topic 4- DNA, Genes, Chromosomes

Question 1

What is a gene?

Answer 1

A base sequence of DNA which codes for the amino acid sequence of a polypeptide and functional RNA.

Question 2

What is a locus?

Answer 2

The fixed position of a particular gene on a chromosome.

Question 3

What is an allele?

Answer 3

Different version of the same gene.

Question 4

What is a chromosome?

Answer 4

How DNA is stored. In eukaryotic cell’s nucleus DNA is stored a chromosomes.

Question 5

What is a homologous pair?

Answer 5

a pair of chromosomes with the same size and genes, but may have different alleles.

Question 6

Describe the structure of DNA molecules in eukaryotes.

Answer 6

Long, linear, and associated with proteins called histones.

Question 7

How is DNA stored in eukaryotic cells to fit in the nucleus?

Answer 7

To tightly coil the DNA to fit in the nucleus as chromosomes, the DNA is tightly wound around proteins called histones.

Question 8

Describe the structure of DNA molecules in prokaryotes.

Answer 8

Prokaryotes carry DNA also in chromosomes, but the DNA molecules are short, circular and not associated with proteins, instead it supercoils to fit into the the cell free in the cytoplasm.

Question 9

Describe the structure of DNA molecules in chloroplast and mitochondria.

Answer 9

The DNA is similar to prokaryotic DNA, in that it is short, circular and not histone bound.

Question 10

What are the 3 features of the genetic code?

Answer 10

Degenerate
Universal
Non overlapping

Question 11

What are stop codons?

Answer 11

The final triplet of bases on the end of the mRNA that do no code for an amino acids. It used to tell the cell when to stop production of a protein.

Question 12

What are start codons?

Answer 12

First triplet of bases at the start of the mRNA which tell the cell when to start protein production, but these code for a specific amino acid.

Question 13

What is meant by the genetic code being degenerate?

Answer 13

Some amino acids are coded for by more than one triplet of bases, as the combinations of 64 possible triplets is more than is needed to code for 20 amino acids.

Question 14

What is the advantage of the genetic code being degenerate?

Answer 14

If there was a point mutation, even though the triplet of bases will be, it may still code for the same amino acids therefore no effect.

Question 15

What is meant by the genetic code being universal?

Answer 15

The same triplet of bases code for the same amino acids in all organism.

Question 16

What is an advantage of the genetic code being universal?

Answer 16

It means genetic engineering is possible between different organisms. e.g. inserting human gene for insulin into bacteria

Question 17

What is meant by the genetic code being non-overlapping?

Answer 17

Each bases in a gene is only part of one triplet of bases that code for an amino acid. Therefore each triplet of bases is read as a discrete unit.

Question 18

What is an advantage of the genetic code being non-overlapping?

Answer 18

This is an advantage because if there was a point mutation it will only affect one triplet of bases and therefore one amino acids.

Question 19

What are introns?

Answer 19

Sections of DNA which do not code of amino acids and therefore polypeptide chains.

Question 20

Where are introns found?

Answer 20

Eukaryotic cell’s DNA.

Question 21

When are introns removed, and why?

Answer 21

They are removed during protein synthesis so it doesn’t affect the amino acid order.

Question 22

Which type of DNA does not have introns?

Answer 22

Prokaryotic DNA.

Question 23

What are exons?

Answer 23

The sequence of bases which fo code for amino acids.