Module 6 Section 2 - Patterns of Inheritance Flashcards
What is Continuous variation?
This is where individuals in a population vary within a range, there are no distinct categories eg height. It is polygenic
What is discontinuous variation?
This is when there are two or more distinct categories, there are no intermediates eg blood group. It is controlled by one or two genes
How does genotype affect phenotype?
Sexual reproduction leads to variation in genotypes within a species. Meiosis makes gametes with a unique assortment of alleles through crossing-over and the independant assortment of chromosomes. The random fusion of gametes during fertilisation also increases genetic variation. This leads to differences in phenotype.
How can the environment affect phenotype?
Climate, food and lifestyle all have an impact on the growth of an individual of an individual or organism
What is a gene?
A sequence of bases that code for a protein.
What is an allele?
Different versions of the same gene
What is a locus?
The allele of a gene is found at a fixed position on each chromosome in a pair
What is genotype?
All the alleles an organism has
What is a phenotype?
The phenotype of an organism is the characteristic all the alleles produce
What are codominant alleles?
Neither allele is recessive so both are expressed.
What is a carrier?
A carrier is a person carrying an allele which is not expressed in the phenotype but can be passed on to offspring
What genetic diagram should be used for monogenic inheritance?
Regular punnet square
What is dihydrid inheritance?
The inheritance of two characteristics, which are controlled by different genes.
What genetic diagram is used for dihybrid inheritance
Dihybrid cross or punnet square, which gives 16 possible outcomes.
What is the ratio for two heterozygous parents in a dihybrid cross
9:3:3:1
What is linkage?
Genes for different characteristics are located at different loci on the same chromosome and so are inherited together
What is sex linkage?
When the expression of an allele dependant on the gender of the individual as the gene is located on a sex chromosome.
Why are males more likely to get X-linked disorders?
Y chromosome is smaller than the X chromosome so more chromomes are carried on the X chromosome.
As males only have one X chromosome, they often only have one allele for sex-linked genes. This means they express the allele even if it recessive, so males are more likely to show recessive phenotypes for genes that are sex linked than females.
What is autosomal linkage?
Genes which are located on the same chromomes (which is not a sex chromosome) tend to be expressed together in the offspring.
Why does autosomal linkage happen?
The genes will stay together during independent assortment in meiosis one, and their alleles will be passed on to the offspring together. The only reason this won’t happen is if crossing over splis them up first
What is epistasis?
The interaction of different loci on the gene, one gene locus affects the other gene locus. This is because the allele of one gene can mask or suppress the expression of alleles of other genes.
What are the degrees of freedom for a chi-squared test?
N - 1
When are the results significant for a chi-squared test?
When the observed value is greater or equal to than the critical value
