Genes, DNA and chromosomes

Question 1

Compare the structure of DNA in eukaryotic cells and prokaryotic cells.

Answer 1

Eukaryotic DNA molecules are :
-very long
-linear
-associated w/ proteins called histones
Prokaryotic DNA molecules are:
-short
-circular
-not associated w/ histone

Question 2

How is the storage of DNA in the (…) and (…) organelles of eukaryotic cells similar to the storage of DNA in prokaryotes?

Answer 2

DNA contained in the chloroplasts and mitochondria of eukaryotes are:
-short
-circular
-not associated w/ protein

Question 3

@What is a gene?

Answer 3

A base sequence of DNA which codes for:
-a/a sequence of a polypeptide
-a functional RNA (including ribosomal RNA and tRNA )

Question 4

Describe the effect of a change in base sequence for an enzyme

Answer 4

-a gene is a base sequence which codes for a/a sequence of polypeptide
-a/a sequence in polypeptide forms primary structure of a protein
-the tertiary structure of a protein/enzyme is affected by the primary structure
-this change in the tertiary structure alters the shape of the active site, so an enzyme-substrate complex cannot form

Question 5

Locus def.

Answer 5

The fixed position which a gene occupies on a particular DNA molecule

Question 6

What is a triplet, and what does it code for?

Answer 6

-A sequence of three DNA bases
-codes for specific a/a ( whereas a chromosome codes for the a/a sequence of a polypeptide )

Question 7

What is a cell’s genome?

Answer 7

-complete set of genes in the cell

Question 8

What is a cell’s proteome?

Answer 8

-the full range of proteins that a cell can produce

Question 9

What does the genetic code being universal mean?

Answer 9

-the same specific base triplets code for the same a/a in all living things

Question 10

What does the genetic code being non-overlapping mean?

Answer 10

-each base triplet is read in sequence, separate from the base triplets before and after it i.e. base triplets don’t share bases - the code in none overlapping

Question 11

What does the genetic code being degenerate mean?

Answer 11

-Amino acids are coded for by more than one triplet

Question 12

In eukaryotes, much of the DNA does not code for what?

Answer 12

Polypeptides

Question 13

What is an example of eukaryotic, nuclear DNA which does not code for polypeptide?

Answer 13

-non-coding multiple repeats of bases between genes

Question 14

What is an exon?

Answer 14

-A DNA sequence within a gene which codes for amino acid sequences ( there are only some of these in a gene )

Question 15

What is an intron?

Answer 15

-Non-coding sequence separating exons, within a gene

Question 16

What happens introns during protein synthesis

Answer 16

they are removed