DNA packing Flashcards
how big is the nucleus of a cell
a human cell nucleus is 5-8um in diameter and has 2m of DNA
What is the human genome
DNA sequence needed to make a human and is split into 23 pairs of chromosomes
what 2 things can cells be
haploid or diploid
what is haploid
only one copy of each chromosome (23 germ cells)
what is diploid
2 copies of each chromosome (46 chromosomes- all other cells)
how many pairs of chromosomes are there
22 pairs + 1 pair of identical sex chromosomes
what are the sex chromsomes
they give gender- males = XY females = XX
What is Down’s syndrome
3 copies of 21 chromosome
what is a karyotype
image of human chromosome set
what is normal cell division
mitosis and occurs in the M phase
what 3 DNA sequences are needed in a chromosome
telomere, replication origin and centromere
what are nucleosomes
DNA is packed into a cell by winding it around special stool structures (each nucleosome has 8 histone proteins)
what are histone proteins
what nucleosomes are built out of
what are scaffold proteins
where coils of nucleosomes are attached to a protein framework
what are protein filaments
inside and outside and they support the nucleus
can the M Phase be viewed
DNA is tightly packed and individual chromosomes are easily seen
can the interphase be seen
loosely packed DNA can be seen on lysing nuclei
what is the nucleolus
where ribosomes are produced. rRNA associate with each other here and ribosomes export through pores
what makes up DNA
DNA is made up of chemical units symbolised by a single letter and since DNA is a continuous strand it Is a string of letters
what is a start codon e.g
Catt
what is a stop codon e.g
tcac
what is a gene
a stretch of DNA that codes for one protein or RNA and produces a given polypeptide
what signals the start or stop of a gene
a certain sequence of nucleotides
