Genetics and Inheritance Flashcards
What is a gene? (1)
A section of DNA that codes for a specific polypeptide
What is the genotype? (2)
The genetic constitution of an organism. All the alleles that an organism possesses
What is the gene pool? (1)
All the alleles within an interbreeding population (at a specific time)
What is a population? (1)
All the individuals of the same species that occupy the same habitat at the same time
What is the phenotype? (2)
The expression of its genetic constitution and its interaction with the environment
What is an allele? (1)
Different version of the same gene
What are multiple alleles and what does this produce? (2)
More than 2 alleles for the same gene. This produces a hierarchy of dominance
What is the genome? (1)
The full sequence of genetic material within a cell/organism
What is a dominant allele? (1)
Always expressed in the phenotype regardless of whether an organism’s genotype is homozygous or heterozygous
What is a recessive allele? (1)
Only expressed in the phenotype if the genotype is homozygous
What are codominant alleles? (1)
Both alleles equally expressed within the phenotype
Diploid meaning
Two copies of a gene
Haploid meaning
One copy of a gene
What is the expected offspring ratio of monohybrid inheritance from heterozygous parents
3:1
What is the expected offspring ratio of codominance inheritance from heterozygous parents
1:2:1
What is the expected offspring ratio of dihybrid inheritance from heterozygous parents
9:3:3:1
What is the expected offspring ratio of epistasis inheritance from heterozygous parents
9:4:3 or 15:1 or 9:7
What is the expected offspring ratio of autosomal linkage inheritance from heterozygous parents
3:1 if no crossing over
What is allelic frequency?
The number of times an allele occurs within a gene pool
Hardy-Weinberg Principle for the frequency of the dominant and recessive allele?
P + q = 1.0
Hardy-Weinberg Principle for the frequency of all individuals?
P2 + 2Pq + q2 = 1.0
What does Hardy-Weinberg principle predict?
The allelic frequency (of a particular gene) from one generation to the next will remain constant if there is no migration, gene mutations or selection for or against a particular allele
There should be a large population and mating within the population should be random
Exam Question - what does the Hardy-Weinberg principle predict?
The allelic frequency of a particular gene will remain constant from one generation to the next, providing:
- mating is random
- there are no mutations
- there is a large population
- there is no migration
- there is no natural selection
What is monohybrid inheritance? (1)
Inheritance of a single gene which determines a single characteristic
What are the dominant characteristic rules?
Affected offspring must have at least one affected parent
Unaffected parents only have unaffected offspring
If both parents are affected and have an unaffected offspring, both parents must be heterozygous
What are the recessive characteristic rules?
Unaffected parents can have an affected offspring if they are heterozygous
What is meant by sex-linkage? (2)
When an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual
Why are males more likely to express a recessive sex-linked allele? (1)
A female would have two copies of a recessive allele for it to be expressed in the phenotype whereas males only need one
To prove a characteristic is not sex-linked, what are the sex link rules for dads and daughters?
If a daughter is affected (homozygous recessive)
Her father is not
And it is a recessive disease
It is not sex-linked
To prove a characteristic is not sex-linked, what are the sex link rules for mums and sons?
If a son is affected
His mum is not
And it is a dominant disease
It is not sex-linked
What are autosomal chromosomes? (1)
Chromosomes that are not directly involved in determining the sex of an organism
What is a linkage group? (1)
A set of genes on the same chromosome which tend to be inherited together
What is epistasis? (1)
An interaction between two genes where one allele affects/influences the expression of another
What is dihybrid inheritance (2)
Involves a phenotype that is inherited as the result of two different genes, thus two characteristics
The two genes either can be on different chromosomes or linked on the same chromosome
What is the chi squared test? (1)
A statistical test to find out whether the difference between observed and expected data is due to chance or a real effect
What are the criteria for the chi-squared test? (4)
Data placed in discrete categories
Large sample size
Only raw count data allowed (i.e. not percentages)
No data values equal to zero
How is a chi-squared test performed? (2)
The formula results in a number which then compared to a critical value
If the number is greater than or equal to the critical value, we conclude there is a significant difference between the observed and expected data and that the results did not occur due to chance
