DNA AND CHROMOSOMES

Question 1

What is DNA composed of ?

Answer 1

2 polynucleotide chains twisted around each other in a double helix

Question 2

what is the backbone of DNA composed of ?

Answer 2

pentosephosphate units ( which is why the DNA has a negative charge )

Question 3

what does the 5’ end usually have ?

Answer 3

a phosphate group on the 5 carbon of its terminal sugar

Question 4

what does the 3’ usually have?

Answer 4

a hydroxyl group on the 3 carbon of its terminal sugar

Question 5

what links the nucleotides of the DNA ?

Answer 5

phosphodiester bonds

Question 6

how do the 4 nitrogen bases bind together ?

Answer 6

adenine binds to thymine by double hydrogen bond while cytosine binds to guanine with triple hydrogen bonds

Question 7

what sugar does DNA contain and what sugar does RNA contain

Answer 7

deoxyribose

ribose

Question 8

what are the 2 categories of nitrogenous bases?

Answer 8

purines ( double rings )

adenine
guanina

pyrimidines (single rings )

thymine
cytosine
uracil

Question 9

whaat takes the place of thymine in RNA?

Answer 9

uracil

Question 10

how is the double helix structure of the DNA maintained /?

Answer 10

is maintained by intra strand base stacking interactions

Question 11

what are some causes of DNA denaturation

Answer 11

high temperature , low salt and high pH

Question 12

what is a gene ?

Answer 12

sequence of nucleotide that encodes of the synthesis of gene products during gene expression

Question 13

what does a chromosome refer to?

Answer 13

level of packaging from the DNA molecule to the chromosomal structure. linear DNA is packed into chromosome which is commonly called the packaging material .

Question 14

what does diploid cell mean?

Answer 14

it means that the cell contains 2 sets of chromosome . 1 inherited from each parent .they contain 23 pairs of chromosomes . these 2 sets of chromosomes are referred too as homologous chromosomes

Question 15

what is a haploid cell?

Answer 15

gametic chromosome that is found in sperm and egg and contain single copy of each chromosome

Question 16

what is chromatin ?

Answer 16

DNA wrapped around histones

Question 17

what is the structural entity of chromatin called?(single histone wrapped with DNA )

Answer 17

nucleosomes

Question 18

what are the parts of a chromosome ?

Answer 18

short arm (P arm)
long arm (Q arm)
centromere 
telomere
origin of replication (multiple)
sister chromatids

Question 19

when can the x structure of chromosome be seen?

Answer 19

during metaphase of cell division when chromosomes duplicate and are joined by centromere

Question 20

what is the centromere ?

Answer 20

specialized DNA sequence (repetitive) .

Question 21

what does the telomere do?

Answer 21

it protects the ends of chromosomes from deterioration and prevents the fusion of neighboring chromosome .

Question 22

what are the 2 major categories of chromatin and how do they differ?

Answer 22

euchromatin
: less condensed regions of chromosomes

transcriptionally active

regions where 30 nm fibers forms radical loop domains

heterochromatin : tightly compacted regions of chromosomes

transcriptionally inactive

radical domains compacted even further