MCBG - Genotype, Phenotype And Inheritance Flashcards
What is the genetic makeup of an individual termed?
Genotype
What is the name given to the physical characteristics of an individual?
Phenotype
Give some examples of environmental factors that can influence the genotype.
Radiation, life style, mutagens, diet, chemicals
Genetics is the study of which two things?
Inheritance and variation
How many copies of each gene does an individual have?
Two (one maternal, one paternal). These may be different alleles of the same gene.
What does “homozygous” mean?
Two alleles of a gene are the same.
What does “heterozygous” mean?
The two alleles of a gene are different.
What does hemizygous mean?
Only one allele of a gene on the X chromosome (males only).
If an individual has genotype Aa, which allele determines the phenotype (A or a)?
A because it is the dominant allele and therefore determines the phenotype. a is recessive.
Which blood group allele (A or B) is dominant over the other?
Neither, as they are co-dominant. They are both dominant to O though.
What would you state as the phenotype for someone with genotype A for glycoproteins on their red blood cells?
Blood group A
What does a square indicate on a pedigree chart?
Male
What does a circle indicate on a pedigree chart?
Female
What does a coloured in shape indicate on a pedigree chart?
Affected individual. Partially coloured in indicates carrier.
What does a diamond indicate on a pedigree chart?
Unknown sex (usually a baby)
What does a diagonal line through a shape indicate on a pedigree chart?
Individual is deceased.
Where does the eldest child go in a pedigree chart?
On the left
Give some characteristics of autosomal recessive inheritance.
Can be observed to “come out of nowhere” on pedigree charts (skipping generations), affects males and females equally, does not affect heterozygotes.
If two individuals with cystic fibrosis had children how many would be affected? What about if two heterozygous carriers had children?
All of them.
1 in four.
Give some characteristics of autosomal dominant inheritance?
Heterozygous are affected, male and females equally affected, cannot skip generations, affected individual has 50% chance of passing on to offspring.
Why are autosomal dominant disorders not often found in homozygous states?
The individual may not be viable for life.
Give an example of an autosomal dominant condition.
Huntington’s Disease
A male with Haemophilia A cannot pass the condition on to his son. Which type of inheritance is this?
X-linked recessive
Why are X-linked recessive conditions more common in males?
They have only one X chromosome, so it is expressed even if it is recessive. Women must have two recessive alleles to be affected by the condition.
Give some characteristics of an X-linked dominant condition.
Hemizygous males and heterozygous females affected, affected males cannot give trait to sons but will give to all daughters.
In mitochondrial inheritance, could a male pass on a condition to his daughters?
No, he could not pass it on to anyone. Mitochondria are inherited solely through the female line.
Why are genes sometimes referred to as “linked”?
They are on the same chromosome. These do not undergo independent assortment at meiosis.
