Dna, Genes And Protein Synthesis (Aqa)

Front 1

What is a gene?

Back 1

A section of DNA that codes for polypeptides/functional RNA in the form of specific base sequences

Front 2

How do genes determine the development of organisms?

Back 2

Genes code for polypeptides=form proteins=form enzymes=control chemical reactions for organisms development/activities

- genes determine nature/development of all organisms

Front 3

What is the locus of a gene?

Back 3

The specific position of a section of DNA

Front 4

Why must there be a minimum of 3 bases that code for a specific amino acid?

Back 4

- 20 different amino acids regularly occur in proteins

- Each amino acid is coded by bases

- If 1 base=amino acid: Only 4 different amino acids

- If 2 bases=amino acid: Only 16

- If 3 bases=amino acid=64 different amino acids=satisfy requirements

Front 5

What are the features of the genetic code?

Back 5

- Degenerate code: Most amino acids are coded by 2-6 triplets

- triplet code always read in one direction along the DNA strand

- Start of DNA sequence always the same triplet

- 3 triplets are stop codes

- Code is non-overlapping (each base only read once)

- Code universal=same in all organisms (evidence for evolution

Front 6

What are exons?

Back 6

A sequence of bases which code for amino acids

Front 7

What are introns?

Back 7

Sequences of bases which doesn't code for amino acids

Front 8

What are the differences between prokaryot and eukaryot DNA?

Back 8

Prokaryot: Short molecules/form a circle/no associated with proteins/no chromosomes

Eukaryot: Longer molecules/Linear/Associated with histones(chromosomes)/DNA in mitochondria and chloroplasts similar to prokaryot DNA

Front 9

What are homologous chromosomes?

Back 9

A set of chromosomes in sexually produced organisms where each pair of chromosomes is half from the mother and half from the father

- chromosomes carry the same gene but not necessarily the same alleles

Front 10

What is the diploid number?

Back 10

The number of individual chromosomes

Front 11

What is an allele?

Back 11

The alternative forms of a gene (2 alleles per gene)

- one allele comes from each parent/can be same or different

Front 12

What happens if the alleles of a gene are different?

Back 12

Each allele has a different base sequence and so produce different polypeptides

Front 13

What is a codon?

Back 13

A sequence of three bases on mRNA that code for a single amino acid

Front 14

What is a genome?

Back 14

A complete set of genes in a cell, including the genes in the mitochondria/chloroplasts

Front 15

What is a protenome?

Back 15

The proteins produced by a given type of cell under a certain set of conditions

Front 16

What is a complete protenome?

Back 16

The full range of proteins produced by a genome

Front 17

What are the two types of RNA involved in protein synthesis?

Back 17

mRNA and tRNA

Front 18

What is mRNA?

Back 18

A long strand of mononucleotides in a single helix/base sequence determined by DNA base sequence/leaves nucleus to cytoplasm/binds with ribosomes/template for protein synthesis

Front 19

What is tRNA?

Back 19

Small molecule of 80 nucleotides/single strand chain in four leaf clover shape/end that extends=binds to amino acid/each type binds to different amino acid/anticodon=specific to amino acid/anticodon complements mRNA codon/structurally suited to line up amino acids

Front 20

Give a short summary of protein synthesis.

Back 20

- DNA provides instructions for a sequence of bases

- Complementary pre-mRNA made through transcription

- pre-mRNA spliced to form mRNA

- template for tRNA to form polypeptide (translation)

Front 21

What is transcription?

Back 21

The process of making pre-mRNA using a DNA strand as a template

Front 22

Describe the process of transcription.

Back 22

- Enzyme causes DNA strands to separate, exposing bases

- Template strand pairs with free complementary bases/RNA polymerase joins free bases into pre-mRNA molecule

- DNA strands rejoin behind RNA polymerase (12 bases exposed at one time)

- RNA polymerase reaches stop codon on DNA=pre-mRNA complete

Front 23

Describe the process of splicing pre-mRNA.

Back 23

- DNA in eukaryots made of exons and introns

- Introns would prevent synthesis of a polypeptide chain

- Intron base sequences removed/exons joined together to form mRNA

Front 24

How many types of tRNA are there?

Back 24

60 different types, each type has a specific anticodon and attaches to a certain amino acid

Front 25

Describe the process of translation.

Back 25

- ribosome attaches to mRNA start codon

- tRNA with complementary anticodon move to ribosome and pairs with mRNA codon (carries specific amino acid)

- tRNA complementary to next codon attaches to mRNA, carrying another amino acid

- Two amino acids join by peptide bond (enzyme/ATP)

- Ribosome moves to third codon=links amino acids on second and third tRNA

- First tRNA released=collects another amino acid

- Continues until ribosome reaches stop codon

Front 26

What are the different ways that proteins are assembled?

Back 26

- polypeptide coiled/folded=secondary structure

- secondary structure folded=tertiary structure

- different polypeptide chains+prosthetic group link=quarternary structure

Front 27

What is the role of ATP in translation?

Back 27

- provide energy to attach amino acids to tRNA

- provide energy to attach amino acids together