Genotype
Key Terms
Genotype
Allele combinations possessed by an organism leading to specific phenotypes
Discontinuous variation
Qualitative differences
Clearly distinguishable categories (categorical)
Monogenic inheritance
One/two genes
An allele has ...
Continuous variation
Quantitative differences
Phenotypic diff have a wide range of variation in a pop. (sig affected by environment)
Each allele has a small...
Monogenic inheritance
One gene w/ 2 or more alleles
Monohybrid cross
1 gene, 2 alleles (r and d)
Drawing genetic crosses
Parental genotype
Parental phenotype
Parental gametes
F1 ratio for genotype then phenotypes
Related Flashcard Decks
| Term | Definition |
|---|---|
Genotype | Allele combinations possessed by an organism leading to specific phenotypes |
Discontinuous variation | Qualitative differences Clearly distinguishable categories (categorical) Monogenic inheritance One/two genes An allele has a large effect |
Continuous variation | Quantitative differences Phenotypic diff have a wide range of variation in a pop. (sig affected by environment) Each allele has a small effect Polygenic inheritance Large number of diff genes involved |
Monogenic inheritance | One gene w/ 2 or more alleles |
Monohybrid cross | 1 gene, 2 alleles (r and d) |
Drawing genetic crosses | Parental genotype Parental phenotype Parental gametes F1 ratio for genotype then phenotypes |
Codominant inheritance | Involves more than one dominant allele |
Multiple alleles genetic crosses | 1 trait 1 gene >2 alleles |
Example of multiple allele genetic cross | Blood group I A I B I O |
3 ways genetic variation arises from sexual reproduction | IA of homologous chromosomes (M1) Crossing over IA of sister chromatids (M2) |
23rd pair of chromosomes | Only pair that varies in shape and size X - v. large and doesn’t carry genes involved in sexual development Y - V. small, no genetic info, but carries gene that causes formation of male embryos |
Sex linked genes | Characteristics determined by genes carried on X and Y |
Why do sex-linked genes affect males | Y is much smaller so only has one copy of the gene, if recessive allele is found on X but no D allele on Y, male will express the recessive trait (usually condition) Most females will have a D allele present on the 2nd X chromosome so are either normal or a carrier |
Examples of sex-linked conditions | Haemophilia - blood clots v. slowly due to a lack of protein blood clotting factor Red-green colour blindness |
Dihybrid cross | Used to show inheritance of 2 diff characteristics, 2 genes at diff loci, >2 alleles on each |
Expected results of a heterozygous dihybrid cross | 9:3:3:1 |
Why may the actual ratio vary from expected | Fertilisation is random If there is no crossing over, alleles for 2 characteristics will be inherited together if on same chromosome |
Autosome | Any chromosome that is not a sex chromosome |
Autosomal linkage | 2 separate genes are found on the same autosome Represented by diff letters Linked genes are inherited together so offspring usually show same combination as parents (certain gametes are more common) |
W/ no crossing over in autosomal linkage | Gametes stay in parental comb. and offspring show 3:1 phenotypic ratio |