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Summary AQA A level Biology Paper 2 Topic 7 notes
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A detailed summary of the AQA A level Biology paper 2 topic 7 which has been edited to learn help the content and the mark scheme too.
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🌿T7: genetics, populations,
ecosystems and evolution
genetics
what is a chromosome?
-thread like structure which contains DNA
what is a gene?
-section of DNA which codes for a protein
what is an allele?
-different forms of a gene
what is a dominant gene?
-allele that is always expressed in the phenotype of organism
what is a recessive gene?
-an allele which there must be 2 copies of for it to be expressed
what does homozygous mean?
-alleles of a gene are identical
what does heterozygous mean?
-alleles of a gene are different
what is a genotype?
-genetic composition or makeup of an organism
what is the phenotype?
-characteristics of organism resulting from genotype and environment
what is a locus?
-position of a gene on a chromosome
what are homologous chromosomes?
T7: genetics, populations, ecosystems and evolution 1
, -pair of chromosomes
-one maternal and one paternal which have the same genes but not the
same alleles
what does co dominant mean?
-both alleles for one gene in heterozygous organism contribute to
phenotype
-both alleles expressed in phenotype
what does diploid mean?
-2 sets of chromosomes= full set
what is a nucleotide?
-single unit of DNA made of pentose sugar, base and phosphate
what is dihybrid inheritance?
-inheritance of 2 characteristics coded for by 2 genes on different
chromosomes
what is F1?
-first generation offspring
ratio for dihybrid cross of heterozygous parents?
-9:3:3:1
ratio for monohybrid cross?
-3:1
what are sex chromosomes?
-the 2 chromosomes sex is determined by
-XX= girl
-XY= boy
which chromosome is larger?
-X chromosome
what does it mean if genes are sex linked?
-genes are carried on X or Y chromosome not both
who is more likely to suffer from x-linked disorders?
T7: genetics, populations, ecosystems and evolution 2
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