Bk 1 Ch5 Genes and genomes

Question 1

Gene

Answer 1

Region of DNA that specifies the amino acid sequence of a polypeptide or in some cases of functional RNA molecule

Question 2

Origin of replication

Answer 2

A single point, Particula sequence of bases at which replication begins

Question 3

DNA polymerases

Answer 3

Enzymes Enzymes that catalyse the assembly of deoxyribonucleoside triphosphates (dNTPs) into DNA during DNA replication. An existing DNA strand is required as a template.

Question 4

Helicases

Answer 4

Enzymes which separates the base pairs and unwind to DNA strands

Question 5

Single strand DNA binding (SSB) proteins

Answer 5

Prevent exposed stretches of single-stranded DNA from Reannealing to form the duplex

Question 6

DNA topoisomerase

Answer 6

Enzyme that is part of the DNA relpication complex; introduces a temporary break in one of the strands of DNA, allowing the DNA helix to swivel around itself and reduce torsional stress during unwinding of the helix. The topoisomerase then reseals it.

Question 7

Nuclease

Answer 7

Enzymes that break the links between the nucleotides in DNA.

Question 8

Leading strand

Answer 8

The DNA strand that is copied continuously during DNA replication.

Question 9

Lagging strand

Answer 9

The DNA strand that is copied discontinuously, as Okazaki fragments, during DNA replication.

Question 10

Replication fork

Answer 10

The arrangement of DNA at the point where the two strands are being separated and replicated. Two replication forks are formed at an origin of replication, and proceed in opposite directions along the DNA.

Question 11

Okazaki fragments

Answer 11

The short sections of DNA synthesised during the replication of the lagging strand of DNA.

Question 12

DNA ligase

Answer 12

Enzyme whose function in the cell is to join DNA fragments produced during DNA replication (or repair). DNA ligase joins any DNA molecules that have complementary ends, and so is used in vitro during gene cloning to join DNA fragments produced by restriction endonucleases.

Question 13

Mismatch repair(MMR)

Answer 13

A DNA repair system that detects and replaces wrongly inserted nucleotide in a newly synthesised DNA chain.

Question 14

Base excision repair(BER)

Answer 14

A process that removes single damaged bases from DNA, and restores the correct nucleotide.

Question 15

Open reading frame (ORF)

Answer 15

A continuous section of DNA sequence that encodes a polypeptide, or part of a polypeptide.

A series of triplet codons, uninterrupted by a stop codon

Question 16

Mutation

Answer 16

Permanent change in DNA sequence

Question 17

Pyrimidine

Answer 17

C ,T,U

Question 18

Purine

Answer 18

A,G

Question 19

Transition

Answer 19

One pyrimidine replaces the other

One purine replaces the other

Question 20

Transversion

Answer 20

One purine replaces pyrimidine

Or vice a versa

Question 21

Missense mutation

Answer 21

Substitution of one amino acid for another

Question 22

Nonsense mutation

Answer 22

Premature stop codon

Question 23

Operon

Answer 23

A group of bacterial genes, usually encoding proteins with related metabolic functions, that are under the control of a single regulatory DNA region (promoter), and which are transcribed as a single polycistronic messenger RNA. The first example described was the lac operon of E.coli.

Question 24

Polycistronic transcript

Answer 24

A single mRNA molecule that is the product of the transcription of several genes arranged in tandem, typically the mRNA transcribed from an operon. The translation products are separate polypeptides.

Question 25

Plasmids

Answer 25

Small autonomously replicating circle of DNA found naturally in many bacteria; some encode functions enabling their own transfer from cell to cell.

Question 26

Restriction endonucleases

Answer 26

Enzymes present in many bacteria that recognise particular sequences in DNA and cut the nucleic acid within that sequence (or sometimes a fixed distance from it). The resulting double strand cuts usually have protruding single-stranded or ‘sticky’ termini which can be rejoined using the enzyme DNA ligase. Restriction endonucleases are widely used in gene cloning.

Question 27

Cloning vectors

Answer 27

Self-replicating DNA molecules used to transfer DNA into cells. Most cloning vectors for use in bacteria are produced from naturally occurring bacteriophages or plasmids, which are engineered to introduce properties that facilitate gene cloning (e.g. restriction enzyme sites, selectable markers).

Question 28

Horizontal gene transfer

Answer 28

The transfer of DNA from one organism to another organism that is not its offspring. The DNA transfer may be between different species.

Question 29

Transformation

Answer 29

Genetic alteration of a bacterial cell by the uptake and incorporation of ‘naked’ DNA from the environment. Transformation occurs naturally in some species of bacteria and can be induced artificially in other cells. Because transformation has an alternative meaning in animal cells (indicating progression to a malignant, cancerous state) the term transfection is often used for this type of DNA uptake in animal cells.

Question 30

Transduction

Answer 30

The transfer of DNA from one cell to another mediated by a virus.

Question 31

Introns

Answer 31

Non-coding regions of a gene (located between exons) that are transcribed, but are spliced out of the primary transcript before the mature mRNA is used in protein translation. Common in eukaryotic genes but rare in prokaryotes.

Question 32

Exons

Answer 32

Coding regions of a gene, i.e. parts of a gene that after transcription into RNA are spliced together by the removal of intervening introns (in eukaryotic cells) to be used as the template for protein synthesis.

Question 33

mRNA splicing

Answer 33

The post-transcriptional process that removes non-coding sections (introns) from the primary RNA transcript in eukaryotic cells to produce the mature messenger RNA (mRNA) molecule.

Question 34

Primary RNA transcript

Answer 34

A eukaryotic RNA transcript immediately after transcription in the nucleus, before any processing e.g. RNA splicing or polyadenylation.

Question 35

TATA box

Answer 35

A consensus sequence present in the core promoter of most eukaryotic genes; the site where the transcription initiation complex (including general transcription factors and RNA polymerase II) assembles.

Question 36

Transposons

Answer 36

A small genetic element that can move, or transpose, from one position to another in a genome; usually by copying itself and inserting into a second site, but sometimes by splicing out of the original site and inserting in a new location.

Question 37

Satellite DNA

Answer 37

Heterochromatin

Contain few genes

Question 38

Telomere

Answer 38

Regions at the ends of eukaryote chromosomes consisting of short non-coding nucleotide repeats. Their presence avoids the loss of coding regions during DNA replication (the 3’ end of the lagging strand cannot be replicated all the way to its end).

Question 39

Telomerase

Answer 39

An enzyme that adds additional nucleotide repeats to the end of the chromosomes, thereby constantly restoring telomere length.

Active in germline cells and stem cells

And cancer cells

Question 40

Single nucleotide polymorphisms (SNPs)

Answer 40

A type of genetic variation consisting of single nucleotide differences between the genomes of individuals.

Question 41

Copy number variation (CNV)

Answer 41

A type of genetic variation where some genes may be present in a variable number of copies in different individuals of the same species, resulting in different levels of expression of the gene product.

Question 42

Null mutation

Answer 42

Results in a complete loss of function of the mutated gene

Question 43

Polymerase chain reaction (PCR)

Answer 43

A laboratory technique for amplifying a few copies of a DNA sequence to generate thousands or millions of copies by a series of in vitro reactions using DNA polymerase

1 denaturation (94*) - separate strands dna
2 primer annealing- base pairing oligonucleotide primers to complementary seq.
3elongation - synthesis 2 new dna strands by dna taq polymerase (not denatured), initiated from oligonucleotide primers
P.153 bk 1