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State that genes code for polypeptides, including enzymes;
Gene: length of DNA (sequence of nucleotides bases) that codes for one or more polypeptides
Polypeptides: polymer consisting of a chain of amino acid residues joined by peptide bonds
Genome: of an organism is the entire DNA sequence of that organism
· Each gene occupies a specific place (locus) on the chromosome
· DNA in chromosome is associated with histone proteins
· Genes code for polypeptides such as antigens, haemoglobin and enzymes
· Since genes code for enzymes they're involved in control of all metabolic pathways and synthesis of all
non-protein molecules found in cells…read more

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Explain the meaning of the term genetic code;
Genetic code: the means by which RNA and DNA molecules carry genetic information in living cells
characteristics:
· Triplet code ­ sequence of 3 nucleotide bases code for an AA
· Degenerate code ­ all AA except methionine have more than one code
· Some codes indicate STOP
· Widespread but not universal…read more

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Describe, with the aid of diagrams, the way in which a nucleotide sequence codes for
the AA sequence in a polypeptide; describe how the sequence of nucleotides within a
gene is used to construct a polypeptide including the roles of mRNA, tRNA and
ribosomes;
· Copy (mRNA) of genetic code must be made which can pass through nuclear envelop to cytoplasm
The first stage is transcription in the nucleus. The gene to be transcribed unwinds and unzips. To do this the
length of DNA that makes up the gene dips into the nucleolus and the hydrogen bonds between the
complementary bases break. Activated RNA nucleotides bind to the exposed bases on the template strand
forming hydrogen bonds. This is catalysed by RNA polymerase. An mRNA is then produced and is a copy of the
coding strand of the DNA. The strand of mRNA then leaves the DNA and exits the nucleus through a nuclear
pore, and attaches to a ribosome.
The second stage is translation. The molecule of mRNA has attached to the ribosome and two codons are
attached to the small subunit of the ribosome and the large subunit is exposed. The tRNA complementary to
the first codon has an amino acid and dorms hydrogen bonds with its anticodon (3 unpaired nucleotide bases)
to the complementary codon. The second tRNA binds to the next codon and a peptide bond is formed between
the amino acids. When a third tRNA comes along, the first leaves the ribosome leaving behind the amino acid
This continues until a STOP codon is reached.
· Ribosomes are assembled in nucleolus of eukaryote cells from rRNA and protein
· Made up of 2 subunits, groove which mRNA can fit
· Ribosome moves along mRNA reading the code and assembling AA in correct order making protein…read more

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State that cyclic AMP activates proteins by altering their 3D structure;
· Some proteins have to be activated by cAMP that is a nucleotide derivative
· It activates proteins by changing their 3D shape so their shape is better fit to complementary molecules…read more

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State that mutations cause changes to the sequence of nucleotides in DNA molecules;
Mutation: change in the amount of, or arrangement of, genetic material in the cell ­ random
Chromosome mutation: involves changes to parts of or whole chromosomes
· may occur during DNA replicaiton
· Certain substances (mutagens) may cause mutation; tar, UV, x-rays
DNA mutation: changes to genes due to changes in nucleotide base sequences
· Mutations associated with mitosis = somatic mutations , not passed onto offspring
· Mutations associated with meiosis and gamete formation can be inherited
2 main classes of DNA mutations:
· Point mutations ­ 1 base pair replaces another called substitutions
· Insertion/deletion mutations ­ one or more nucleotide base inserted/deleted from length of DNA called
frameshift
Genetic diseases are a result of DNA mutations:
· 70% of CF, mutation is deletion of triplet base pair (deleting AA from sequence of polypeptide)
· Sickle-cell anaemia results from point mutation (AA inserted instead of another AA)
· Growth promoting genes = proto-oncogenes, some changed into oncogenes by point mutation…read more

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Comments

Kamara-7

Thanks for the helpful Powerpoin! :D

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