Cell and Molec Ch 5: DNA and Chromosomes

Griffith Experiment

through testing strains of bacteria in mice, they found that a pathogenic S strain of bacteria could permanently transform the nonlethal R strain into the deadly S strain, showing that bacteria can transfer genetic info

Avery, Macleod, and McCarty experiment

fractionated the S strain into RNA, protein, DNA, lipids, and carbohydrates, showed that DNA served as genetic material

Hershey and Chase experiment

bacteriophages with sulfur and phosphorus infected cells and were centrifuged together to see which element remained in the cell after blending, the phosphorus stayed in the infected bacteria, showing that DNA is the genetic material bacteria can transfer

genes

store genetic information to determine the characteristics of a species

Watson and Crick

determined DNA double helix antiparallel structure and revealed how it may be copied and make protein

Rosalind Franklin

got x-ray diffraction patterns of crystalline B-form DNA and found the structure of DNA, her work was used by Watson and Crick in their findings and conclusions

chromatin

the combination of DNA and proteins that make up the nucleus

nitrogenous bases

adenine, guanine, cytosine, and thymine make up DNA and are covalently bonded together to make polynucleotide chains where they extend from the sugar-phosphate backbone

deoxyribose

sugar found in DNA

ribose

sugar found in RNA, it has an OH group on the 2’ carbon, so it is less stable

purines

adenine, thymine, have two rings

pyrimidines

cytosine, uracil, thymine

phosphodiester bonds

hold DNA and RNA nucleotides together between sugars and phosphates

DNA shape

2 polynucleotide chains run antiparallel to each other and the bases are held together with 2 hydrogen bonds (A and T) or 3 hydrogen bonds (C and G) to form base pairs

karyotype

a chart to visualize the homologous chromosomes in the cell before mitosis when they are highly compacted

chromosomal translocation

a segment of 1 chromosome is swapped with the segment of another, causing a genetic defect

noncoding DNA

sequences of DNA that doesn’t encode proteins and instead regulate protein-coding sequences, act as attachment points for scaffold proteins, are origins of replication, or are centromere and telomeres

interphase

when the cell is actively expressing its genes and DNA is replicated

mitosis

the division of the nucleus in the cell

m phase

the chromosomes condense, gene expression ceases, and the mitotic spindle forms from microtubules to capture condensed chromosomes and relocate them to each end of the cell

nuclear envelope

the envelope that forms around the chromosome sets so the cell can divide and produce two daughter cells at the end of M phase

origins of replication

the points on the DNA strand when the strand is opened and the DNA is replicated left and right from the origin

s phase

when DNA is replicated starting at the origins and proceeding bidirectionally

centromere

where the duplicated chromosomes attach to the mitotic spindle in M phase with help from the kinetochore, it holds the chromosomes together until separation

telomere

the ends of the DNA strands where nucleotide sequences cap the end of the chromosome to prevent it from being mistaken as broken

nuclear pores

openings in the nuclear envelope that allow proteins and material to move in and out of the nucleus

nuclear lamina

a network of protein filaments that supports the nuclear envelope by being a thin layer under the membrane

nucleolus

the most prominent structure in interphase, it is where the chromatin appears

heterochromatin

gene-poor chromatin around the periphery of the nucleus under the envelope

ribosomal RNA

RNA that creates ribosomes which is made and kept in the nucleolus

DNA supercoiling

when DNA coils coil around themselves to compact the DNA and help it fit In the cell since there is so much of it

histones

found in eukaryotic cells and make up the nucleosome core with 8 histone molecules: H2A, H2B, H3, H4, packages DNA

linker histone H1

pulls nucleosomes together into a 30 nm fiber, has a globular region

looped domains

this is what the chromatin in human chromosomes is folded into using nonhistone chromosomal proteins that bind to the DNA to clamp the domain together at the base

chromatin remodeling complexes

reposition DNA wrapped around nucleosomes using ATP hydrolysis to change the DNA’s position and make it more accessible to other proteins

position effect

when the activity of a gene depends on its position in the chromosome, it can activate or silence a gene