6.1.2 patterns of inheritance Flashcards
variation causes
- environmental (eg diet and etoliation)
- genetic
complimentary epistasis
the presence of a particular allele at each locus is required for the expression of a particular phenotype
sexual reproduction variation
- crossing over
- independent assortment
- random fusion of gametes during fertilisation
eg things that can cause mutations
- x rays
- mustard gas
- some viruses
etiolation
A condition in plants characterised by weak stems and small, pale leaves, due to insufficient exposure to light.
monogenic inheritance
inheritance determined by a single gene
punnet square monogenic inheritance
eg tT X tt
dihybrid inheritance
2x dominant traits
genotype of. a parent DIHYBRID
eg YyRR
punnet square of dihybrid inheritance
gametes are (Yy)
dihybrid cross NORMAL ratio
9:3:3:1
multiple alleles
characteristics for which there are 3+ alleles
parents in multiple alleles
I b I o
gametes of multiple alleles
Io … Ib … etc
offspring genotype for multiple alleles
Io Ib
non sex chromosome
autosome
autosomal linkage
gene loci present on the SAME AUTOSOME that are often inherited together
autosomal linkage NO CROSSING OVER
the 2x genes on the same autosome are inherited together as one unit
recombinant gametes
crossing over between genes
chance of reecombinant gametes increases with …
DISTANCE AWAY the gene loci are. the further apart the gene loci, the greater the chance of recombinant gametes
epistasis
interaction of non linked gene loci where one masks the expression of the other
recessive epistasis
when you hace the recessive aa, this takes over and masks the expression of whatever is on the second locus, the aa recessive phenotype is expressed
common recesssive epistasis ratio
9:3:4
dominant epistasis ratios
12:3:1
13:1
d ominant epistasis
having one of the dominant A alleles anywhere = it;s the A colour
null hypothesis chi squared
NO signifcant difference between observed + expected
probability and d o f chi squared
probability: 0.05
doe: number of categories - 1
continuous variation is usuallt
polygenic
affected by genes and environment
describe autosomal linkage
-alleles
- loci close together on chromosome
- inherited together
- corssing over produced some recombinant
- eg allele for red body and yellow tail imherited together
