chapter 8

Question 1

gene

Answer 1

a selection of DNA that contains a code for making of polypeptide and functional RNA

Question 2

allele

Answer 2

a different form of the same gene

Question 3

homologous pair of chromosome

Answer 3

pair of chromosome with the same genes but different alleles

Question 4

locus

Answer 4

location of particular gene on a chromosome

Question 5

start codon

Answer 5

at the start of every gene there are three bases which help initiate translation

Question 6

stop codon

Answer 6

causes ribosomes to detach and therefore stop translation

Question 7

genome

Answer 7

an organisms complete set of DNA in one cell

Question 8

proteome

Answer 8

the full range of proteins a cell can produce

Question 9

compare DNA in a eukaryote and a prokaryote

Answer 9

similarities:
- nucleotide structure is identical
- nucleotides joined by a phosphodiester bond
- DNA in mitochondria/ chloroplast have similar structure to DNA

contrast:
- eukaryotic DNA is longer
- eukaryotic DNA contains introns, prokaryotes doesn’t
- eukaryotic DNA is linear, prokaryotic is circular

Question 10

compare DNA in the nucleus and chloroplast

Answer 10

in chloroplast:
-DNA is shorter
-DNA is circular
-fewer genes
-not associated with proteins
- introns are absent

Question 11

features of the genetic code

Answer 11

• DEGENERATE:
  more than one codon/triplet codes for the same amino acid
  -UNIVERSAL:
  the same triplet codes for the same amino acids in all organisms
  -NON-OVERLAPING:
  each base is part of only one triplet
  -STOP+START CODONS
  -INTRONS+EXONS

Question 12

what is a codon

Answer 12

a triplet of bases on mRNA that codes for amino acids

Question 13

difference between exon and introns

Answer 13

exon- coding section of DNA
intron - non-coding section of DNA

Question 14

mRNA structure

Answer 14

mRNA is a single-stranded molecule
It is made up of a sugar-phosphate backbone and exposed unpaired bases
Uracil bases are present instead of thymine bases (which are found in DNA)

Question 15

tRNA structure

Answer 15

tRNA is a single-stranded molecule
It has a sugar-phosphate backbone
It has a folded shape
There are hydrogen bonds between some of the complementary bases
Amino acids bind to a specific region of the molecule
The specific anticodon found on the tRNA molecule is complementary to a specific codon on an mRNA molecule

Question 16

transcription

Answer 16

-The DNA helix unwinds to expose the bases to act as a
template.
-Only one chain of the DNA acts as a template.
-The unwinding is catalyzed by DNA helicase. DNA
helicase breaks the hydrogen bonds between bases.
-Free mRNA nucleotides in the nucleus align opposite
exposed complementary DNA bases.
-The enzyme RNA polymerase bonds together the RNA
nucleotides to create a new RNA polymer chain. One
entire gene is copied.

Question 17

translation

Answer 17

-mRNA attaches to a ribosome in the cytoplasm. The
ribosome attaches at the start codon.

-The tRNA molecule with the complementary
anticodon to the start codon aligns opposite the
mRNA, which is held in place by the ribosome.

-The ribosome will move along the mRNA molecule to
enable another complementary tRNA to attach to the
next codon on the mRNA.

-The two amino acids that have been delivered by the
tRNA molecule are joined by a peptide bond. This is
catalysed by an enzyme and requires ATP.

• ribosome reaches the stop codon at the end of the mRNA molecule. The stop codon does not code for an amino acid and therefore the ribosome detaches and translation ends.

Question 18

protein associated with DNA in a chromosome

Answer 18

histone

Question 19

non-coding base sequence

Answer 19

DNA that does not code for amino acid sequence
positioned between genes