Biology- Genetics Flashcards
Define DNA
A polynucleotide that codes for amino acids.
Define chromosome
Threadlike structure made form protein and DNA in which genetic (hereditory) information is passed from one generation to the next.
Define Gene
Section of DNA on a chromosome coding for one or more polypeptide.
Define Allele
An alternative form of a gene located at a specific position.
An allele is a different form of a gene.
Define Genome
Minimum group/set of chromosomes derived form a gamete.
Define Locus
The location/position of a gene on a chromosome
Define Genotype.
The genetic make up of an organism- what alleles are present for a particular gene.
Define Phenotyoe
Any observable characteristic of an organism- physical or biochemical.
Results from expression of an organisms genes and environmental factors.
Define Homozygous
Homozygote
An organism where identical alleles of the gene are present on both homologous chromosomes.
Define Heterozygous
Heterozygote
For a particular gene when two different alleles occupy the genes position of homologous chromosomes.
Define Recessive
Recessive allele
An allele that produces its characteristic phenotype only when it’s paired allele is identical- homozygous.
Define Dominant
Dominant allele
An allele that produces the same phenotype whether it is paired allele is identical or different, it is always expressed.
What are the first Filial (F1) generation?
The offspring to the parent organisms are the F1 generation.
Define Monohybrid inheritance.
The inheritance of a characteristic/ one allele pair of one gene.
Define Dihybrid inheritance.
Where 2 alleles from 2 different genes located on different chromosomes are inherited.
What is Mendels law of Independent assorment?
Each member of a pair of alleles may combine randomly with either of another allele pair.
Define Codominance.
Condition in which both alleles for one gene in a heterozygous organism contributeto the phenotype.
Both alleles are expressed in the phenotype.
Define the term “Multiple Alleles”
Where a gene has more than 2 possible alleles.
Eg. Blood group
Immunoglobulin gene (gene I) has 3 alleles
I^A I^B I^O
What are the ratios of offspring of monohybrid and dihybrid inheritance?
Monohybrind inheritance- 3:1
Dihybrid inheritance- 9:3:3:1
If the ratio is different then consider the possibility of co-dominance.
What are the Sex chromosomes for Male and Female?
Male- x,y chromosomes
Female- x,x chromosomes
DEfine sex-linked inheritance
Any gene that is carried on either the x or y chromosome is sex linked.
The pattern of inheritance that many result from a mutant gene located on either the x or y chromosome.
(eg. Disease such as haemophilia)
Define Autosomal linkage.
Where any two or more genes are carried on the same autosome is called autosomal linkage.
Autosome- Chromosomes (22 of the 23 chromosomes) that aren’t sex chromosomes.
Define Epistasis.
Epistasis arises when the allele of one gene affects or masks the expression of another in the phenotype.
Define the Hardy-Weinburg Principle.
The allele and genotype frequencies in population remain constant from generation to generation when in the absence of evolutionary influences.
What is the Hardy-Weinburg Equation?
Frequency of Dominant allele= p
Frequency of Recessive allele= q
principle: p+q=1
Equation: p^2+2pq+q^2=1
Define gene pool.
All the alleles of all individuals in a population at one time.
Define allele frequency.
How common a specific allele is within a gene pool on a scale of 0 to 1.
No presence ——–> 100% presence
What assumptions are made when using the Hardy-Weinburg principle?
- Large population
- No migration
- No mutations
- No selection/selective pressures
- Random mating (allele cross)
What is the Chi Squared test for?
Chi-Square Test. Chi-square is a statistical test commonly used to compare observed data with data we would expect to obtain according to a specific hypothesis.
Used to compare allele ratios both observed and expected.
What does a small Chi Squared test mean?
If Chi Squared is smalle that the critical value then there is no significant difference between the expected and observed values.
Therefore there is a greater than 5% probability that the difference in results between the expected and observed values occurred by chance so there is no statistical difference in the expected and observed values.
What does a large or small Chi squared mean?
Small Chi Squared = Fits ratio expecting
Large Chi squared = Does not fit expected ratio.
From which phenotype can you always tell the genotype?
Recessive allele
Phenotypes expressed by homozygous recessive allele
