Genotype Phenotype and Inheritance Flashcards
What is genotype?
genes on a chromosome
What is phenotype?
physical characteristics: proteins in the cytoplasm
What is the difference between heterozygous, homozygous and hemizygous?
Homozygous –> 2 alleles of a gene are the same: homozygote.
Heterozygous –> 2 alleles of a gene are different: heterozygote.
Hemizygous –> only 1 allele of a gene on the X chromosome: males only
What is co-dominance?
neither allele A or B is dominant over the other e.g. AB blood type, two different alleles of a gene can be expressed, and each version makes a slightly different protein. Both alleles influence the genetic trait or determine the characteristics of the genetic condition.
Describe autosomal recessive inheritance
(cystic fibrosis): homozygotes affected, heterozygotes unaffected, M+F equally affected, can skip generations, both parents of affected child are heterozygous carriers
Describe autosomal dominant inheritance
(Huntington’s disease): don’t skip generations, heterozygotes affected, M+F equally affected, disease rarely found in homozygous state (embryonically lethal), affected have 50% risk offspring affected,
What is x-linked recessive?
(haemophilia A): hemizygous males, homozygous females, more common in males (F need both), affected males cannot give trait to son
What is x-linked dominant?
(Rett syndrome): hemizygous males, heterozygous females, affected males will not give to son but will to all daughters
Describe Y-linked inheritance
(infertility): few traits are Y-linked, Y-linked diseases are rare, only passed from father to son
What is polygenic/complex inheritance?
(CHD, asthma) More than 1 gene involved.
Linked - genes on same chromosome, do not show independent assortment at meiosis, recombination frequency dependent on distance between genes, close together = ‘tightly linked’, genes far apart on same chromosome behave as unlinked genes.
Not linked - genes on diff chromosomes
describe mitochondrial inheritance
inherit from mother
