Revision of cellular structure and DNA topics

50 practice flashcards covering DNA, RNA, replication, transcription, translation, mutation, and DNA profiling.

What is the basic structure of DNA?

A double helix made of two long strands of nucleotides paired by base pairs.

What are the three components of a DNA nucleotide?

Phosphate group, deoxyribose sugar, and a nitrogenous base.

Name the four DNA bases.

Adenine, Thymine, Cytosine, Guanine.

Which bases pair with each other in DNA?

Adenine with Thymine; Cytosine with Guanine.

What sugar is found in DNA nucleotides?

Deoxyribose.

What sugar is found in RNA nucleotides?

Ribose.

Which bases are found in RNA?

Adenine, Uracil, Cytosine, Guanine.

Which base is unique to RNA?

Uracil replaces Thymine.

What are the three main types of RNA?

mRNA, tRNA, and rRNA.

What is the function of mRNA?

Carries the genetic code from DNA to the ribosome.

What is the function of tRNA?

Brings amino acids to the ribosome; contains an anticodon.

What is the function of rRNA?

Forms part of ribosomes; site of protein synthesis.

Where is nuclear DNA located?

In the cell nucleus.

Where is extranuclear DNA found?

Outside the nucleus—in mitochondria and chloroplasts.

What is a genome?

The complete set of genetic material; in humans, organized into 23 chromosome pairs.

What is a chromosome?

A DNA molecule wrapped with histones that carries genes.

What is chromatin?

The DNA–protein network in the nucleus that forms chromosomes.

What is a nucleosome?

A unit of chromatin: DNA wrapped around histone proteins.

What is the function of ribosomes?

Site of protein synthesis; can be free in cytoplasm or attached to the endoplasmic reticulum.

What are the main steps of DNA replication?

DNA unwinds; hydrogen bonds break; each strand serves as a template; free nucleotides attach; two identical DNA molecules form.

What is transcription?

The process of making mRNA from DNA in the nucleus.

What is translation?

The process of producing a protein from mRNA in the cytoplasm at the ribosome.

What is a codon?

A three-base sequence on mRNA that codes for an amino acid.

What is an anticodon?

A three-base sequence on tRNA that pairs with a codon on mRNA.

How many amino acids exist?

Twenty.

What is a peptide bond?

A bond that links amino acids together to form a protein.

What is the structure of DNA?

Two strands forming a double helix.

What does hereditary mean?

Genetic information passed from parents to offspring.

What is a gene?

A short section of DNA that codes for a specific trait or protein.

What is the role of DNA in protein synthesis?

DNA carries hereditary information and contains the code for protein synthesis.

What is a mutation?

A change in the DNA sequence that can alter codons and proteins; sometimes no change.

What is DNA profiling?

A pattern of DNA fragments on a film that is unique to an individual.

What are common uses of DNA profiling?

Paternity testing, tracing missing persons, identifying genetic disorders, establishing family relations, matching tissues for transplants, identifying crime suspects.

If a DNA sample has 20% thymine, what percent is adenine?

20% (A = T).

If thymine is 30%, what percent is cytosine?

20% cytosine (and 20% guanine).

If guanine is 40%, what percent is adenine?

10% adenine (and 10% thymine).

How do DNA replication and transcription differ?

Replication uses both strands as templates to copy the whole molecule; transcription uses one strand as a template to copy a small section into mRNA.

What is mitochondrial DNA?

DNA located in mitochondria outside the nucleus; used for tracing ancestry.

What is chloroplast DNA?

DNA located in chloroplasts outside the nucleus (in plant cells).

Where do transcription and translation occur?

Transcription in the nucleus; translation in the cytoplasm at the ribosome.

What encloses the nucleus?

A double membrane called the nuclear envelope.

What is the nucleoplasm?

The jelly-like fluid inside the nucleus containing nucleotide bases.

What are histones and what is their role?

Proteins around which DNA winds to form chromatin.

What is the nuclear pore?

A small opening that allows passage of substances in and out of the nucleus.

What is the function of the nucleolus?

A dark body inside the nucleus that contains free nucleotide bases and produces ribosomes.

Where are ribosomes located?

Attached to the endoplasmic reticulum or free in the cytoplasm (also inside chloroplasts/mitochondria in small numbers).

What is a gene's coding role?

Genes code for specific traits by specifying sequences of amino acids in proteins.

What are the two stages of protein synthesis?

Transcription and translation.

What is the role of anticodons during translation?

Anticodons on tRNA pair with codons on mRNA to insert the correct amino acid.

Which process creates identical copies of a DNA molecule?

DNA replication.

What is the effect of a mutation on protein structure?

A change in DNA sequence can change codons and amino acids, potentially altering the protein; sometimes no change occurs if the same amino acid is coded.