Unit 1 KA3

Question 1

Gene

Answer 1

A section of DNA that carries the code for the production of protein molecules.

Question 2

Genotype

Answer 2

The genetic composition of a cell, which is determined by the sequence of bases.

Question 3

Phenotype

Answer 3

The characteristics of an organism, which are determined by the proteins produced as a result of gene expression.

Phenotype can also be affected by environmental factors.

Question 4

RNA

Answer 4

Ribonucleic acid - another type of nucleic acid.

It is single stranded, and is made of nucleotides that contain ribose sugar instead of deoxyribose, and one different base (uracil instead of thymine).

Question 5

Ribose

Answer 5

5 carbon sugar found in RNA nucleotides (ribonucleotides).

Question 6

Uracil

Answer 6

One of the 4 bases found in RNA (replaces thymine).

Pairs with adenine : A - U

Question 7

mRNA

Answer 7

Messenger RNA.

Carries a copy of the DNA code for a specific protein from the nucleus to ribosomes in the cytoplasm.

The code is transcribed in the nucleus, to form mRNA.

Question 8

Transcription

Answer 8

Synthesis of mRNA.

The base sequence of a gene is copied onto a messenger molecule known as mRNA.

Transcription happens in the nucleus.

Question 9

Codon

Answer 9

A triplet of 3 bases on mRNA or DNA that corresponds to a specific amino acid.

Question 10

tRNA

Answer 10

A type of RNA that collects specific amino acids which are joined on at an attachment site.

It transports the amino acids to the ribosome for translation.

Question 11

Anti-codon

Answer 11

A triplet of bases on the tRNA molecule which lines up with the mRNA codon by complementary base pairing inside the ribosome.

This ensures that amino acids are joined together in the correct sequence.

Question 12

Translation

Answer 12

The mRNA base sequence (which was transcribed from DNA) is converted into an amino acid sequence.

Translation happens inside ribosomes in the cytoplasm.

Question 13

rRNA

Answer 13

Ribosomal RNA.

Combines with protein to form the structure of a ribosome.

Question 14

Polypeptide

Answer 14

A chain of amino acids joined by peptide bonds.

Formed at the ribosome.

Only becomes a protein when folded.

Question 15

RNA polymerase

Answer 15

The enzyme responsible for mRNA synthesis.

It unwinds and separates the DNA strand, then synthesises an mRNA strand by joining free ribonucleotides which line up along the gene by complementary base pairing.

Question 16

Primary transcript

Answer 16

A piece of mRNA which is an exact complementary copy of the DNA base sequence in the gene.

It includes introns.

Question 17

RNA splicing

Answer 17

Introns are removed from the primary transcript and exons are spliced together to create the mature transcript of mRNA.

This is the version that is translated.

Question 18

Mature transcript

Answer 18

The piece of mRNA formed by RNA splicing.

It contains exons spliced together.

Question 19

Introns

Answer 19

Non-coding sections of a gene.

They need to be removed during RNA splicing.

Question 20

Exons

Answer 20

The coding regions of genes.

They are spliced together to form the mature transcript of mRNA

Question 21

Promoter region

Answer 21

The section of a gene where transcription begins.

Transcription is controlled by transcription factors.

Question 22

Alternative mRNA splicing

Answer 22

Different mature transcripts can be made from the same primary transcript, by splicing different exons together.

This produces different proteins.

Question 23

Protein

Answer 23

Many amino acids join together to form a polypeptide chain, which is then coiled and folded to form a protein.

There are 20 different types of amino acid, resulting in a huge variety of proteins.

The sequence of amino acids is known as the primary structure

Question 24

Structural proteins

Answer 24

These are made of alpha helices (spirals), arranged in parallel and bonded together with hydrogen bonds to form strong fibres for building cell structures.

Examples include collagen and keratin.

Question 25

Globular proteins

Answer 25

The alpha helices (spirals) are folded into 3D shapes, maintained by hydrogen and other bonds.

Examples of globular proteins are enzymes, receptors and antibodies.

Their function depends on their precise shape, as they are able to bind to specific molecules.