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Genetics ( It is the science of inheritance) (Mutations ( is any change,…
Genetics ( It is the science of inheritance)
Gene is the chemical basis of genetic inheritance which occurs in multiple forms known as
Alleles
Genotype
The type of allele that a single individual has are called genotype.
Phenotype
The expression of the alleles in the individual's size, shape, or metabolism is called Phenotype.
DNA ( It is deoxyribonucleic acid and carrier of genetic information)
Replication of DNA
Occurs in S phase of the cell cycle.
Step 1
DNA double helix unwinds.
Step 2
DNA helicase unzips DNA
Step 3
DNA polymerase helps in pairing up free nucleotides with exposed bases. Polymerase adds nucleotides to the 3' end of the growing nucleic acid.
Step 4
Weak hydrogen bonds form between complimentary bases.
Step 5
Covalent bonds form between adjacent nucleotides.
Step 6
Two identical daughter molecules are formed. Semi conservative replication occurs as each resulting double helix contains one new molecule and has conserved one old one.
Mutations ( is any change, however large or small , in DNA.)
Point mutation ( is in which a single base is converted to another base)
Deletion ( is when a piece of DNA is lost)
Insertion ( is when the extra DNA is added)
Inversion ( is when a piece of DNA becomes tangled and breaks, and during repair, it is put in backward as an inversion)
Causes of Mutation
Mutagen ( is something that causes Mutation)
Transposable mutations ( are responsible for insertion and delete mutations)
Effects of Mutations
An insertion mutation may cause the gene to code for protein so long that it cannot fold properly.
Mutations in promoter regions can completely inactivate a gene or cause it to be active at the wrong time or place.
Somatic mutations ( is when mutations happen in cells that never lead to sex cells)
Cross ( sexual reproduction between two individuals )
Monohybrid cross ( Only a single character is analyzed and studied)
Incomplete dominance in Monohybrid cross
Neither parental trait dominates the other, so the pair of alleles shows incomplete dominance.
Crossing heterozygotes
When a plant's own pollen is used to fertilize its own eggs, the cross is selfing.
Monohybrid crosses with complete dominance
Dominant allele is exposed and Recessive is not exposed.
Multiple alleles
Genes exist in many forms.
Heterozygous ( has two different alleles for the gene)
Dihybrid cross ( is one in which two genes are studied and analyzed)
Genes on separate chromosomes : Independent Assortment
Alleles of Genes on separate chromosomes move independently to alleles of another gene.
Linkage ( Two genes are said to be linked if they occur close together on a chromosome)
Recombinant chromosomes ( forms from a crossing over of a homologous chromosomes and recombination of alleles )
Homozyous (has two identical alleles for the gene)
Multiple Genes for One Character : Quantitative Trait Loci
Extremely complex crosses involves determination of what fraction of a particular phenotype is correlated with particular gene.
Maternal inheritance
Zygote receives all its plastid and mitochondrion genome from the maternal parent.
Lethal Alleles ( It's presence can kill the plants or Animals)
Multiple set of chromosomes (All plants with more than two set of chromosomes are polypoid.)
