Biology Unit C3 Flashcards

Continuity of life

A succession of offspring that share structural similarities with those of their parents

Bacteriophage

A virus that infects bacteria

Isotope

One of two or more atoms of the same element containing the same number of protons but a different number of neutrons

Radioisotope

An unstable isotope that decays spontaneously by emitting radiation

Nucleotide

A molecule having a five-carbon sugar with a nitrogenous base attached to its 1’ carbon and a phosphate group attached to its 5’ carbon

Deoxyribose sugar

A sugar molecule containing five carbons that has lost the -OH (hydroxyl group) on its 2’ position

Nitrogenous base

An alkaline cyclic molecule containing nitrogen

Phosphate group

A group of four oxygen atoms surrounding a central phosphorus atom found in the backbone of DNA

Complementary base pairing

Pairing of the nitrogenous base of one strand of DNA with the nitrogenous base of another strand

Antiparallel

Paralel, but running in opposite directions; the 5’ end of one strand of DNA aligns with the 3’ end of the other strand in a double helix

DNA replication

The process whereby DNA makes exact copies of itself

Semiconservative replication

Process of replication in which each DNA molecule is composed of one parent strand and one newly synthesize strand

Template

A single-stranded DNA sequence that acts as the guiding pattern for producing a complementary DNA strand

DNA helicase

The enzyme that unwinds double-helical DNA by disrupting hydrogen bonds

DNA polymerase III

THe enzyme that synthesizes complementary strands of DNA during DNA replication. It adds nucleotides to a growing strand in only one direction: the 5’ to 3’ direction. 

Leading strand

The new strand of DNA that is synthesized towards the replication fork and continuously during DNA replication

Lagging strand

The new strand of DNA that is synthesized away from the replication fork and in short fragments, which are later joined together

DNA polymerase I

An enzyme that removes RNA primers and replaces them with the appropriate nucleotides during DNA replication. A small gap is left between the DNA fragments, which must be fused together by another enzyme. 

DNA ligase

An enzyme that joins DNA fragments together.

Gene expression

Conversion of a gene into a specific trait through the production of a particular polypeptide

Ribonucleic acid (RNA)

A nucleic acid consisting of nucleotides composed of the sugar ribose and nitrogenous bases. It is single stranded. Ribose has an extra hydroxyl group compared to deoxyribose. Instead of the base thymine in DNA, RNA has uracil.

Transcription

The process of converting DNA into messenger RNA

Messenger RNA (mRNA)

The product of transcription of a gene; mRNA is translated by ribosomes into protein

Translation

The process of synthesizing a specific polypeptide as coded for by mRNA

RNA polymerase

Enzyme that transcribes DNA

Promoter

Sequence of DNA that binds RNA polymerase in front of a gene

Template strand

The strand of DNA that the RNA polymerase uses as a guide to build complementary mRNA

Termination sequence

Sequence of bases at the end of a gene that signals the RNA polymerase to stop transcribing

Initiation (transcription)

RNA polymerase binds to the segment of DNA to be transcribed, and unwinds the double helix. A promoter identifies the region where RNA polymerase initially binds to.

Elongation (transcription)

RNA polymerase begins building a single stranded mRNA in the 5’ to 3’ direction, using the template strand to build a complementary strand. Only one strand is copied. Uracil is used instead of thymine.

Termination (transcription)

When RNA polymerase reaches the end of the gene, a termination sequence tells the enzyme to stop transcribing. DNA returns to original state.

Codon

Sequence of 3 bases in DNA or complementary mRNA that serves as a code for a particular amino acid.

Start codon

Specific codon (AUG) that signals the start of translation

Stop codon

Specific codon that signals the end of translation

Ribosome

An organelle composed of RNA and protein and located int he cytoplasm that carries out protein synthesis

Transfer RNA (tRNA)

The form of RNA that delivers amino acids to a ribosome during translation

Anticodon

Group of three complementary bases on tRNA that recognizes and pairs with a codon on the mRNA

Initiation (translation)

Translation starts when a ribosome identifies a specific sequence on mRNA (the start codon) and binds to it. The ribosome moves in eh 5’ to 3’ direction, and always reads the start codon first. tRNA carries the corresponding amino acid to the codon, and the anticodon to the mRNA which will bind to the codon and place the appropriate amino acid along the polypeptide.

Elongation (translation)

Different tRNA molecules bind to each codon on mRNA in order, each time adding the corresponding amino acid to the polypeptide strand. The first polypeptide is methionine (corresponds to the start codon). After each amino acid is added, the ribosome shifts over 1 codon and another tRNA attaches.

Termination (translation)

When the ribosome reaches the stop codon, there is no tRNA that codes for the stop codon so the ribosome is released from the mRNA and translation stops. 

Recombinant DNA

Fragment of DNA composed of sequences originating from at least two different sources

Genetic transformation

Introduction and expression of foreign DNA in a living organism

Restriction Endonuclease/Enzyme

An enzyme that cuts double stranded DNA into fragments at a specific sequence. The result is two, shorter double stranded DNA fragments

• Each one is coded to read a specific recognition site

Recognition site

Specific sequence within double stranded DNA that a restriction enzyme recognizes and cuts

Sticky ends

Fragment of a DNA molecule with short single stranded overhangings, resulting from cleavage by a restriction enzyme

• Restriction enzymes don’t always produce them

Blunt ends

Fragment ends of a DNA molecule that are fully base paired, resulting from cleavage by a restriction enzyme

Gel Electrophoresis

Technique to determine the lengths of DNA matter

• DNA is charged and placed in a chamber with one end oppositely charged

• The DNA are attracted to the opposite end of the chamber

• There is gel inside the chamber which DNA must pass through

• Longer strands of DNA find it harder to move through the gel, so move a small distance

• Short strands of DNA can fit through the matrix in the gel, and move further

• A DNA ladder contains DNA of many different lengths, and can be used to determine the length of the unknown DNA. The ladder separates into segments of known length, and you can compare the distances travelled to the ladder to find the length of the unknown DNA

Polymerase chain reaction (PCR)

A technique for amplifying a DNA sequence by repeated cycles of strand separation and replication

1. Heat the solution: the DNA breaks into 2, single stranded DNAs

2. Cool the solution: Primers bind to locations on the single stranded DNA

3. Taq Polymerase makes complementary strands using free floating DNA nucleotides

4. Repeat!!!

Number of DNA strands = 2ⁿ (n = number of cycles)

Vector

A vehicle by which foreign DNA may be introduced into a cell

Transgenic

A cell or organism that is transformed by DNA from another species

Plasmid

A small double-stranded circular DNA molecule found in some bacteria

Silent multation

A mutation that does not result in a change in the amino acid coded for (eg. ACA and ACU both code for Thr)

Missense mutation

A mutation that results in the single substitution for one amino acid in the polypeptide

Nonsense mutation

A mutation that converts a codon for amino acid into a stop codon → can cause significant change to the final polypeptide (eg. AAA → UAA (stop))

Deletion

The elimination of a base pair or group of base pairs from a DNA sequence

Insertion

The placement of an extra nucleotide in a DNA sequence

Frameshift mutation

A mutation that causes the reading frame of codons to change (can be insertion or deletion) → changes the ordering of codons