Cellular Control

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  • Created by: Phil
  • Created on: 25-05-13 15:35
What is a gene?
A legnth of dna that codes for one or more polypeptides.
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What is a polypeptide?
A polymer consisting of a chain of amino acids.
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What is the genetic code?
The sequence of bases on a gene is a code with instructions for the construction of protein.
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3 Characteristics of genetic code?
1.triplet code, 2.degenerate 3.widespread.
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What is meant by triplet code?
Three bases code for an amino acid.
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What is meant by degenerate?
All amino acids (except methionine) have more than one code.
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What is meant by widespread?
Codons generally always code for the same amino acid in every organism, this is not always the case.
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PROCESS TRANSCRIPTION
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PROCESS TRANSLATION
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Define transcription.
The creation of a single-stranded mRNA copy of the DNA coding strand.
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Define translation
The assembly of polypeptides at ribosomes.
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How does protein synthesis occur in prokaryotes?
Dna is not inside a nucleus, so translation begins as soon as the mRNA is amde.
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What is a mutation?
A change to the amount of, or arrangement of genetic material in a cell.
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What are chromosome mutations and DNA mutations?
Chromosome mutations involve changes to parts of or whole chromosomes. Dna mutations are changes to genes due to a change in the nucleotide base sequence.
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What are point mutations?
A type of DNA mutation where one base pair is replaced by another. (also called substitution.
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What are insertion/deletion mutations.
DNA mutations where one or more nucleotide pairs are inserted or deleted from a legnth of DNA. This causes a frameshift in the code which effects every other triplet code.
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Give three examples of diseases that are a result of genetic mutations.
1. Cystic fibrosis. 2.Sickle-cell Anaemia. 3.Huntington Disease.
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What causes CF in most cases? (70%)
A deletion mutation.
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What causes Sickle-Cell anaemia?
A point mutation on codon 6 of the gene for the beta-polypeptide chains of haemoglobin.
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What causes huntington disease?
Results from an expanded triple nucleotide repeat.
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What is an allele?
An alternative version of a gene. It is still on the same locus on the chromosome and still codes for the same polypeptide as the gene. However the change in dna base sequence may change the final structure of the protein.
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What is a beneficial mutation?
A mutuation that causes a change in the sequence of the amino acids and therefore a change in the phenotype. This change gives the organism an advantageous advantage.
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Give an example of beneficial mutation?
Paler skin in more temperate climates absorb more vitamin D.
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What is a neutral mutation?
A mutation that either, has no effect on the resulting phenotype or does have an effect, but the effect offers no advantage or disadvantage to the organism.
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Give an example of a neutral mutation that is a result of a change in the phenotype?
Toungue rolling in humans.
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What 2 ways can a neutral mutation that has no effect on the resulting phenotype occur
1. A silent mutation, where a mutation occurs, but the resulting amino acid stays the same so there is no change in the protein. 2. The mutation occurs on a non-coding strand of DNA/
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What is Harmful Mutation?
A mutation that changes the sequence of amino acids, resulting in a negative change to the phenotype.
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An example of Harmful mutation.
Paler skin in hotter climates burn more easily.
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What does Cyclic AMP do?
Activates proteins by altering their 3d structure.
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What is the overall effect of adding lactose to E.Coli?
The rate of synthesis of the two enzymes ( B-galactosidase and lactose permease) is increased by about 1000 times.
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What is the B-Galactosidase involved in?
The hydrolysis of lactose to gluceose and galactose.
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What is lactose permease involved in?
The transport of lactose into the cell.
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What is the general structure of the Lac Operon and what to the letters represent?
I POZY, I is the regulatory gene. P is the promotor region. O is the operator region. Y and Z are the strucural genes.
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What is the structural genes?
They code for the enzymes needed to repire lactose. y= lactose permease and z codes for B-galactosidase.
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What is the function of the operator region?
Legnth og DNA next to the structural genes that can turn them on or off. The repressor protien binds to this region in the absence of lactose.
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What is the function of the promotor region?
A legnth of DNA in which RNA polymerase binds to, to start the synthesis of the structural genes.
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What is the purpose of the regulatory Gene?
To be transcribed and translated to synthesise the repressor protein.
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What is the repressor protein?
a protein that can bind to the operator region (stopping RNA polymerase from binding to the p region) or it can bind to lactose, which changes the shape of the repressor protein.
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PROCESS LAC OPERON WITH OR WITHOUT LACTOSE PRESENT
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What are homeobox genes?
Genes that control the development of an organism, including the polarity(head and tail ends) and the positioning of organs.
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Drospillia
arggh
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arr
arr
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arr
arr
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arr
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What is Apoptosis?
Is programmed cell death that occurs in multicellular organisms. It results in an orderly and tidy cell death.
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What is the opposite of apoptosis?
Cell necrosis that results in an untidy and damaging cell death, occurs after trauma and releases hydrolytic enzymes.
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What is the significence of apoptosis?
It ensures that the rate of cells produced by mitosis is the same as the rate of cells dying. It also is used to seperate digits during development.
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What does too much apoptosis lead to?
Cell loss or degeneration.
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What does too little apoptosis lead to?
The formation of tumours or Cancer.
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PROCESS APOPTOSIS
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Define meiosis.
Meiosis is a reduction division. The resulting daughter cells have half the original chromosomes. They are haploid and can be used for secual reproduciton.
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PROCESS MEIOSIS
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Define the term Bivalent.
A Pair of synapsed (joined) Homologous chromosomes during prophase and metaphase of meiosis 1.
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What main events occur during prophase 1?
1.chromatin condenses and supercoils. 2.Chromosomes come together in their homologous pairs to from a bivalent. Each pair consists of a paternal and a maternal chromosome. 3.Chismata form. 4.Nucleolus disapears,nuclear mem breaks down.5.Spindle forms
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What are chiasmata and how do they form.
They from by non-sister chromatids wrapping around each other. Sections of chromatids may be swapped between the chromatids in a process called crossing-over.
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What main events occur during metaphase one?
1. Bivalents formed in P1 line up across the equator of the spindle, attached to the spindle by their centromeres. 2. The bivalents are arranged randomly.
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What main events occur during anaphase one?
1. The homologous pairs that make up the bivalents are pulled to oppo poles. 2.The centromeres do not deivde. 3.The chiasmata seperate, the legnths of chromatids that have been crossed over remain with the new chromatid.
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What main events occur in Telophase 1?
Two new nuclear envelopes form around the 2 sets of chromosomes. The cell divides by cytokinesis.
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Where does meiosis 2 take place?
At right angles to meiosis one.
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What is the difference in meiosis 1 between plant cells and animal cells?
Animal cells skip telophase one and go straight to meiosis 2 from anaphase 1. (Likely due to cell walls)
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What main events occur during prophase 2?
Nuclear envelope breaks down again (if reformed). 2.Nucleolus disapears, chromosomes condense spindles form.
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What main events occur during metaphase 2?
Chromosomes are Randomly assorted at the centre of the spindle fibres, attached by centromeres.
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What main events occur during anaphase 2?
The centromeres divide and the chromatids are pulled to oppo poles. The chromatids randomly segregate.
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What occurs during telophase 2?
Nuclear envelope reforms around the haploid daughter nuclei.
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What is the difference in meiosis 2 between plant cells and animal cells?
During telophase 2, in animals, the two cells divide to give 4 haploid cells. In plants a tetrad of four hapolid cells is formed.
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What is the significence of meiosis?
Increases genetic variation, which increases the chances of evolution as natural selection can favour the organism that is more adapted to it;s environment.
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In what 4 ways does meiosis cause genetic variation?
1.Crossing over during P1. 2.Random assortment of homologous pairs during metaphase 1. 3. Random assortment of sister chromatids during metaphase 2. 4. Genetic mutation(during interpahse).
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How does fertilisation increase genetic variation?
Randomly combining two sets of chromosomes from two genetically unrelated individuals.
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What is a polypeptide?

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A polymer consisting of a chain of amino acids.

Card 3

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What is the genetic code?

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Card 4

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3 Characteristics of genetic code?

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Card 5

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What is meant by triplet code?

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