- A change in genetic material.
- Point mutations are substitutions.
- Insertion and deletion cause a frameshift.
- Cystic fibrosis is deletion of a codon.
- Sickle cell anaemia is a point mutation.
- Huntington disease is caused by a repeated CAG sequence.
- A repressor protein coded for by the regulatory gene prevents transcription of the two structural enzymes that metabolise lactose, by binding to the operator and blocking the promotor.
- In the presence of lactose the repressor protein undergoes a conformational change in shape and falls away from the operator so that the structural genes (z) beta-galactosidase and (y) lactose permease can be transcribed.
Genes and body plans
- Homeobox genes controll how the body plan develops.
- Some genes determine the embryos polarity and others teh polarity of each segment.
- Other genes identifiy the segments as individual parts.
- Transcription factors nind to genes to initiate transcription and regulating expression of the other genes.
- Homeobox genes are arranged in Hox clusters.
- Prophase I - Chromatin condenses, chromosomes form bivalents, nucleus disappears.
- Metaphase I - Bivalents attach to spindles, independent assortment.
- Anaphase I - Chromosomes plled to poles.
- Telophase I - Cytokinesis and new nucleus formed in new cells.
- Prophase II - Nucleus breaks down and chromosomes condense.
- Metaphase II - Chromosomes line up on equator and attach to spindles.
- Anaphase II - Centromeres divide as chromatids pulled to poles.
- Teleophase II - Nucleus reforms around haploid cells.
- Nitric oxide can induce apoptosis.
- Enzymes break down cytoskeleton.
- Cytoplasm thickens and membrane changes and forms blebs.
- Chromatin condenses and breaks into fragments and nuclear envelope breaks.
- Cell breaks into vesicles that are taken in by phagocytes.
- Genotype - alleles present.
- Homozygous - two identical alleles.
- Heterozygous - two different alleles.
- Phenotype - characteristics expressed.
- Codominance - two different alleles expressed.
- Linkage - two or more genes located on same chromosome.
- Sex linkage - genes for characteristics are on sex chromosome.
- Epistasis is the interaction of different genes so that one masks or suppresses the expression of another.
- Used to test the significance of the difference between observed and expected results.
- chi - squared = sum of (observed numbers - expected numbers) squared/ expected numbers
Continuous and discontinuous variation
- Discontinuous - qualitative eg. blood groups. Different alleles for a single gene locus effect phenotype.
- Continuous - quantitative eg. height. Controlled by two or more genes and each adds to the phenotype and then are on different chromosomes.
- Hardy-Weinberg principle worked example. CFcf are symptomless carriers and cfcf have cystic fibrosis. 1/2000 have cystic fibrosis.
- p represents frequency of dominant allele, CF.
- q represents frequency of recessive allele, cf.
- q² represents frequency of geneotype cfcf.
- p² represents frequency of geneotype CFCF.
- 2pq is the frequency of CFcf assuming random mating, where and two CFcf can mate to produce offspring that could be CFCF, CFcf, CFcf, cfcf. This translates to p²+ 2pq + q² .
- p+q = 1 or 100%
- p²+ 2pq + q² = 1…
Similar Biology resources: