Topic 3 Inheritance Flashcards
What is a chromosome?
A long coiled molecule of DNA that carries genes (genetic info)
What are alleles?
Different versions of the same gene
Define genotype
An organisms genetic composition, describes all alleles
Define phenotype
An organisms observable characteristics
Define homozygous
Having two identical alleles of a gene e.g FF of ff
Define heterozygous
Having two different alleles of a gene e.g Ff
What is a dominant allele?
Describes an allele that is always expressed
Represented with a capital letter e.g F
What is a recessive allele?
An allele that is only expressed in the absence of a dominant allele
Represented with a lower case letter e.g f
What is monohybrid inheritance?
The inheritance of a single gene
What is the problem with single gene crosses?
Most characteristics are controlled by multiple alleles rather than just one
What are sex chromosomes?
A pair of chromosomes that determine sex
Why does the inheritance of a Y chromosome mean that an embryo develops into a male?
Testes development in an embryo is stimulated by a gene present on the Y chromosome
Other than using a punnet square how can monohybrid inheritance be represented?
Using a family pedigree
What is a sex-linked characteristic?
A characteristic that is coded for by an allele found on a sex chromosome.
Name the four different blood groups
A,B,AB,O
Why are the majority of genes found on the X chromosome rather than the Y chromosome?
The X chromosome is bigger than the Y chromosome so more genes are carried on it.
Why are men more likely to show the phenotype for a recessive sex linked trait than women?
- Many genes are found on the X chromosome that have no counterpart on the Y chromosome
- Women have two alleles for each sex linked gene whereas men often only have one allele and only one recessive allele is required to produce the recessive phenotype in males
