4b Inheritance Flashcards
Allele
One or more alternative versions of a gene, the order mid bases in each allele is slightly different - they code for different versions of the same characteristic. Represented using letters B b bb BB
Genotype
The genetic constitution if an organism - the alleles an organism has is BB Bb or bob for eye colour
Phenotype
The expression of genetic constitution and it’s interaction with the environment
Dominant allele
An allele who’s characteristics appear in the phenotype even when there’s only one copy. Dominant alleles are shown by capital letters.
Recessive allele
An allele who’s characteristics only appear in the phenotype if two copies are present. Recessive alleles are shown by lower case letters.
Co-dominant alleles
Allele that are both expressed in the phenotype. Neither one is recessive - e.g. The allele for haemoglobin
Locus
The fixed position if a gene on a chromosome. Alleles of a gene are found at the same locus on each chromosome in a pair.
Homozygote
An organism that carried two copies of the same allele - e.g. BB or bb
Heterozygote
An organism that carries two different alleles - e.g. Bb
Species
A group if similar organisms that can reproduce to give fertile offspring
A population
Is a group if organisms of the SAME species living in a particular area
A gene pool
Is the complete range if alleles present in a population
Hardy-Weinberg Equation.,,
P + Q = 1
What does the Hardy-Weinberg principle predict?
That the allele frequencies in a population won’t change from one generation to the next.
Certain conditions needed for the Hardy-Weinberg principle to be true?
It has to be a large population with no immigration, emigration, mutations or natural selection.
There also needs to be random mating - all possible genotype a can breed with all others!
Equation to predict genotype frequency (hardy Weinberg)
p2 + 2pq +q2 = 1
Gene
A sequence of bases in a DNA molecule that codes for a protein (polypeptide) which results in a characteristic e.g. The gene for eye colour
Change made to the phenotype due to environmental factors is called a??
A modification and it is not part of the genotype - not inherited
Change made to the genotype (by gametes) is called?
Called a genetic mutation that can be inherited by offspring
A sex cell is called a….
Gamete!
A characteristic is said to be sex-linked when…. ?
…when the allele that codes for it is located on the sex chromosome!
Compare Y and X chromosomes ?
Y chromosomes are smaller and carry fewer genes!
Males are more likely to show recessive phenotype a for genes that are sex-linked???
As males only have one X chromosome they often have one allele for sec linked genes. So they express the characteristic for this allele even if it’s recessive.
