Rec Reading Mol Cell Bio Chapter 1 Cells and Genomes

Question 1

Eukaryote genomes are bigger than bacteria because

Answer 1

• more DNA = larger cell size, larger predator

- accumulation of selfish genes that insert themselves at multiple sites on the genome

Question 2

Eukaryotes also have non coding DNA - introns that

Answer 2

• can have important functions in the expression of adjacent genes
• this sophisticated gene regulation is crucial for the formation of complex multicellular organisms

Question 3

Evidence for introns being ‘junk genes’

Answer 3

• The puffer fish has a quarter of the nucleotide pairs of the zebrafish, even though they have similar numbers of genes

Question 4

C. elegans

Answer 4

eel worm
life cycle of a few days
ability to survive in a freezer in suspended animation
simple body plan
precise development from fertilized egg to adult worm with exactly 959 cells
minutely detailed description of sequence of cell division and differentiation - strict and predictable
genome = 97 million nucleotide pairs, 19000 proteins
conservation of biological cell processes make good model

Question 5

Drosophila melanogaster

Answer 5

fruit fly
oldest model organism - proved that genes were carried on chromosomes
giant chromosomes with bands - easily visualized
very important in observing effects from genotype to phenotype - drosophila genome was sequenced, vertebrate genes found to have high homology
9 days from egg to adult
cheap
small genome - 170 million nps, 14000 proteins
little gene duplication or redundancy

Question 6

Mus musculus

Answer 6

mammals have 3/4 times as many genes as drosophila
mammals are a uniform group genetically - many orthologs
small, rapid breeder
foremost model for vertebrate genetics
effects of gene mutation can be seen in all different cells of the body

Question 7

Gene redundancy

Answer 7

most genes in vertebrates exist in several versions that were once identical
these related genes are functionally interchangeable and called ‘redundant genes’
makes detailed genetic analysis very hard
why drosophila is good!

Question 8

Genome duplication has allowed the

Answer 8

development of more complex life forms
mutant genes can diverge
ADDITIONAL GENES ALLOW FOR INCREASED COMPLEXITY AND SOPHISTICATION

Question 9

Ortholog

Answer 9

same gene/protein in different species

Question 10

Paralog

Answer 10

same genes/proteins within the genome of a species

Question 11

Homolog

Answer 11

divergent evolutionary relationship between genes and proteins based on their sequence similarity/identity

orthologs and paralogs are subcategories of homologs; they are types of homologs