Variation And Inheritance Flashcards
What are dominant alleles?
Alleles that will always be expressed in the phenotype if present.
What are recessive alleles?
Alleles that will only be expressed in the phenotype if 2 copies of the allele are present.
What does homozygous mean?
When an organism has 2 identical alleles for a particular gene.
What does heterozygous mean?
When an organism has 2 different alleles for a particular gene.
What are polymorphic genes?
Genes that have more than one possible allele.
What are monomorphic genes?
Genes that have 1 possible gene.
Why are most genes monomorphic? (2)?
- Necessary for many proteins we need to make.
- A useful characteristic as any mutations to other alleles can be fatal.
What does a high proportion of polymorphic genes mean?
The individual will have an increased genetic variation.
What is the equation for working out the proportion of polymorphic genes?
Number of polymorophic genes in population/the total number of genes in the population.
What is continuous variation? Example?
When the individual in a population vary within a range and not distinct categories. For example, height or fur length.
What is the gene locus in continuous variation and discontinuous variation?
C: many loci on different chromosomes.
D: usually only one or a very small number.
What is discontinuous variation? Example?
When there are two or more distinct categories with no intermediates.
What is the number of alleles in continuous variation and discontinuous variation?
C: many genes contribute to inheritance, each has alleles.
D: often just a pair of alleles, can be a very small number.
What is the effect on the phenotype in continuous variation and discontinuous variation?
C: many intermediates between the extremes.
D: feature is either present or absent.
What is the environmental influence in continuous variation and discontinuous variation?
C: significant effect.
D: environment has little effect.
How can the environment affect variation? Example? (2)?
- A person’s offspring will not inherit an accent through genes, only through hearing others speak.
- For example, losing a limb/having a scar.
How can variation in plants be caused by the environment interacting with genes?
Chlorotic plants don’t photosynthesise but have a gene for chlorophyll but the environment can prevent the expression of the gene.
How can variation in animals be caused by the environment interacting with genes?
Obesity can be caused by the environment interacting with genes;
- Overfed.
- Reduced activity.
- Health conditions.
- Specific genes in obesity.
What is an example of how variation in animals can be caused by the environment interacting with genes?
A mouse has a mutation of chromosome number 7 that causes the pattern of fat deposition to be altered.
What is interspecific variation?
Variation between members of species.
What is intraspecific variation?
Variation within members of the same species.
What is a genotype?
The genetic material of an organisms (alleles present).
What is a phenotype?
The physical characteristics of an organism (not always visible):
- the genotype and environmental effects.
Where does genetic variation arise from?
Meiosis.
What does meiosis produce?
Genetically different gametes.
What may genetic variation result from in meiosis? (3)?
- Alleles shuffling (swapping of alleles between non-sister chromatids) during crossing over in prophase 1.
- Independent assortment of chromosomes during metaphase 1 and anaphase 1.
- Independent assortment of chromatids during crossing over in metaphase 2 and anaphase 2.
What are the gametes produced like in meiosis?
They are individual and genetically dissimilar and haploid (contain only one of each pair of homologous chromosomes and one allele for every gene).
How does random fertilisation in meiosis cause genetic variation?
Any male gamete can potentially combine with any female gamete from an organism of the same species and so random fertilisation produces extensive genetic diversity among offspring.
