Inheritance - Monohybrid Inheritance Flashcards
Causes of variation
Chiasma formation - crossing over of chromosome from homologous pair
-split apart in anaphase 1 then split homo pair traded like wise gene
Independent assortment - chromosome flip to other polar end
Random fertilisation - mother + dad gametes random
Key terms
Genes - sequence of DNA that codes for specific protein to produce a trait
Allele - different variation of traits within a gene
Dominant - the one always produce effect
Recessive - only present effect when both allele is recessive
Genotype - The combination of alleles found in an individual.
Phenotype - The appearance of an organism based on genotype
Homozygous - both alleles of a gene are the same of the gene
Heterozygous - the pair of alleles of a gene are different
F1 - first filial generation - first generation of offspring from a genetic cross.
F2 - second filial generation - second generation of offspring from a genetic cross
Autosomal chromosomes - 22 pair of chromosome not incharge of gender
Sex chromosomes- 23 rd chromosome that control gender
Mono hybrid inheritance (single trait inheritance)
Tt, TT if even 1 dominant allele present traits is defined (capital letter is first letter of trait)
If:
Parent phenotype: Tall x small
Patent genotype: TT x tt
Gametes: T T t t (1 allele in each gametes)
F1 Genotype: All Tt (from punnet square)
F1 punnet square: Tt x Tt
F2 genotype: TT Tt tt
Genotype ratio: 1:2:1
Phenotype ratio 3 tall : 1 small
Eventually all will be 3:1
Test cross
Use to determine is heterozygous dominant or homozygous dominant
1)breed with another known recessive plant
2)if homo - no recessive offspring
3) if hetero - yes recessive offspring
Co-dominant inheritance
Dominant and recessive allele can combine
RR = red
rr= white
Rr = pink
Sex linked inheritance
XY
Y = testis determining factor (turn embryonic gonads to testis)
Dihybrid inheritance (two trait inheritance)
Used for assessing the pattern of 2 characteristics (colour + shape of pea)
R= red r = white S = square s = round
Possible genotype: RRSS, Rrss, etc
Gamete: Rs, rS, etc
2 outcomes:
Gene are linked - allele exist on same chromosomes (false as it only has 4 variations of alleles 3:1)
-R = red and round r = white and square
Gene are not lines - allele exist on different allele
-more variation leading to 16 different outcome if both gamete are heterozygous on both trait
Diagram of dihybrid inheritance cross (must read)
https://resource.download.wjec.co.uk/vtc/2020-21/el20-21_1-3/img/4.3-inheritance-image-10.png
Cross test with two inheritance
Breed with a recessive parent on both trait
(Diagram next page)
Cross test with two inheritance diagram
https://resource.download.wjec.co.uk/vtc/2020-21/el20-21_1-3/img/4.3-inheritance-image-12.png
Mendel 3 law of inheritance
Segregation - one copy of gene (gamete) inherited from each parent
Independent assortment - different alleles are inherited differently (on different chromosome)
Dominance - dominant allele will present trait in phenotype
