ORGANISATION OF GENETIC INFO

Question 1

LEARNING OUTCOMES

Answer 1

• understand DNA packaging in cells
• recognise structural differences in prokaryotic and eukaryotic genomes
• understand chromosomal organisation in cells
• understand how genes are arranged and organised.

Question 2

Prokaryotic DNA packaging

Answer 2

DNA STRUCTURE - double helix compacted due to supercoiling - a property of DNA that is positive or negative

positive - same direction as helix

• negative supercoiling - opposite direction - is common and helps with DNA unwinding for replication, transcription and recombination

Question 3

eukaryotic DNA packaging

Answer 3

supercoiled DNA stabilised by nucleosomes which contain DNA wrapped around histone proteins
chromatin consists of tightly packed coiled nucleosomes

Question 4

chromatin regions

Answer 4

euchromatin - least condensed and rich in genes = more accessible

heterochromatin - most condensed contains non coding DNA and few genes

Question 5

gene

Answer 5

sequence DNA nucleotides that determine a trait or phenotype

Question 6

genes in prokaryotes

Answer 6

have only one copy of each gene and genes in clusters that are controlled by same promoter, likely genes that are involved in similar/same metabolic processes

LAC OPERON = several genes involved in lactose uptake, all controlled by same promoter and expressed at same time.

Question 7

plasmids in prokaryotes

Answer 7

extrachromosomal DNA in prokaryotes that carry non essential genes like ones for antibiotic resistance

can be transferred

Question 8

eukaryotic gene organisation

Answer 8

individual genes have own promoters

exons and introns in genes

introns allow for alternative splicing of mRNA resulting in different proteins sequences and structures

Question 9

prokaryotes

Answer 9

Circular chromosomes, no membrane-bound nucleus.
Nucleoid: Region where DNA and associated proteins are concentrated.

Question 10

eukaryotes

Answer 10

Linear chromosomes present in pairs (homologues).

Karyotyping is used to stain and identify chromosome pairs.

Homologous chromosomes consist of two sister chromatids joined at the centromere.

Chromosomes condense during prophase and are loosely packed during interphase.

Chromosome territories are defined areas in the nucleus.

Question 11

genome

Answer 11

complete set of genetic material in organisms

prokaryotic - small genome and genes close together

eukaryotic - large genome but only 1% encodes proteins

Question 12

comparative genomics

Answer 12

• Comparing the organisation of human genome with other species to see how species evolutionarily diverged.

The genome of 2 species can be arranged into blocks where the order of genes is the same as their most recent ancestor - called a synteny