4 - Genetic info, variation, and relationships between organisms

Question 1

Describe how mRNA is produced:

Answer 1

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

Question 2

Describe the role of ATP in translation:

Answer 2

-ATP releases energy
-so peptide bond forms between AA’s

Question 3

Describe the importance of meiosis in sexually-reproducing organisms:

Answer 3

-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

Question 4

Other than mutations, crossing over, and independent assortment, how is genetic variety within a species increased?

Answer 4

random fusion of gametes forms new allele combinations

Question 5

Describe how crossing over occurs:

Answer 5

-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