Chapter 17 - Inherited Change Flashcards
Genotype def.
The genetic constitution of an organism
Phenotype def.
The expression of the genes and its interaction with the environment
Homozygous def.
A pair of chromosomes carrying the same the same alleles for a single gene
Heterozygous def.
A lair of homologous chromosomes carrying two different alleles for a single gene
Recessive allele def.
An allele only expressed if no dominant allele is present
Dominant allele def.
An allele that will always be expressed in the phenotype
Codominant def.
Both alleles are equally dominant and expressed in the phenotype
Multiple alleles def.
More than two alleles for a single gene
Sex linkage def.
A gene who’s locus is in the X chromosome
Autosomal linkage def.
Genes that are located on the same chromosome
Epistasis def.
When one gene masks or modifies the expression of a different gene on a different locus
Monohybrid def.
Genetic inheritance cross if characteristics determined by one gene
Dihybrid def.
Genetic inheritance cross for a characteristic determined by two genes
Why do the actual phenotype observations differ from the predicted phenotypic ratios from tue dihybrid cross
- Gamete fusion
- Small sample sizes can lead to skewed ratios whilst larger samples minimise these random effects
- crossing over can change the allele combinations by separating the linked genes
How many alleles of a specific gene can an individual hold
2
Suggest one reason why the expected phenotype ratio may differ from the actual ratio
- crossing over during meiosis’s as a new combination of gametes will produce
What are the effects of crossing over on autosomal linkage
- Crossing over seperates linked genes.
- fewer recombinant offspring tend to be produced (offspring that have a different combination of alleles from their parents due to crossing over) so less genetic variation being introduced from crossing over when genes are linked.
- The probability of linked genes being separated during crossing over is inversely proportional to how close they are on a chromosome i.e., the closer the genes, the more likely they will be inherited together.
What is a hypostatic gene
The gene whose expression is blocked by another gene
What is an epistatic gene
The gene whose allele affects the expression of the hypostatic gene
Two types of epistatic interactions and what occurs during them
- recessive epistasis - occurs when the epistatic gene must be homozygous recessive to block the expression of the hypostatic gene
- dominant epistasis - Occurs when the epistatic gene is dominant and actively modifies or blocks the expression of the hypostatic gene.
Two types of epistatic interactions and what occurs during them
- recessive epistasis - occurs when the epistatic gene must be homozygous recessive to block the expression of the hypostatic gene
- dominant epistasis - Occurs when the epistatic gene is dominant and actively modifies or blocks the expression of the hypostatic gene.
Know how to do chi squared