R2 genetic organisation

Question 1

DNA can be negatively and positively supercoiled, which one is it in a cell that favours unwinding ?

Answer 1

negative

Question 2

Describe the arrangement on eukaryotic DNA

Answer 2

Eukaryotic DNA is packaged into chromatin within the membrane-bound nucleus.
- Eukaryotic supercoiled DNA is stabilised by nucleosomes (contains DNA wrapped around a histone protein), histones are the basic unit of the nucleosome
- Chromatin is tightly packed, coiled nucleosomes

Question 3

whats the difference between euchromatin and heterochromatin ?

Answer 3

euchromatin is less tightly packaged than heterochromatin

Question 4

what is the definition of a gene ?

Answer 4

a sequence of DNA nucleotide responsible for a trait or phenotype

Question 5

How many copies of a gene are in eukaryotes and prokaryotes ?

Answer 5

eukaryotes - 2, prokaryotes - 1

Question 6

what are plasmids ?

Answer 6

extrachromosomal pieces of DNA, containing non-essential genes like antibiotic resistance

Question 7

what is the chromosomal DNA called in a prokaryote ? What does it code for ?

Answer 7

nucleoid - codes for proteins involved in DNA replication, recombination, transcription and translation

Question 8

do prokaryotes undergo alternative splicing

Answer 8

No, only eukaryotes - allows multiple proteins to be made by one sequence.

prokaryotes have no introns or exons

Question 9

why dont prokaryotes have introns and exons ?

Answer 9

It would inhibit the coupled transcription and translation.

Question 10

what is a genome and what does it include

Answer 10

The entire genetic material of a cell or organism including mitochondrial DNA

Question 11

what is gene density and what is it measured in ?

Answer 11

how many genes are in 1 megabase (Mb) (1 million bases), measured in genes/Mb

Question 12

what is a pseudogene ?

Answer 12

a non-functional gene

Question 13

what is synteny ?

Answer 13

the comparison of two species’ genomes that are arranged into blocks to compare to the common ancestors. Blocks show the matching of a chromosome

Question 14

what is copy number variation (CNV) ?

Answer 14

increased or decreased copies of a gene number, the number of copies of a specific segment of DNA varies between individuals

Question 15

How do prokaryotes and eukaryotes compare on the DNA arrangement ?

Answer 15

prokaryotes - supercoiling, eukaryotes - nucleosomes and chromatin.

Question 16

what is the fundamental unit of a chromosome ?

Answer 16

nucleosome

Question 17

what is the fundamental unit of the nucleosome ?

Answer 17

histone proteins

Question 18

how do prokaryotes and eukaryotes compare on the gene level ?

Answer 18

prokaryotes - operons, single promoters for many genes, eukaryotes - exons and introns, individual promoters

Question 19

How do prokaryotes and eukaryotes compare on the chromosome level ?

Answer 19

prokaryotes - mostly circular, one copy of each gene, nucleoids, eukaryotes - linear, paired, two copies of each gene, membrane-bound nucleus

Question 20

how do prokaryotes and eukaryotes compare on the genome level

Answer 20

prokaryotes - most encodes for proteins, eukaryotes - 1% encodes for proteins, comparative genomics can be used to study the evolutionary differences