Genotype, Phenotype And Inheritance Flashcards
What is meant by genotype?
An organisms genotype is the set of genes that it carries
What is meant by phenotype?
The observable characteristics of an organism
What is genetics the study of?
Inheritance and variation
How many alleles of a particular gene does each individual have?
2
What is the meaning of homozygous?
Two alleles of a gene are the same
What is the meaning of heterozygous?
Two alleles of a gene are different
What is the meaning of hemizygous?
Only one allele of a gene on the X chromosome (so males only)
Which alleles are dominant in terms of blood type?
Allele A dominant over O
Allele B dominant over O
Allele A and B are co dominant
How would you identify an autosomal recessive trait?
Heterozygotes unaffected
Males and females equally affected
Can skip generations, seems to come out of nowhere
Both parents of affected individual are heterozygous carriers
How would you identify an autosomal dominant trait?
Heterozygotes affected
Males and females equally affected
Rarely found in homozygous state
Every affected individual has at least one affected parent, cannot skip generations
What is an example of an autosomal recessive disease?
Cystic fibrosis
What is an example of an autosomal dominant disease?
Huntingtons disease
How do you identify an X linked recessive trait?
Males and females unequally affected
Every affected male has at least a carrier mother
Every affected female has affected father and carrier mother
Affected males have at least carrier daughters
Affected males cannot give trait to sons
What is an example of an X linked recessive disease?
Haemophilia
How is albinism inherited?
Recessive
How many genes does each huma have?
25,000
What is the percentage of two heterozygotes having affected offspring?
25%
How is Huntington’s disease inherited?
Autosomal dominant
How is Cystic Fibrosis inherited?
Autosomal recessive
How is Haemophilia A inherited?
X-linked recessive
Why are X-linked diseases more common in males?
Only need one copy of X chromosome to be affected while females need two
Why can’t affected males of X-linked conditions give the trait to their sons?
Father can only give Y chromosome to offspring
True or Flase:
With X-linked conditions, every affected male will have at least a heterozygous mother.
True!
Will the daughters of men with X linked conditions be, at least, carriers?
Yes
What is an example of an X linked dominant condition?
X-linked hypophosphatemia (type of rickets)
What is an example of a Y-linked condition? (very rare)
Retinitis Pigmentosa (night blindness)
What are genes on the same chromosome said to be?
Linked
What do linked genes not show?
Independent assortment at meiosis
What is recombination frequency between two linked genes dependent on?
The distance between the genes
What can be used to calculate allelic frequencies and therefore ratios of frequencies in a population?
Hardy-Weinberg principle
