Molecular Biology and the Central Dogma

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Questions and Answers

What is the primary function of transcription in gene expression?

To synthesize proteins from amino acids

To convert DNA into a single-stranded RNA molecule (correct)

To edit introns from mRNA

To translate RNA into amino acids

What process occurs after transcription in gene expression?

Splicing

Replication

Transcriptional silencing

Translation (correct)

Which of the following statements is true regarding the transcribing of a DNA sequence?

All bases in DNA remain unchanged

Thymine is replaced by Adenine

Cytosine is complementary to Guanine (correct)

Guanine is always transcribed into Uracil

During translation, how many bases of RNA are read at a time by the ribosome?

Three bases Signup and view all the answers

What constitutes the coding region of eukaryotic genes?

A series of expressed exons with intervening introns Signup and view all the answers

What are the components of a nucleotide?

A phosphate group, ribose sugar, and a base Signup and view all the answers

Which bases are classified as purines?

Adenine and Guanine Signup and view all the answers

What process involves the synthesis of mRNA from DNA?

Transcription Signup and view all the answers

Which statement best describes ribosomal RNA (rRNA)?

It forms part of the structure of ribosomes. Signup and view all the answers

What term describes the total DNA content of a cell?

Genome Signup and view all the answers

How many types of RNA exist and what is one of their roles?

Three types; mRNA synthesizes proteins Signup and view all the answers

What is the main role of transfer RNA (tRNA)?

To carry amino acids to the ribosome Signup and view all the answers

Which of the following is NOT a type of gene mentioned?

Transcription genes Signup and view all the answers

What is the primary role of messenger RNA (mRNA) in molecular biology?

To translate genetic information into proteins Signup and view all the answers

Which base is paired with adenine (A) during transcription?

Uracil (U) Signup and view all the answers

What defines the genome of an organism?

The total DNA content of a cell Signup and view all the answers

Which of the following statements about eukaryotic cells is correct?

They have organized and membrane-bound organelles Signup and view all the answers

How many pairs of chromosomes do humans have?

23 pairs Signup and view all the answers

Transcription involves the conversion of which type of biological material?

DNA to mRNA Signup and view all the answers

What is the genetic composition of male and female humans in terms of sex chromosomes?

Male (XY), Female (XX) Signup and view all the answers

Which of the following is NOT a function of bioinformatics?

Directly performing cellular functions Signup and view all the answers

Study Notes

Introduction

Molecular biology is the study of molecules like RNA, DNA, and proteins, which are involved in transcription and translation.
Bioinformatics uses computers to store, retrieve, manipulate, and distribute information about biological macromolecules.
The central dogma of genetics explains how DNA information flows to proteins.
DNA sequence is transcribed into messenger RNA (mRNA).
mRNA sequence is translated into proteins.

The Central Dogma of Life

Transcription is the process of copying DNA into mRNA.
Translation is the process of converting mRNA into proteins.
Transcription follows the rule of complementary base pairing between DNA and RNA.
- A in DNA transcribes to U in RNA.
- T in DNA transcribes to A in RNA.
- G in DNA transcribes to C in RNA.
- And vice versa.

Cells

The basic unit of life is a cell.
Different types of cells exist, each with distinct functions (e.g., skin, brain, red blood cells).
Cells are produced through cell division (mitosis), resulting in two daughter cells.
Eukaryotic cells have a nucleus.

Nucleus and Chromosomes

Every cell has a nucleus.
Rod-shaped particles inside the nucleus are chromosomes.
Chromosomes always exist in pairs.
Different species have different numbers of chromosomes
- Humans have 46
- Tobacco has 48
- Goldfish have 94
- Chimps have 48
X and Y chromosomes determine sex.
- Humans: Male (XY), Female (XX)
- Birds: Male (XX), Female (XY)

DNA

DNA stores the complete genetic information of an organism.
It determines the structure and function of an organism.
Proteins are built using the genetic code of DNA.
DNA is short for deoxyribonucleic acid.
It is composed of nucleotides.
Each nucleotide has three parts:
- A phosphate group
- A pentose sugar (ribose sugar)
- A base
There are four types of bases:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T)
- A and G are purines.
- C and T are pyrimidines.
Bases on one DNA strand connect to bases on the opposite strand through hydrogen bonds:
- (A = T)
- (G ≡ C)
This base pairing is specific, and the base sequence on one strand is complementary to the sequence on the other.

RNA

RNA is a nucleic acid molecule.
It plays a key role in protein synthesis.
RNA is transcribed from DNA.
There are three types of RNA:
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)

Messenger RNA (mRNA)

Synthesized in the nucleus from DNA.
Carries genetic information to the ribosomes in the cytoplasm.
Directs the synthesis of specific proteins.
3 consecutive bases on the mRNA are called a "codon" and code for a specific amino acid.
The process of mRNA synthesis in the nucleus under DNA directions is called "transcription."

Transfer RNA (tRNA)

Found in the cytoplasm, also known as soluble RNA (sRNA).
Transports amino acids to the ribosome.
Each amino acid has a specific tRNA.

Ribosomal RNA (rRNA)

Present in the ribosomes of the cytoplasm.
The ribosome is a nucleoprotein structure in the cytoplasm.
The ribosome particle is formed by at least 4 rRNA molecules complexed with several proteins.

Gene and Genome

A gene is a segment of DNA that contains specific genetic information, coding for a specific protein.
A genome is the total DNA content of a cell which equals the total number of genes in a cell.
Three types of genes exist:
- Protein-coding genes: transcribed into RNA and then translated into proteins.
- RNA-specifying genes: only transcribed into RNA.
- Regulatory genes: include untranscribed sequences.

Inheritance and Information Conversion

Three processes are responsible for inheriting genetic information and converting it between forms:
- Replication: duplicates a double-stranded nucleic acid to create identical copies.
- Transcription: reads and transcribes a gene segment of DNA into a single-stranded RNA sequence.
- Translation: converts RNA sequence into a sequence of amino acids.

Gene Expression

The synthesis of protein under the influence of a gene is called gene expression.
It involves two stages:
- Transcription: forming mRNA.
- Translation: converting mRNA's nucleotide sequence (codons) into an amino acid sequence of a protein.

Transcription

The process of copying DNA into RNA.
- One strand of DNA is used as a template.
- The complementary strand of DNA is created.
- Thymine (T) is replaced with Uracil (U) in the RNA strand.
Example:
- Start: GGATGCCAATG
- Transcribed: CCUACGGUUAC

Translation

The process of converting the information from the language of nucleotides to the language of amino acids.
Proteins are chains of amino acids.
There are 20 standard amino acids used in life.
Translation uses a "genetic code" or "codon table" to convert three bases (a codon) from RNA into one amino acid.

Coding Regions

The coding region of eukaryotic genes typically consists of a series of expressed exons with intervening introns.

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Description

Explore the fundamentals of molecular biology, focusing on the central dogma which outlines the processes of transcription and translation. This quiz delves into the mechanisms by which DNA is converted into RNA and then into proteins, as well as the significance of cells in the life of organisms.