InheritanceEdexcel GCSE Biology: Flashcards

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Shape of DNA?

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Shape of DNA?: Double helix — two strands coiled, linked by weak hydrogen bonds between complementary bases.
Three parts of a nucleotide?: Sugar, phosphate group, base.
Define genome.: The entire DNA of an organism.
Define gene.: A DNA section coding for a specific protein.
Stages of protein synthesis in order?: Transcription (mRNA made) then translation (polypeptide built from codons).
Where does RNA polymerase bind?: Non-coding DNA in front of the gene.
Effect of non-coding DNA variant?: Alters RNA polymerase binding, changing protein quantity.
Effect of coding DNA variant?: Alters amino acid sequence, changing protein shape/activity.
What did Mendel discover?: Inheritance via separate hereditary units (alleles), not understood until genes/DNA discovered.
Difference between genotype and phenotype?: Genotype = alleles present; phenotype = observable characteristic.
Define homozygous/heterozygous.: Homozygous = 2 identical alleles; heterozygous = 2 different alleles.
How is sex determined at fertilisation?: Eggs carry X; sperm X or Y. XX=female, XY=male, 1:1 ratio.
Explain ABO codominance/multiple alleles.: I^A and I^B codominant; I^O recessive; three alleles = multiple alleles.
Why do sex-linked disorders affect males more?: Males have only one X, so one recessive allele causes the disorder.
Two causes of variation?: Genetic (mutation, sexual reproduction) and environmental (acquired).
Typical effect of a mutation?: Usually none, sometimes small, rarely significant.
What did the Human Genome Project achieve?: Mapped the complete human gene sequence, aiding diagnosis and personalised medicine.