Introduction

Question 1

In humans, like in other organisms, ____ is the carrier of genetic information and has a structure that is ideally suited to this function.

Answer 1

nucleic acid

Question 2

There are 2 main types of nucleic acid,
_____ and _____, w/c each consist of a sugar – phosphate backbone w/ projecting nitrogenous bases.

Answer 2

DNA (deoxyribonucleic acid); RNA (ribonucleic acid)

Question 3

There are 2 main types of nucleic acid,
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), w/c each consist of a _____ w/ projecting _____.

Answer 3

sugar – phosphate backbone; nitrogenous bases

Question 4

The nitrogenous bases are of 2 types, _____ & _____. In DNA, there are 2 purine bases, ____, and 2 pyrimidine bases, _____.

Answer 4

purines; pyrimidines; adenine (A) and guanine (G); thymine (T) and cytosine (C)

Question 5

RNA also contains A, G and C, but contains ____ (U) in place of T. In DNA, the sugar is _____, whereas in RNA it is _____.

Answer 5

uracil; deoxyribose; ribose

Question 6

The nitrogenous bases are attached to the _____ position of each sugar, & the phosphate links _____ of two succeeding nucleotide.

Answer 6

1 ′ (one prime); 3 ′ and 5 ′ hydroxyl groups.

Question 7

Each unit of purine or pyrimidine base together w/ the attached sugar and phosphate group(s) is called a ______.

Answer 7

nucleotide

Question 8

A molecule of DNA is composed of 2 nucleotide chains, w/c are coiled _____ around one another to form a _____ with _____ nucleotides per complete turn of DNA

Answer 8

clockwise; double helix; 10 nucleotides

Question 9

The 2 chains run in opposite directions (i.e. 5 ′ to 3 ′ for one and 3 ′ to 5 ′ for the other) & are held together by _____ between A in one chain and T in the other or between G & C.

Answer 9

hydrogen bonds

Question 10

DNA/RNA base pairing is very specific, although rarely erroneous combinations may occur. As A:T & G:C pairing is obligatory, the parallel strands must be _____ to one another.

Answer 10

complementary

Question 11

The ratio of A to T is 1:1 and of G to C is likewise 1:1. This is also called the _____.

Answer 11

Chargaff ’ s rule

Question 12

Wide variation exists in the AT:GC ratio. Higher plants & animals tend to have an excess of ____ & in humans the ratio is _____.

Answer 12

A + T ; 1:4:1

Question 13

The unit of length of DNA is the _____ w/ 1000 bp in a _____ & 1,000,000 bp in a ______.

Answer 13

base pair (bp); kilobase (kb); megabase (Mb)

Question 14

The total length of DNA in a half (haploid) set of human chromosomes is approximately _____ &, as the distance between base pairs in the DNA helix is _____. The total length of haploid DNA if extended, per cell, would be 1 m.

Answer 14

3280 Mb (3.28 × 10^9 bp); 0.34 nm; 1 m

Question 15

Each protein - coding gene usually possesses only _____ in the haploid genome but with well - known exceptions being the _____ genes, and the average gene size is _____ with an average intergenic distance of _____.

Answer 15

one copy; α - globin genes, histone genes and ubiquitin genes; 53.6 kb; 60 – 70 kb

Question 16

The majority of the genome is _____ and _____ and has no proven function.

Answer 16

non - coding; repetitive

Question 17

Repetitive DNA is subdivided into _____ & _____.

Answer 17

tandem repeats; interspersed repeats

Question 18

Tandem repeats are subdivided according to their length. Microsatellite repeat arrays are under _____ in length & the most common repeat motifs are A, CA, AAAN (where N is any nucleotide), AAN & AG.

Answer 18

1 kb

Question 19

The arrays of CA motifs commonly have _____ , w/ corresponding lengths of _____, and are found approximately every _____ kb.

Answer 19

10 – 60 repeats; 20 – 120 bp; 36 kb

Question 19

The repeat number on corresponding chromosomes commonly differs & these common genetic differences or _____ can be used to track the inheritance of that region of each chromosome.

Answer 19

polymorphisms

Question 20

Minisatellite repeat arrays are usually ____ in length & have longer repeat motifs than the microsatellite repeats.

Answer 20

1 – 30 kb

Question 21

As minisatellites are generally located close to the _____, they are less useful than microsatellites for genome – wide linkage analyses.

Answer 21

telomeres

Question 22

Owing to their hypervariable sequences and the ease of detecting large numbers of them simultaneously (by using hybridisation to a common core sequence that they contain), the _____ provide an individual - specific pattern of bands that has been invaluable for forensic identification

Answer 22

multilocus minisatellites

Question 23

_____ repeats are larger still and may be many megabases in length. They are found at the ends, _____ of the chromosomal arms and in the central chromosomal constriction, the ____.

Answer 23

Macrosatellitel; telomeres; centromere

Question 24

Length variation of macrosatellite is common & accounts for visible differences in the size of _____.

Answer 24

chromosomal centromeric regions

Question 25

_____ usually occur as single copies & these are subdivided according to length. Short interspersed repeats (SINES) are under ____ bp and the commonest type is the ____.

Answer 25

interspersed repeats; 500 bp; Alu repeat

Question 26

Alu repeats are about ____ bp long, possess relatively high ____ content and contain a cutting site for the restriction enzyme _____.

Answer 26

300; GC; AluI

Question 26

What’s the restriction site for Alul?

Answer 26

AG/CT

Question 27

Alu repeats are very common, constituting ____ percent of all human DNA, are specific to humans and other high primates and occur every ____ kb.

Answer 27

11%; 5-10

Question 28

Long interspersed repeats (LINES) vary from _____ in length and include three families, w/c in total constitute about _____ % of the human genome.

Answer 28

500 bp to 10 kb; 20

Question 29

The most common type of LINE is ____ element, w/c, like other LINES, possesses structural similarities to _____. L1 has the capacity to replicate itself via _____, and insert a copy at a new location in the genome.

Answer 29

LINE - 1 (L1); retroviruses; reverse transcription

Question 30

The ability of certain DNA elements to replicate and insert themselves at a new location in the genome is called? This may disrupt a gene at the new location & cause a genetic disorder such as _____.

Answer 30

retrotransposition; haemophilia

Question 31

_____ are synthesized directly on DNA templates that occur as multiple clustered copies (the nucleolus organizer regions on the short arms of chromosomes 13 – 15, 21 and 22, and on chromosome 1).

Answer 31

Ribosomal RNAs (rRNAs).

Question 32

Ribosomal RNAs (rRNAs) are synthesized directly on DNA templates that occur as _____.

Answer 32

multiple clustered copies.

Question 33

rRNAs are synthesized from DNA templates corresponding to _____.

Answer 33

nucleolus organizer regions on the short arms of chromosomes 13 – 15, 21 and 22, and on chromosome 1

Question 34

The rRNAs are synthesised as _____ in the ____ and then enzymatically cleaved.

Answer 34

large precursors; nucleolus

Question 35

Transfer RNAs (tRNAs) are also synthesised directly on a DNA template and, although _____ different types might be expected, surprisingly only _____ are found, as some tRNAs can bind to more than one mRNA codon. This results from ____ at the ____ position of the codons.

Answer 35

64; 49; relaxed base - pairing/wobble; third – base

Question 36

T/F. The DNA templates for tRNAs tend to occur as multiple copies, w/c may be clustered or dispersed.

Answer 36

T