DNA, RNA, and Protein Synthesis - Practice Flashcards

A comprehensive set of practice questions covering DNA structure and replication, transcription, translation, the genetic code, and epigenetics.

Where is most of a cell's DNA located and what is the exception?

Most DNA is in the nucleus; a small amount, mitochondrial DNA, is located in the mitochondria.

What determines which proteins a cell can make?

Genes determine protein production by coding for specific amino acid sequences.

What forms a chromosome?

A number of genes together form a chromosome.

What are the three components of a DNA nucleotide as described in the notes?

Sugar (ribose), a phosphate group, and a nitrogenous base.

Name the four DNA bases.

Adenine, Thymine, Cytosine, Guanine.

Which base pairs with Adenine in DNA?

Thymine pairs with Adenine.

Which base pairs with Cytosine?

Guanine pairs with Cytosine.

What is the overall shape of DNA?

A double helix.

What is the function of mitochondrial DNA (mtDNA) as described?

mtDNA codes for transfer RNA and enzymes for cellular respiration.

What is DNA replication?

The process by which a cell makes a copy of its DNA to pass to daughter cells.

Which enzyme unwinds the DNA double helix during replication?

DNA helicase.

Which enzyme synthesizes new DNA strands using free nucleotides?

DNA polymerase.

Which enzyme joins short DNA fragments during replication?

DNA ligase.

What does semi conservative replication mean?

Each new DNA molecule contains one parental strand and one new strand.

During replication, what provides the template for new bases?

The parental strands provide the template.

What guarantees correct base pairing during replication?

Complementary base pairing (A with T, G with C).

What is the approximate rate of DNA elongation by DNA polymerase in human cells?

About 50 nucleotides per second.

What is the structure and count of mtDNA per mitochondrion?

MtDNA consists of small circular molecules; each mitochondrion has 5 to 10 copies.

Why is mtDNA passed maternally?

Mitochondria from the sperm are destroyed during fertilization, so egg mitochondria are inherited.

What is the genetic code?

DNA codons code for amino acids; genes code for proteins via transcription and translation.

What is a gene?

A segment of DNA that codes for a specific protein.

What is a codon?

A triplet of nucleotides in mRNA that specifies an amino acid.

How many amino acids exist and how many codons are there?

20 amino acids and 64 codons.

What codon marks the start of translation and which amino acid does it code for?

Start codon AUG; Methionine.

What codons signal termination of translation?

Stop codons (UAA, UAG, UGA).

What bridges DNA and protein synthesis?

RNA acts as the bridge between DNA and proteins.

What is mRNA and its role?

Messenger RNA carries genetic instructions from DNA to the ribosome in the cytoplasm.

What is tRNA and its role?

Transfer RNA reads mRNA and brings the correct amino acids to the ribosome via its anticodon.

Where does protein synthesis occur?

At the ribosomes in the cytoplasm.

Which amino acid is the first in a growing polypeptide chain?

Methionine, coded by AUG.

What is the overall function of RNA in protein synthesis?

RNA carries the message from DNA and participates in assembling amino acids into proteins.

What is transcription?

The process of copying DNA into mRNA in the nucleus using RNA polymerase.

What enzyme separates DNA strands during transcription?

RNA polymerase; helicase separates strands earlier in replication, but transcription involves RNA polymerase starting on DNA.

What is the difference between the DNA template and the coding strand in transcription?

The template strand is complementary to the mRNA; the coding strand has the same sequence as the mRNA (with T instead of U).

Where does mRNA go after transcription?

Through a nuclear pore into the cytoplasm to guide translation.

What is the role of the ribosome in translation?

The ribosome reads codons on mRNA and assembles the corresponding amino acids into a protein.

What is the role of anticodons?

Anticodons on tRNA pair with codons on mRNA to place the correct amino acids.

What is epigenetics?

Heritable changes in gene expression that do not involve changes to the DNA sequence.

What is chromatin?

DNA wrapped around histone proteins forming a structural unit that can be open or condensed.

What is histone acetylation and its effect on gene expression?

Addition of acetyl groups to histones that relaxes chromatin and promotes transcription.

What is DNA methylation and its effect on gene expression?

Addition of methyl groups to cytosine at CpG sites, leading to tighter chromatin and inhibited transcription.

What is the epigenome?

The sum of all epigenetic factors including environmental influences that determine gene expression.

Why can epigenetic changes be heritable?

Some epigenetic marks can be transmitted to subsequent generations, affecting gene expression.

What are CpG sites?

Locations in DNA where cytosine is followed by guanine and often targets for methylation.

What is the effect of chromatin modification on gene expression?

Modifications like acetylation or methylation can turn genes on or off by altering chromatin structure.