Genetic variation essay | Life Science Grade 12

Genetic variation essay

Describe different stages of meiosis and mutations that contribute to genetic variation and name two genetic disorders you have studied

Meiosis

❖ Prophase 1 crossing over occurs
❖ Non-sister chromatids overlap at point called chiasma
❖ Genetic material are exchanged leading to genetic variation
❖ Metaphase 1
❖ Independent assortment of paired homologous chromosome
❖ So chromosomes separate randomly
❖ Resulting in new combination of characteristics

Mutations
❖ Gene mutations(point and frame shift) occurs
❖ Resulting in the change of sequence of Nitrogenous base
❖ Chromosomal aberration occurs
❖ Resulting in the change if chromosome
❖ Which will form an abnormal organ
❖ Mutations that occur in sex cells
❖ Are inherited by the subsequent generation
❖ Creating new traits

Genetic disorders
❖ Hemophilia
❖ The inability of blood clotting caused by a recessive allele
❖ Down syndrome
❖ Due to extra copy of chromosome 21
❖ As a result of non-disjunction during

GENETIC VARIATION AND GENETIC DISORDERS
Describe how a change in sequence of DNA nitrogenous bases can lead to the formation of a different protein and how that lead to altered traits in two genetic disorders you have studied. Also describe three other sources of variation

Changes in different protein
❖ Altered nucleotide bases
❖ May cause the DNA structure to change
❖ That will produce mRNA
❖ With a different code
❖ During Transcription
❖ Resulting in usage of different tRNA
❖ To pick-up a different amino acid
❖ The sequence of amino acids will change
❖ Leading to formation of a different protein
❖ Thus leading to genetic disorders

Genetic disorders
❖ Haemophilia
❖ Blood don’t clot
❖ Due to unproduced protein for blood clotting
❖ Colour blindness
❖ The person can’t differentiate between different colours
❖ Due to gene mutations
❖ Which caused the absence of necessary protein

Variation sources
❖ Crossing over*
❖ During prophase 1 of meiosis chromatids overlap
❖ Genetic material is exchanged
❖ Each gamete formed has mixture of parental genes
❖ Random arrangement of chromosomes at equator
❖ Each pair of homologous chromosomes align either way at equator
❖ Independent assortment
❖ Resulting in mixture of parental chromosomes
❖ Random fertilization
❖ Fertilization between different ova and sperm cell brings a out
different offspring
❖ RANDOM MATING
❖ Mating between organisms in a species