Genetics Key Terms Flashcards
Continuous Variation
There is no distinct categories, there are a range of values eg height weight etc
Discontinuos variation
There are two or more distinct categories.
Eg blood group
Hair colour
What is a gene?
The sequence of bases on a section of DNA that codes for a protein
What is an allele?
Different versions of the same gene
Eg eye colour, same gene but different versions of
What is the locus?
The fixed position of the allele of each gene on the chromosome
What is genotype?
The combination of alleles an organism has
Eg combination for blue eyes is bb
What is phenotype?
The characteristic the alleles produce eg blue eyes
What does homozygous mean?
Two copies of the same allele
What does heterozygous mean?
Two different alleles
What does dominant mean?
One copy of a dominant allele is needed for the dominant characteristic to be seen. Represented by capital letters
What does recessive mean?
Two copies are needed for the recessive characteristic to be seen
Shown by lower case letters
What does codominant mean?
Both alleles expressed in the phenotype because neither one is recessive.
In between phenotypes
What is a carrier?
When you are heterozygous you can carry an allele not seen in the phenotype, can be passed on to offspring
What is a mono hybrid cross?
Crosses show inheritance pattern controlled by a single gene. You get a 3:1 ratio when crossing heterozygous parents
Dihybrid cross?
These crosses show the inheritance of two characteristics controlled by different genes. Get a 9:3:3:1 phenotypic ratio when crossing 2 heterozygous parents
What is an auto some?
Any chromosome that isn’t a sex chromosome
What is autosomal linkage?
Genes on the same autos one are linked (found on same chromosome arm) their alleles will be passed onto offspring together, unless crossing over occurs during meiosis and splits the alleles up
What is epistasis?
When the allele of one gene blocks or masks the expression of the alleles of other genes
Recessive epistasic alleles?
Two copies of recessive allele is needed to mask the expression of another allele. You get a 9:3:4 phenotypic ratio in the f2 gen when crossing homozygous recessive and dominant parents
Dominant epistatic alleles?
At least one copy of the dominant allele is needed to mask the expression of the other gene. You get a 12:3:1 ratio phenotypic ratio in the f2 gen when crossing homozygous recessive and dominant parents.
What is the Critical value?
The value of chi squared that corresponds to a 0.05 (5%) level of probability that the difference between the observed and expected results is due to chance.
