DNA and Cell Division Quiz

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Questions and Answers

What must occur before a cell undergoes mitosis or meiosis?

The cell must metabolize nutrients.

The cell must synthesize mitochondria.

The cell must replicate its chromosomes. (correct)

The cell must undergo apoptosis.

What is the term for the process of copying DNA?

DNA recombination

DNA replication (correct)

DNA transcription

DNA translation

Which of the following processes is a prerequisite for both mitosis and meiosis?

S phase of the cell cycle (correct)

Protein synthesis

Apoptosis induction

Transcription of RNA

Which statement about chromosome division is accurate?

It requires DNA replication beforehand. Signup and view all the answers

What is the significance of DNA replication in a cell's lifecycle?

It prepares genetic materials for cell division. Signup and view all the answers

What percentage of DNA on chromosomes is specifically identified as noncoding DNA?

97% Signup and view all the answers

Which term describes the sections of DNA that do not directly code for proteins?

Junk DNA Signup and view all the answers

If 3% of DNA codes for proteins, what is the primary function of the remaining 97%?

To regulate gene expression and unknown functions Signup and view all the answers

What is a common misconception about the 97% of DNA that is considered noncoding?

It has no function at all. Signup and view all the answers

Which of the following statements is accurate regarding genes?

Only 3% of DNA contains genes that code for proteins. Signup and view all the answers

What was the initial belief about the substance associated with cells?

It was considered hereditary matter. Signup and view all the answers

By the year 1900, which of the following was known about DNA?

Its components were identified. Signup and view all the answers

Which of the following statements accurately reflects the understanding of hereditary matter prior to modern discoveries?

Beliefs about its hereditary nature lacked substantial evidence. Signup and view all the answers

What aspect of the substance's nature was particularly emphasized before major discoveries in genetics?

Its capacity to act as hereditary material. Signup and view all the answers

Before major advancements in genetics, how would the understanding of heredity be best characterized?

Still largely theoretical and speculative. Signup and view all the answers

What is the role of DNA replication during cell division?

It provides daughter cells with a complete set of genetic information identical to the parent cell. Signup and view all the answers

In which cellular structure does DNA replication occur?

Nucleus Signup and view all the answers

What is a consequence of errors during DNA replication?

Daughter cells may contain genetic mutations. Signup and view all the answers

What outcome would result if DNA replication did not occur before cell division?

The daughter cells would have incomplete or missing genetic information. Signup and view all the answers

Which statement accurately describes the genetic information in daughter cells after replication?

It is identical to that of the parent cell. Signup and view all the answers

What describes the structure of the two molecules of DNA resulting from replication?

Each molecule consists of one old strand and one newly synthesized strand. Signup and view all the answers

Which enzyme is responsible for unwinding the DNA strands during replication?

Gyrase Signup and view all the answers

What is the role of Topoisomerase in DNA replication?

It unwinds and relieves the torsional strain of unwinding DNA. Signup and view all the answers

Which statement correctly reflects a byproduct of DNA replication?

Both daughter molecules are identical and include strands from the parent. Signup and view all the answers

In the context of DNA replication, what is the significance of having half of the strand old?

It helps maintain genetic integrity and accuracy. Signup and view all the answers

How many amino acids are coded by the first two nucleotides of codons?

5 Signup and view all the answers

Which of the following amino acids is specified by multiple codons?

Serine Signup and view all the answers

What is the total number of different codons that specify either Arg, Leu, or Ser?

6 Signup and view all the answers

Which amino acid is NOT specified by the first two nucleotides of its respective codon?

Arginine Signup and view all the answers

How many additional amino acids are specified by six different codons?

3 Signup and view all the answers

Study Notes

DNA and Protein Synthesis

DNA, named by Johann Friedrich, was identified as an acidic substance rich in phosphorus found in salmon sperm. Early researchers believed it held the key to heredity, but lacked definitive evidence.
The structure of DNA was elucidated in 1953. By then, the components of DNA were known but not its arrangement. X-ray diffraction techniques determined the structure.
A Nobel Prize was awarded in 1962 to Watson, Crick, and Wilkins for their contribution to the discovery of the double helix structure of DNA, which included important data from Rosalind Franklin.
DNA codes for proteins, including structural proteins, enzymes (like catalysts), and hormones.

Function of DNA

The sequence of nitrogenous bases carries the instructions to build proteins.
Proteins control metabolic traits, regulate growth, and development.

Chromosome Organization

Chromosomes are super-coiled strands of DNA.
Genes are sections of DNA that code for proteins. Most of DNA is not involved in coding (non-coding DNA or "junk DNA")
Non-coding DNA may have a regulatory function, which is yet unknown.

Building Blocks of DNA

DNA is made of nucleotides.
Nucleotides consist of three parts:
- 5-carbon sugar (deoxyribose)
- Phosphate group
- Nitrogenous base (adenine, guanine, thymine, cytosine)

Nitrogenous Bases

Purines: Adenine and Guanine (double-ring structure)
Pyrimidines: Cytosine, Thymine, and Uracil (single-ring structure).
Uracil replaces thymine in RNA.

Composition of DNA

Chargaff's rule: The amount of adenine equals thymine, and the amount of guanine equals cytosine.

Watson-Crick Model

DNA is a double helix.
Two nucleotide strands run in opposite directions.
Strands are held together by hydrogen bonds between bases: Adenine pairs with Thymine, and Guanine pairs with Cytosine.

DNA Replication

Before cell division, DNA replicates, creating identical copies of the chromosomes.
DNA polymerase copies the DNA, with identical base pairings.

Results of DNA Replication

Two identical DNA molecules are produced.
Each molecule has one original strand (from the parent) and one new strand.

Enzymes in DNA Replication

Enzymes involved in DNA replication include: Topoisomerase, DNA polymerase III, and DNA ligase.
These enzymes unwind, replicate and join strand fragments.

Replication Fork

The area where the DNA strands separate during replication.
DNA polymerase moves towards the replication fork.
In the lagging strand, DNA is replicated in short fragments (Okazaki fragments), and DNA ligase joins these fragments.

Protein Synthesis

Cells build proteins based on the instructions in DNA.
This process involves two parts:
- Transcription (DNA to RNA)
- Translation (RNA to proteins)

Transcription (DNA to RNA)

DNA is copied into a complementary strand of mRNA (messenger RNA).
RNA polymerase copies the information in DNA.
RNA polymerase binds to a promoter region, a specific base sequence signaling the start of a gene.
The copied sequence is transcribed into mRNA, which is then used for protein synthesis.

RNA Structure

RNA is a single-stranded molecule.
RNA contains the sugar ribose, instead of deoxyribose.
RNA contains uracil (U) instead of thymine (T).

RNA Function

Three kinds of RNA are involved in protein synthesis:
- mRNA (messenger RNA): carries the genetic code from DNA to the ribosome.
- rRNA (ribosomal RNA): forms the ribosome, the site of protein synthesis.
- tRNA (transfer RNA): delivers amino acids to the ribosome.

The Genetic Code

A set of 64 codons (sequences of three bases).
61 codons specify amino acids.
3 codons signal the end of protein synthesis (stop codons).

Translation (RNA to proteins)

mRNA carries the genetic code to the ribosome.
tRNA molecules bring amino acids matching each codon.
Ribosomes catalyse the formation of peptide bonds between amino acids.
The resulting chain of amino acids folds into a functional protein.

Translation Stages

Initiation, Elongation, Termination.

Promoters

A base sequence in the DNA that signals the start of a gene.

Classes of RNA

Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

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Description

Test your knowledge on the processes that precede mitosis and meiosis, as well as the intricacies of DNA replication. This quiz covers key concepts related to chromosome division, noncoding DNA, and the historical understanding of genetics. Perfect for students studying cell biology and genetics.