Chromosomes Chromosomes are made of DNA. Gene for cystic fibrosis (chromosome 7) Chromosomes are made of DNA. Each contains genes in a linear order. Human body cells contain 46 chromosomes in 23 pairs – one of each pair inherited from each parent Chromosome pairs 1 – 22 are called autosomes. The 23rd pair are called sex chromosomes: XX is female, XY is male. In the slide you can see chromosomes arranged in pairs, this is called a karyotype (chromsome complement) One of each pair is inherited from the mother, the other from the father Ask participants - what sex is this individual? (Male, XY) Gene for sickle cell disease (chromosome 11)

Chromosomes p Centromere q Chromosome 5 http://learn.genetics.utah.edu/content/begin/traits/karyotype/ Different forms of a gene that codes for a specific trait are carried on chromosomes. These are called Alleles. Chromosome 5

The Karyotype A normal male chromosome pattern would be described as: 46,XY. 46 = total number of chromosomes XY = sex chromosome constitution (XY = male, XX = female). Any further description would refer to any abnormalities or variants found

Total Genes On Chromosome: 723 373 genes in region marked red, 20 are shown FZD2 AKAP10 ITGB4 KRTHA8 Genes are arranged in linear order on chromosomes WD1 SOST MPP3 MLLT6 STAT3 BRCA1 breast cancer 1, early onset GFAP NRXN4 NSF NGFR CACNB1 HOXB9 HTLVR ABCA5 CDC6 ITGB3 Chromosome 17 source: Human Genome Project

Summary of Chromosome Anomalies Change in number e.g. trisomy 21 Down syndrome; Edwards’ syndrome; Turner syndrome. Usually an isolated occurrence. Change in structure e.g. deletions May be inherited. Down’s Syndrome An example of a chromosomal abnormality which causes learning difficulties The karyotype shows a case of Down’s syndrome (trisomy 21) For more information about Down’s syndrome, visit: www.screening.nhs.uk/downs/index.htm [NOTES FOR TRAINING FACILITATORS IN CASE OF QUESTIONS ONLY In total, there are normally 23 pairs of chromosomes, but in a trisomy there is an extra chromosome (tri somy = three bodies) A normal karyotype is written 46,XY or 46,XX The karyotype, or complement of chromosomes, seen in a regular trisomy 21 is written as 47,XX +21 if female or 47, XY +21 if male Note that Down’s syndrome can be inherited, although this is rare. These cases are due to a change in chromosome structure (a translocation)] Trisomy 21

The DNA Double Helix

Disease-Associated Mutations Alter Protein Function

Mutation – an alteration or change in the genetic material In clinical use usually = “harmful” Inherited From exposure to mutagenic agents but more arise spontaneously through errors in DNA replication / repair More likely to be recognized if effects are detrimental What is a mutation?

A karyotype is when chromosomes are grouped from largest to smallest. They are also grouped by the centromere position and the banding patterns. These chromosomes are incredibly small. If they are to be studied, the pictures can be cut up and the chromosomes arranged and glued down as shown in a karyotype. We now do this on the computer with digital pictures. A karyotype is a picture of the chromosomes arranged in order from largest to smallest. They are also grouped in order by the centromere position. (The centromere is where the two sides of the chromosomes come together.) A third thing to look at when arranging chromosomes on a karyotype is the banding patterns.

Before a body cell divides it copies every one of the chromosomes. When the body cell divides, each new body cell gets a copy of each chromosomes. The new body cell is exactly like the original cell!! They have the same number and same type of chromosomes. Chromosomes are made inside the cells. Just before a cell divides, it copies every one of its chromosomes. In this way, the two new cells are identical to the original cell. They have the same number and same type of chromosomes. In this way, the two new cells are identical to the original cell. They have the same number and same type of chromosomes. The whole process is amazing if you stop to think about it. Normally, a human cell has 46 chromosomes. Right before the cell divides, it contains 92 chromosomes. All of these chromosomes have to be equally shared so that each new cell gets 46 of them-two chromosomes 1s, two number, 2s etc. Just any combination of 46 chromosomes won’t do. Click here to see an animation of this.

Human Genome Project: Recessive – the allele that is masked when the dominant allele is present (tt) Dominant – an allele whose trait always shows up when the allele is present (TT, Tt) Allele – another name for a gene or form of a gene Haploid – having one set of chromosomes, such as males or female sex cells (23) Diploid – body cells like muscle cells and bone cells Probability – a number that describes the likelihood of an event occurring Heredity – the passing of traits from parent to offspring through genetics (DNA) Genotype – an organisms genetic makeup (what it is made of) gen-gene Gregor Mendel – father of genetics – studied pea plants to figure out how traits were passed on to plants through multiple generations Phenotype – an organisms physical appearance Ph-physical Hybrid – An organism that has two different alleles for a trait; an organism that is heterozygous for a particular trait Heterozygous – Having two different alleles (Tt, tT) (Bb, bB) Homozygous – having two of the same alleles either recessive or dominant (TT, tt) (BB, bb) Inherited Trait – Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype; ex: eye color Acquired trait - An acquired trait is a characteristic that a living thing gets during its lifetime; ex: a scar, hair color, broken bone

Adenine: a compound that is one of the four constituent bases of nucleic acids. A purine derivative, it is paired with thymine in double-stranded DNA Cytosine – is one of the fundamental components of DNA and RNA, in which it forms a base pair with guanine Meiosis – the process by which chromosomes are reduced by half to form sex cells (sperm or egg) Zygote– a fertilized egg produced by the joining of a sperm and egg Genetics – the study of the components of DNA, chromosomes and human life Mitosis – stage of the cell cycle where the nucleus divides into two nuclei and a copy of the DNA is moved to one daughter cell Gametes – haploid cells such as males or female sex cells Guanine – is one of the four main nucleobases found in the nucleic acids DNA and RNA, it is paired with cytosine Punnett Square– a way of showing the probability or likelihood of an event occurring Thymine – is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. It is paired with adenine DNA – deoxyribonucleic acid found inside the chromosomes, and are the genetic code of life Mutation – any change to a chromosome or gene due to substitution, deletion or addition of a pair of proteins. Tt TT tt