DNA and chromosomes

Question 1

describe viral and bacterial genomes

Answer 1

relatively small, single nucleic acid molecule, largely devoid of associated proteins

Question 2

dna histones

Answer 2

dna double helix is packaged by proteins called histones

Question 3

what are the selenoid ?

Answer 3

supercoiled arrangements of DNA in eukaryotic nuclear chromosomes produced by coiling the continous string of nucleosomes.

Question 4

what is the order of chromatin structure

Answer 4

• naked DNA structure
• nucleosomes
• selenoid
• chromatin fibre
• chromosomes

Question 5

describe features of euchromatin

Answer 5

• the histone is not methylated
• histone is acetylated
• active cells

Question 6

describe features of heterochromatin

Answer 6

• histones are methylated
• histones have a low degree of acetylation
  resting cells

Question 7

what is a chromosome

Answer 7

a single long DNA that contains a linear array of many genes

Question 8

what is a karyotype ?

Answer 8

arrangements of full chromosome set is called karyotype
chromosomes are paired with the homologue pair which are the same size shape and carry same gene

Question 9

what is the replication origin ?

Answer 9

nucleotide sequence at which replication starts

Question 10

describe what is a telomere and what is contains

Answer 10

telomeres form caps at the end of chromosomes = contain unique repetitive sequences

Question 11

why do telomeres shorten with each cell division ?

Answer 11

due to RNA polymerase and discontinous replication of the lagging strand of DNA affecting ageing