Patterns Of Inheritance + Variation Flashcards
(35 cards)
Genotype
The genetic makeup of an organism
Genetic variation
A variety of different combinations of alleles in a population
Genetic bottleneck
When large numbers of a population die before reproducing, leading to reduced genetic biodiversity within the population
Phenotype
The expression of the organisms genes and its interaction with environment - observable characters it’s
Founder effect
When a few individuals of a species colonise a new area, their offspring initially experience a loss in genetic variation, and rare alleles can become much more common
Homozygous
Two identical alleles for a characteristic
Heterozygous
Two different alleles for a characteristic
Allele
A version of a gene
Epistasis
When one gene modifies of masks the expression of a different gene at a different locus
Multiple alleles
Some genes have more than two versions of, these are multiple alleles
- an organism can only carry two versions
- blood group is determined by a gene with multiple alleles (immunoglobin gene, codes for different antigens present of surface of red blood cell)
- three allele of this gene, Ia, Ib, Io
- results in four blood groups, A,B, AB, O
Codominance
Occurs when two different alleles occur for a gene, both of which are equally dominant.
Sex Linkage
Some characterstics are determined by genes carried on the sex chromosomes - those genes are sex linked.
Haemophilia
Is an example of a sex linked genetic disorder
- people with disorder have blood that clots very slowly, therefore any injury can result in prolonged bleeding which is potentially fatal
- More common in men, this is because if they inherit the recessive allele on their X chromosome, they are unable to have the corresponding dominant allele on the Y chromosome
- Females who are heterozygous (XH,Xh) are known as carriers, they don’t suffer from condition as they have the dominant allele, but they can pass it on
Dihybrid Inheritance
Genetic inheritance for a characteristic determined by two genes
Autosomal Linkage
Genes that are located on the same chromosome, these linked genes are inherited as one unit
Recombinant offspring
They have different combinations of alleles than either parent, as a result of crossing over (prophase 1)
- the closer the genes are on a chromosome, the less likely they are to be separated during crossing over
- and fewer recombinant offspring produced
Recombinant Frequency
Is the measure of the amount of crossing over that has happened during meiosis
= number of recombinant offspring / total number of offspring
If it = 50% then indicates no linkage
50%> (less than) means that there is gene linkage
Epistasis
Is the interaction of genes at different loci
- gene regulation is a form of Epistasis with regulatory genes controlling the activity of structural genes (e.g. lac operon)
- colour of Labrador dogs depend of which alleles are present at each locus
Gene pool
Sum of all genes in a population at any given time
Allele frequency
Is the relative frequency of a particular allele in a population
Evolution
Long term change in the allele frequency of a population
The Hardy-Weinberg Principle
States that in a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next
Genetic Drift
This occurs in small populations, it is the change in allele frequency due to the random nature of mutation.
Gene flow
Is the movement of alleles between populations.
- Immigration and emigration result in changes of allele frequency within a population
