Inherited change Flashcards
What does codominant mean?
Alleles which are both expressed in the phenotype (if they occur together)
What is the genotype?
The combination of alleles expressed by an organism
What is a phenotype?
The observable characteristics of an organism due to their genotype and environment
What is an example of co-dominance?
Flower colour in snap dragons, the can be red (CrCr), white (CwCw) or pink (CrCw)
What allele exist for blood groups and how do they interact?
Ia, Ib and Io for blood group A, B and O, A and B exist in co-dominance, causing AB blood group, O is reccesive to both
What combination of alleles is used in the test cross?
Homozygous dominant + homozygous recessive produces all dominant alleles, heterozygous and homozygous recessive produces half and half
What is the difference between blood group?
A or B antigen is displayed on the membrane of red blood cells, the O group displays neither
Which sex chromosome carries more alleles?
The Y chromosome is shorter than the X chromosome, so it carries fewer alleles
How is colour vision affected by gender?
The allele for colour vision is only on the X chromosome, colour blindness is recessive therefore boys, who only have one X chromosome are more likely to have the colour blindess
What are some other inheritance sex linked?
Haemophilia
What is a Barr Body?
Supercoiled inactivated X chromosome, which occurs early in females embryonic development
What are dihybrid crosses?
Consideration of two characteristics at the same time
If the genotype is RrYy, what are the gametes produced?
RY, Ry, rY, ry
What is an autosome?
A non-sex chromosome
What is autosomal linkage?
When two genes are located on sex chromosomes, so are inherited today
How does distance relate to chances of autosomal links crossing over?
The further away they are the more likely crossing-over will occur
If a population has 5,000 people, how many alleles of each gene are there?
10,000
What 5 things are assumed in the Hardy-Weinberg equation?
No mutations, population is isolated, no selection, large population and mating is random
What is the Hardy-Weinberg equation?
p^2 +2pq+ q^2, where p represents the dominant allele and q represents the recessive allele
What are the types of variation?
Intraspecific (differences that exist between same species) and interspecific (differences that exist between different species)
What causes variation?
Genetic causes- random mutation, meiosis and random fertilisation
Environmental causes
Combinations
What types of adaptations are there?
Behavioural, physiological and anatomical
What is selection pressure?
An environmental factor that confers a greater chance of survival to reproductive age on some members of the population
What are the three types of selection?
Directional- for or against an extreme phenotype
Stabilising- selects against both extreme phenotypes
Disruptive- selects against the most common/average phenotype
What is genetic drift?
The change in frequency of an existing gene variant in the population due to random chance
What is speciation and what are the types?
The formation of a new and distinct species in the course of evolution
Allopatric and sympatric speciation
What is allopatric speciation?
Involves the geographical isolation of individuals
What are the possible types of barriers in allopatric speciation?
Mountain ranges, the sea(for terrestrial species) or bodies fo freshwater, the land(for aquatic species), glacial masses and valleys
What is sympatric speciation?
When there is no geographical isolation of the population, it involves reproductive isolation within a randomly mating population, this leads to a rapid genetic change which alters morphology, behaviour and habitat preferences
What is polyploidy?
Cell division error that leads to the chromosomes doubling, this is an example of sympatric speciation
What’s genetic bottlenecks?
When the population is reduced, with the genetic diversity, so when the population rises again, inbreeding is likely, this means the population will not be able to adapt as readily
