Variation and Inheritance Flashcards
Reasons for genetic variation in humans?
- The great amount of variation in gametes due to meiosis
- Fertilisation is random
Define cloning
The process that produces a group of genetically identical cells (a clone) from part of the parent organism
What is a pedigree?
A pedigree is a diagram showing a family tree for an inherited characteristic
Polydactyly is dominant or recessive?
Dominant
Define codominance
A pattern of inheritance where no allele is dominant over each other and so both are expressed in the phenotype
How can codominance be determined?
If two breeds are crossed and there’s an appearance of a third phenotype then there is codominance
How many alleles are involved in the inheritance of the ABO blood group?
3 { Ia, Ib, Io }
Define polygenic inheritance
A form of inheritance where a characteristic is controlled by the presence of two or more genes working together
Define polygene
Examples?
A group of several genes working together to determine a characteristic
Examples: Height
Weight
Skin color
What are sex-linked genes?
Genes that are inherited on sex chromosomes
How does hemophilia occur?
A mutant allele
Hemophilia is due to a genetic mutation that affects the production of a chemical (a protein in the plasma) essential in the clotting process
How do boys inherit hemophilia?
Boys inherit this gene from their mother
Either a (usually) carrier or a homozygous recessive mother
How does red-green color blindness occur?
A mutant allele
A gene mutation results in the lack of formation of a protein that forms the pigment in the cones of the eye that detects green light
How does CF occur?
A gene mutation that affects the production of mucus. Mucus is more thick, sticky (viscous).
Problems resulting from CF:
Mucus blocks airways - infection, breathing difficulty, and inefficient gas exchange
Mucus blocks the intestine - poor absorption of nutrients and a low rate of growth
Mucus blocks the pancreatic duct - enzymes don’t reach the small intestine
Mucus blocks the tubes leading from the testes
