what is mendelian genetics
traits are inheritable
named after Grefor mendel
performed cross-pollination experiments on peas
what dd the pea experiment include
- cross-pollination = true breeding
- then allowed F1 to self-pollinate or cross-polinate to see resutling F2 phenotypes
what is a locus
- the location of a gene on a chromosome
what is a phenotype
- physical expresson of genotype
what is homzygotic vs heterozygotic
- homo = two of same allele for a gene
- hetero = two different alleles for a gene
how are alleles masked
if domnant allele is present in coding, this code is used for enxyme production instead
what are punnet squares for
- show possible genotypes
- show probability of phenotypes
how to do a two trait punnet square
e.g. RrYy -> cross RY, rY, Ry, rY
- each trait will retain a 3:1 ratio in F2
what are the laws of medelian inheritance
- law of dominance
- law of segregation
- law of independent assortment
what is law of dominance
in cross-fertillisation, dominant trait always masks the recessive
what is law of segregation
- two alleles of a gene are separate entities and separate from each other during gametogenesis
what is law of independent assortment
- chromosomes distrivuted to gametes individually
- alleles for different traits are also distributed independently if are on different chromosomes
- all combnations of traits are possible
e.g. alleles for colour gene are distributed independently only if on different chromosomes (e.g. yellow allele on one chromosome and green on another could be separated)
what s incomplete dominance
- neither allele is wholly dominant
- heterozygous individuals will exhibit a BLENDED phenotype
what is codominance
- heterozygous individuals will express both alleles equally
- phenotype of both alleles is present
how is blood type determined
- the carbohydrates on red blood cell surface/antigens
- alleles for antigens include IA, IB, i
what are the possible genotypes for blood groups
type AB = heterozygous for IA,IB
type A = AA or Ai
type B = BB or Bi
type O = ii
what is the dominance pattern for type AB blood
codominant
what is different about the Y chromosome
- smaller (less DNA)
- contains Sex Determining Region - initiates sexual differentiation
what are autosomal alleles vs sex linked
- alleles located on an autosome
- daughter and sons have equal opporttunity to inherit
- alleles located on sex chromosome
- phenotypes are unequally distributed
what is a pedigree
- chart that illustrates inheritance pattern through different generations of a family
autosomal dominant
- sexes affected equally (but chance over 50%)
- from mum or dad
- black = have a dominant allele
autosomal recessive
- equal chance
- trait only present when two recessives
- trait present if two recessive - 25% chance of inheritance
-BOTH parents must have a recessive allele - look for two unaffected parents, but affected young
X-linked dominant
- allele on X chrom - by mother or father in daughters
- only 1 dominant X chrom needed
- affected dad and daughter
X-linked recessive
- recessive allele on X chrom
- male needs one X-recessive, female needs two for trait to be expressed
- look for unaffected mother, but affected son!! or affected dad, unaffected daughter
