Chromosomes

Chromosomes CCCChromosomes are strands of DNA bound to proteins EEEEach cell has two sets of chromosomes, one from the mother and one from the father.

One Chromosome Identical copies Centromere (joining point) (The real thing) Coiled DNA

Homologous pairs The members of a pair are referred to as homologous chromosomes. Each pair: is the same size, has the joining point in the same place, has the same gene loci in the same sequence

A homologous pair Human chromosome 9 Chromosome from mother Chromosome from father Deafness/hearing gene

Chromosome numbers  In humans there are 23 pairs of chromosomes. One member of each pair comes from the mother, and one from the father.  Other species have different numbers.

Genome & karyotype GGGGenome — this is the total of an individual’s genetic material. AAAA karyotype is a full complement of chromosomes. It is usually shown as a drawing or photograph of stained chromosomes arranged in homologous pairs, from the biggest to the smallest.

E.g. Karyotype of a pig

Chromosomes of a human female

Chromosomes of a human male

DNA Structure DDDDNA molecules are polymers of nucleotides. = chains of nucleotide units NNNNucleotides have 3 parts The 5 Carbon (pentose) sugar A phosphate group A base Adenine, Thymine, Cytosine or Guanine A simple model

AAAA DNA molecule consists of two chains of nucleotides twisted around each other to form a double helix. AAAAlternating sugars and phosphates form the sides of the DNA “ladder” TTTThe rungs are formed by the bases in complementary pairs. A – T and C – G

Here is the ladder Let’s give it a twist to make the double helix And this is a space- filling model of DNA

Packaging of DNA