Genetic Diagrams Flashcards
What causes differences in the inherited characteristics of an organism?
Alleles
What are alleles?
Different versions of a gene
Define the term ‘genotype’.
The combination of alleles an organism has
Define the term ‘phenotype’.
The visible characteristics an organism has
What is meant by ‘homozygous’?
Having two of the same allele for a particular gene
What is meant by ‘heterozygous’?
Having two different alleles for a particular gene
How is a dominant characteristic expressed?
An organism can have either:
- Two dominant alleles for a particular gene (e.g. BB)
- One dominant and one recessive allele for a gene (e.g. Bb)
(Dominant alleles overrule recessive alleles)
How is a recessive characteristic expressed?
Both of the organism’s alleles must be recessive (e.g. bb)
Some characteristics are controlled by a single gene.
What are most phenotypic features controlled by?
Multiple genes interacting
What is monohybrid inheritance?
The inheritance of a single characteristic
(Example)
Demonstrate how you can show monohybrid inheritance in a punnett square.
What can you use monohybrid crosses to show?
How recessive and dominant traits for a single characteristic are inherited
(Example)
Show how you can use a monohybrid cross to determine the sex of offspring at fertilisation.
How many matched pairs of chromosomes are there in every human body cell?
23 pairs
(this is because they each have 46 chromosomes altogether)
What type of allele causes cystic fibrosis?
A recessive allele
(Exam-style question)
Mark and his wife (who is not shown in the diagram) have a baby with cystic fibrosis.
Use the family pedigree to find the possible genotypes of Mark’s wife.
Ff or ff
