DNA Structure and Function

DNA Nucleotide

• A subunit of DNA, consisting of a deoxyribose sugar, a phosphate group, & a nitrogenous base
• The nitrogenous bases are Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
• They are linked together in long chains called DNA strands

DNA Strand

• A chain of linked DNA nucleotides
• They run in opposite directions (antiparallel)

DNA Molecule (Double Helix)

• Two DNA strands twisted together
• Joined by hydrogen bonds between complementary base pairs
  • Adenine pairs with Thymine (A-T)
  • Guanine pairs with Cytosine (G-C)

Antiparallel DNA Molecule

• Two DNA strands run in opposite directions
• One strand runs from 5' to 3'
• The other runs from 3' to 5'

DNA Sequence

• The order of nitrogenous bases in a DNA strand
• A, T, C, G are used to represent the bases
• The sequence holds genetic information

Histone

• Proteins that DNA wraps around
• They help compact DNA in chromosomes

Chromosome Packaging

• The process of organizing DNA within chromosomes
• DNA is tightly coiled using histones to fit into the nucleus

Chromosome (Unreplicated)

• One long piece of DNA containing genes
• Found in the nucleus of eukaryotic cells
• Consists of a single strand of tightly packed DNA

Chromosome (Replicated)

• Contains two identical sister chromatids
• The sister chromatids are held together by a centromere
• Replicated chromosome is ready for cell division

Telomere

• Protective caps at the ends of chromosomes
• They prevent the ends of chromosomes from being degraded or sticking together

Centromere

• Region of a chromosome that connects the sister chromatids together
• It plays a crucial role in chromosome segregation during cell division

Gene

• A segment of DNA that codes for a specific protein or RNA molecule
• It is the functional unit of heredity

DNA Template Strand

• The strand of DNA that is used as a template for RNA synthesis
• It is read by RNA polymerase to create a complementary RNA molecule

Gene Locus (Loci pl.)

• The specific location of a gene on a chromosome

Allele

• One of two or more alternate forms of a gene
• Different alleles can produce different traits

Homozygous Genotype

• Two identical alleles for a gene
• Example: AA or aa

Heterozygous Genotype

• Two different alleles for a gene
• Example: Aa

Sister Chromatids

• Two identical copies of a chromosome
• They are linked together at the centromere until cell division

Homologous Chromosomes

• Pair of chromosomes containing the same genes
• One chromosome comes from each parent
• They can have different alleles for the same genes

Non-homologous Chromosomes

• Chromosomes that do not contain the same genes
• They are not paired up during meiosis

Diploid Cell

• Cell with two sets of chromosomes
• One set from each parent

Haploid Cell

• Cell with one set of chromosomes
• Example: Gametes (sperm and egg cells)

RNA Nucleotide

• Similar to DNA nucleotides, but with a ribose sugar and uracil (U) instead of thymine (T)
• The nitrogenous bases are adenine (A), uracil (U), guanine (G), and cytosine (C)

Protein

• Complex molecules made of amino acids
• They perform a variety of functions in the body, including structural support, catalysis, transport, and signaling

Amino Acid

• The building blocks of proteins
• There are 20 different amino acids that can be combined in various sequences to form different proteins

Protein Synthesis

• When an amino acid chain builds a protein using genetic instructions
• It involves two steps: transcription and translation

Transcription

• The process of copying a gene's DNA sequence into RNA
• It involves the use of an enzyme called RNA polymerase

Transcription (Steps)

• RNA polymerase binds to a promoter site on the DNA
• RNA polymerase unwinds the DNA and reads the template strand
• RNA polymerase uses the DNA template to create a pre-mRNA molecule
• Pre-mRNA molecule is a complementary copy of the DNA template strand

Translation

• The process of using the mRNA code to build a protein
• It involves the use of ribosomes and transfer RNA (tRNA)

Translation (Steps)

• mRNA codons (3-base sequences) bind to complementary tRNA anticodons
• Each tRNA molecule carries a specific amino acid
• Ribosomes join the amino acids together to form a polypeptide chain
• The polypeptide chain folds into a specific three-dimensional structure, forming a protein

This quiz explores the fundamental components of DNA, including nucleotides, strands, and double helix formation. Additionally, it covers concepts of DNA sequence and chromosome packaging. Test your understanding of these essential building blocks of genetic material.