved in contraction of muscle cells, division in all cells, and transport of substances within cells (a fibrous protein)
Explain how proteins influence the physical attributes of individuals within a species (i.e. variation).

Relationship Between DNA Bases Genes, Proteins and Traits
By John Brennan; Updated April 26, 2018
Although you might have heard people talk about a gene for red hair, green eyes or other characteristics, it’s important to remember that genes code for proteins, not traits. While your genetic makeup does indeed determine physical traits like eye color, hair color and so forth, your genes affect these traits indirectly by way of the proteins created via DNA.

DNA Sequence
Your DNA carries information in the sequence of base pairs of its nucleotides. These biological molecules, the building blocks of DNA, are often abbreviated with the first letter of their names: adenine (A), thymine (T), guanine (G) and cytosine (C).

The types and sequence of nucleotides in DNA determine the types and sequence of nucleotides in RNA. This in turn determines the types and order of amino acids included in proteins. Specific three-letter groups of RNA nucleotides code for specific amino acids. The combination TTT, for example, codes for the amino acid phenylalanine. Regulatory regions of the gene also contribute to protein synthesis by determining when the gene will be switched on or off.

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Proteins
In active genes, genetic information determines which proteins are synthesized and when synthesis is turned on or off. These proteins fold into complicated three-dimensional structures, somewhat like molecular origami.

Because each amino acid has specific chemical characteristics, the sequence of amino acids determine the structure and shape of a protein. For example, some amino acids attract water, and others are repelled by it. Some amino acids can form weak bonds to each other, but others cannot. Different combinations and sequences of these chemical characteristics determine the unique three-dimensional folded shape of each protein
Structure & Function
The structure of a protein determines its function. Proteins that catalyze (accelerate) chemical reactions, for example, have “pockets,” which can bind specific chemicals and make it easier for a particular reaction to occur.

Variations in the DNA code of a gene can change either the structure of a protein or when and where it is produced. If these variations change the protein structure, they could also change its function. For example, a single, specific mutation in hemoglobin — the oxygen-carrying protein abundant in your red blood cells — affects oxygen transport and is enough to cause sickle-cell anemia.

Traits
Variations in a gene can affect traits in several ways. Variations in proteins involved in growth and development, for example, can give rise to differences in physical features like height. Pigments of skin and hair color are produced by enzymes, proteins that catalyze chemical reactions. Variations in both the structure and quantity of the proteins produced give rise to different amounts of skin and hair pigment and therefore different colors of hair and skin.

 
If you complete the above correctly then you will achieve AC. D1
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P1: Describe how the functioning or organisms relates to the genes in their cells
M1: Describe how variation within a species brings about evolutionary change
D1: Explain how genes control variation within a species using a simple coded message
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