7A Genetics Flashcards
Gene
A sequence of DNA bases that code for a specific protein which results in a characteristic
Allele
Different versions of a gene
Diploid organisms
Contain two copies of the same gene (one from each parent) So we have two alleles of each gene
Locus
The allele position of a gene on a chromosome pair
Genotype
The genetic construction e.g RR or Rr
Phenotype
The expression of the genetic constitution and its interaction with the environment- the characteristic that is expressed
Codominant
Alleles are expressed equally in the phenotype because neither allele is recessive
Homozygous
Two alleles of the same type
Heterozygous
Two different alleles
Haploid
Gametes contain only one set of chromosomes
Dihybrid inheritance
The inheritance of two characteristics which are controlled by different genes
Sex-linked
The alleles that code for certain characteristics are located on a sex chromosome
Why are sex-linked genotypes usually singular in males?
The gene is only carried on the X chromosome, so in a male, there is only one allele
Examples of sex-linked genetic disorders
Colour blindness and haemophilia
Autosome
Any chromosome that isn’t a sex chromosome
Autosomal genes
Genes located on the same autosome. Genes on the same autosome are said to be linked
Linkage of autosomal genes
Stay together during independent segregation of chromosomes in meiosis I and their alleles will be passed on to the offspring together, unless crossing over splits them. Closer two genes are on the autosome, the less likely they are to be separated by crossing over, so the are said to be more closely linked
Epistasis
When an allele of one gene blocks the expression of another allele of another gene
What is an example of epistasis?
If someone has an allele that codes for baldness, it will block the allele for a widows peak, so the widows peak will not be expressed as a phenotype
What is a null hypothesis?
There is no significant difference between the observed and expected results
When would you use chi squared?
When dealing with frequencies
What does the critical value show?
Gives the level of probability that the difference observed is due to chance
When do you reject the null hypothesis?
When the chi squared is less than the critical value
