3.7 Genetics, population and ecosystems Flashcards
Define genotype
The genetic constitution of an organism (the alleles it has for a gene)
Define phenotype
expression of the genes and its interaction with the environment
What is a homozygous chromosome?
a pair of homologous chromosomes carrying the same alleles for a single gene
What is a heterozygous chromosome?
a pair of homologous chromosomes carrying two different alleles for a single gene
What is a recessive allele?
an allele only expressed if no dominant allele is present
What is a dominant allele?
an allele that will always be expressed in the phenotype
What is a codominant allele?
When both alleles are equally dominant and expressed in the phenotype
What is a sex linkage?
A gene whose locus is on the X chromosome
What is the autosomal linkage?
Genes that are located on the same chromosome (not on the sex chromosomes)
What is epistasis?
When one gene modifies or masks the expression of a different gene at a different locus.
What is a monohybrid cross?
A genetic inheritance cross of a characteristic determined by one gene
What is a dihybrid cross?
A genetic inheritance cross for a characteristic determined by two genes at the same times
What happens in a genetic cross?
you must show parental phenotype and genotype, the possible gametes, the offspring genotype and phenotype and the proportion of each phenotype.
What happens in a dihybrid cross?
Figure out F1 and then cross F1 offspring together
•Each possible gamete should have one copy of each gene
•When homozygous dominant is crossed with homozygous recessive the offspring will be heterozygous
•Ratio of each phenotype is 9:3:3:1
When is the ratio of a dihybrid cross not 9:3:3:1?
There is autosomal linkage or crossing over in meiosis
How does crossing over in meiosis affect a dihybrid cross?
New combinations of alleles in the gametes, means the predicted gametes in the punnet square may differ
How does autosomal linkage affect a dihybrid cross
Alleles for each gene linked on the same chromosome will be inherited together.
What is a Hardy- Weinberg principle?
This is a mathematical model which can be used to predict the allele frequencies within a population.
What is a gene pool?
All the alleles of all the genes within a population at one time
What is a population?
All the individuals of one species in one area at one time
What is an allele frequency?
The proportion of an allele within the gene pool
What is the equation for Hardy Weinberg principle?
p2 + 2pq + q2 = 1 or p + q =1
What is the ‘p’ in the Hardy Weinberg principle?
The frequency of the dominant allele
What is the q in the Hardy Weinberg principle?
The frequency of the recessive allele
