chromosomes

a nucleosome consists of a complex of

8 histone proteins & a double-stranded DNA strand that consists of about 146 nucleotide pairs

heterochromatin

transcriptionally inactive

euchromatin

actively transcribing

Turner syndrome

X, females without secondary reproductive characteristics

klinefelter syndrome

XXY, males with secondary female reproductive characteristics

X-linked genetic disorders

color blindness, hemophilia, muscular dystrophy

aneuploidy

individuals have one extra or one less chromosome, most miscarriages are aneuploids

polyploidy

individuals have 3 or more of each type of chromosome, 99% of human polyploids die before birth

telomeres are found at the

ends of the chromosome and they contain repeated nucleotide sequences rich in guanine

telomeres protect DNA from

digestive enzymes

telomeres: each time a DNA molecule is replicated some DNA is

lost from the ends of the chromosomes

the enzyme telomerase

adds multiple copies of the same telomere DNA sequence to the ends of the chromosome