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| Question | Answer |
| Define genotype | Genetic makeup of an organism |
| Define phenotype | Visible characteristics of an organism |
| What are mutagens? | Are certain physical and chemical agents that increase the rate of mutation |
| Example of physical agents? | •X-rays •gamma rays •UV light |
| Example of chemical agents? | •benzopyrene (found in tobacco smoke) •mustard gas •nitrous acid •aromatic amines (some synthetic dyes) •reactive oxygen species colchicine |
| Example of biological agents? | •some viruses •transposons (jumping genes, remnants of viral nucleic acids incoporated into our genomes •food contaminants (chemicals in charred meat and alcohol) |
| Types of chromosome mutations? | •deletion •inversion •translocation •duplication •non-disjunction •aneuploidy •poluploidy |
| What is deletion? | Part of chromosome, containing genes and regulatory sequences, is lost |
| What is inversion? | A section of a chromosome may break off, turn 180 degrees and then join again Genes may be too far away from regulatory nucleotide sequence to be expressed properly |
| What is translocation? | A piece of one chromosome breaks off and then becomes attached to another chromosome May interfere with the regulation of the genes on the translocated chromosome |
| What is duplication? | A piece of a chromosome may be duplicated Overexpression of genes can be harmful, too many of certain proteins or gene-regulating nucleic acid may disrupt metabolism |
| What is non-disjunction? | One pair of chromosomes or chromatids fails to separate, one gamete has an extra chromosome Zygote will have one extra chromosome, e.g. Down syndrome or trisomy 21 |
| What is aneuploidy? | Chromosome number is not an exact multiple of the haploid number for the organism (chromosomes/chromatids fail to separate - trisomy) |
| What is polyploidy? | When diploid gamete is fertilised by a haploid gamete, zygote will be triploid Fusion of two diploid gametes can make a tetraploid zygote (like plants) |
| How does genetic variation arise during meiosis? | •allele shuffling (swapping over of alleles between non-sister chromatids) •independent assortment of chromosomes during metaphase/anaphase 1 and metaphase/anaphase 2 |
| How does fertilisation lead to genetic variation | •Gametes produced by meiosis are genetically dissimilar and haploid •Random fusion of gametes creates more genetic diversity •Gametes can potentially combine at any time |
| How can phenotypic variation can be caused by environmental factors only? | •speaking with a particular regional dialect •losing a digit/ limb or having a scar following an injury |
| How can phenotypic variation be caused by the environment interacting with genes? | •Plants kept in dim lights after germination do not have enough magnesium to develop chlorophyll resulting in a yellow colour •Known as Chlorosis, plant cannot photosynthesis |
| Define allele | A version of a gene |
| Define heterozygous | Not true breeding Have different alleles at a particular gene locus on a pair of homologous chromosomes |
| Define homozygous | True-breeding Having identical alleles at a particular gene locus on a pair of homologous chromosomes |
| Define monogenic | Determined by a single gene |
| One fruit fly parent is homozygous for normal wings and the other parent is homozygous for vestigial wings. What is the genotypes of the second generation? | |
| Define dihybrid inheritance | Inheritance of two characteristics controlled by different genes |
| The parents are heterozygous and both have a round and yellow seed. What is the genotype of the offspring an calculate the ratio? | |
| What is the phenotypic ratio of the F2 generation in a dihybrid cross? | 9:3:3:1 |
| What are multiple alleles? | Characteristic for when there are three if more alleles in the population's gene pool |
| What are the four blood groups | • Group A •Group B •Group AB •Group O |
| What is codomiance? | Where both alleles represent in the genotype of a heterozygous individual contribute to the individual's phenotype |
| What alleles are codominant and recessive for blood groups? | •Iº is recessive •Iᴬ and Iᴮ are codominant |
| What blood group will the offspring be of a parent who is heterozygous for blood group A and a parent heterozygous for blood group B | |
| Define sex-linked? | Gene present on (one of) the sex chromosomes |
| What are autosomes? | Not sex chromosomes Are homolougous |
| What the human sex chromosomes? | Females: XX Male: XY |
| State the expected ratio for F2 generation for monohybrid, dihybrid and codominant | |
| What the main differences in the male sex chromosomes? | •The Y chromosome is a smaller than the X chromosome and carries fewer genes - most genes carried on X chromosome •Only carry one X chromosome for only carry one allele, so are more likely to express recessive phenotypes |
| Give examples of genetic disorders caused by faulty alleles on sex chromosomes | •Haemophilia •Colour blindness |
| Explain why the phenotypic ratio is 3:1 when a heterozygous normal vision female have children with a normal vision male | |
| Why are genes on the same autosome linked? | They will stay together on during indepednet assortment of meiosis 1 and alleles will be passed on to offspring together Only own't happen if crossing over occurs |
| What is codominant? | Where both alleles present in the genotype of a heterozygous individual contribute to an individual's phenotype |
| What is the MN blood group system | The Gene M and N codes for a particular protein on the surface of erthryocytes ad are codiminant |
| Explain why the phenotypic ratio is 2:1:1 for the offspring of parents who have sickle-cell trait | |
| Define epistasis | Interaction of non-lined gene loci where one masks the expression of the other (stoppage) |
| What is recessive epistasis |
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