Topic 4 - Genetic information

Question 1

What are the properties of eukaryotic DNA ?

Answer 1

DNA molecules are very long, linear and compacted into chromosomes by histoness.

Question 2

What are properties of eukaryotic mitochondria and chloroplast DNA ?

DNA, Genes and Chromosomes

Answer 2

Shorter, circular DNA molecules with no histone proteins.

Question 3

What are the properties of prokaryotic DNA ?

DNA, Genes and Chromosomes

Answer 3

DNA molecules (chromosomes) are circular and shorter with no histone proteins associated.

Question 4

What is a gene ?

DNA, Genes and Chromosomes

Answer 4

A sequence of bases that code for an amino acid or a functional RNA.

Question 5

What determines the order of amino acids in a polypeptide ?

DNA, Genes and Chromosomes

Answer 5

The order of bases in a gene.

Question 6

What is a triplet ?

DNA, Genes and Chromosomes

Answer 6

3 bases in a gene which code for an amino acid.

Question 7

What do introns code for ?

DNA, Genes and Chromosomes

Answer 7

Functional RNA
e.g. tRNA and rRNA.

Question 8

What is a cell’s genome ?

DNA, Genes and Chromosomes

Answer 8

The complete set of genes in a cell.

Question 9

What is a cell’s proteome ?

DNA, Genes and Chromosomes

Answer 9

The full range of proteins that the cell is able to produce.

Question 10

How many genes code for 1 polypeptide ?

DNA, Genes and Chromosomes

Answer 10

One gene codes for one mRNA molecule, which codes for one polypeptide.

Question 11

What are introns ?

DNA, Genes and Chromosomes

Answer 11

Sections of a gene that dont code for amino acids, instead they code for functional RNA.

Question 12

What are exons ?

DNA, Genes and Chromosomes

Answer 12

All of the parts of a gene which code for a specific order of amino acids.

Question 13

What happens to introns during protein synthesis ?

DNA, Genes and Chromosomes

Answer 13

They’re removed so they dont effect the order of amino acids.

Question 14

What are non coding repeats ?

DNA, Genes and Chromosomes

Answer 14

regions of multiple repeats that do not code for amino acids. They are located between genes.

Question 15

What are alleles ?

DNA, Genes and Chromosomes

Answer 15

Different forms of a gene

Question 16

How do alleles form slightly different versions of the same polypeptide ?

DNA, Genes and Chromosomes

Answer 16

The order of bases in each allele is slightly different

Question 17

How many chromosomes does a eukaryotic nucleus have ?

DNA, Genes and Chromosomes

Answer 17

23 pairs, 46 in total

Question 18

What are homologous pairs of chromsomes ?

DNA, Genes and Chromosomes

Answer 18

• pairs of matching chromosomes, they have the same genes but they could have different alleles. Alleles coding for the same charactersistic will be found at a same fixed potiton (locus) on each chromosome in the pair.
• An example is the gene that determines blood type exists as one of 3 alleles, type O, A and B.

Question 19

What is a locus ?

DNA, Genes and Chromosomes

Answer 19

The same fixed postiton where alleles cpding for the same characteristsic are found.

Question 20

What is messsenger RNA ?

RNA and Protein Synthesis

Answer 20

It is made during transcription, it carries the genetic code from DNA to the ribosomes where it is used to make proteins during translation. mRNA is a single polynucleotide strand.

Question 21

What is a codon ?

RNA and protein synthesis

Answer 21

3 bases in a mRNA polynucleotide

Question 22

What is transfer RNA ?

RNA and Protein Synthesis

Answer 22

• tRNA is involved in translation.
• It carries amino acids that are used to make porteins to the ribosomes.
• It is a songle polynucleotide strand thats folded into a clover shape.
• Hydrogen bonds between specific base pairs hold the molecules in this shape.
• Every tRNA molecule has a specific sequence of 3 bases at one end called an anticodon.
• The other end is an amino acid binding site.

Question 23

What is an anticodon ?

RNA and Protein Synthesis

Answer 23

a sequence of 3 specific bases at one end of a tRNA molecule.

Question 24

Name the first stage of protein synthesis

RNA and Protein Synthesis

Answer 24

Transcription

Question 25

Describe what happens during transcription RNA and Protein Synthesis

Answer 25

1. RNA polmerase attaches to the DNA molecule at the beginning of a gene. 2. The hydogen bonds between the complimentary base pairs of the double helix are broken down by DNA helicase which is attached to RNA polymerase. This separates the DNA molecule, uncoiling, and exposing the bases. 3. RNA polymerase lines up free RNA nucleotides alongside te exposed DNA bases on the template strand. Specific, complimentary base pairing occurs casuing a complimentary copy of the DNA strand to be made, however as it is RNA, uracil is in place of Thymine. 4. RNA polymerase joins the nucleotides by phosphodiester bonds and an mRNA molecule is formed. 5. When RNA polymerase reaches a stop signal, the mRNA detaches from the DNA. 6. pre- mRNA is spliced to remove the introns and connect exons, forming an mRNA stranf which leaves the nuceus through a nuclear pore.

Question 26

What is the last stage of protein synthesis? RNA and Protein Synthesis

Answer 26

Translation

Question 27

Describe what happens during translation. RNA and Protein Synthesis

Answer 27

1. mRNA attaches to a ribosome. 2. A tRNA molecule with an anticodon complimentary to the mRNA’s first codon attaches itself to the mrna by specific complimentary base pairing. 3. This tRNA molecule contains an amino acid. ATP provides energy needed for the bond between the tRNA and the amino acid to form. 4. A second tRNA molecule attaches to the second codon in the same way. 5. The two amino acids join by peptide bonds and the first tRNA molecule moves away, leaving the amino acid behind. This process continues until there is a stop signal on the mrna strand, producing a polypeptide chin. 6. The polypeptide chain moves away from the ribosome.

Question 28

Where does translation take place ? ##Footnote RNA and protein synthesis

Answer 28

Ribosome

Question 29

Where does transcription take place ? ##Footnote RNA and protein synthesis

Answer 29

Nucleus

Question 30

What is the genetic code ? ##Footnote The genetic code

Answer 30

The sequence of codons in mRNA which code for specific amino acids.

Question 31

What three properties does the genetic code have ? ##Footnote The genetic code

Answer 31

* It is non overlapping - codons do not share bases * It is degenerate - some amino acids can be coded for by more than one codon * It is universal - the same codon will code for the same specific amino acid in all living things