DNA Structure and Function

Flashcards containing terms and definitions related to DNA structure and function.

Nuclein

Phosphate-rich chemicals isolated from white blood cells (leukocytes).

DNA Structure

A double-helix structure.

DNA Structure

The specific base-pairing of nitrogen bases.

DNA Structure

Repetitive sugar and phosphate units.

Nucleic Acids

Organic molecules to which DNA and RNA belong

DNA

Deoxyribonucleic acid.

RNA

Ribonucleic acid.

Nucleotides

The small subunits or monomers of nucleic acids (polymers).

Nucleotide Components

A phosphate group, a sugar called deoxyribose, and 1 of 4 possible nitrogen-containing bases (A, T, C, G).

Relationship among DNA, a gene, and a chromosome

A chromosome contains hundreds of genes which are composed of DNA.

DNA structure and genes

The nitrogen bases and their sequences comprise the structure of DNA that serves the function of ' genes '.

Height example nucleotide strands

Tall = TT or Tt; Short = tt.

ATG

Codes for G.

GCC

Codes for C.

TT

The nucleotide strand - ATGATG.

Tt

The nucleotide strand - ATGGCC.

tt

The nucleotide strand - GCCGCC.

Base-Pairing

Base-pairing occurs when there are equal amounts of adenine and thymine, and equal amounts of guanine and cytosine.

Base-pairing rules

A always pairs with T, and G always pairs with C

Purines

A & G are and are larger in size.

Pyrimidines

T & C are and are smaller in size.

DNA Base Amounts

The amount of cytosine is always equal to the amount of guanine, and the amount of adenine is always equal to the amount of thymine.

Sequence

Each sequence of bases represents a unique set of genetic instructions (like Morse code).

DNA Structure

DNA consists of 2 separate strands linked by nucleotides – looking much like a ladder.

DNA double helix

Looking much like a ladder – that is twisted (helix).

DNA molecule: rungs of the ladder

The rungs of the ladder would be: the nitrogenous bases linked together.

DNA molecule: sides of the ladder

The uprights or sides of the ladder would be: the deoxyribose sugar linked to the phosphates (the sugar-phosphate backbone).

DNA produced during cell cycle

A cell makes two identical daughter cells – including identical DNA, which happens in interphase prior to mitosis.

Semi-conservative replication

This process produces two DNA double helices, each with one old strand and one new strand.

DNA helicase

Enzymes pull apart the parent DNA double helix, breaking apart the hydrogen bonds.

DNA polymerase

Takes free nucleotides and base pairs them up with the new strands that have been pulled apart.

DNA ligase

Enzymes glue each of the individual piece of DNA into their new double strands to finally form 2 newly synthesized DNA strands each containing one old strand and one new strand.

Gene mutation

A change in the nucleotide sequence of DNA.

Mutations

These mutations or mistakes are most significant in meiosis

Point mutations

Change in an individual nucleotide.

Insertion mutations

When one or more extra nucleotides are inserted into a strand.

Deletion mutations

When one or more nucleotides are removed from a gene.

Genotype

Each gene gives instructions for or encodes the information for a single protein.

RNA

Carries the information from DNA in the nucleus to the ribosomes.

RNA characteristic

RNA is single stranded.

RNA characteristic

RNA has the sugar Ribose instead of deoxyribose.

RNA characteristic

RNA has the base uracil instead of thymine.

DNA Codes

DNA codes for the synthesis of three major types of RNA.

Three major types of RNA

Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

3 major types of RNA: Function

These all are involved in converting the nucleotide sequence of genes into the amino acid sequence of protein.

Base pair rule

Cytosine equals that of guanine.

Transcription

The information in DNA is copied into a complementary single stranded mRNA.

Translation

Pairing up with a complementary tRNA molecule on a ribosome.

Translation result

A sequence of amino acids create a protein.

RNA

In RNA, thymine is replaced with a uracil, so that adenine base-pairs with uracil in RNA.

AUG

Codes for Methionine

UAG

Stop codon

Protein transcription and translation steps

DNA undergoes transcription and the information in the DNA template is copied into an mRNA transcript (copy), which then undergoes translation by pairing up with tRNA, making sequences of amino acids into a protein.

Terminator

Sequence that causes RNA polymerase to release the mRNA strand or transcript.

mRNA transcript

mRNA transcript contains exons and introns.

Introns

Non-coding segment of DNA removed by spliceosomes before mRNA leaves nucleus.

Exon

Parts of mRNA that can code for the protein.

spliceosomes

Enzymes that cut the primary mRNA transcript and then rejoin adjacent exons.

Translation

The process where the sequence of bases of mRNA assembles (synthesizes) specific amino acids into a protein by using tRNA as a translator.

Translation

Steps by which gene expression leads to protein synthesis.

Transfer RNA (tRNA)

Attached to amino acids.

tRNA

There is at least one tRNA molecule for each of the 20+ amino acids found in proteins.

tRNA's

Pair with more than one codon.

tRNA synthases

Enzymes that recognize which amino acid should join which tRNA molecule.

Ribosomal RNA (rRNA)

Produced from a DNA template in the nucleolus of nucleus.

Ribosome

rRNA combines with dozens of proteins to form a complex structure called a ribosome.

Ribosomes

They facilitate complementary complementary base pairing between tRNA anti-codons and mRNA codons; rRNA reads the codons.

Translation

Ribosomes move down the mRNA molecule, new tRNA's arrive; amino acids join; and a polypeptide (protein) forms.

Translation

Exminates once the polypeptide is formed.

Ribosome

Some have a series of amino acids called a signal sequence that enables the ribosome to bind to the endoplasmic reticulum.

Chain Initiation

A small ribosomal subunit attaches to mRNA in the vicinity of the start codon: a base triplet (AUG).

Chain Termination

Termination of protein synthesis occurs at a stop codon that does not code for an amino acid.

genetic code

Some general qualities that describe the genetic code is universal for all organisms

genetic code

Some general qualities that describe the is based on 64+ codons

UNCHANGED, protein

The new codon may specify the same amino acid as the old codon

Mrna codon

UUA-AGU

Mutation on Evolution

Mutations create new gene sequences and are the ultimate source of genetic variation

tRNA anticodons

If the DNA triplets were AAG-CAT, the tRNA anticodons would be AAG-CAU