3: Genes and Genomes

Question 1

Describe the main differences between prokaryotic and eukaryotic genomes and genes

Answer 1

• Bacteria are known to have a relatively small genome
• Bacterial genome is full of protein coding genes (no introns)
• Bacterial genome is linear, whereas eukaryotic genome is circular

Question 2

Know the structure of protein coding genes

Answer 2

Draw out structure

look throughs slides

Question 3

Describe the properties of highly repetitive sequences

Answer 3

• Short regions of highly repetitive DNA -also known as short tandem repeats or satellite DNA
• The difference in how many of the repeats is present in the length of the region is the basis for DNA fingerprinting
• Makes up ~3% of the genome

Question 4

What are moderately repetitive sequences?

Answer 4

The presence of many copies of sequences derived from transposons are responsible for much of the variation in genome sizes

Makes up ~45% of the human genome

Question 5

How much of the genome encodes proteins?

Answer 5

Only ~1.2% of genome encodes protein

The human genome contains ~20,000 genes

Question 6

draw the sequence of pre-mRNA –> mRNA: cap and polyA tail

Answer 6

slides

insert picture later

Question 7

How much of the genome is transcribed?

Answer 7

~60% of the genome is transcribed and most of this does not encode proteins (called non-coding RNA)

Question 8

What are some examples of non-coding RNA?

Answer 8

• tRNA
• ribosomal RNA
• microRNA
• Long non-coding RNA

Question 9

Breifly describe alternative splicing

Answer 9

• Carried out by a protein complex called the spliceosome
• Alternative splicing is the major mechanism to increase protein diversity (i.e. one gene encodes more than one protein)

Question 10

Why do we have chromosomes?

Answer 10

Cells have a lot of DNA that has to be fitted into a very small volume. But the cell needs access to it.

Solution:
Chromosomes=DNA + associated proteins
• Compacts DNA
• Protect DNA from damage
• Ensures replicated DNA is properly segregated
Provides an overall organisation to DNA which facilitates recombination, and gene expression

Question 11

What does a nucleosome consist of?

Answer 11

DNA + histone protein

Question 12

Describe how DNA is packaged

Answer 12

slides