Inheritance- BP Flashcards
What is inheritance?
offspring inheriting a combination of alleles (2 types – paternal/maternal) for each gene which will help determine characteristics
What is a gene?
a section of DNA that codes for a protein
What is an allele?
a type/form of a gene
What is a dominant allele?
an allele that is always expressed if present
What is a recessive allele?
an allele that is only expressed if 2 are present
What is genotype?
combination of alleles for a particular gene
What is phenotype?
expressed/observed characteristic (if discontinuous – only determined by genotype, if continuous – determined by genotype and environment)
What is homozygous?
having 2 of the same alleles
What is heterozygous?
having 2 different alleles
What is Monohybrid Inheritance?
inheritance dealing with One Characteristic
Examples of Monohybrid Inheritance?
Dominant/Recessive
Codominant
Multiple Allele
Sex Linkage
What is the Expected Ratio for Monohybrid Dominant/Recessive?
3 Dominant to 1 Recessive
Why are Observed Ratios different from Expected Ratios?
random fertilisation of gametes
small sample size
mutation
selection
How can 2 parents with a dominant characteristic give birth to a child with a recessive characteristic?
if both parents are Heterozygotes (carriers for recessive allele) they have a 25% chance of giving birth to a child who is Homozygous Recessive (has the recessive characteristic)
What is co-dominance?
when 2 different dominant alleles are inherited, both will be expressed in the phenotype
What are multiple alleles?
when the gene has more than 2 alleles (e.g. blood group)
What is a sex-linked gene?
a gene carried on one of the sex chromosomes, normally the X chromosome
What is an inherited disease?
- inheriting a mutated allele that leads to production of a faulty protein
- normally a recessive allele (dominant allele will decrease in frequency by natural selection, recessive allele can be carried by heterozygotes)
What is a sex-linked disease?
inheriting a mutated allele carried on one of the sex chromosomes, normally a recessive allele & normally carried on X chromosome
Why do males have increased chance of inheriting a sex linked disease rather than females?
males only have 1 X chromosome, females have 2 X chromosomes, females can be carriers, males cannot be carriers
What is Dihybrid Inheritance?
inheritance dealing with Two Characteristics
Examples of Dihybrid Inheritance?
Dominant/Recessive
Autosomal Linkage
Epistasis
What is the Expected Ratio for Dihybrid Dominant/Recessive?
9:3:3:1
What is Autosomal Linkage?
2 Genes (characteristics) carried on the same Chromosome
What is Epistasis?
interaction between different genes
What are the 3 Types of Epistasis?
Dominant and Recessive and Complementary
What is Dominant Epistasis?
dominant genotype on one gene inhibits expression of other gene
What is Expected Ratio for Dominant Epistasis?
12:3:1
What is Recessive Epistasis?
recessive genotype on one gene inhibits expression of other gene
What is Expected Ratio for Recessive Epistasis?
9:3:4
What is Complementary Epistasis?
dominant genotype required on both genes to achieve final product
What is Expected Ratio for Complementary Epistasis?
9 Final Product
7 None
