biological molecules: DNA replication and the genetic code

Question 1

DNA replication

Answer 1

when a cell prepares to divide, the 2 strands of DNA double helix seperate and each strand serves as a template for the creation of a new double-stranded DNA molecule.
the complementary base rule pairings ensure each strands are identical to the original

Question 2

semi - conservative replication

Answer 2

for DNA to replicate the double helix structure has to unwind and then seperate into 2 strands so the hydrogen bonds holding the bases together must be broken.
free dna nucleotides will then pair with their complementary bases which have been exposed as the strands seperate.
hydrogen bonds are formed between them
nucleotides join to adjacent nucleotides to form phosphodiester bonds
2 molecules of dna are produced one is old and one is new

Question 3

DNA helicase

Answer 3

catalyses hydrogen bonds between complementary bases which have pairings, unwinding and seperating the 2 strands of DNA

Question 4

DNA polymerase

Answer 4

catalyses formation of phosphodiester bonds between the nucleotides

Question 5

leading strand

Answer 5

continuously replicated as the strands unzip cause dna polymerase travels in the 3’ to 5’ direction

Question 6

okazaki fragments

Answer 6

dna polymerase has to wait cause its unzipped from 5’ end
which means dna is produced in sections called okazaki fragments
lagging strand

Question 7

mutation

Answer 7

sequences of bases arent always matched correctly
these errors occur spontaneously and lead to a change in the sequence of bases

Question 8

genetic code

Answer 8

The order of bases on DNA is called the genetic code which consists of triplets of bases,
each triplet of bases codes for a particular amino acids and is known as a codon. The amino
acids are then joined together by peptide bonds and form a polypeptide chain. Therefore, a
gene is a sequence of bases on a DNA molecule coding for a sequence of amino acids in a
polypeptide chain. However, not all the genome codes for proteins – the non-coding sections
of DNA are called introns and the coding regions are called exons.

Question 9

features of genetic code

Answer 9

The genetic code is non-overlapping meaning that each triplet is only read once and
triplets don’t share any bases.
Genetic code is also degenerate meaning that more than one triplet codes for the
same amino acids, this chance of mutations
A change in the base sequence of DNA may alter the amino acid sequence and the
protein therefore it can have various effects.

Question 10

types of mutations

Answer 10

Some mutations are harmful such as the
mutation which leads to production of sticky mucus and causes cystic fibrosis or
sickle cell anaemia in which a mutated form of haemoglobin distorts the shape of red
blood cells

Question 11

types of mutations

Answer 11

Some mutations are harmful such as the
mutation which leads to production of sticky mucus and causes cystic fibrosis or
sickle cell anaemia in which a mutated form of haemoglobin distorts the shape of red
blood cells