7A genetics Flashcards
What is a gene
Sequence of bases on a dna molecule that codes for a polypeptide resulting in a characteristic
What is an allele
One or more versions of the same gene
What is a diploid cell
This is where there are 2 copies of each chromosome (one from each parent) which ends up in 2 alleles of each gene
What is the name of the position where the allele is at a fixed point
Locus
What is the genotype
Genetic constitution made up of the different alleles an organism has
What is a phenotype
The expression of the genetic constitution and its interaction with the environment
What is a dominant allele
Always expressed in phenotype even when theres just one copy
What is a recessive allele
Characteristics only appear in the phenotype if two copies are present
What is a codominant allele
Neither is recessive so both expressed
What is the difference between homozygous and heterozygous
Homozygous is where it carries 2 copies of the same allele and heterozygous where it carries 2 different alleles for a gene
What is a haploid cell?
Only one allele for each gene contained
What is the importance of monohybrid inheritance and crosses
It is the inheritance of a characteristic controlled by one gene so the crosses show the different likelihoods of that gene being inherited by offspring of certain parents
What is the phenotypic ratio for monohybrind crosses
3:1 (dominant to recessive)
What is the expected phenotypic ratio for 2 heterozygous parents
1:2:1
Importance of dihybrid inheritance and crosses
Inheritance of 2 characteristics controlled by different genes so the cross will show the likelihood of offspring inheriting certain combinations of the 2 characteristics from particular parents
What is sex linkage
Alleles that code for them are located on a sex chromosome
Why are males more likely to show recessive phenotypes for those that are sex linked
Males only have one copy of X chromosome so they express it
What is the dominant epistatic phenotypic ratio?
crossing homozygous recessive with homozygous dominant will produce 12:3:1
dominant epistatic : recessive epistatic : dominant other : recessive both
What causes x linked disorders
Where the faulty alleles are carried on the x chromosome
When do you reject the null hypothesis?
When your x2 value is larger/equal to critical so there is a significant difference between O and E which could be due to something other than chance
What is the chi squared formula?
chi squared = sum of (observed - expected)^2 / expected
What is a critical value?
The value of x^2 that corresponds to a 0.05 level of probability that the difference between observed and expected is due to chance
What is a null hypothesis?
This is where there is no significant difference between expected and observed results which sould be due to chance or a wrong theory
How do you work out the degrees of freedom?
number of classes (phenotypes) - 1
What is the chi squared test?
A statistical test that is used to see if the results of an experiment support a theory
What is epistasis?
The allele of one gene masks the expression of another gene
For recessive epistatic alleles what is the phenotypic ratio?
If you cross homozygous recessive with a homozygous dominant you produce a 9:3:4
dominant both: dominant epistatic: recessive other : recessive epistatic
What is the expected ratio for 2 heterozygous parents in a dihybrid cross
9:3:3:1
What is autosomal linkage
Genes located on the autosome that will stay together during independent segregation passing on their alleles to offspring together
