Inheritance Flashcards
Who created the concept of inheritance?
Gregor Mendel
What did Gregor Mendel study?
Peas
What did Gregor Mendel find in his studies?
That some traits are recessive and some are dominant
Define phenotype
A physical characteristic of an organism, which is determined by the organisms genotype as well as the environment.
Define genotype
A set of alleles possed for a particular gene or genes of an organism
When doing testing for inheritance what is good features and factors to have of the trial?
- Breed often and have lots of offspring
- Observable phenotypes
- Short lifecycle
- Produce statistically significant results
Define homozygous
If an individual contains two alleles that are coding for the same dominant or recessive trait (also known as pure breeding)
Define heterzygous
Individuals with one allele coding for the recessive trait and one allele coding for the dominant trait. Also known as hybrids)
What is complete dominance?
When a phenotype trait is completely dominant over the other trait
Why does complete dominance occur?
Enough protein being produced from a single allele for a particular phenotype, or two alleles coding for a dominant trait.
Define Dominant Trait
A trait that is expressed with a heterozygous genotype. Only a single copy of the allele is required for the traits expression
Deine Recessive Trait
Refers to a trait that is only expressed in a homozygous genotype.
Define Pure Breeding
An organism that contains two exact alleles and when crossed with it self or others like t, it will always produce an offspring with a phenotype the same.
Define Codominance
When both alleles in the genotype are expressed equally in the phenotype, resulting in both traits being exhibited
Define Incomplete Dominance
Two pure breeding parents that can have an offspring that have a blend of their parental phenotype
Define Dihybrid crosses
When two genes are crossed they can either be on the same chromosome or different
What will the test cross for a heterozygous individual result in reagrds to the ratio
1:1:1:1
When are alleles considered to be linked?
When they are on the same chromosome
Define alleles
Alternative forms of a gene
Define Chromosomes
Strand of DNA encoded of genes
Define Autosomal Recessive
A genetic condition that appears only in individuals who have recieved two copies of an autosomal gene, one from each parent
Define Autosomal Dominant
Requires only one of the affected trait in the genotype for it to be expressed in the phenotype
Define a gene
Short section of DNA that codes for a specific protein
Where are genes located?
Chromosomes
what do alleles code for?
traits
Define chromosome
One long DNA molecule surrounded by many histone proteins
Why are DNA supercoiled chromatin?
In order to fit within a cell
Why is the centromere important?
Helps anchor the chromosome to spindle fibres during the cell division process of miitosis and meiosis.
Define autosomal chromosomes
Form homologous pairs that do not differ between sexes
Define sex chromosomes
Determine the sex of an organism
Define somatic cells
They are body cells
What are egg or sperm cells?
Haploid
What are somatic cells?
Diploidd
Define hemizygous
One gene is deleted
What are lethal genotypes
In some cases homozygous genotypes can be lethal,
will produce a ratio of 2:1
will be double dominant
Define pedigree
A family tree that shows the frequency and occurence of a particular phenotype over many generations
what is polygenetic inheritance
Chracteristic is controlled by more than one gene
What variation are polygenic inhertiance
Continous varitation
Discontinous Variation
When members of a population can be grouped into a few discrete and non-overlapping classes of a trait
what is discontinous variation caused by?
A single gene monogenic
Continous variation
characteristics which exhibit a continous range of phenotypes across a population
what is continous variation caused by?
polygenes
What are charactersitics of an autosomal dominant pedigree?
- Both males and females can equally be affected
- No gender bias
- everyone will have an effected parent
What are charactersitics of an autosomal recessive pedigree?
- both males and females will be equally affected
- can skip a generation
Pedigree: X linked dominant
An affected male will pass the trait to all his daughters
Affected person has at least one affected parent
X linked recessive pedigree
Father of affected female must show trait
