DNA Structure and Gene Expression

These flashcards cover essential topics in DNA structure and gene expression, including the processes of DNA replication, transcription, translation, and the implications of mutations on cell function.

What is the purpose of DNA in living organisms?

DNA stores genetic information necessary for the development, structure, and metabolism of cells.

What are the three subunits of a nucleotide in DNA?

Phosphoric acid (phosphate), a pentose sugar (deoxyribose), and a nitrogen-containing base.

Who determined the structure of DNA and in what year?

James Watson and Francis H. C. Crick determined the structure of DNA in 1953.

What are the four nitrogenous bases found in DNA?

Adenine (A), Guanine (G), Thymine (T), and Cytosine (C).

What is meant by complementary base pairing?

Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C) in DNA.

What is the significance of the 5' and 3' ends of a DNA strand?

The strands of DNA are oriented in opposite directions, which influences how DNA is replicated and transcribed.

What is the process of DNA replication?

DNA replication is copying one DNA double helix into two identical double helices, with each original strand serving as a template.

What does semiconservative replication mean?

Each daughter DNA double helix consists of one new strand and one old strand conserved from the parent DNA molecule.

What role does DNA helicase play in DNA replication?

DNA helicase unwinds and unzips the double-stranded DNA by breaking hydrogen bonds between paired bases.

What are Okazaki fragments?

Short DNA segments synthesized on the lagging strand during DNA replication.

What is transcription in the context of protein synthesis?

Transcription is the process where a portion of DNA serves as a template for synthesizing messenger RNA (mRNA).

What role does mRNA play in gene expression?

mRNA carries genetic information from DNA to the ribosomes for protein synthesis.

What are codons?

Codons are triplet sequences of nucleotides on mRNA that specify particular amino acids.

How do tRNA molecules assist in translation?

tRNA transports amino acids to ribosomes and matches its anticodon with the corresponding codon on mRNA.

What is the significance of the ribosome in protein synthesis?

Ribosomes are the sites of protein synthesis where mRNA and tRNA interact to form polypeptides.

What are stop codons?

Stop codons (UAA, UGA, UAG) signal the termination of protein synthesis.

How do mutations affect protein synthesis?

Mutations can change DNA sequences, potentially altering the expressed proteins or rendering them nonfunctional.

What are mutagens?

Mutagens are environmental factors that can cause changes (mutations) in DNA.

What is the role of tumor suppressor genes?

Tumor suppressor genes regulate cell division and maintain genomic stability; mutations can lead to uncontrolled cell growth.

What is the function of the p53 gene?

p53 is a major tumor suppressor gene that helps control the cell cycle and promotes apoptosis.