patterns of inheritance Flashcards
what is continuous variation
when the individual in a population vary within a range and there’s no distinct categories
e.g height
normal distribution curve
what is discontinuous variation
when there are 2 or more distinct categories and no intermediates
e.g blood type
what is phenotypic variation
the variation in an organisms phenotype
displayed characteristics
how does genotyping variation affect phenotypic variation
alleles vary between organisms of the same species so genotype varies. sexual reproduction, meiosis, crossing over and independent assortment also cause genotypes to vary
what are polygenic and monogenic characteristics
polygenic- inherited characteristics that show continuous variation and are influenced by many genes
monogenic- inherited characteristics that show discontinue variation are influenced by only one gene
how does the environment affect phenotypic variation
variation can be caused by diffeeence in the environment e.g food, climate, lifestyle
genotype influence characterises an organism is born with but environment factors can affect the developed these characteristics
what is a gene
a short section of DNA which codes for a protein
what is an allele
an alternate version. of the same gene
what is a locus
the position in the chromosome where a particular allele is found
what is a genotype
the allele an organism has
what is phenotype
the characteristics of an organism produced by the alleles
what are codominant alleles
both alleles are expressed in the phenotype and neither is recessive
what is monogenic inheritance
the inheritance of a characteristic controlled by a single gene
phenotypic ratios for different types of cross
monogenic 3:1
dihybrid 9:3:3:1
codominiant 1:2:1
what is sex linkage
when the allele that codes for the characteristic is found on sex chromosome
what are the sex chromosomes for males and females
XY male
XX female
what is an autosome
any chromosome that is not a sex chromosome
what is autosomal linkage
genes on the same autosome are linked as they aren’t split up during independent assortment and allele will be passed together
they can only be split up during crossing over so the closer together they are the less likely they will be split up
what is epistasis
when an allele of one gene mask/ blocks the expression of the alleles on another gene
what effects do dominant epistatic alleles have
having at least one copy will result in masking of other genes
what effect do recessive epistatic alleles have
having 2 copies will mask the expression of other genes
phenotypic ratio for epistatic genes
recessive epistatic allele
homozygous recessive and homozygous dominant
9:4:3
dominant epistatic allele
12:3:1
what is the chi squared test
a statistical test use to see if the results of an experiment supports a theory
what is a null hypothesis
the hypothesis should be that there is no significant different between the observed and expected value
how can you reject / accept the null hypothesis
if chi squared value is greater then critical value reject null
then other way round allie
