4 - Genetic info, variation, and relationships between organisms
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Describe how mRNA is produced:
transcription -helicase breaks H-bonds in DNA double helix -only one strand acts as a template, and RNA nucleotides are attracted to the exposed bases -complementary base pairing occurs, and RNA polymerase joins them by phosphodiester bonds -forms pre-mRNA, which is then spliced to remove introns
Describe the role of ATP in translation:
-ATP releases energy -so peptide bond forms between AA’s
Describe the importance of meiosis in sexually-reproducing organisms:
-meiosis halves the chromosome number (diploid to haploid) -at fertilisation, fusion of gametes restores the original chromosome number -introduces genetic variation through independent assortment and crossing over
Other than mutations, crossing over, and independent assortment, how is genetic variety within a species increased?
random fusion of gametes forms new allele combinations
Describe how crossing over occurs:
-homologous pairs of chromosomes associate and entangle their chromatids -some parts of the chromatids may break off and rejoin on the opposite chromosome at the chiasmata