variation + inheritance Flashcards
How do genetic factors contribute to phenotypic variation? (3)
Different genotypes (combinations of alleles) cause variation in phenotypes (characteristics displayed by an organism)
Monogenic characteristics (controlled by one gene) show discontinuous variation (e.g., blood group)
Polygenic characteristics (controlled by multiple genes) show continuous variation (e.g., height, skin color)
How do environmental factors contribute to phenotypic variation? (3)
Environmental factors like climate, food availability, and lifestyle affect phenotype
Examples include etiolation (long, spindly growth due to lack of light) and chlorosis (yellowing due to lack of magnesium)
Most traits influenced by both genes and the environment show continuous variation
How does sexual reproduction lead to genetic variation within a species? (2)
Meiosis creates unique gametes through crossing over and independent assortment of chromosomes
Random fusion of gametes during fertilisation further increases genetic variation in offspring
What is a gene? (1)
A sequence of DNA bases coding for a polypeptide
What is an allele? (1)
Different versions of a gene
What is genotype? (1)
The genetic makeup of an organism
What is phenotype? (1)
The characteristics displayed due to the genotype and environment
What is a dominant allele? (1)
Always expressed in the phenotype
What is a recessive allele? (1)
Expressed only when homozygous
What are codominant alleles? (1)
Both alleles are expressed in the phenotype
What is a sex-linked gene? (1)
A gene located on the X or Y chromosomes
What is meant by locus? (2)
The position of a gene on a chromosome
Alleles of the gene are found at the same locus on each chromosome
What is meant by homozygote? (1)
An organism carrying two copies of the same allele
What is meant by heterozygote? (1)
An organism carrying two different alleles
What is a carrier? (1)
A person carrying an allele not expressed in the phenotype but can be passed on to offspring
What is monohybrid inheritance? (1)
The inheritance of a characteristic controlled by a single gene
What is dihybrid inheritance? (1)
The inheritance of two pairs of alleles
What are multiple alleles? (2)
More than two alleles of the same gene exist in the gene pool
E.g., the ABO blood group system
