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F215-Module 1-Cellular Control and Variation

5.1.1 Cellular Control
a. State that genes code for polypeptides including enzymes
o A length of DNA.
o A sequence of nucleotide bases that code for one or more polypeptides.
o There are about 25,000 genes in a human genome.
o Each gene occupies…

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d. Describe how the sequence of nucleotides within a gene is used to construct a
polypeptide, including the roles of messenger RNA, transfer RNA and ribosomes
Transcription Translation

1. A molecule of mRNA binds to a ribosome. Two codons (six bases) attach to the
small subunit and are exposed to…

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3. A peptide bond forms between the two amino acids which is catalysed by an
enzyme present in the small ribosomal subunit.

4. The ribosome moves along the mRNA to read the next codon. A third tRNA
brings another amino acid. A peptide bond forms between it and the other…

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5. The polypeptide chain grows until a stop codon is reached. This is because there
are no corresponding tRNA's.

e. State that mutations cause some changes to the sequence of nucleotides in
DNA molecules
Mutation=a random change to the genetic materials.
Point mutation=Where one base pair replaces another. Also known…

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o Huntington's disease is caused by a repeating CAG sequence, if the
number goes over a threshold then the protein is changed sufficiently
enough to cause it.
g. State that cyclic AMP activates proteins by altering their three-dimensional
h. Explain genetic control of protein production in a prokaryote using…

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5. The lactose permease enzyme means that it can take up lactose into their
6. -galactosidase can convert lactose to glucose. Glucose can then be used
for respiration.
i. Explain that the genes that animal development of body plans are similar in
plants, animals and fungi in reference to…

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During development it separates the fingers and toes.
Between the ages of 8 and 14, 20-30 billion cells each year undergo apoptosis.
The role of cells dying should balance the role of cells made by mitosis. If it is
not it can lead to the formation of tumours if there…

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Prophase I
The homologous chromosomes are pulled apart by the spindle fibres
to opposite poles.
The chismata separate and the lengths of chromatid that have been
crossed over stay attached to the newly attached chromatid.

Telophase I
In animal cells, two new nuclear envelopes form around each set of

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Chromatids randomly segregate.

Telophase II
Nuclear envelope reforms.
In animals, the two cells divide into four haploid
In plants, a tetrad of four haploid cells is formed.

b. Explain the terms allele, locus, phenotype, genotype,
dominant, codominant and recessive.
Allele-An alternative version of a gene
Locus-Specific position on a…

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Random fertilisation
o Randomly combines two sets of chromosomes from two individuals.
Random mutation during DNA replication in Interphase.
e. Use genetic diagrams to solve problems involving sex linkage and codominance
Sex linkage
o Haemophilia is carried on the X chromosome
o Parental phenotypes: Carrier mother x Normal father


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