genetics lecture 10+11

bacterial dna

circular dna, condensed by supercoiling, arranged in a single loop, no telomeres

bacterial chromosome positively and negatively supercoiled

dna is overrotated, dna is underrotated

bacterial plasmid

small circular dna that replicates independently

bacterial conjugation

plasmids replicated and copies transferred to another bacterium

bacterial resistance factors

proteins that protect against antibiotics

bacterial fertility factors

proteins that enable them to engage in conjugation with other bacteria

eukaryotic dna

linear, condensed around histone protein, arranged in multiple chromosomes, has telomeres

eukaryotic nucleosome

dna wound around cluster of eight histone proteins

histone 1 protein

locks dna around histones

linker dna

connects chromatosomes

chromatosomes

nucleosome and h1

scaffold proteins

hold the coils together

chromatin

combination of dna and protein, relaxes for gene expression

p arm, centromere, q arm

smaller arm, middle, longer arm

metacentric, submetacentric, acrocentric, teolocentric

centromere in middle, centromere off center, longer q arm, no p arm

centromere

has characteristic repeated sequence, contain histone h3 and adopt chromatin configuration

kinetochore

specialized protein in centromere, spindle fiber bind to pull apart homologous chromosome

telomeres must be stabilized

shelterin binds telomeres and keeps them from being repaired

euchromatin

less condensed, genes are active

heterochromatin

more condensed, gene inactive

human chromosome

46 ch, 23 pairs, chromosome 1 large, chromosome 22 small, xx, xy

karyotype purpose

refer to individual’s chromosome status or a picture of individual’s actual chromosome

how to write karyotype

total number chromosomes, sex chromosome, any abnormalities

g banding process

cells grown in culture, additives added, cells burst open and chromosomes spread, enzymes added and dyed with giemsa, unique pattern shown

aneuploidy

not having standard number of chromosomes

nullisomy

no copies of specific ch

monosomy

1 copy of specific ch

disomy

2 copies of specific ch

trisomy

3 copies of specific ch

tetrasomy

four copies of specific ch

polyploidy

having one or more extra set of ch

haploid

having one set of ch

diploid

having two sets of ch

triploid

having three sets of ch

tetraploid

having four sets of ch

polyploidy triploid

when two sperm fertilize one egg

chromosome deletion

a segment of chromosome deleted

deletion causes pseuododominance

individual loses dominant allele, only recessive allele present

deletion causes haploinsufficicney

one working copy of gene cannot make enough protein

displaced duplication

not side by side

reverse duplication

inverted duplication

insertion or nonreciprocal translocation

a piece of chromosome breaks off and inserted in another chromosome

reciprocal translocation

two chromosomes break and exchange pieces

balanced reciprocal translocation

no dna lost

unbalanced reciprocal translocation

dna lost

balanced reciporal translocations cause what

breaks in middle of genes, move active gene to silence gene

robertsonian translocation

fusion of two acrocentric chromosome, short arm of one is exchanged with long arm of another makes large metacentric chromosome and small fragment

Robertsonian tranloction can result in trisomies

two fully functioning chromosome with one centromere, second copy of second chromosome pulled in during division

inversion

a segment of chromosome is turned 180

pericentric inversion

breakpoints lie on either side of centromere

paracentric

breakpoints lie within the same chromosome arm

unbalanced inversion

some dna may or may not be lost at one or both breakpoints

balanced inversion

one or both breakpoints fall inside gene sequence

probability of nondisjunction

increases with age

autopolyploidy

chromosomes from same species, result from wholesale nondisjunction of chromosomes or failure of cell to split

allopolyploidy

chromosomes from two different species

FISHing for chromosome abnormalities

probe dna, labeling with fluorescent dye, grow cells and stop mitosis, put culture on glass slide, denature chromosome and probe, incubate slide, view chromosomes