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neurologyYou need to know

• Asexual reproduction involves one parent, no fusion of gametes, and produces genetically identical offspring called clones.
• Sexual reproduction involves the fusion of male and female gametes, produces genetically varied offspring, and usually involves two parents.
• Mitosis produces two genetically identical diploid body cells for growth, repair and asexual reproduction.
• Meiosis produces four genetically different haploid gametes, with half the number of chromosomes found in body cells.
• Sexual reproduction causes variation because gametes contain different combinations of alleles and fertilisation combines alleles from two parents at random.
• DNA is a polymer made of two strands twisted into a double helix, and it contains chemical bases that form a genetic code.
• A gene is a section of DNA that codes for a specific sequence of amino acids, which form a protein.
• A chromosome is a long, coiled molecule of DNA, and a genome is the complete set of genetic material in an organism.
• The human genome is important because it helps scientists identify genes linked to disease, trace human migration, and develop personalised medicine.
• An allele is a different version of the same gene, a genotype is the combination of alleles an organism has, and a phenotype is the observable characteristic produced by the genotype and environment.
• A dominant allele is expressed in the phenotype when one copy is present, while a recessive allele is only expressed when two copies are present.
• Biological sex in humans is usually inherited through sex chromosomes: females are XX and males are XY, and sperm determine the sex of the offspring because they may carry X or Y.
• Cystic fibrosis is an inherited disorder caused by a recessive allele, and symptoms include thick sticky mucus in the lungs and digestive system.
• Polydactyly is an inherited condition that causes extra fingers or toes and is usually caused by a dominant allele.
• Genetic screening tests DNA, embryos, fetuses or adults for alleles linked to genetic disorders.
• Embryo screening can reduce the chance of a child having a genetic disorder, but it raises ethical, social and economic issues such as embryo destruction, access to treatment, and possible discrimination.
• Variation within a population can be caused by genes, the environment, or a combination of both.
• A mutation is a change in DNA that can create a new allele, and most mutations have no effect but some can affect phenotype.
• Evolution by natural selection happens when individuals with advantageous alleles are more likely to survive, reproduce, and pass those alleles to offspring, making the alleles more common over generations.
• Selective breeding is when humans choose organisms with desirable characteristics and breed them over many generations, but it can reduce genetic variation and increase inherited health problems.

• Compare mitosis and meiosis by stating the number of cells produced, whether the cells are genetically identical or different, and whether the cells are diploid or haploid.
• Construct a Punnett square by writing parental genotypes, listing possible gametes, combining alleles in offspring boxes, and calculating predicted genotype and phenotype ratios.
• Interpret a family tree by identifying affected and unaffected individuals, using inheritance patterns to infer possible genotypes, and predicting risk for offspring.
• Represent variation data from a population using an appropriate graph, such as a bar chart for discontinuous variation or a histogram/line graph for continuous variation.
• Explain natural selection as a sequence of variation, selection pressure, differential survival and reproduction, inheritance of advantageous alleles, and change in allele frequency over time.
• Describe genetic engineering by explaining that a useful gene is cut out using enzymes, inserted into a vector such as a plasmid, and transferred into a host organism.
• Evaluate genetic engineering in medicine and agriculture by weighing benefits such as insulin production or pest-resistant crops against risks such as ecological effects, cost and ethical concerns.
• Explain antibiotic resistance by linking random mutation, antibiotic selection pressure, survival of resistant bacteria, reproduction, and spread of resistance genes.
• Interpret evolutionary trees by identifying common ancestors, branching points, relatedness between species, and the order in which groups diverged.
• Name species using the binomial system by writing the genus with a capital letter followed by the species name in lower case.