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Inheritance in Biology Flashcards
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Work through the key concepts of genetic inheritance, from Mendelian genetics and Punnett squares to sex linked traits and codominance, using these free Biology flashcards.
Question
What is a gene?
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Answer
A section of DNA that codes for a specific protein. Genes are located on chromosomes and determine inherited characteristics.
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Question
What is an allele?
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Answer
An alternative version of a gene. For example, the gene for eye colour has alleles for brown and blue. Organisms carry two alleles for each gene (one on each homologous chromosome).
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Question
What is the difference between genotype and phenotype?
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Answer
Genotype is the genetic makeup of an organism (the alleles it carries). Phenotype is the observable characteristic produced by the genotype interacting with the environment.
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Question
What is the difference between dominant and recessive alleles?
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Answer
A dominant allele is expressed whenever present (even with one copy). A recessive allele is only expressed when two copies are present (homozygous recessive).
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Question
What does homozygous mean?
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Answer
Carrying two identical alleles for a gene (e.g. BB or bb).
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Question
What does heterozygous mean?
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Answer
Carrying two different alleles for a gene (e.g. Bb). The dominant allele will be expressed in the phenotype.
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Question
What is a Punnett square used for?
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Answer
To predict the probability of offspring genotypes and phenotypes from a genetic cross between two parents.
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Question
What is codominance?
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Answer
When both alleles in a heterozygote are expressed equally in the phenotype. Neither is dominant over the other. Example: AB blood type, where both A and B antigens are present.
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Question
What are the ABO blood group alleles and how are they inherited?
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Answer
There are three alleles: Iᴬ (dominant, produces A antigen), Iᴮ (dominant, produces B antigen), and i (recessive, no antigen). Iᴬ and Iᴮ are codominant with each other.
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Question
What is sex determination in humans?
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Answer
Determined by the sex chromosomes: XX = female, XY = male. The Y chromosome carries the SRY gene that triggers male development. A 50:50 ratio of male to female offspring is expected.
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