Molecular Genetics

Question 1

What do nucleotides consist of?

Answer 1

A 5 carbon cyclic structure called deoxyribose

A phosphate group

One of 4 nitrogenous bases

Question 2

What are the four nitrogenous bases?

Answer 2

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Question 3

What is DNA Replication?

Answer 3

The process in which DNA makes an exact copy of itself

Occurs during interphase

Question 4

What happens in the Splitting phase of DNA replication?

Answer 4

DNA is split in half and each half is used as a template strand to make a new copy

DNA helicase unwinds the DNA strand by breaking hydrogen bonds between the complimentary base pairs (like a zipper)

The point at which the two DNA strand are separated is called the replication fork

Question 5

What happens during the building complimentary strands phase of DNA replication?

Answer 5

New strands are synthesized by DNA polymerase III

It works by linking together free nucleotides to appropriate complimentary base pairs

A short piece of RNA called a primer attaches to the template strand and gives the DNA polymerase a place to start

DNA polymerase III adds nucleotides on the side towards the replication fork

DNA Polymerase I then cuts out the primers and replaces them with nucleotides

DNA Ligase then joins the backbones of these fragments together

Question 6

What is the leading strand?

Answer 6

DNA Polymerase III adds nucleotides on the side towards the replication fork

Question 7

What is the lagging strand?

Answer 7

DNA polymerase III is synthesized in short Okazaki fragments

Question 8

What happens during the DNA Repair phase in DNA Replication?

Answer 8

Proofreading: polymerase backtracks and cut out any incorrect nucleotides

Question 9

What does DNA Helicase do?

Answer 9

Unwinds double helix

Question 10

What does DNA Polymerase III do?

Answer 10

Synthesizes complimentary strand

Question 11

What does DNA Polymerase I do?

Answer 11

Removes RNA primers and replaces with nucleotides

Question 12

What does DNA Ligase do?

Answer 12

Joins DNA fragments together

Question 13

What is gene expression?

Answer 13

The conversion of a gene into a specific trait through the production of a particular polypeptide

A polypeptide is a long chain of amino acids, polypeptides make up proteins, proteins for many structures such as skin, muscle, and enzymes

This is done with the help of RNA

Question 14

What is the difference between DNA and RNA?

Answer 14

RNA is single stranded

RNA contains ribose sugar (one more oxygen than deoxyribose)

Uracil instead of thymine

Question 15

What is transcription?

Answer 15

DNA is converted to RNA

Question 16

What is translation?

Answer 16

Converts RNA to protein

During translation RNA is read in groups of 3 nucleotides called codons

Each codon calls for a specific amino acid to be placed in the polypeptide chain

Redundant but not Ambiguous
Redundant: several amino acids are coded for by different codons
Not Ambiguous: certain codons code for certain amino acids

Question 17

What happens during the initiation phase of transcription?

Answer 17

RNA polymerase binds to a segment of DNA called the promoter

This sequence tells the enzyme where transcription should begin

The promoter will sit upstream of the DNA sequence to be transcribed

Question 18

What happens during the elongation phase of transcription?

Answer 18

RNA polymerase starts building single-stranded in RNA (messenger RNA) in the 5’ to 3’ direction

Thymine (T) in DNA are replaced with Uracil (U) in mRNA

Exons are expressed, introns are not

Question 19

What happens during the termination phase of transcription?

Answer 19

RNA polymerase will continue to transcribe DNA until it reaches a termination sequence

RNA polymerase falls off DNA molecule and the mRNA separates from DNA

Question 20

What happens during the initiation phase of translation?

Answer 20

Ribosome recognizes a specific sequence on the mRNA and binds to it

In eukaryotes, the ribosomes consists of two subunits: large and small, the subunits clamp the mRNA between them

The ribosome read the mRNA 5’ to 3’

Question 21

What happens during the elongation phase of translation?

Answer 21

tRNA (transfer RNA) bring amino acids to the ribosome, tRNA molecules have an anticodon that is complimentary to the codon in the mRNA

Amino acids continue to be added

Question 22

What are mutations?

Answer 22

Mutations are changes in the sequence of DNA

Mutations are a source of new genetic variation and can be acted upon by natural selection

Mutations can be seen at the chromosomal level involving large segments of DNA

Question 23

What is a point mutation?

Answer 23

A mutation at a specific base pair (substitution)

Question 24

What is a gene mutation?

Answer 24

A mutation that changes the coding for amino acids (missense)

Question 25

What is a silent mutation?

Answer 25

Does not result in a charge in amino acid coded for (same sense)

Question 26

What is a nonsense mutation?

Answer 26

Converts a codon for an amino acid into a stop codon

Question 27

What is a frame shift mutation?

Answer 27

A mutation that causes the reading frame of codons to change (insertion or deletion)

Question 28

What causes mutations?

Answer 28

Spontaneous mutations: a mutation occurring as a result of errors made in DNA replication

Induced mutation: a mutation caused by a chemical agent or radiation

Question 29

What is phylogeny?

Answer 29

Proposed evolutionary history of a species or group of organisms

Closer DNA sequence, closer evolutionary relationship

Question 30

What is mitochondrial DNA (mtDNA)?

Answer 30

Can be used to provide clues about the evolutionary history of modern humans

Question 31

What is DNA Sequencing?

Answer 31

Determines the exact sequence of based pairs for a particular DNA fragment or molecule

Question 32

What is recombinant DNA?

Answer 32

A fragment of DNA composed of sequences originating from at least two different sources