A1.2 necluectic acids

What is DNA?

DNA (deoxyribonucleic acid) is a nucleic acid that stores genetic information and provides the instructions needed for life. It is an essential component of living organisms.

Where is DNA located?

DNA is found in cells and contains the genetic information used by cells. In eukaryotic cells, most DNA is located in the nucleus.

What is the monomer of DNA?

The monomer of DNA is a nucleotide. DNA is a polymer made from many nucleotide monomers linked together.

What are the three components of a nucleotide?

A nucleotide consists of a phosphate group, a pentose sugar, and a nitrogenous base.

What is the pentose sugar in DNA?

The pentose sugar in DNA is deoxyribose.

What is the pentose sugar in RNA?

The pentose sugar in RNA is ribose.

What are the four nitrogenous bases in DNA?

Adenine (A), thymine (T), cytosine (C), and guanine (G).

What are the four nitrogenous bases in RNA?

Adenine (A), uracil (U), cytosine (C), and guanine (G).

How do you draw a simplified nucleotide?

Draw three connected components: a phosphate group, a pentose sugar, and a nitrogenous base. Label each component clearly.

What is the charge of the phosphate group in a nucleotide?

The phosphate group is negatively charged.

What are the purine bases?

Adenine (A) and guanine (G) are purines.

What are the pyrimidine bases?

Cytosine (C), thymine (T), and uracil (U) are pyrimidines.

How can you remember the purines?

Purines = Adenine and Guanine (A and G).

How can you remember the pyrimidines in DNA?

Pyrimidines = Cytosine and Thymine (C and T). In RNA, uracil replaces thymine.

What is the difference between ribose and deoxyribose?

Ribose is the sugar found in RNA, while deoxyribose is the sugar found in DNA. Deoxyribose has one less oxygen atom than ribose.

What bond joins the components within a nucleotide?

The components of a nucleotide are joined by covalent bonds.

How are nucleotides joined together to form a nucleic acid strand?

Nucleotides are joined by covalent bonds between the phosphate group of one nucleotide and the 3′ carbon of the sugar of the previous nucleotide.

What does the sugar-phosphate backbone consist of?

The sugar-phosphate backbone consists of alternating pentose sugars and phosphate groups joined by covalent bonds.

What is the directionality of a DNA strand?

A DNA strand has directionality from the 5′ end to the 3′ end, based on the numbered carbons of the sugar.

What do 5′ and 3′ mean in DNA?

5′ and 3′ refer to specific carbon atoms in the sugar. They give a DNA strand its direction and polarity.

What is DNA's overall structure?

DNA is usually double stranded and forms a double helix. The two strands run in opposite directions and are held together by hydrogen bonds between complementary bases.

What is a hydrogen bond in DNA?

A hydrogen bond is a weak attraction between complementary nitrogenous bases on opposite DNA strands.

What bonds form the sugar-phosphate backbone?

Covalent bonds link the nucleotides together to form the sugar-phosphate backbone.

What bonds hold complementary DNA strands together?

Hydrogen bonds between complementary nitrogenous bases hold the two DNA strands together.

What is complementary base pairing?

Complementary base pairing means that specific bases pair with each other: adenine pairs with thymine, while cytosine pairs with guanine.

What base does adenine pair with in DNA?

Adenine (A) pairs with thymine (T).

What base does cytosine pair with in DNA?

Cytosine (C) pairs with guanine (G).

What base does guanine pair with in DNA?

Guanine (G) pairs with cytosine (C).

What base does thymine pair with in DNA?

Thymine (T) pairs with adenine (A).

What does "complementary DNA strand" mean?

A complementary DNA strand has bases that pair with the bases of the original strand according to complementary base-pairing rules: A-T and C-G.

What does antiparallel mean in DNA?

The two DNA strands run in opposite directions. One strand runs 5′ → 3′ while the complementary strand runs 3′ → 5′.

Why is DNA described as a double helix?

The two antiparallel DNA strands twist around each other to form a helical structure.

What should you label when drawing a 4-nucleotide DNA diagram?

Label the phosphate groups, deoxyribose sugars, nitrogenous bases, covalent bonds in the sugar-phosphate backbone, hydrogen bonds between complementary bases, and the 5′ and 3′ directions.

What is the difference between a covalent bond and a hydrogen bond in DNA?

Covalent bonds form the strong sugar-phosphate backbone within each strand. Hydrogen bonds are weaker attractions that connect complementary bases between the two strands.

What is the diversity of DNA base sequences?

Diversity of DNA base sequences means that the four bases can be arranged in many different sequences, allowing DNA to store a huge amount of genetic information.

Why can DNA store so much information?

The four bases can be arranged in an enormous number of different sequences. The more bases in a DNA molecule, the greater the number of possible combinations.

How many possible sequences are there for 10 DNA bases?

There are 4^10 possible sequences, which is over one million different combinations.

Why is DNA a good molecule for storing information?

DNA is extremely compact and can store enormous amounts of information through different base sequences.

What is replication?

Replication is the process by which DNA is copied, producing new DNA molecules.

What is transcription?

Transcription is the process of forming RNA using DNA as the template.

What is translation?

Translation is the process in which the information in mRNA is used to build a protein.

What is the central dogma?

The central flow of genetic information is DNA → RNA → protein. DNA can be replicated, DNA can be transcribed into RNA, and RNA can be translated into protein.

What are the three main types of RNA?

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

What is mRNA?

mRNA carries genetic instructions from DNA and provides the information used to build proteins.

What is tRNA?

tRNA helps bring amino acids to the ribosome during protein synthesis.

What is rRNA?

rRNA is a major component of ribosomes and helps with protein synthesis.

What is a codon?

A codon is a sequence of three bases on mRNA that codes for a specific amino acid or acts as a start or stop signal.

Where is a codon found?

A codon is found on mRNA.

How many bases make up one codon?

Three bases make up one codon.

What is the relationship between codons and proteins?

Each codon specifies a particular amino acid or a start/stop signal. A sequence of codons provides the instructions for assembling a protein.

What is the genetic code?

The genetic code is the set of rules that determines how sequences of bases in mRNA correspond to amino acids or start/stop signals.

What does conservation of the genetic code mean?

The genetic code has been conserved throughout evolution, meaning that the same basic coding system is shared across life forms.

What does universality of the genetic code mean?

The genetic code is essentially universal: the same codons specify the same amino acids in organisms across the different forms of life.

Why is the universality of the genetic code important to scientists?

It allows scientists to transfer genes between organisms because the recipient organism can read and express the genetic information. For example, a human gene can be placed into bacteria and the bacteria can express the gene.

How does the universality of the genetic code provide evidence for common ancestry?

Because organisms use the same basic genetic coding system, this supports the idea that all life shares a common evolutionary ancestry.

What are the main structural similarities between DNA and RNA?

Both are nucleic acids made from nucleotide monomers. Both contain a phosphate group, a pentose sugar, and nitrogenous bases, and both have a sugar-phosphate backbone.

What are the main structural differences between DNA and RNA?

DNA usually consists of two strands and contains deoxyribose and thymine. RNA is usually single stranded and contains ribose and uracil.

Which sugar is found in DNA and RNA?

DNA contains deoxyribose; RNA contains ribose.

Which base is found in DNA but not RNA?

Thymine is found in DNA, while RNA uses uracil instead.

Which base is found in RNA but not DNA?

Uracil is found in RNA, while DNA uses thymine instead.

Is RNA always single stranded?

No. RNA is usually single stranded, although some RNA molecules and some viruses can have double-stranded RNA.

Is DNA usually single or double stranded?

DNA is usually double stranded.

What is the function of complementary base pairing in DNA?

It allows accurate copying of genetic information during DNA replication and helps genetic information be expressed through transcription.

What is semi-conservative replication?

Semi-conservative replication produces two DNA molecules, each containing one original strand and one newly synthesized strand.

Why is complementary base pairing important during replication?

Each original DNA strand acts as a template. Complementary base pairing allows the correct bases to be added to form a new complementary strand.

What is the role of DNA in genetic information?

DNA stores genetic information in the sequence of its bases.

What is the role of RNA in gene expression?

RNA carries and helps interpret genetic information so that proteins can be produced.

What is meant by "DNA as a polymer"?

DNA is a polymer because it is a long chain made from repeating nucleotide monomers.

What is meant by "nucleotide sequence"?

It is the specific order of nitrogenous bases along a nucleic acid strand.

Why does changing the DNA base sequence matter?

Different base sequences can contain different genetic information, allowing DNA to encode different proteins and biological traits.