A-Level Biology (WJEC - Eduqas) > 3: DNA & Protein Synthesis > Flashcards

3: DNA & Protein Synthesis Flashcards

Explain how DNA structure enables genetic information to be expressed as proteins. (27 cards)

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1
Q

In prokaryotic cells, what is the shape of the DNA molecule and is it associated with proteins?

A

Short circular DNA not associated with histone proteins.

Prokaryotes lack histones and typically have a single circular chromosome in the cytoplasm.

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2
Q

In the nuclei of eukaryotic cells, DNA molecules are long and linear. Which proteins are they associated with to form chromosomes?

A

Histones

DNA wraps around histone proteins to form chromatin, which condenses into chromosomes.

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3
Q

What structure is formed when a DNA molecule combines with its associated proteins in eukaryotic cells?

A

Chromosome

A chromosome consists of one long DNA molecule packaged with proteins.

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4
Q

Besides the nucleus, which two organelles in eukaryotic cells also contain their own DNA?

A

Mitochondria and chloroplasts

These organelles have circular DNA similar to that found in prokaryotes.

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5
Q

True or False:

DNA in mitochondria and chloroplasts is linear and associated with histone proteins.

A

False

Their DNA is short, circular and not associated with histone proteins, similar to prokaryotic DNA.

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6
Q

What do we call a sequence of DNA bases that codes for a polypeptide or a functional RNA molecule?

A

Gene

Genes can code for polypeptides or functional RNA such as rRNA and tRNA.

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7
Q

What term describes the fixed position that a gene occupies on a DNA molecule?

A

Locus

Each gene is located at a specific locus on a chromosome.

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8
Q

What is the name given to a sequence of three DNA bases that codes for a specific amino acid?

A

Triplet or codon

Each triplet of DNA bases corresponds to one amino acid in a polypeptide.

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9
Q

True or False:

The genetic code is overlapping, meaning a base can belong to multiple triplets.

A

False

The genetic code is non-overlapping, so each base is part of only one triplet/codon.

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10
Q

What property of the genetic code means that several different base triplets can code for the same amino acid?

A

Degenerate

For example, multiple codons can specify the same amino acid.

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11
Q

Fill in the blank:

Within a gene, the sequences that actually code for amino acid sequences are called ______.

A

Exons

Exons remain in the mature mRNA after RNA processing.

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12
Q

Fill in the blank:

Non-coding sequences found within genes that separate coding regions are called ______.

A

Introns

Introns are removed during RNA splicing before translation occurs.

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13
Q

True or False:

Much of the DNA in eukaryotic nuclei does not code for polypeptides.

A

True

Eukaryotic genomes contain large amounts of non-coding DNA including repeats and introns.

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14
Q

What is the term for the complete set of genes present in a cell or organism?

A

Genome

Includes all coding and non-coding DNA sequences within a cell.

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15
Q

What term describes the entire range of proteins that a cell is capable of producing?

A

Proteome

Varies between cell types because different genes are expressed.

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16
Q

Which type of RNA carries a copy of genetic information from DNA to a ribosome?

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A

mRNA

Messenger RNA is complementary to the DNA template strand.

17
Q

Which RNA molecule carries specific amino acids to the ribosome during protein synthesis?

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A

tRNA

Each tRNA has an anticodon that pairs with a codon on mRNA.

18
Q

Which enzyme catalyses the joining of RNA nucleotides during the formation of an RNA strand from DNA?

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A

RNA polymerase

The enzyme moves along the DNA template strand during transcription.

19
Q

What is the process called in which a strand of RNA is produced using a DNA template?

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A

Transcription

Produces RNA that is complementary to the DNA template strand.

20
Q

What is the name of the RNA molecule initially produced in eukaryotic transcription before processing occurs?

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A

pre-mRNA

This molecule still contains introns that must be removed.

21
Q

What process removes introns and joins exons to produce a functional RNA transcript in eukaryotic cells?

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A

Splicing

Occurs in the nucleus before the mRNA leaves for translation.

22
Q

What process produces a polypeptide using the sequence of codons on an mRNA molecule?

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A

Translation

Occurs at ribosomes in the cytoplasm or on rough ER.

23
Q

What three-base sequence on an mRNA molecule specifies a particular amino acid during protein synthesis?

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A

Codon

The genetic code is read in triplets during translation.

24
Q

Fill in the blank:

During protein synthesis, energy used to attach amino acids to tRNA molecules is supplied by ______.

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A

ATP

ATP provides energy for amino acid activation before translation.

25
# True or False: In **prokaryotes**, the RNA produced during **transcription** can be used directly for protein synthesis without further processing.
True ## Footnote Prokaryotes do not produce pre-mRNA or carry out splicing.
26
# True or False: In **eukaryotic cells**, **introns** remain in the final mRNA molecule used in **translation**.
False ## Footnote Introns are removed during RNA splicing before translation.
27
# Fill in the blank: The structure within cells where **mRNA** is decoded to produce a **polypeptide** is the \_\_\_\_\_\_.
Ribosome ## Footnote Ribosomes coordinate codon–anticodon pairing and peptide bond formation.
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