genetics Flashcards
what are autosomes
all other chromosomes that are not sex chromosomes
define homogametic
female XX
describe haemophillia
-passed on the X chromosome
- recessive disorder
- blood clots slowly because DNA that codes for blood clotting proteins aren’t coded for
-
-
which genes are said to be linked
genes on the same autosome
what is the genetic ratio for a recessive epistatic allele in a dihybrid cross
9:3:4
define epistasis
a gene at one location can mask the expression of a gene at another location
what is the genetic ratio of a dominant epistatic allele in a dihybrid cross
12:3:1
define codominance
where both alleles are expressed in the phenotype
define genotype
it describes all the alleles an organism has
define phenotype
observable characteristics of an organism. it is a result of the interaction between expression of the genotype and the environment
define a gene
a length of DNA
what did gregor mendel investigate
seed shape - where round shape is dominant to a wrinkled shape
seed colour where yellow seeds are dominant to a green coloured seed
what is expected ratio in a dihybrid cross of RRGG rrgg
9:3:3:1
what conclusions can be drawn when expected ratios do not align with observed ratios
linked genes
- epistasis
what does it meant by having multiple alleles
where there are more than two alleles, of which only two may be present at the loci of an individuals homologous chromosomes
which is longer X or Y chromosome
X
what does the length of the X chromosome mean for the world
as the X chromosome is longer than the Y there is no equivalent portion on the Y chromosome. therefore those controlled by recessive characteristics will appear more frequently on the male chromosome
why would linked genes not remain together during meiosis
crossing over
what type of data does a chi squared test produce
categorical
REMEMBER
FOR DEGREES OF FREEDOM IN A CHI SQUARED = NUMBER OF CLASSES MINUS 1
what are condition for gene linkage
no crossing over therefore all the linked genes remain together during meiosis
if genes are further apart on the homologous chromosome what does this mean
it is more likely that they will be separated by crossing over and will not gene linked
