genotype, phenotype and inheritance Flashcards
factors able to effect genotype/phenotype
environment- radiation, lifestyle, mutagens, diet, chemicals
explain the scale of disease causation from genotype to environment
cystic fibrosis is caused by your genotype and infection is caused by the environment but most diseases eg cancer and diabetes are caused by a combination of your environment and genotype
what does hemizygous mean
only 1 copy of gene because on X chromosome. (if mutation causes other gene to be deleted this also counts but this is rare)
example of codominance
blood type. A and B are equally dominant so are combined to form a new codominant allele (AB)
pedigree tree code
white square -MALE
black square- AFFECTED MALE
white circle - FEMALE
black circle- AFFECTED FEMALE
half white and black square/circle- MALE/FEMALE CARRIER
square/circle with black dot - MALE/FEMALE CARIER
diamond- UNKOWN SEX
square/circle with line through - DECEASED
EVERY GENERATION IS A SEPARATE LINE INDICATED BY Roman numerals
autosomal recessive inheritance pattern
heterozygotes are unaffected. 2 heterozygotes= 25% chance of having affected offspring. 2 affected individuals will have 100% affected offspring.
e.g cystic fibrosis
carrier if heterozygous - this is why disease seems to come out of nowhere because parents are unaffected.
autosomal dominant inheritance pattern
heterozygotes affected and homozygotes of the disease are very rare because become unviable if 2 present. 50% chance of having affected offspring. Cant skip generation. must have one affected in each generation.
e.g huntingtons
x-linked recessive inheritance patterns
hemizygous males and homozygous females affected. Much more common in males, don’t have the “back up gene”. Affected males can only give traits to daughter and not to son because pass x to daughter and y without gene to son. heterozygous female has 50% chance of giving disease to son.
affected males will have at least a carrier mother
affected daughters will have affected father and heterozygous mother.
e.g haemophilia A
x linked dominant inheritance patterns
hemizygous males and heterozygous females affected.
Affected father gives trait to ALL daughters and mother has 50% chance of giving it to offspring.
e.g ricketsm
Y linked inheritance patterns
Affected father will pass trait to all sons. No females affected
mitochondrial inheritance patterns
all mitochondria is inherited from mother. Therefore is mother mitochondria is affected then all of the offsprings will also be affected.
monogenic inheritance patterns
phenotype caused by one gene
polygenic inheritance patterns
phenotype caused by more than 1 gene. This maybe because more than 1 enzyme required to created this phenotype.
e.g albinism
albinism is recessively inherited but 2 parents with albinism will not have an affected child. This is because they have the reccseeive trait in different genes and when these are combined the child has one dominant allele per gene (look up for genetic diagram)
linked genes
when they are linked the polygenic genes are on the same chromosome. Do not undergo independent assortment during meiosis. more likely to be inherited together. The closer they are on the chromosomes the more likely they are inherited together and not separated by crossing over. ( this distance is called the recombination frequency )
