DNA, genes and chromosomes

Question 1

what is a nucleotide formed from

Answer 1

• phosphate group
• pentose sugar
• nitrogenous base

Question 1

How do bases in nucleic acids pair with each other

Answer 1

• complementary base pairing through hydrogen bonding
• Adenine always pairs with Thymine ( T replaced by Uracil in RNA)
• Guanine always pairs with Cytosine

Question 2

similarities in structure of prokaryotic DNA and eukaryotic DNA

Answer 2

similarities:

• nucleotide structure is identical in both
• nucleotides are joined by phosphodiester bonds in both

Question 3

How is the structure of DNA related to its function

Answer 3

sugar - phosphate backbone gives strength

(coiling gives) compact shape

long molecule stores large amount of information

double stranded helix prevents code being corrupted

chains held together by weak hydrogen bonds; chains can split for replication / transcription

Question 4

differences in structure of prokaryotic DNA and eukaryotic DNA

Answer 4

differences:

• eukaryotic DNA is longer
• eukaryotic DNA = linear , prokaryotic DNA = circular
• introns only in eukaryotic DNA
• eukaryotic DNA associated with proteins prokaryotic DNA not

Question 5

what are multiple repeats in DNA

Answer 5

short base sequences between genes repeated over and over again.

Question 6

similarities in structure of RNA and DNA

Answer 6

• both contain nitrogenous bases
• both have a phosphate group

Question 7

differences in structure of RNA to DNA

Answer 7

• DNA contains deoxyribose, RNA contains ribose
• the base Thymine in DNA is replaced with Uracil in RNA
• mRNA and tRNA are single stranded in comparison to double stranded DNA

Question 8

what is a homologous pair of chromosomes

Answer 8

• a pair of chromosomes which carry the same gene in the same loci but not necessarily the same allele

Question 9

what is a base triplet

Answer 9

a sequence of three nucleotide bases that code for a specific amino acid

Question 10

what is an allele

Answer 10

different forms of a gene

Question 11

describe 3 features of the genetic code

Answer 11

degenerate triplet code - some amino acids are coded for by more than one triplet

non overlapping code - each base is only read once as part of a specific triplet

‘universal’ code - the same triplets code for the same amino acids in all organisms

Question 12

what is a genome and proteome

Answer 12

genome-complete set of genes in a cell.

proteome-full range of proteins that a cell is able to produce.

Question 13

what is the diploid number

Answer 13

the total number of chromosomes in a normal body cell ( in humans it’s 46)