chromosome
A structure found inside the nucleus of a cell. A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.
Sister chromatid
One of two attached members of a duplicated eukaryotic chromosome/BOTTOM
Centromere
Constricted region in a eukaryotic chromosome where sister chromatids are attached/MIDDLE
Nucleosome
• A length of DNA wound around a spool of histone proteins
How many chromosomes are in a human body cell
46/23pairs
Diploid
Cells having two of each type of chromosome characteristic of the species (2n)
haploid
a cell that contains a single set of chromosomes. The term haploid can also refer to the number of chromosomes in egg or sperm cells, which are also called gametes
autosomal chromosomes
Any chromosome other than a sex chromosome
• Paired chromosomes with the same length, shape, centromere location, and genes
sex chromosomes
Members of a pair of chromosomes that differ between males and females
karyotype
Image of an individual’s chromosomes arranged by size, length, shape, and centromere location
mutation
A permanent change in DNA sequence
Erwin Chargaff
A = T and C = G Proportions of A and G vary among species
Rosalind Franklin
▪ Discovered the basic structure of DNA by x-ray crystallography
Maurice Wilkins \n ▪ James Watson, and Francis Crick
▪ Built the first accurate model of a DNA molecule
DNA Molecule
Consists of two strands of nucleotide monomers
• running in opposite directions
• coiled into a double helix
• held together by hydrogen bonds between nucleotide
The double helix
a term used to describe the physical structure of DNA. A DNA molecule is made up of two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups.
DNA nucleotide
A five-carbon sugar (deoxyribose)
• Three phosphate groups
• One nitrogen-containing base (adenine, thymine, guanine, or cytosine)
DNA sequence
The order of nucleotide bases in a strand of DNA
• Varies among species and among individuals
DNA Replication
Duplication of a cell’s DNA before cell division
▪ The double-helix unwinds
DNA polymerase
• uses each strand as a template to assemble new, complementary strands of DNA
DNA ligase
• seals any gaps to form a continuous strand
DNA repair mechanisms
Proofreading by DNA polymerase corrects most base-pairing errors
Clones
Exact genetic copies of DNA or an organism
▪ Now a common practice in research and animal husbandry
Reproductive cloning
Technology that produces genetically identical individuals
▪ Produced by somatic cell nuclear transfer
Somatic cell nuclear \n transfer (SCNT)
• Method of reproductive cloning in which nuclear DNA from an adult somatic cell is transferred into an unfertilized, enucleated egg
• Common practice for livestock breeders
reasons of Therapeutic cloning
▪ To learn about molecular basis of genetic diseases
▪ To make replacement tissues or organs for people with fatal diseases
▪ Save endangered animals from extinction
The Hershey Chase Experiments
the DNA of a virus needs to enter a bacterium to infect it.