CHAPTER 7 lecture

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

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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.