Patterns of inheritance (6) Flashcards
What is continuous variation?
This is when the individuals in a population vary within a range, there are no distinct categories.
What is discontinuous variation?
This is when there are two or more distinct categories, each individual falls into only one of these categories, there are no intermediates
What are alleles?
They are different versions of the same gene.
What process leads to variation in genotypes within a species?
Sexual reproduction leads to variation in genotypes within a species. Meiosis makes gametes with a unique assortment of alleles through crossing over and independent assortment of chromosomes. The random fusion of gametes during fertilizations also increases genetic variation in the offspring.
What is phenotypic variation?
The differences in genotype of organisms result in variations of phenotype, the characteristics displayed by an organism.
What are polygenic characteristics?
Inherited characteristics that show continuous variation are usually influenced by many genes.
What are monogenic characteristics?
Inherited characteristics that show discontinuous variation are usually influenced by only one gene.
What are the two factors that can affect variation?
- genes
- environment
How can both genes and the environment affect variation?
Genetic factors determine genotype and the characteristics an organism’s born with, but environmental factors can influence how some characteristics develop. Most phenotypic variation is caused by the combination of genotype and environmental factors. Phenotypic variation influenced by both usually shows continuous variation.
What is a gene?
A sequence of bases on a DNA molecule that codes for a protein which results in a characteristic.
What is an allele?
A different version of a gene
What is a genotype?
The alleles that an organism has
What is a phenotype?
The characteristics that the alleles produce
What does dominant mean?
An allele whose characteristic appears in the phenotype even when there is only one copy
What does recessive mean?
An allele whose characteristic only appears in the phenotype if two copies are present.
What does codominant mean?
Alleles that are both expressed in the phenotype
What is a locus?
It is the fixed position of a gene on a chromosome
What does homozygous mean?
It means that there are two copies of the same allele
What does heterozygous mean?
It means that there are two different alleles
What are monogenic crosses and monogenic inheritance?
Monogenic crosses show the likelihood of the different alleles of that gene being inherited by offspring of particular parents.
Monogenic inheritance is the inheritance of a characteristic controlled by a single gene.
What is a carrier?
It is a person carrying an allele which is not expressed in the phenotype but that can be passed on to offspring.
How is codominance and sickle cell anemia related?
- People who are homozygous for normal hemoglobin do not have the disease
- People who are homozygous for sickle hemoglobin do have the disease and all their red blood cells are sickle shaped.
- People who are heterozygous have an in between phenotype called the sickle cell trait where they have some normal hemoglobin and some sickle hemoglobin. The two alleles are codominant so are both expressed in the phenotype
What is a Punnett square?
It is a way of showing a genetic diagram and can be useful to predict the genotypes and phenotypes of offspring.
What is dihybrid inheritance and what are dihybrid crosses?
Dihybrid inheritance is the inheritance of two characteristics which are controlled by different genes.
A dihybrid cross is used to show how two different genes are inherited at the same time.