B1h - variation and inheritance Flashcards
What does dominant and recessive characteristics depend on(3)
Dominant and recessive alleles
Dominant alleles are those expressed if present
Recessive alleles are those only expressed if the dominant allele is absent
What is homozygous
2 identical alleles
What is heterozygous
2 different alleles
What is genotype
The genetic makeup
What is phenotype
The characteristics expressed
How many chromosomes do most body cells contain(2)
23 matched pairs(for humans)
Different for different species
What are alleles
Different versions of the same gene
How is sex determined in mammals
By sex chromosomes(XX for female and XY for male)
How is there an equal chance of the offspring being male or female(3)(practice genetic diagrams)
A sperm will carry either an X or a Y chromosome
All eggs will carry an X chromosome
There is a random chance of which sperm fertilises an egg, so the sperm has an equal chance of containing an X or a Y chromosome
What causes genetic variation(3)
Mutations(random changes in genes or chromosomes)
Rearrangement of genes during the formation of gametes
The random nature of fertilisation resulting in a zygote with alleles from the father and mother
What are inherited disorders are caused by(2)
Faulty genes
-most of which are recessive
What issues can be raised by knowledge of inherited disorders in a family(2)
Whether to have children or not
Whether to abort an affected foetus
Use genetic diagrams to predict the probabilities of
inherited disorders passing to the next generation(no answer)
practice
