GENETIC CODE, GENES, GENOMIC

Question 1

WHAT ARE THE 4 MOST IMPORTANT ASPECTS OF DNA?

Answer 1

1. Lasting and stable
2. Capability of change during evolution
3. Capability of reproducing
4. Easily available for realisation (expression)

Question 2

WHAT IS GENETIC INFORMATION?

Answer 2

internal information of the cell passed on from parental cell to daughter cell

Question 3

WHAT IS A GENEOPHORE?
GIVE SOME EXAMPLES.

Answer 3

it is a carrier of genetic information
-prokaryotes and eukaryotes = DNA
-viruses = RNA
-cytoplasm geneophore = plasmids (not vital for the functioning of the cell)

Question 4

WHAT IS THE FUNCTION OF CHROMOSOMES?

Answer 4

carry large amounts of DNA

Question 5

WHAT IS THE GENETIC CODE?

Answer 5

RULE = base sequence determines which corresponding amino acid is added
-genetic information is saved as a sequence of individual bases and codes the sequence of amino acids of the protein
-universal

Question 6

WHAT IS THE GENETIC CODE BASED ON?

Answer 6

triplets

Question 7

WHAT IS THE CODON?

Answer 7

a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule

Question 8

HOW MANY COMBINATIONS OF TRIPLETS ARE THERE?

Answer 8

4 bases (A, G, C, T) → 64 (4^3) combinations of triplets (codons)

Question 9

HOW MANY PROTEOIGENIC AMINO ACIDS ARE THERE?

Answer 9

20 (21 selenocysteine)

Question 10

WHAT DOES THE GENETIC CODE BEING REDUNANT MEAN?
IS IT GOOD?

Answer 10

the genetic code is redundant as there are more available combinations of triplets than there are coded amino acids
-this is good as it means that there is a lower chance of mistakes occurring

Question 11

WHAT ARE THE STOP CODONS?

Answer 11

UAA, UAG, UGA

Question 12

WHAT IS THE INITIATION CODON?

Answer 12

AUG = Methionine

Question 13

WHAT IS DEGENERACY?

Answer 13

once protein is made one cannot get the amino acid sequence from it

Question 14

WHAT IS MEANT BY THE READING FRAME?

Answer 14

there are 3 possible ways of reading the sequence of triplets

Question 15

WHAT IS A GENE?

Answer 15

functional segment of DNA which which encodes a single polypeptide chain or a single strand of RNA

Question 16

WHAT IS A GENE LOCUS?

Answer 16

the position of the gene on the chromosome or DNA sequence

Question 17

WHAT IS AN EXON?

Answer 17

coding section

Question 18

WHAT IS AN INTRON?

Answer 18

non coding section

Question 19

WHAT ARE PROMOTORS?

Answer 19

regulatory regions of genes
-specific genes regulating gene expression bind to them
-not transcribed and do not encode proteins or RNA
-lay infront of their own gene and contain introns + exons
-binding site is recognised by RNA polymerase and transcription begins

Question 20

HOW ARE GENES ARRANGED IN DNA?

Answer 20

anti-parallel

Question 21

WHAT IS THE FUNCTION OF STRUCTURAL GENES?

Answer 21

they encode proteins

Question 22

WHAT IS THE FUNCTION OF RNA GENES?

Answer 22

encode all types of RNA, except mRNA

Question 23

HOW MANY BASE PAIRS DOES THE HUMAN GENOME CONSIST OF?

Answer 23

3x10^4

Question 24

WHAT IS THE STRUCTURE OF THE PROKARYOTIC GENE?

Answer 24

-only uninterrupted DNA sequence which encodes corresponding polypeptide chain
-ORFs are often grouped into a polycistronic operon under the control of a shared set of regulatory sequences. These ORFs are all transcribed onto the same mRNA and so
are co-regulated and often serve related functions, only possible in prokaryotes because their transcription and translation take place at
the same time and in the same subcellular location
-Each ORF typically has its own ribosome
binding site (RBS) so that ribosomes simultaneously translate ORFs on the same mRNA
-The operator sequence next to the promoter is the main regulatory element in prokaryotes. Repressor proteins bound to the operator sequence physically obstructs the RNA polymerase enzyme, preventing transcription
(ORF = open reading frame)

Question 25

WHAT IS THE STRUCTURE OF THE EUKARYOTIC GENE?

Answer 25

-more regulatory elements to control gene expression compared to prokaryotes
-exon and intron regions
-post-transcriptional modification of pre-mRNAs to produce mature mRNA ready for translation into protein
-Eukaryotic post-transcriptional processing also adds a 5’ cap to the start of the mRNA and
a poly-adenosine tail to the end of the mRNA. These additions stabilise the mRNA and direct its transport from the nucleus to the cytoplasm

Question 26

GIVE EXAMPLES OF NON-GENE DNA

Answer 26

1: REGULATORY GENES: involved in the regulation of gene expression

2: REPETITIVE SEQUENCE: short repeating sequence of unexplained origin
- highly variable and unique for each individual, are therefore used in DNA fingerprinting

3: MOBILE ELEMENTS: do not have a stable position within the DNA sequence
-transposons

4: PSEUDOGENES: genes which lost their function due to the accumulation of mutations

Question 27

WHAT IS A RETROTRANSPOSON?

Answer 27

A transposition of sequences in DNA that does not originate in the DNA but rather in an mRNA, that is transcribed back into the genomic DNA by reverse transcription
(COPY AND PASTE MECHANISM)

Question 28

WHAT IS THE GENOME?

Answer 28

the complete set of DNA in a cell

Question 29

WHERE IS THE GENOME OF THE PROKARYOTIC CELL?

Answer 29

chromosome and possible plasmids

Question 30

WHERE IS THE GENOME OF THE EUKARYOTIC CELL?

Answer 30

nuclear chromosomes + mitochondrial chromosomes + chloroplast chromosomes (in plants)
-possible plasmids

Question 31

HOW MANY PROTEIN CODING GENES DOES THE HUMAN GENOME CONSIST OF?

Answer 31

HAPLOID SET = 20 000 - 25 000

Question 32

T/F: THE NUMBER OF GENES IN AN ORGANISM CORRELATES WITH THE SIZE OF THE GENOME AND ITS COMPLEXITY

Answer 32

false

Question 33

HOW MANY PROTEIN CODING GENES DOES ECOLI K12 CONSIST OF?

Answer 33

4,315