3.2 Chromosomes Flashcards
chromosomes of prokaryotic cells
- singular chromosome = only one copy of each gene
- coiled up in nucleoid region
- genes are needed for basic life processes
- chromosome is makes, no histones
- second copy is made before binary fission
plasmids in prokaryote bacteria
small extra DNA molecules
- small, circular, naked
- few genes that are not essential for cell function but might be helpful (eg. antibiotic resistance)
- not replicated at the same time as chromosome (cell can have many copies)
- can be transferred between prokaryotic cells
plasmids are also used…
by scientists to artificially transfer genes between species
audioradiography
- grown with thymine nucleotides with radioactive hydrogen isotope
- e. coli cells placed on dialysis membrane and lysed with enzymes
- cell contents applied to photgraphic emulsion palced in dark
- radioactive isotopes reacted with emultion making dark areas
- dark areas= presence of DNA
conclusion of cairn’s technique
- e.coli has single cirular chromosome
- provided evidence for semi conservative replication
eukaryotic chromosomes
- linear strands of dna in helix
- nucleosomes formed by wrapping dna around histones
- coiled into chromatin during interphsse
- supercoiled to form characteristic chromosome shape in mitosis
Eukaryotic cells possess…
multiple chromosomes with different genes
each chromosome carries….
a different set of genes in a specific order
chromosomes can vary by
- length (number of base pairs in dna molecule)
- position of the centromere
all individuals of a species…
have same chromosomes with same gene/locus
genome:
complete set of genetic info in organism
genomic size:
vary among organisms
proportion of DNA
that acts as functional genes is variable
homologous chromosomes
- same size and structure, same sequence of genes, may have different alleles for genes
- to interbreed two organisms must have homologous chromosome sets
- each chromosome type comes from the egg and otehr comes from the sperm to make homogolous pairs
- unless motehr gives x and father gives y (not homogolous)
diploids
- 2 homologous pairs
- 2 copies of each gene
- 46 chromosome in human
- somatic cell