Session 7-Genotype, Phenotype And Inheritance Flashcards
Define homozygous
Two alleles of a gene are the same (individual is a homozygote)
Define heterozygous
Two alleles of a gene are different (individual is heterozygote)
Define hemizygous
Only one allele of a gene is present on the X chromosome (ie males only)
Define dominant
Dominant allele in heterozygote determines phenotype
Define recessive
Non-dominant allele in heterozygote is recessive
Give an example of a co-dominant gene and explain its alleles
Human isoglutamin gene which codes for glycoproteins on the surface of RBCs
Alleles A and B are dominant over allele O
Alleles A and B are co-dominant
True or false: heterozygotes are affected in an autosomal recessive condition
FALSE
True or false: males and females are equally affected in an autosomal recessive condition
TRUE
What % chance do two heterozygotes have of producing offspring with an autosomal recessive condition?
25%
True or false: in an autosomal recessive condition, two affected (homozygous) individuals will have affected offspring only
TRUE
Give an example of an autosomal recessive condition
Cystic fibrosis
True or false: autosomal recessive conditions cannot skip generations
FALSE
True or false: heterozygotes are affected in autosomal dominant conditions
TRUE
True or false: males and females are not equally affected in autosomal dominant conditions
FALSE
What % chance does every affected individual have of producing offspring with an autosomal dominant condition?
50%
Give an example of an autosomal dominant condition
Huntington’s disease
True or false: autosomal dominant conditions cannot skip generations
TRUE
Which males and females are affected by X-linked recessive conditions?
Hemizygous males and homozygous females
True or false: X-linked recessive conditions are more common in males
TRUE
What % chance does a heterozygous female carrier have of having sons with an X-linked recessive condition?
50%
True or false: males with an X-linked recessive condition cannot give the trait to their sons
TRUE
Give an example of an X-linked recessive condition
Haemophilia A
Which males and females are affected by X-linked dominant conditions?
Hemizygous males and heterozygous females
True or false: affected males cannot give X-linked dominant traits to their sons but they will give it to all of their daughters
TRUE
Give an example of an X-linked dominant condition
Rett syndrome
Give an example of a Y-linked condition
Swyer syndrome
True or false: all individuals with mitochondrial diseases inherit the trait from their mothers
TRUE
True or false: more than one gene can be involved in producing a particular phenotype
TRUE
Give an example of a polygenic condition
Albinism
