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38 Cards in this Set
- Front
- Back
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What do genes code for? |
Genes are lengths of DNA which code for 1 or more polypeptides, including: Antibodies Enzymes Hormones Structural proteins, such as keratin or elastin Receptor molecules in cell signalling |
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Genome |
The entire library of genes in an organism. The Human Genome contains approx. 25 000 genes. |
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Characteristicsof the genetic code:
Triplet code |
Three nucleotide bases codes for an amino acid
Four bases arranged into groups of three so the number of different triplet sequences is 4³ is 64 More than enough for 20 amino acids |
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Characteristics of the genetic code:
Degenerate code |
All amino acids have more than one code
EXCEPT METHIONINE |
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Characteristics of the genetic code:
Stop codons |
Some codes don’t correspond to an amino acid
These indicate STOP and end the polypeptidechain |
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Characteristics of the genetic code:
Widespread but NOT universal |
Base sequence TCT codes for amino acid serine inany organism
Useful for genetic engineering as we cantransfer a gene from one organism to another and still produce the same protein Some variations include: Mammalian mitochondria: two codes for methionineand one standard stop codes codes for tryptophan Ciliated protoctists: two of the standard stopcodes code for glutamic acid |
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What is messenger RNA synthesised from? |
Messenger RNA is synthesised form free activated RNA nucleotides which are found in the nucleolus. They are activated through the addition of 2 additional phosphate groups. i.e. ATP (from AMP), GTP (from GMP), UTP (from UMP) and CTP (from CMP) |
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Describe the role of ribosomal RNA in translation |
Assembled in the nucleolus of eukaryote cellsfrom ribosomal RNA and protein
Made up of two subunits between which is a grovethrough which mRNA can fit Ribosome move along the mRNA reading the codeand assembling the amino acids |
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Describe the role of messenger RNA in translation
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Made in the nucleus
Three adjacent bases are called a codon Carries the genetic code from the DNA in thenucleus to the cytoplasm, where it’s used to make a protein during translation |
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Describe the role of transfer RNA in translation
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Another form of RNA
Made in the nucleus and passes into thecytoplasm Folded into hairpin shapes 2 binding sites: - The anti-codon which is complementary to the condon on the mRNA - A site which binds the corresponding amino acid |
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How does cyclic AMP work? |
Once the polypeptides have been synthesised they may not be immediately active. Cyclic AMP activates proteins by altering their 3D structure. (Cyclic AMP is synthesised from ATP using the enzyme adenyl cyclise) |
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The Lac Operon: Explain why the Lac Operon, an example of an inducible protein (one that can be turned on and off), exists |
E. Coli can respire both glucose and lactose (glucose + galactose) Usually their environment is louses rich so they don't want to make the enzymes necessary for lactose respiration Why? Making proteins that are not essential will tie up resources such as amino acids Uses a lot of energy unnecessarily |
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The Lac Operon: State the role of Beta-Galactosidase |
Beta-Galactosidase catalyses the hydrolysis of lactose into glucose |
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The Lac Operon: State the role of Lactose Permease |
Lactose Permease increases the cell's permeability to lactose so it can take in more lactose from the surrounding environment |
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The Lac Operon:
State the role of the regulatory gene |
The regulatory gene codes for a repressor protein |
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The Lac Operon:
State the role of the promoter region |
The promoter region is where RNA polymerase binds |
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The Lac Operon: State the role of the operator region |
The operator region is where the repressor protein binds |
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The Lac Operon: State the role of the structural gene (Z and Y) |
The structural genes Z and Y code for Beta-Galactosidase and Lactose Permease, the enzymes required for lactose respiration |
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What is apoptosis? |
Apoptosis is programmed cell death. |
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What is the process of apoptosis like? |
It is ordered, tidy and does not affect neighbouring cells or tissues. |
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Why is the process of apoptosis carried out? |
It removes excess cells allowing their components to be recycled into new cells. It allows organisms to develop, i.e. digit formation. Removes harmful cells (T-Lymphocytes that are complementary to our own antigens) Removes ineffective cells (cells at the end of their lifecycle) |
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How is apoptosis controlled? |
Hormones Cytokines (from infected cells) Growth factors - protein signals which control growth Nitric Oxide: - Mitochondrial inner membranes become permeable - H⁺ concentration dissipates - ATP production decreases or stops |
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Outline the process of apoptosis |
1. Enzymes digest the cytoskeleton 2. Cytoplasm becomes dense as organelles become more tightly packed together 3. Blebs form (bulging) 4. Chromatin (DNA & proteins) condense and the nuclear envelope breaks 5. DNA fragments 6. The cell breaks apart forming apoptotic bodies (vesicle like structures) 7. These bodies package the harmful hydrolytic enzymes preventing damage to other cells 8. Phagocytosis of the cellular debris, some of which can be recycled |
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What is necrosis? What is it caused by? |
Necrosis is premature cell death Necrosis is caused by infection, trauma and toxins Necrosis is harmful to the body and in some cases be fatal |
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What are mutations? What happens if a mutation occurs in a somatic cell vs. a gamete cell? |
Changes to the sequences of DNA nucleotides in a gene. Somatic (body) cell: the effects are only present in that individual Gamete (sex) cell: the effects will be present in future generations. |
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What are the three levels that a mutation can occur? |
DNA level mutations: changes in the arrangement of bases in an individual gene Gene mutations: changes in the chromosome, changing the arrangement of genes Chromosome mutations: addition of deletion of a chromosome |
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What causes mutations? |
Cigarette tar UV light X-Rays Gamma-rays |
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Describe a point mutation (substitutions) Give an example |
Point Mutations: - 1 bases of 1 base triplet is swapped for another E.g. orignal DNA sequence: the fat cat ate the wee rat mutant DNA sequence: the fat hat ate the wee rat Example: Sickle cell anaemia - Deoxygenated haemoglobin becomes fibrous in nature and cannot carry oxygen - Caused by 1 amino acid VALINE replacing glutamic acid |
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Describe a deletion mutation
Give an example |
Deletion Mutation: - Removal of 1 or more bases, results in a frameshift mutation E.g. original DNA sequence: the fat cat ate the wee rat mutant DNA sequence: the fat ca^a tet hew eer at Example: Cystic Fibrosis - Over production of mucus in the respiratory, digestive and reproductive tracts - Deletion of 1 base triplet in a polypeptide 1,480 amino acids long |
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Describe an insertion mutation
Give an example |
Insertion Mutation: - Addition of 1 or more bases, results in a frameshift mutation E.g. original DNA sequence: the fat cat ate the wee rat mutant DNA sequence: the fat cat hat ate the wee rat Example: Huntington's Disorder - Onset in over 40s with symptoms such as forgetfulness, confusion, unbalance and slurred speech - Insertion of a stutter where CAG is repeated |
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Describe how mutations can be harmful
Give examples of harmful mutations |
Harmful mutations have a negative effect on an organisms phenotype and can affect its ability to survive and reproduce Examples: - Huntington's Disorder - Cystic Fibrosis - Sickle Celled Anaemia |
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Describe how mutations can be neutral Give examples of this can occur |
Neutral mutations have no affect on the phenotype or its ability to survive and reproduce This can happen if: - The mutation occurs in a non-coding region - The triplet code changes but it still results in the same amino acid (silent mutation) - The mutation codes for a new protein, however the protein has no effect on the organisms survivability Examples: tongue rollers, honey suckle smellers, ear lobe shape, PTC tasters |
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Describe how mutations can be beneficial |
All the living things you see around are the result of positive mutations |
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Give the definition of a homeotic gene |
A homeotic gene regulates the expression of other genes in an organisms genome. |
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How can homeotic genes go wrong? |
Retinoic Acid is a derivative of Vitamin A andtriggers homeobox genes causing birth defects in pregnant women who takeretinol during the first month of pregnancy.
Mutations in homeobox genes can cause changes inthe body plan. E.g. a mutation in the genes controlling leg placement can causelegs to grow when the antennae are normally found. |
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Homeobox genes are present in the genomes of most organisms, e.g. plants, animals and fungi, what does this suggest? |
- Homeobox genes control development of body parts of different organisms in similar ways - Little variation in many regions of the homeoboxgenes in different organisms suggests these have been highly conservedthroughout evolutionary history - Thought to be especially important to the basicdevelopment of organisms |
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What do homeobox genes do? |
Homeobox genes control the development of bodyplans.
a. Control the polarity of the organism (the headand tail end); and b. Control the positioning of organs2. ‘Switching on’ the expression of a gene orkeeping it switched off determines the development of features. |
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What do homeobox genes code for? When are they activated and expressed? In what form do they occur? |
They code for transcriptional factors that regulate the expression of other genes important in development.
They are expressed and activated in a specific order during the development of the embryo. They occur in groups that are referred to as a cluster or ‘set’, with each Hox-Cluster containing 9-11 Homeobox genes. |
