3.2 CHROMOSOMES Flashcards
PROKARYOTES
Prokaryotes have circular DNA without association of protein.
There is one copy of each gene except when the cell and its DNA are replicating
PLASMID IN PROKARYOTES
Plasmids are small separate (usually circular) DNA molecules located in some
prokaryotic cells
Plasmids are also naked (not associated with proteins) and are not needed for daily life processes in the cell.
PLASMID GENES
The genes in plasmids are often associated with antibiotic resistant and can
be transferred from one bacterial cell to another. ␣
USE OF PLASMID
Plasmids are readily used by scientists to artificially transfer genes from one
species to another (ie. Gene for human insulin)
PLASMID FEATURES (6)
Naked DNA without association of protein such as histone
Small circular ring of DNA
Not responsible for normal life process
Contain survival characteristics, e.g. antibiotic resistance
Can be passed on between bacteria
Can be incorporated into nucleoid chromosomes (save permanently)
EUKARYOTIC CHROMOSOMES
Eukaryotic chromosomes are linear and are made up of DNA and histone proteins.
HISTONES
Histones are globular shaped protein in which the DNA is wrapped around.
VARIATION OF EUKARYOTIC LINEAR CHROMOSOMES
length, centromere location and genes contained
NUMBER OF CHROMOSOMES IN HUMAN
23
NUMBER OF AUTOSOMES IN HUMANS
22
23RD PAIR
SEX CHROMOSOMES
WHAT DOES EACH CHROMOSOME CARRY?
specific sequence of genes along the linear DNA molecule
CHROMOSOME NUMBER AKA
‘N’ number
NORMAL CELLS CONTAIN
diploid nucleus
2N
two pairs of homologous chromosomes
SEX CELLS CONTAIN
haploid nucleus
N
one pair of homologous chromosome
IMPORTANT CHARACTERISTIC OF A SPECIES
chromosome number
HOMOLOGOUS CHROMOSOMES
chromosomes within each cell that carry the same genes at the same loci
They have the same structure and size
HOMOLOGOUS CHROMOSOME ORIGIN
One chromosome came from an individual’s mother and one from the father
WHAT DO HOMOLOGOUS CHROMOSOMES DO DURING MEIOSIS?
These chromosomes pair up during meiosis
EVEN THOUGH HOMOLOGOUS CHROMOSOMES CARRY THE SAME GENES…
they could have different alleles
SEX CHROMOSOMES
The X and Y chromosome determine the sex of an individual
X CHROMOSOME
The X chromosome is quite large in comparison to the Y chromosome
and has a centromere that is located near the centre or middle of the
chromosome
Y CHROMOSOME
The Y chromosome is relatively small with its centromere located near
the end of the chromosome
SEDX DETERMINATION?
If an individual has two X chromosomes they will be a female and if
they have an X and a Y chromosome they will be a male
NOT SEX CHROMOSOMES
AUTOSOMES
AUTOSOMES
do not affect the
sex of an individual
SRY
SRY genes on Y chromosomes lead to male development
KARYOGRAM
we distinguish sex, it shows the chromosomes of
an organism in homologous pairs of decreasing length
